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Background: Despite extensive vaccinations, pertussis remains endemic and epidemic in multiple countries. The persistence of cases can be partly attributed to the significant individual variation in vaccine responses. This study evaluated the association of baseline cytokines (before booster vaccination) on antibody concentrations to Tdap-vaccine antigens., Methods: Healthy Finnish children (7-10y, n = 36), adolescents (11-15y, n = 37), young adults (20-34y, n = 25), and older adults (60-70y, n = 23) received a Tdap3-IPV booster. Serum antibodies against pertussis toxin (PT), filamentous hemagglutinin (FHA), pertactin (Prn), fimbriae 2/3, diphtheria toxoid (DT), and tetanus toxoid (TT), as well as PT neutralizing antibodies were measured before, one month, and one year after the booster. Baseline serum concentrations of IFN-γ, IL-2, IL-5, IL-10, IL-13, IL-17 A and IL-17F were determined., Results: The proportion of detectable and undetectable baseline cytokines varied between age groups 58.3 % of children had a higher proportion of detectable IL-5, IL-10, IL-13, and IL-17F compared to adolescents (IL-5, 37.8 %; IL-10, 48.6 %; IL-13, 48.6 %; IL-17F, 37.7 %), young adults (IL-5, 36.0 %; IL-10, 28.0 %; IL-13, 36.0 %; IL-17F, 44.0 %), and older adults (IL-5, 26.1 %; IL-10, 21.7 %; IL-13, 39.1 %; IL-17F, 30.4 %). IFN-γ had a lower detectability in children (44.4 %) and young (40.0 %) and older adults (39.1 %) in contrast to adolescents (62.2 %). IL-2 was undetectable in all age groups while the proportion of detectable IL-17 A decreased with age. A mixed model showed that undetectable baseline levels of IFN-γ, IL-2, IL-10, and IL-17 A were associated with higher antibody concentrations in children before and after vaccination, particularly against PT. Positive associations were observed in adolescents for anti-TT concentrations and young adults for anti-FHA IgA concentrations., Conclusion: These findings indicate a possible role of existing cytokines in pertussis booster antibody concentrations in children and warrant further studies in different populations. However, the results should be interpreted with caution as the number of subjects is limited., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Since April 2024, a pertussis epidemic has been ongoing in Finland with 2,215 notified cases by end October. Of them, 30.1% (n = 667) were aged 10-14 years. Of the 462 Bordetella pertussis isolates characterised, one was macrolide-resistant (minimum inhibitory concentration (MIC) of erythromycin, azithromycin and clarithromycin > 256 μg/mL). The resistant isolate was serotype FIM2, vaccine antigen pertactin-deficient and harboured ptxP3 allele. The emergence of macrolide-resistant B. pertussis in Europe is worrisome and its rapid identification is important.

In Slovenia, primary acellular pertussis vaccines (ACVs) containing pertactin (PRN) were mostly used during 1999-2016; ACVs without PRN were introduced in 2017. Among 123 Bordetella pertussis strains collected during 2002-2020, a total of 48 were PRN-deficient; 44 were collected after 2017. Changes to ACVs could increase PRN-deficient B. pertussis and infections.

Background: Bordetella pertussis continues to cause whooping cough globally even in countries with high immunisation coverage. Booster vaccinations with acellular pertussis vaccines are thus used in children, adolescents, and adults. T cell immunity is crucial for orchestrating the immune response after vaccination. However, T cell assays can be expensive and difficult to implement in large clinical trials. In this study, a whole blood (WB) stimulation assay was developed to identify secreted T cell associated cytokines in different age groups after acellular pertussis booster vaccination., Material and Methods: Longitudinal WB samples were collected from a small set of subjects (n = 38) aged 7-70 years participating in a larger ongoing clinical trial. For assay development, samples were diluted and incubated with purified inactivated pertussis toxin (PT), filamentous haemagglutinin (FHA), inactivated B. pertussis lysate, and complete medium (M) as stimulating conditions, with anti-CD28 and anti-CD49d as co-stimulants. Different timepoints around the vaccination (D0, D7, D14, D28), WB dilution factor (1:2, 1:4) and incubation time (24 h, 48 h, 72 h) were compared. Responses to 15 cytokines were tested with Luminex/multiplex immunoassay., Results: The optimized assay consisted of WB incubation with M, PT, and FHA (including the two co-stimulants). After 48 h incubation, supernatants were collected for measurement of seven selected T cell associated cytokines (IL-2, IL-5, IL-10, IL-13, IL-17 A, IL-17F, and IFN-y) from samples before and 28 days after vaccination. PT stimulation showed a trend for upregulation of IL-2, IL-13, and IL-17 A/F for adult subjects, whereas the responses of all cytokines were downregulated for the paediatric subjects. Furthermore, PT and FHA-stimulated WB showed diverse cytokine producing profiles., Conclusions: The developed WB-based cytokine assay was shown to be less costly, easy to perform, and functional in differently aged individuals. Further, it requires only a small amount of fresh blood, which is beneficial especially for studies including infants. Our results support the use of this assay for other immunological studies in the future., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2024. Published by Elsevier B.V.)

Objectives: In Finland, whole cell pertussis vaccine (wP) was introduced in 1952 and was replaced by acellular pertussis vaccine (aP) without fimbrial (FIM) antigen in 2005. We aimed to analyse the changes in serotypes of circulating Bordetella pertussis before and after acellular vaccination and to explore the relationship between biofilm formation and serotype diversity after the introduction of aP vaccine., Methods: Serotyping of 1399 B. pertussis isolates collected at the Finnish National Reference Laboratory for Pertussis and Diphtheria in Turku, Finland, from 1974 to 2023 was performed by slide agglutination or indirect ELISA. Of 278 isolates collected after 2005, 53 were selected, genotyped for fim3 and fim2 alleles, and tested for biofilm formation. The selection criteria included maintaining a relatively equal distribution of isolates per time interval, ensuring approximately a 50:50 ratio of FIM2 (N = 26) and FIM3 (N = 27) serotypes. The reference strain Tohama I was used as a control., Results: During the wP era, the majority of circulating B. pertussis exhibited the FIM2 serotype. However, FIM3 strains have appeared since 1999 and become prevalent. After the implementation of aP vaccines, the distribution of serotypes has exhibited substantial variability. FIM3 isolates displayed an enhanced biofilm formation compared to FIM2 isolates (Geometric mean value (95% CI): 0.90 (0.79-1.03) vs. 0.75 (0.65-0.85); p < 0.05). Of the 27 FIM3 isolates, 8 harboured fim3-1 and 19 fim3-2 alleles. FIM3 isolates with fim3-2 allele were significantly associated with increased biofilm formation when compared to those with fim3-1 (1.07 (0.96-1.19) vs. 0.61 (0.52-0.72); p < 0.0001)., Conclusion: Following the implementation of aP vaccines, the distribution of serotypes in Finland has exhibited substantial variability. FIM3 isolates with the fim3-2 allele displayed an enhanced biofilm formation capability compared to FIM2 isolates., (Copyright © 2024 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Pertussis toxin (PT) is a unique virulence factor of Bordetella pertussis , and therefore a key component of acellular pertussis vaccines. Although immunity after infection seems to persist longer than after vaccination, the exact mechanisms are not fully known. In this study the overall binding strength (avidity) of anti-PT IgG antibodies was compared after acellular booster vaccination and infection, as a parameter to evaluate long-lasting protection.Danish and Finnish serum samples from a total of 134 serologically confirmed patients and 112 children who received acellular booster vaccines were included in this study. The concentration of anti-PT IgG was first determined by ELISA, followed by two separate ELISAs to evaluate antibody avidity: either with a dilution series of urea as a bond-breaking agent of antibody and antigen binding and a constant anti-PT IgG concentration between the samples or with a constant dilution ratio of sera and detergent. In addition to urea, the use of diethylamine and ammonium thiocyanate as disruptive agents were first compared between each other.A strong Spearman correlation ( R  > 0.801) was noted between avidity and concentration of anti-PT IgG antibodies if a constant serum dilution method was used, and avidity was noted to be higher in patients in comparison to vaccinees in Denmark, but not in Finland. However, no correlation between antibody concentration and avidity was found if a constant anti-PT IgG concentration was used ( R  = -0.157). With this method, avidity after vaccination was significantly higher in comparison to that after infection in both Danish and Finnish subjects ( p  < 0.01). A shorter time since the latest booster vaccination was found to affect avidity positively on the next PT-antigen exposure with either vaccination or infection.

Immunization during pregnancy (IP) against pertussis is recommended in many countries to protect infants. Although maternal antibodies can influence the infants' antibody responses to primary vaccinations, their effect on the development of functional antibodies and B cells remain poorly studied. We investigated the maternal immune response to IP and the effect of IP and pre-existing antibodies on infants' primary vaccine responses in an open-label, non-randomized trial. Forty-seven mothers received tetanus-diphtheria-acellular pertussis (Tdap) vaccine during pregnancy, and 22 mothers were included as controls. Sixty-nine infants received primary doses of DTaP at three and five months of age. Geometric mean concentrations of antibodies to pertussis toxin, filamentous haemagglutinin, pertactin, diphtheria, and tetanus toxins, pertussis toxin neutralizing antibodies (PTNAs), and plasma and memory B-cell frequencies were studied at delivery, and at three, five and six months. Levels of antibodies, PTNAs, and frequencies of memory B-cells were significantly increased at delivery and up to six months after in mothers with IP compared to those without IP (all p  < 0.05, except for PT-specific memory B-cells). In vaccinated pregnant women, high pre-existing antibody levels were positively correlated with higher antibody responses after IP. IP blunted the infants' antibody and plasma B-cell responses to all vaccine antigens, except for tetanus toxin. This blunting effect was the strongest in infants with high concentrations of maternal antibodies. In conclusion, IP resulted in significantly higher concentrations of antibodies in infants up to three months of age (all p  < 0.05); but was associated with blunting of various infants' vaccine responses.

Background: The determination of serum anti-pertussis toxin (PT) IgG antibodies is recommended for the diagnosis and surveillance of pertussis. However, the diagnostic power of anti-PT IgG can be hampered by possible interference from previous vaccinations. We aim to assess if anti-PT IgA antibodies can be well induced by Bordetella pertussis (B. pertussis) infections in children, and their capacity to improve pertussis serodiagnosis., Methods: Serum samples from 172 hospitalized children younger than 10 years old with confirmed pertussis were tested. Pertussis was confirmed by culture, PCR and/or serology. Anti-PT IgA antibodies were determined with commercial ELISA kits., Results: Sixty-four (37.2 %) subjects had anti-PT IgA antibodies greater than or equal to 15 IU/ml, and 52 (30.2 %) of them had anti-PT IgA antibodies greater than or equal to 20 IU/ml. No children with negative anti-PT IgG (less than 40 IU/ml) were observed to have anti-PT IgA antibodies greater than or equal to 15 IU/ml. Of patients younger than one year of age, about 50 % had an IgA antibody response. Moreover, the proportion of subjects with anti-PT IgA antibodies greater than or equal to 15 IU/ml among PCR negative subjects was significantly higher than that among PCR positive subjects (76.9 % vs 35.5 %)., Conclusions: The determination of anti-PT IgA antibodies does not seem to have added value for the serodiagnosis of pertussis in children older than one year of age. However, for infants, determination of serum anti-PT IgA antibodies appears to be useful for the diagnosis of pertussis especially when PCR and culture are negative. The results should be interpreted with caution as the number of subjects included in this study was limited., Competing Interests: Declaration of Competing Interest The author has no conflict of interest to declare., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Bordetella pertussis epidemics persist as transmission remains unabated despite high acellular pertussis vaccination rates. BPZE1, a live attenuated intranasal pertussis vaccine, was designed to prevent B pertussis infection and disease. We aimed to assess the immunogenicity and safety of BPZE1 compared with the tetanus-diphtheria-acellular pertussis vaccine (Tdap)., Methods: In this double-blind, phase 2b trial at three research centres in the USA, healthy adults aged 18-50 years were randomly assigned (2:2:1:1) via a permuted block randomisation schedule to receive BPZE1 vaccination followed by BPZE1 attenuated challenge, BPZE1 vaccination followed by placebo challenge, Tdap followed by BPZE1 attenuated challenge, or Tdap followed by placebo challenge. On day 1, lyophilised BPZE1 was reconstituted with sterile water and given intranasally (0·4 mL delivered to each nostril), whereas Tdap was given intramuscularly. To maintain masking, participants in the BPZE1 groups received an intramuscular saline injection, and those in the Tdap groups received intranasal lyophilised placebo buffer. The attenuated challenge took place on day 85. The primary immunogenicity endpoint was the proportion of participants achieving nasal secretory IgA seroconversion against at least one B pertussis antigen on day 29 or day 113. Reactogenicity was assessed up to 7 days after vaccination and challenge, and adverse events were recorded for 28 days after vaccination and challenge. Serious adverse events were monitored throughout the study. This trial is registered with ClinicalTrials.gov, NCT03942406., Findings: Between June 17 and Oct 3, 2019, 458 participants were screened and 280 were randomly assigned to the main cohort: 92 to the BPZE1-BPZE1 group, 92 to the BPZE1-placebo group, 46 to the Tdap-BPZE1 group, and 50 to the Tdap-placebo group. Seroconversion of at least one B pertussis-specific nasal secretory IgA was recorded in 79 (94% [95% CI 87-98]) of 84 participants in the BPZE1-BPZE1 group, 89 (95% [88-98]) of 94 in the BPZE1-placebo group, 38 (90% [77-97]) of 42 in the Tdap-BPZE1 group, and 42 (93% [82-99]) of 45 in the Tdap-placebo group. BPZE1 induced broad and consistent B pertussis-specific mucosal secretory IgA responses, whereas Tdap did not induce consistent mucosal secretory IgA responses. Both vaccines were well tolerated, with mild reactogenicity and no serious adverse events related to study vaccination., Interpretation: BPZE1 induced nasal mucosal immunity and produced functional serum responses. BPZE1 has the potential to avert B pertussis infections, which ultimately could lead to reduced transmission and diminished epidemic cycles. These results should be confirmed in large phase 3 trials., Funding: ILiAD Biotechnologies., Competing Interests: Declaration of interests CK, KS, MT, PG, KR, and SN are equity holders in, and current or former employees of or consultants to, ILiAD Biotechnologies. VEM reports leadership of the Pearl institutional review. SN is a former employee of Novartis. AG has received honoraria from Sanofi Pasteur. CL holds patents on the BPZE1 vaccine (licensed to ILiAD Biotechnologies) and reports consulting fees from, and holds equity in, ILiAD Biotechnologies. All other authors declare no competing interests., (Copyright © 2023 Elsevier Ltd. All rights reserved.)

Introduction. Current serological diagnosis of pertussis is usually performed by ELISA, which is typically performed in larger diagnostic or reference laboratories, requires trained staff, and due to sample batching may have longer turnaround times. Hypothesis and Aim. A rapid point-of-care (POC) assay for pertussis serology would aid in both the diagnosis and surveillance of the disease. Methodology. A quantitative lateral flow (LF)-based immunoassay with fluorescent Eu-nanoparticle reporters was developed for the detection of anti-pertussis toxin (PT) and adenylate cyclase toxin (ACT) antibodies from oral fluid samples ( N =100), from suspected pertussis cases with respiratory symptoms. Results. LF assay results were compared to those obtained with anti-PT IgG oral fluid ELISA. For an ELISA cut-off value of 50 arbitrary units, the overall agreement between the assays was 91/100 (91 %), the sensitivity was 63/70 (90 %) and the specificity was 28/30 (93 %). No ACT-specific antibodies were detected from oral fluid samples; however, the signal readout positively correlated to those patients with high anti-PT IgG antibodies. Conclusion. The developed LF assay was a specific, sensitive and rapid test for serological diagnosis of pertussis with anti-PT antibodies and is a suitable POC test using oral fluid samples.

Current serological diagnosis of pertussis is usually done by ELISA to determine serum specific anti-pertussis toxin (PT) IgG antibodies. However, the ELISAs are often central-laboratory based, require trained staff, and have long turnaround times. A rapid point-of-care (POC) assay for pertussis serology would aid in both diagnosis and surveillance of the disease. In this study, a quantitative lateral flow assay (LFA) with fluorescent Eu-nanoparticle reporters was used for the detection of anti-PT antibodies from whole blood. The assay was evaluated by testing overall 141 samples including 25 before and 116 one month after acellular pertussis booster vaccination. LFA results were compared to those obtained with standardized anti-PT IgG ELISAs with paired serum samples. Correlation between the assays was high (Pearson R = 0.832), and the achieved analytical sensitivity of the LFA was 29 IU/mL, which would be sufficient for clinically relevant cutoffs for determining recent infections. The paired samples, collected pre- and post-booster, demonstrated a significant increase in anti-PT IgG antibodies similar to that detected by ELISA. The developed LFA opens up several alternatives for a suitable POC test also in middle- and low-income countries., Competing Interests: Declaration of Competing Interest None., (Copyright © 2022 The Author(s). Published by Elsevier B.V. All rights reserved.)

As with other pathogens, competitive interactions between Bordetella pertussis strains drive infection risk. Vaccines are thought to perturb strain diversity through shifts in immune pressures; however, this has rarely been measured because of inadequate data and analytical tools. We used 3344 sequences from 23 countries to show that, on average, there are 28.1 transmission chains circulating within a subnational region, with the number of chains strongly associated with host population size. It took 5 to 10 years for B. pertussis to be homogeneously distributed throughout Europe, with the same time frame required for the United States. Increased fitness of pertactin-deficient strains after implementation of acellular vaccines, but reduced fitness otherwise, can explain long-term genotype dynamics. These findings highlight the role of vaccine policy in shifting local diversity of a pathogen that is responsible for 160,000 deaths annually.

The reported incidence of pertussis in European countries varies considerably. We aimed to study specific Bordetella pertussis seroprevalence in Europe by measuring serum IgG antibody levels to pertussis toxin (anti-PT IgG). Fourteen national laboratories participated in this study including Belgium, Denmark, Finland, Greece, Hungary, Italy, Lithuania, Malta, Norway, Poland, Portugal, Romania, Spain, and Sweden. Each country collected approximately 250 samples (N = 7903) from the age groups 20-29 years (N = 3976) and 30-39 years (N = 3927) during 2010-2013. Samples were anonymous residual sera from diagnostic laboratories and were analyzed at the national laboratories by a Swedish reference method, a commercial ELISA kit, or were sent to Sweden for analysis. The median anti-PT IgG concentrations ranged from 4 to 13.6 IU/mL. The proportion of samples with anti-PT IgG ≥100 IU/mL, indicating a recent infection ranged from 0.2% (Hungary) to 5.7% (Portugal). The highest proportion of sera with anti-PT IgG levels between 50 and <100 IU/mL, indicating an infection within the last few years, was found in Portugal (12.3%) and Italy (13.9%). This study shows that the circulation of B. pertussis is quite extensive in adults, aged 20-39 years, despite well-established vaccination programs in Europe., (© 2021 APMIS. Published by John Wiley & Sons Ltd.)

Pertussis toxin (PT) is considered the main virulence factor causing whooping cough or pertussis. The protein is widely studied and its composition was revealed and sequenced already during the 1980s. The human immune system creates a good response against PT when measured in quantity. However, the serum anti-PT antibodies wane rapidly, and only a small amount of these antibodies are found a few years after vaccination/infection. Therefore, multiple approaches to study the functionality (quality) of these antibodies, e.g., avidity, neutralizing capacity, and epitope specificity, have been investigated. In addition, the long-term B cell memory (Bmem) to PT is crucial for good protection throughout life. In this review, we summarize the findings from functional PT antibody and Bmem studies. These results are discussed in line with the quantity of serum anti-PT antibodies. PT neutralizing antibodies and anti-PT antibodies with proper avidity are crucial for good protection against the disease, and certain epitopes have been identified to have multiple functions in the protection. Although PT-specific Bmem responses are detectable at least five years after vaccination, long-term surveillance is lacking. Variation of the natural boosting of circulating Bordetella pertussis in communities is an important confounding factor in these memory studies.

Reported incidence of pertussis in the European Union (EU) and the European Economic Area (EEA) varies and may not reflect the real situation, while vaccine-induced protection against diphtheria and tetanus seems sufficient. We aimed to determine the seroprevalence of DTP antibodies in EU/EEA countries within the age groups of 40-49 and 50-59 years. Eighteen countries collected around 500 samples between 2015 and 2018 (N = 10,302) which were analysed for IgG-DTP specific antibodies. The proportion of sera with pertussis toxin antibody levels ≥100 IU/mL, indicative of recent exposure to pertussis was comparable for 13/18 countries, ranging between 2.7-5.8%. For diphtheria the proportion of sera lacking the protective level (<0.1 IU/mL) varied between 22.8-82.0%. For tetanus the protection was sufficient. Here, we report that the seroprevalence of pertussis in these age groups indicates circulation of B. pertussis across EU/EEA while the lack of vaccine-induced seroprotection against diphtheria is of concern and deserves further attention.

Objectives: To determine neutralizing antibodies to pertussis toxin (PTNAs) in children with suspected pertussis and to compare results of PTNAs and anti-PT IgG antibodies., Methods: 172 hospitalized children with suspected pertussis were included. Pertussis was confirmed by culture, PCR and/or serology. PTNAs were determined by Chinese hamster ovary (CHO) cell assay., Results: A correlation between titers of PTNAs and anti-PT IgG levels was noticed in 172 patients (Spearman R = 0.68, P < 0.001). Subjects with same concentrations of anti-PT IgG antibodies could have different titers of PTNAs and the maximum difference observed reached to 1024 times in ELISA-confirmed patients. Moreover, subjects with same titers of PTNAs could have different concentrations of anti-PT IgG antibodies., Conclusions: Our results indicated that in some children high concentrations of anti-PT IgG antibodies do not always mean effective PTNAs induced after infection, stressing the importance of detecting PTNAs after infection and vaccination. Clinical trial registry: Not applicable., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Background: Pertussis can lead to serious disease and even death in infants. Older adults are more vulnerable to complications as well. In high-income countries, acellular pertussis vaccines are used for priming vaccination. In the administration of booster vaccinations to different age groups and target populations there is a substantial between-country variation. We investigated the effect of age on the response to acellular pertussis booster vaccination in three European countries., Methods: This phase IV longitudinal intervention study performed in Finland, the Netherlands and the United Kingdom between October 2017 and January 2019 compared the vaccine responses between healthy participants of four age groups: children (7-10y), adolescents (11-15y), young adults (20-34y), and older adults (60-70y). All participants received a three-component acellular pertussis vaccine. Serum IgG and IgA antibody concentrations to pertussis antigens at day 0, 28, and 1 year were measured with a multiplex immunoassay, using pertussis toxin concentrations at day 28 as primary outcome. This trial is registered with ClinicalTrialsRegister.eu (2016-003,678-42)., Findings: Children (n = 109), adolescents (n = 121), young adults (n = 74), and older adults (n = 75) showed high IgG antibody concentrations to pertussis toxin at day 28 with GMCs of 147 (95% CI 120-181), 161 (95% CI 132-196), 103 (95% CI 80-133), and 121 IU/ml (95% CI 94-155), respectively. A significant increase in GMCs for vaccine antigens in all age groups by 28 days was found which had decreased by 1 year. Differences in patterns of IgG GMCs at 28 days and 1 year post-vaccination did not have a consistent relationship to age. In contrast, IgA antibodies for all antigens increased with age at all timepoints., Interpretation: Acellular pertussis booster vaccination induces significant serum IgG responses to pertussis antigens across the age range which are not uniformly less in older adults. Acellular boosters could be considered for older adults to reduce the health and economic burden of pertussis., Competing Interests: Declaration of Competing Interest None of the authors received payment or service from a third part at any time, nor does anyone have a financial relationship with entities in the bio-medical arena. None of the authors have any patents relevant to the work. MVP is a member of the Portuguese National Immunisation Technical Advisory Group (Comissão Técnica de Vacinação da Direcção Geral de Saúde)., (Copyright © 2021 The Authors. Published by Elsevier B.V. All rights reserved.)

Pertussis is an acute respiratory disease caused by Bordetella pertussis . Due to its frequency and severity, prevention of pertussis has been considered an important public health issue for many years. The development of the whole-cell pertussis vaccine (wPV) and its introduction into the pediatric immunization schedule was associated with a marked reduction in pertussis cases in the vaccinated cohort. However, due to the frequency of local and systemic adverse events after immunization with wPV, work on a less reactive vaccine was undertaken based on isolated B. pertussis components that induced protective immune responses with fewer local and systemic reactions. These component vaccines were termed acellular vaccines and contained one or more pertussis antigens, including pertussis toxin (PT), filamentous haemagglutinin (FHA), pertactin (PRN), and fimbrial proteins 2 (FIM2) and 3 (FIM3). Preparations containing up to five components were developed, and several efficacy trials clearly demonstrated that the aPVs were able to confer comparable short-term protection than the most effective wPVs with fewer local and systemic reactions. There has been a resurgence of pertussis observed in recent years. This paper reports the results of a Consensus Conference organized by the World Association for Infectious Disease and Immunological Disorders (WAidid) on June 22, 2018, in Perugia, Italy, with the goal of evaluating the most important reasons for the pertussis resurgence and the role of different aPVs in this resurgence.

Objectives: This study was aimed to determine pertussis specific serum PT-IgG antibodies in healthy individuals during 2010 and 2015/2016 in Beijing, China., Methods: A total of 3884 healthy individuals were included: 3058 aged 3-69 years randomly selected from an epidemiological survey conducted in 2010, and 826 aged 20-39 years selected from those who attended an annual medical examination in 2015/2016. Serum PT-IgG antibodies were determined using the Serion/Virion ELISA kits., Results: Of 3058 subjects in 2010, 167 (5.5%) and 39 (1.3%) subjects had PT-IgG antibodies ≥40 IU/ml and ≥100 IU/ml, respectively. No differences were observed among different age groups. Altogether, 26.2% had undetectable PT-IgG antibodies (<5 IU/ml), and the highest undetectable rate of 56.8% was found in children aged 3-5 years. When the age group of 20-39 years was compared between the two periods, no difference was found in seroprevalence of PT-IgG antibodies ≥ 40 IU/ml (5.1% vs. 4.0%). However, an undetectable rate of PT-IgG antibodies was significantly higher in 2015/2016 than that in 2010 (57.4% vs. 29.1%, p < 0.001)., Conclusions: Our results showed that about 5% of individuals had PT-IgG antibodies indicative of a recent infection, and adults at childbearing age have an increased risk to pertussis in China., (Copyright © 2019. Published by Elsevier Ltd.)

Purpose: Serological analysis is an essential tool for the diagnosis of pertussis or whooping cough, disease surveillance and the evaluation of vaccine effectiveness against Bordetella pertussis. Accurate measurement of anti-pertussis toxin (anti-PT) IgG antibody levels in sera is essential. These measurements are usually performed using immunological methods such as ELISA and multiplex immunoassays. However, there are a large number of different assay systems available, and therefore standardization and harmonization between the methods are needed to obtain comparable data., Methodology: In collaboration with ECDC, the EUPert-LabNet network has organized three External Quality Assessment (EQA) schemes (2010, 2012 and 2016), which initially identified the diverse range of techniques and reagents being used throughout Europe. This manuscript discusses the findings of each of the EQA rounds and their impact on the participating laboratories., Results: The studies have shown an increasing number of laboratories (from 65% to 92%) using only the recommended coating antigen, purified PT, in immunoassays, as this allows exact quantification of serum anti-PT IgG and since PT is only produced by Bordetella pertussis this prevents cross-reactivity with other species. There has also been an increase in the numbers of laboratories (from 59% to 92%), including a WHO reference serum in their assays, which allows anti-PT IgG concentrations to be measured in International Units, thus enabling the comparison of results from different methods and laboratories. In addition, manufacturers have also considered these recommendations when they produce commercial ELISA kits., Conclusion: The three EQA rounds have resulted in greater harmonization in methods among different laboratories, showing a significant improvement of the ELISA methods used for serodiagnosis of pertussis.

IntroductionPertussis outbreaks have occurred in several industrialised countries using acellular pertussis vaccines (ACVs) since the 1990s. High prevalence of pertactin (PRN)-deficient Bordetella pertussis isolates has been found in these countries.AimsTo evaluate in Europe: (i) whether proportions of PRN-deficient strains increased in consecutive collections of B. pertussis clinical isolates; (ii) if the frequency of PRN-deficient strains in countries correlated with the time since ACV introduction; (iii) the presence of pertussis toxin (PT)-, filamentous haemagglutinin (FHA)- or fimbriae (Fim)-deficient isolates.Methods B. pertussis clinical isolates were obtained from different European countries during four periods (EUpert I-IV studies): 1998 to 2001 (n = 102), 2004 to 2005 (n = 154), 2007 to 2009 (n = 140) and 2012 to 2015 (n = 265). The isolates' selection criteria remained unchanged in all periods. PRN, PT, FHA and Fim2 and Fim3 expression were assessed by ELISA.ResultsIn each period 1.0% (1/102), 1.9% (3/154), 6.4% (9/140) and 24.9% (66/265) of isolates were PRN-deficient. In EUpert IV, PRN-deficient isolates occurred in all countries sampled and in six countries their frequency was higher than in EUpert III (for Sweden and the United Kingdom, p < 0.0001 and p = 0.0155, respectively). Sweden and Italy which used ACVs since the mid 1990s had the highest frequencies (69%; 20/29 and 55%; 11/20, respectively) while Finland, where primary immunisations with ACV containing PRN dated from 2009 had the lowest (3.6%). Throughout the study, no PT- or FHA-deficient isolate and one Fim2/3-deficient was detected.ConclusionResults suggest that the longer the period since the introduction of ACVs containing PRN, the higher the frequency of circulating PRN-deficient isolates.

Although vaccination has been effective, Bordetella pertussis is increasingly causing epidemics, especially in industrialized countries using acellular vaccines (aPs). One factor behind the increased circulation is the molecular changes on the pathogen level. After pertussis vaccinations were introduced, changes in the fimbrial (Fim) serotype of the circulating strains was observed. When bacterial typing methods improved, further changes between the vaccine and circulating strains, especially among the common virulence genes including pertussis toxin (PT) and pertactin (PRN) were noticed. Moreover, development of genome based techniques including pulsed-field gel electrophoresis (PFGE), multiple-locus variable number tandem repeat analysis (MLVA) and whole-genome sequencing (WGS) have offered a better resolution to monitor B. pertussis strains. After the introduction of aP vaccines, B. pertussis strains that are deficient to vaccine antigens, especially PRN, have appeared widely. On the other hand, antimicrobial resistance to first line drugs (macrolides) against B. pertussis is still low in many countries and therefore no globally evaluated antimicrobial susceptibility test values have been recommended. In this review, we focus on the molecular changes in the bacteria, which have or may have affected the past and current epidemiology of pertussis.

Background: A pertussis outbreak was studied in a primary school in Xi'an, China, in March 2016. The school consisted of 536 pupils 6-12 years of age who were divided into 12 classes of 6 grades (2 classes for each grade). The identified index case was an 11-year-old girl at class 2 of grade 5., Methods: Interview was conducted and nasopharyngeal swabs were taken from all pupils (N = 94) in the 2 classes of grade 5. Nasopharyngeal swabs were tested by both culture and polymerase chain reaction (PCR)., Results: Four culture- and 17 PCR-positive cases were identified in 94 pupils. Infection rate was significantly higher in class 2 compared with that in class 1 [37.0% (17/46) vs. 14.6% (7/48), χ(2) = 4.26, P < 0.05]. All Bordetella pertussis isolates were macrolide-resistant, harbored prn1/ptxP1/fim3-1 as previously reported and belonged to multilocus variable tandem repeat analysis type MLVA 195. Of the 17 DNAs positive for diagnostic PCR, 12 were also positive for 23S ribosomal RNA PCR. All the 12 DNAs had the A2047G mutation of 23S rRNA gene of B. pertussis., Conclusions: This study described a pertussis outbreak caused by macrolide-resistant B. pertussis in a primary school and indicated that close contact of index case causes the bacterial transmission.

One reason for increased pertussis incidence is the adaptation of Bordetella pertussis to vaccine-induced immunity by modulating its genomic structure. This study, EUpert IV, includes 265 isolates collected from nine European countries during 2012 to 2015 ( n = 265) and compares the results to previous EUpert I to III studies (1998 to 2009). The analyses included genotyping, serotyping, pulsed-field gel electrophoresis (PFGE), and multilocus variable-number tandem-repeat analysis (MLVA). Genotyping results showed only small variations among the common virulence genes of B. pertussis The frequencies of serotypes Fim2 and Fim3 varied among the four collections. Genomic analyses showed that MLVA type 27 increased to 80% between the periods of 1998 to 2001 and 2012 to 2015. Two PFGE profiles, BpSR3 (29.4%) and BpSR10 (27.2%), constituted more than 50% of the circulating isolates in the present collection. Our study indicates that the European B. pertussis population is changing and became more homogenous after the introduction of acellular pertussis vaccines., (Copyright © 2018 American Society for Microbiology.)

Current serological diagnosis of pertussis is usually done by ELISA. However, the ELISAs are often central-laboratory based, require trained staff and have long turnaround times. A rapid point-of-care (POC) assay for pertussis serology would aid in both diagnosis and surveillance of the disease. While lateral flow immunoassays (LFIA) are simple to use and ideal for point-of-care diagnostics, they were limited to qualitative assays until recently. In this study, we developed a quantitative LFIA with fluorescent Eu-nanoparticle reporters for the detection of anti-pertussis toxin (PT) IgG. The assay was evaluated by testing 198 serum samples with varying anti-PT IgG levels and the result was compared to those obtained with standardized anti-PT IgG ELISA. At the diagnostic cutoff of 100 IU/mL in ELISA, the LFIA had a concordance of 92% with the ELISA, with a specificity of 96% [95% confidence interval (CI): 89-99%] and a sensitivity of 88% [CI: 77-94%]. The developed LFIA has a turnaround time of one hour and requires only a simple manipulation by the user and an instrument for the quantitative detection of the signal. We conclude that the LFIA is specific and sensitive for serological diagnosis of pertussis and is suitable for a POC test., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Pertussis is one of the most prevalent vaccine-preventable diseases worldwide. The true infection rate is significantly higher than the reported incidence rate. An increased prevalence of pertussis in older populations has been found, mainly caused by waning immunity after vaccination. Vaccine-induced immunity differs due to variation in vaccine content, schedule and coverage. Protection following acellular pertussis vaccines has been suggested to wane faster than whole cell pertussis vaccines. However, long-term immune persistence of whole cell pertussis vaccines may be confounded by a progressive acquisition of natural immunity. The World Health Organization has recommended that a switch from whole cell to acellular pertussis vaccines for primary immunization in infants should only be considered if additional periodic boosters or maternal immunization can be ensured and sustained in the national immunization schedules. In this review, we present data on immune persistence after different pertussis vaccinations and compare the findings from countries with different vaccination strategies. Future aspects in serological studies are briefly discussed.

Individual variation in immune responses is always encountered after vaccination. This phenomenon is also seen after acellular pertussis vaccination. The aim of this present study was to investigate whether single nucleotide polymorphisms (SNPs) in the IL-10 gene promoter region (rs1800890, rs1800896, rs1800871), IL-12B (rs2546890), IL-12RB1 (rs372889), IL-17A (rs2275913), and IL-23R (rs11209026) affect the immune responses after acellular pertussis vaccination. The T cell proliferative response was evaluated in 38 Finnish young adults who received a second booster dose of a vaccine combination of diphtheria, tetanus, and acellular pertussis, 10 years after the previous booster. The response was evaluated with a proliferation assay in which vaccine antigens pertussis toxin (PT), filamentous hemagglutinin (FHA), and pertactin (PRN) were used for the stimulation, before and 1 month after the second vaccination. Specific proliferation of peripheral blood mononuclear cells against pertussis antigens was affected by IL-10 SNP in the promoter region at position -1082 (A>G, rs1800896). One month after the vaccination, subjects with the AA and AG genotypes had a significantly higher T cell proliferative response against PT and FHA compared to those with the GG genotype. Subjects with the GG genotype had the lowest responses. As a conclusion, our preliminary results indicate that IL-10 SNP -1082 might play an important role in T cell-mediated immune responses after acellular pertussis vaccination.

Objective: To estimate the true incidence of pertussis in Chinese adults who are at a childbearing age., Methods: A total of 897 serum samples from healthy individuals aged 20-39 years were selected randomly from a large number of serum samples collected in 2010 in Beijing, China. Anti-pertussis toxin (Ptx) IgG antibodies were determined with the Virion/Serion ELISA kits using purified Ptx as a coating antigen., Results: Only 124 (13.8%) were found to have undetectable anti-Ptx IgG antibodies. The mean concentration was 13.76 IU/ml (95% CI, 12.37-15.15). Forty-six (5.1%) subjects had anti-Ptx IgG levels greater than or equal to 40 IU/ml, indicative of a pertussis infection, and nine (1%) had IgG antibodies greater than or equal to 100 IU/ml, indicative of a recent infection within a year. No significant differences were observed between age groups of 20-29 and 30-39 years, or between genders., Conclusions: Our study showed that about 5% of adults aged 20-39 years had positive anti-Ptx IgG antibodies, suggesting that adult pertussis is common in China. Giving a booster vaccination to pregnant women should possibly be considered in order to protect young infants who are too young to be vaccinated in this country., (Copyright © 2016 The British Infection Association. Published by Elsevier Ltd. All rights reserved.)

Background: One of the reasons for pertussis resurgence is waning immunity. Both humoral and cell mediated immunity (CMI) are essential for protection. The aim of this study was to evaluate CMI responses after acellular pertussis vaccination in young adults., Methods: Fifty-seven young adults were followed for ten years after a diphtheria-tetanus acellular pertussis (dTpa) booster vaccination. A second booster was administrated at year 10. CMI was determined from peripheral blood mononuclear cells (PBMC) stimulated with vaccine antigens pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) before and one month after the second vaccination, using proliferation and IFN-γ and IL-17 ELISpot. In addition, the response to ten selected cytokines was measured from 14 subjects., Results: Before the booster dose, positive proliferation was recognized in 51%, 53% and 89% of the subjects against PT, PRN and FHA, respectively. One month after, the positivity rate increased to 81%, 81% and 96%. Although the number of IFN-γ and IL-17 secreting cells was increased, the expression of most of the tested cytokines was found to be downregulated. After PT stimulation, only one (7.1%) subject had increased production in all cytokines, whereas six (42.9%) had decreased production of all cytokines. Ten subjects (71.4%) had decreased concentration of IFN-γ, the cytokine important for pertussis protection., Conclusions: CMI persists even when antibodies have decayed, and acellular pertussis vaccine enhances the CMI response. Further studies are needed to illustrate what factors cause the low production of some important cytokines., (Copyright © 2015 Elsevier Ltd. All rights reserved.)

Bordetella pertussis is a pathogen-causing whooping cough (pertussis) in humans. Although vaccination against the disease is effective, the bacterium is still circulating among population and can even cause death. Especially young infants, who lack protection, are vulnerable. The laboratory diagnostic methods to detect B. pertussis are culture, PCR and ELISA serology. Reported cases of the disease vary among countries but usually the incidence rates are low, <1 to 10/100 000. However, pertussis often goes unrecognized among patients as it presents itself like the common cold, especially in adults and elders who are often the source of the infection. This makes pertussis difficult to monitor and control. Serological surveillance is an easy manner to estimate the real burden of the disease among population. Furthermore, to have reliable results, anti-PT IgG antibodies should be measured, as PT is the only specific antigen to B. pertussis. This review aims to evaluate available pertussis seroprevalence studies throughout the world, and to compare the findings from countries with different vaccination histories and strategies. Estimation of the real burden of pertussis is compared to reported numbers. In addition, future aspects in seroprevalence studies are considered., (© FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.)

Bordetella pertussis causes pertussis, a respiratory disease that is most severe for infants. Vaccination was introduced in the 1950s, and in recent years, a resurgence of disease was observed worldwide, with significant mortality in infants. Possible causes for this include the switch from whole-cell vaccines (WCVs) to less effective acellular vaccines (ACVs), waning immunity, and pathogen adaptation. Pathogen adaptation is suggested by antigenic divergence between vaccine strains and circulating strains and by the emergence of strains with increased pertussis toxin production. We applied comparative genomics to a worldwide collection of 343 B. pertussis strains isolated between 1920 and 2010. The global phylogeny showed two deep branches; the largest of these contained 98% of all strains, and its expansion correlated temporally with the first descriptions of pertussis outbreaks in Europe in the 16th century. We found little evidence of recent geographical clustering of the strains within this lineage, suggesting rapid strain flow between countries. We observed that changes in genes encoding proteins implicated in protective immunity that are included in ACVs occurred after the introduction of WCVs but before the switch to ACVs. Furthermore, our analyses consistently suggested that virulence-associated genes and genes coding for surface-exposed proteins were involved in adaptation. However, many of the putative adaptive loci identified have a physiological role, and further studies of these loci may reveal less obvious ways in which B. pertussis and the host interact. This work provides insight into ways in which pathogens may adapt to vaccination and suggests ways to improve pertussis vaccines. IMPORTANCE Whooping cough is mainly caused by Bordetella pertussis, and current vaccines are targeted against this organism. Recently, there have been increasing outbreaks of whooping cough, even where vaccine coverage is high. Analysis of the genomes of 343 B. pertussis isolates from around the world over the last 100 years suggests that the organism has emerged within the last 500 years, consistent with historical records. We show that global transmission of new strains is very rapid and that the worldwide population of B. pertussis is evolving in response to vaccine introduction, potentially enabling vaccine escape.

Mannose-binding lectin (MBL) is an important molecule of the innate immunity. The low level of MBL in the serum is associated with increased susceptibility to respiratory infections. In this study, MBL concentrations were determined from the sera of 125 Finnish pertussis patients and from 430 control subjects. Severe MBL deficiency (<50 ng/mL) was found more often in the patients than in the controls (11.2% vs 5.8%, p = 0.038). Moreover, the deficiency was detected more frequently in the adult patients than in the controls [20.4% vs 8.6%, p = 0.021; odds ratio 2.7 (95% confidence interval 1.1-6.5)]. Our findings suggest, for the first time, that MBL deficiency predisposes to pertussis infection, at least in adults., (© 2012 The Authors APMIS © 2012 APMIS.)

Between 1998 and 2009, Bordetella pertussis clinical isolates were collected during three periods, i.e., 1998 to 2001 (n = 102), 2004 to 2005 (n = 154), and 2007 to 2009 (n = 140), from nine countries with distinct vaccination programs, i.e., Denmark, Finland, France, Germany, The Netherlands, Norway, Poland, Sweden, and the United Kingdom. Pulsed-field gel electrophoresis (PFGE) analysis was performed according to standardized recommendations for epidemiological typing of B. pertussis. There were 81 different PFGE profiles, five of which (BpSR3, BpSR5, BpSR10, BpSR11, and BpSR12) were observed in 61% of the 396 isolates and shown to be predominant in almost all countries. The major profile, BpSR11, showed a decreasing trend from 25% to 30% in 1998 to 2005 to 13% in 2007 to 2009, and there were increases in BpSR3 and BpSR10 from 0% and 8% to 21% and 22%, respectively. One difference between these profiles is that BpSR11 contains isolates harboring the fim3-2 allele and BpSR3 and BpSR10 contain isolates harboring the fim3-1 allele. The total proportion of the five predominant profiles increased from 44% in 1998 to 2001 to 63% in 2004 to 2005 to 70% in 2007 to 2009. In conclusion, common PFGE profiles were identified in B. pertussis populations circulating in European countries with different vaccination programs and different vaccine coverages. These prevalent isolates contain the novel pertussis toxin promoter ptxP3 allele. However, there is evidence for diversifying selection between ptxP3 strains characterized by distinct PFGE profiles. This work shows that, even within a relatively short time span of 10 years, successful isolates which spread through Europe and cause large shifts in B. pertussis populations may emerge.

Background: Pertussis toxin (PT) is a specific virulence factor of Bordetella pertussis and it is included in all acellular pertussis vaccines (aP). Although immunity after infection seems to persist longer than that after vaccination, the exact mechanism(s) is not known. Primary aim of this study was to develop an ELISA method for measuring avidity index (AI) of IgG-anti-PT antibodies and to compare antibody responses after booster vaccination and infection. Secondary aim was to evaluate if the AI-ELISA has potential in the serodiagnosis of pertussis., Material: Serum samples from a total of 409 subjects were included in the study. Paired sera were taken from 97 adolescents who received booster vaccine ten years ago (dTpa-004) and from 80 young adults who received a second booster dose ten years after the previous booster vaccine (dTpa-040). Thirty-two paired sera from culture-confirmed pertussis patients, 161 single sera from serologically diagnosed patients and 39 single sera from healthy controls were included. AI of IgG-anti-PT antibodies were determined with newly developed ELISA using diethylamine (DEA) as a bond breaking agent. The IgG-anti-PT antibodies were measured by standardized ELISA., Results: A significant increase was found in antibody concentrations and AI between PRE and one month POST vaccination ten years ago [GMC for antibody: 7.9 IU/ml vs. 98.3 IU/ml (p=0.0001); for AI: 40.4% vs. 56.1% (p=0.0001)]. Similar result was observed after the second booster dose [GMC for antibody: 9.2 IU/ml vs. 92.4 IU/ml (p=0.0001); for AI: 36.1% vs. 59.5% (p=0.0001)] and between the first and second sera of culture-confirmed patients [GMC for antibody: 6.9 IU/ml vs. 285.1 IU/ml (p=0.0001); for AI: 40.5% vs. 68.4% (p=0.0001)]. Healthy controls showed lower levels of both antibodies and AI., Conclusions: Our results suggest that there may be difference in quality and quantity of antibodies to PT after vaccination and after infection. Furthermore, AI could be a help for vaccine studies., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Pertussis is a reported vaccine-preventable respiratory disease in China. Because the routine laboratory methods for diagnosis are not in use, the reported cases are mainly in infants with classical paroxysmal cough and the true incidence related to pertussis is most likely under estimated. In China, however, few studies have attempted to address this issue. The purpose of this cross sectional study was to estimate the incidence rates using the method of sero-epidemiology of immunoglobulin (Ig) G antibodies against pertussis toxin (PT) among healthy populations in China., Methods: Blood samples were obtained from 1313 healthy individuals aged 0 to 95 years in Guangdong province of China throughout September 2010. Serum IgG antibodies against PT were determined by commercial ELISA kits. Subjects with concentration of anti-PT IgG higher than 30 IU/mL were indicated to have recent Bordetella pertussis infection, if they have not received a booster dose of pertussis vaccine within one year., Results: Of the 1313 study subjects, 117 (8.91%) were found to have anti-PT antibodies higher than 30 IU/mL. The estimated incidence of recent infection was thus 9395 per 100,000 for individuals older than 7 years. Peaks of the estimated incidence rate of recent infection were found to be 11561 per 100,000 in age group of 41-50 years and 11428 per 100,000 in the group aged 13-19 years., Conclusions: Our study indicated that B.pertussis infections are considerablely common, particularly in adolescents and adults in China. The study also stresses the importance of laboratory diagnosis for pertussis and employment of booster dose of pertussis vaccine in adolescents and adults in this country.

Objectives: Despite extensive childhood immunization, pertussis remains one of the world's leading causes of vaccine-preventable deaths. Incidence of pertussis in adolescents and adults has increased in many countries despite high vaccination coverage. In China, booster vaccinations against diphtheria, tetanus and pertussis are not used in adults, and little is known about pertussis incidence in the age group. The aim of this study was to determine seroprevalence of IgG antibodies to pertussis toxin (PT) and diphtheria among adults in China., Methods: Blood samples were obtained from 210 healthy adults aged 18-50 years in Weifang city, China during the period of May and June 2010. Serum IgG antibodies against PT (anti-PT IgG) and diphtheria were determined by the commercial ELISA kits, respectively. According to the kit, concentration of anti-PT IgG higher than 30 IU/mL was considered positive. An antibody concentration of ≥ 0.1 IU/mL was defined as evidence of seroprotection against diphtheria., Results: The mean concentration of anti-PT IgG antibodies was 9.95 IU/mL (95% confidence interval (CI) 8.45-11.44). Eleven (5.24%) of the studied subjects were proved to be seropositive to pertussis. Of the 210 subjects, 161 (76.6%) had anti-diphtheria antibody concentration ≥ 0.1 IU/mL and 49 (23.3%) had the antibody concentration between 0.01 and 0.099 IU/mL., Conclusions: Our study indicated that about 5% of adults aged 18-50 years had positive anti-PT IgG antibodies, suggesting that adult pertussis is not uncommon in China. Although a high proportion of studied subjects had a protective level of immunity against diphtheria, the antibody level decreased with the increasing age of adults. Booster vaccinations against pertussis should be considered in adults in China., (Copyright © 2011 The British Infection Association. Published by Elsevier Ltd. All rights reserved.)

As part of the new EUVAC.NET contract with ECDC (Pertussis Work Area 4), a collaborative study was organised in July-December 2010. Two well-defined reference preparations with high and low IgG antibodies to pertussis toxin (PT), were sent to participants. The purposes of this study were to assess current laboratory performance of serological assays for pertussis; to compare in-house reference preparations that are currently used by participants for the serological assay; and to identify needs for standardisation of the serological assay. Reference Laboratories in Europe currently performing serological assays for the diagnosis of pertussis by measuring antibody to PT, were invited to participate in the study. A total of 17 laboratories/countries participated in this study. Results were reported from a total of 9 participants who used in-house ELISA assays and 10 participants who used commercial kits. All participants using in-house ELISA with purified PT coating plates distinguished the 2 preparations and gave results that were comparable to the expected values. A total of 6 commercial kits included in the study showed different results. The kits coated with mixture antigens did not appear to be able to give results that were correlated to the WHO reference preparations., (Copyright © 2011 Elsevier B.V. All rights reserved.)

In Serbia, whole cell pertussis vaccine was introduced in 1957. Current composition of the vaccine has been used since 1985 and contains four autochthonous strains of Bordetella pertussis isolated from 1957 to 1984. To monitor changes in bacterial population, 70 isolates collected from 1953 to 2000 were studied together with the vaccine strains. The methods included serotyping of fimbriae (Fim), genotyping of pertactin (prn) and pertussis toxin S1 subunit (ptxA), and pulsed-field gel electrophoresis analysis. Shift from ptxA2 to ptxA1 has been observed in isolates since the late of 1960s. All isolates from 1980 to 1984 harbored ptxA1. Re-appearance of the ptxA2 allele followed an addition of the two strains harboring ptxA1 in the vaccine in 1985. The allele prn1 was predominant among the Serbian isolates, though prn3 and prn11 have been detected since 1981 and 1984. The allele prn2 was found only in two strains isolated in 2000. Serotype Fim2.3 disappeared before 1980 and serotype Fim2 became predominant since then. The Serbian vaccine strains showed differences in ptxA and prn. The results of this present study indicate that the B. pertussis population in Serbia is different from other vaccinated populations and that this difference may be related to the vaccine used., ((c) 2009 Elsevier Ltd. All rights reserved.)

In Finland, the whole-cell pertussis vaccine was replaced with acellular pertussis vaccine in the national immunisation schedule in 2005. Adolescent booster vaccinations were also included in the programme. The aim of this study was to evaluate the effects of these changes on the epidemiology and strain characteristics of Bordetella pertussis. From the national register, we first analysed all the laboratory diagnosed cases during the study years in 1999-2006. The major pool of the 6876 cases was among adolescents and adults. After the change of the programme and the introduction of the adolescent boosters, a general reduction of the incidence was noticed but this might be related to the natural epidemic cycles of pertussis. Secondly, a questionnaire was sent to the families of the 517 young children (<2 years of age) with registered, laboratory confirmed pertussis diagnosed during the study years. Of these, 319 (62%) participated the study. Forty-five percents of the cases in this cohort were younger than 3 months, the age of the first pertussis immunisation in schedule. Only 4% of the children in vaccination age were totally unimmunised. Thirdly, isolates of B. pertussis were analysed and found to differ from the used whole-cell pertussis vaccine strains by their prn, ptxA and PFGE profiles. However, no significant differences were found between the strains from patients with different immunisation status or age. Despite marked changes in the virulence genes and the genomes of the circulating B. pertussis strains have occurred, the epidemiological data from the national reporting system indicates that the whole-cell and acellular vaccines still protect against pertussis, but the results stress the importance of early primary immunisations and the need for booster immunisations.

Before childhood vaccination was introduced in the 1940s, pertussis was a major cause of infant death worldwide. Widespread vaccination of children succeeded in reducing illness and death. In the 1990s, a resurgence of pertussis was observed in a number of countries with highly vaccinated populations, and pertussis has become the most prevalent vaccine-preventable disease in industrialized countries. We present evidence that in the Netherlands the dramatic increase in pertussis is temporally associated with the emergence of Bordetella pertussis strains carrying a novel allele for the pertussis toxin promoter, which confers increased pertussis toxin (Ptx) production. Epidemiologic data suggest that these strains are more virulent in humans. We discuss changes in the ecology of B. pertussis that may have driven this adaptation. Our results underline the importance of Ptx in transmission, suggest that vaccination may select for increased virulence, and indicate ways to control pertussis more effectively.

Bordetella pertussis is a Gram-negative bacterium that causes pertussis or whooping cough in humans. The incidence of pertussis has increased in young infants, adolescents and adults in many countries where the vaccination against pertussis has been used extensively. Marked changes have been found in the B. pertussis population and differences have been observed between vaccine strains and circulating isolates. Moreover, clonal expansion of certain B. pertussis strains has been associated with the recent epidemics of pertussis in several European countries. In this review, we present data on strain variation and evolution of B. pertussis in different vaccinated populations and summarize the common methods for typing of B. pertussis and their relative discriminatory power.

Background: Bordetella pertussis causes whooping cough or pertussis in humans. It produces several virulence factors, of which the fimbriae are considered adhesins and elicit immune responses in the host. B. pertussis has three distinct serotypes Fim2, Fim3 or Fim2,3. Generally, B. pertussis Fim2 strains predominate in unvaccinated populations, whereas Fim3 strains are often isolated in vaccinated populations. In Finland, pertussis vaccination was introduced in 1952. The whole-cell vaccine contained two strains, 18530 (Fim3) since 1962 and strain 1772 (Fim2,3) added in 1976. After that the vaccine has remained the same until 2005 when the whole-cell vaccine was replaced by the acellular vaccine containing pertussis toxin and filamentous hemagglutinin. Our aims were to study serotypes of Finnish B. pertussis isolates from 1974 to 2006 in a population with > 90% vaccination coverage and fimbrial expression of the isolates during infection. Serotyping was done by agglutination and serotype-specific antibody responses were determined by blocking ELISA., Results: Altogether, 1,109 isolates were serotyped. Before 1976, serotype distributions of Fim2, Fim3 and Fim2,3 were 67%, 19% and 10%, respectively. From 1976 to 1998, 94% of the isolates were Fim2 serotype. Since 1999, the frequency of Fim3 strains started to increase and reached 83% during a nationwide epidemic in 2003. A significant increase in level of serum IgG antibodies against purified fimbriae was observed between paired sera of 37 patients. The patients infected by Fim3 strains had antibodies which blocked the binding of monoclonal antibodies to Fim3 but not to Fim2. Moreover, about one third of the Fim2 strain infected patients developed antibodies capable of blocking of binding of both anti-Fim2 and Fim3 monoclonal antibodies., Conclusion: Despite extensive vaccinations in Finland, B. pertussis Fim2 strains were the most common serotype. Emergence of Fim3 strains started in 1999 and coincided with nationwide epidemics. Results of serotype-specific antibody responses suggest that Fim2 strains could express Fim3 during infection, showing a difference in fimbrial expression between in vivo and in vitro.

Background: Whooping cough caused by Bordetella pertussis in humans, is re-emerging in many countries despite vaccination. Several studies have shown that significant shifts have occurred in the B. pertussis population resulting in antigenic divergence between vaccine strains and circulating strains and suggesting pathogen adaptation. In the Netherlands, the resurgence of pertussis is associated with the rise of B. pertussis strains with an altered promoter region for pertussis toxin (ptxP3)., Results: We used Multi-Locus Sequence Typing (MLST), Multiple-Locus Variable Number of Tandem Repeat Analysis (MLVA) and microarray-based comparative genomic hybridization (CGH) to characterize the ptxP3 strains associated with the Dutch epidemic. For CGH analysis, we developed an oligonucleotide (70-mers) microarray consisting of 3,581 oligonucleotides representing 94% of the gene repertoire of the B. pertussis strain Tohama I. Nine different MLST profiles and 38 different MLVA types were found in the period 1993 to 2004. Forty-three Dutch clinical isolates were analyzed with CGH, 98 genes were found to be absent in at least one of the B. pertussis strains tested, these genes were clustered in 8 distinct regions of difference., Conclusion: The presented MLST, MLVA and CGH-analysis identified distinctive characteristics of ptxP3 B. pertussis strains -the most prominent of which was a genomic deletion removing about 23,000 bp. We propose a model for the emergence of ptxP3 strains.

Despite extensive immunization, the disease pertussis remains one of the world's leading causes of vaccine-preventable deaths. An estimated 50 million cases and 300,000 deaths occur every year. A resurgence of pertussis is observed in highly immunized populations. Increasing numbers of pertussis are reported in adolescents and adults who transmit bacteria to newborns and infants to whom pertussis may be a life-threatening disease. Many studies have shown that the causes for the resurgence are multiple, such as increased awareness of disease, use of better diagnostic tools, improved surveillance methods and waning vaccine-induced immunity. Recently, antigenic divergence has been found between vaccine strains and clinical isolates in many countries with high vaccination coverage. Here, we summarize these findings and discuss the factors contributing to pertussis resurgence in immunized populations.

Although vaccines against Bordetella pertussis, the causative agent of whooping cough, have been in use for over 50 y, the disease has remained endemic and is still a public health problem in many countries. It has been shown that antibody titres against pertactin, which is 1 of the exposed virulence factors of pertussis, correlate with protection and pertactin is now 1 of the components of most acellular pertussis vaccines. However, little is known about the structure and location of protective epitopes on pertactin. Here we set out to investigate the antibody response using naturally occurring pertactin variants and deletion derivates. We found the N-terminus of pertactin to be immunodominant in both rabbits and humans. In contrast to vaccinated rabbits, we could not detect pertactin type-specific antibodies in human sera. In conclusion, these results show for the first time to which defined regions of the pertactin molecule antibody responses are induced. It also suggests that the amount of pertactin type-specific antibodies will not be very large and that the variation in pertactin probably will not constitute a problem in highly immune individuals.

Background: We conducted a 5-year follow-up study on the persistence of pertussis-specific antibody and cell-mediated immunity after booster immunization of adolescents aged 11-13 years with a tricomponent acellular pertussis vaccine (Boostrix; trials diphtheria-tetanus-acellular pertussis [Tdap]-004/030)., Methods: Cellular and humoral immunity to pertussis toxin (PT), filamentous hemagglutinin, and pertactin were measured in adolescents (age, 16 years) 5 years after booster immunization. Similar investigations were performed for control adolescents who had received only diphtheria and tetanus booster vaccination., Results: Five years after pertussis booster vaccination, the geometric mean concentrations of immunoglobulin G (IgG) elicited by each of the 3 pertussis vaccine antigens decreased from 1-month and 3-year postvaccination levels, but with the exception of PT IgG, were still higher than the prevaccination levels. PT IgG levels were undetectable in 28% of the subjects, but 44% of those subjects still tested positive for cell-mediated immunity to PT. Filamentous hemagglutinin IgG and pertactin IgG levels were significantly higher in Tdap-boosted adolescents than in the control subjects. Antibody concentrations at 1 month after vaccination strongly predicted antibody persistence. Cell-mediated immunity levels to PT, filamentous hemagglutinin, and pertactin persisted above the prebooster levels measured 5 years earlier., Conclusions: The results of the present study of adolescents indicate that the interval between acellular pertussis booster immunizations might be extended beyond 5 years.