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Background: According to Norwegian registries, 91% of individuals ≥ 16 years had received ≥ 1 dose of COVID-19 vaccine by mid-July 2022, whereas less than 2% of children < 12 years were vaccinated. Confirmed COVID-19 was reported for 27% of the population, but relaxation of testing lead to substantial underreporting. We have characterized the humoral immunity to SARS-CoV-2 in Norway in the late summer of 2022 by estimating the seroprevalence and identifying antibody profiles based on reactivity to Wuhan or Omicron-like viruses in a nationwide cross-sectional collection of residual sera, and validated our findings using cohort sera. Methods: 1,914 anonymized convenience sera and 243 NorFlu-cohort sera previously collected from the Oslo-area with reported infection and vaccination status were analyzed for antibodies against spike, the receptor-binding domain (RBD) of the ancestral Wuhan strain and Omicron BA.2 RBD, and nucleocapsid (N). Samples were also tested for antibodies inhibiting RBD-ACE2 interaction. Neutralization assays were performed on subsets of residual sera against B.1, BA.2, XBB.1.5 and BQ.1.1. Results: The national seroprevalence estimate from vaccination and/or infection was 99.1% (95% CrI 97.0-100.0%) based on Wuhan (spike_W and RBD_W) and RBD_BA2 antibodies. Sera from children < 12 years had 2.2 times higher levels of antibodies against RBD_BA2 than RBD_W and their seroprevalence estimate showed a 14.4 percentage points increase when also including anti-RBD_BA2 antibodies compared to Wuhan-antibodies alone. 50.3% (95% CI 45.0-55.5%) of residual sera from children and 38.1% (95% CI 36.0-40.4%) of all residual sera were positive for anti-N-antibodies. By combining measurements of binding- and ACE2-RBD-interaction-inhibiting antibodies, reactivity profiles indicative of infection and vaccination history were identified and validated using cohort sera. Residual sera with a profile indicative of hybrid immunity were able to neutralize newer Omicron variants XBB.1.5 and BQ.1.1. Conclusions: By late summer of 2022, most of the Norwegian population had antibodies to SARS-CoV-2, and almost all children had been infected. Antibody profiles indicated that children mostly had experienced a primary Omicron infection, while hybrid immunity was common among adults. The finding that sera displaying hybrid immunity could neutralize newer Omicron variants indicates that Wuhan-like priming of the immune response did not have a harmful imprinting effect and that infections induce cross-reacting antibodies against future variants. [ABSTRACT FROM AUTHOR]

Diagnostic assays currently used to monitor the efficacy of COVID-19 vaccines measure levels of antibodies to the receptor-binding domain of ancestral SARS-CoV-2 (RBDwt). However, the predictive value for protection against new variants of concern (VOCs) has not been firmly established. Here, we used bead-based arrays and flow cytometry to measure binding of antibodies to spike proteins and receptor-binding domains (RBDs) from VOCs in 12,000 serum samples. Effects of sera on RBD-ACE2 interactions were measured as a proxy for neutralizing antibodies. The samples were obtained from healthy individuals or patients on immunosuppressive therapy who had received two to four doses of COVID-19 vaccines and from COVID-19 convalescents. The results show that anti-RBDwt titers correlate with the levels of binding- and neutralizing antibodies against the Alpha, Beta, Gamma, Delta, Epsilon and Omicron variants. The benefit of multiplexed analysis lies in the ability to measure a wide range of anti-RBD titers using a single dilution of serum for each assay. The reactivity patterns also yield an internal reference for neutralizing activity and binding antibody units per milliliter (BAU/ml). Results obtained with sera from vaccinated healthy individuals and patients confirmed and extended results from previous studies on time-dependent waning of antibody levels and effects of immunosuppressive agents. We conclude that anti-RBDwt titers correlate with levels of neutralizing antibodies against VOCs and propose that our method may be implemented to enhance the precision and throughput of immunomonitoring. [ABSTRACT FROM AUTHOR]

Background: Understanding how booster vaccination can prevent moderate and severe illness without hospitalization is crucial to evaluate the full advantage of mRNA boosters.Methods: We followed 85 801 participants (aged 31-81 years) in 2 large population-based cohorts during the Omicron BA.1/2 wave. Information on home testing, PCR testing, and symptoms of coronavirus disease 2019 (COVID-19) was extracted from biweekly questionnaires covering the period 12 January 2022 to 7 April 2022. Vaccination status and data on previous SARS-CoV-2 infection were obtained from national registries. Cox regression was used to estimate the effectiveness of booster vaccination compared to receipt of 2-dose primary series >130 days previously.Results: The effectiveness of booster vaccination increased with increasing severity of COVID-19 and decreased with time since booster vaccination. The effectiveness against severe COVID-19 was reduced from 80.9% shortly after booster vaccination to 63.4% in the period >90 days after vaccination. There was hardly any effect against mild COVID-19. The effectiveness tended to be lower among subjects aged ≥60 years than those aged <50 years.Conclusions: This is the first population-based study to evaluate booster effectiveness against self-reported mild, moderate, and severe COVID-19. Our findings contribute valuable information on duration of protection and thus timing of additional booster vaccinations. [ABSTRACT FROM AUTHOR]

Background: The durability of vaccine-induced humoral immunity against SARS-CoV-2 in patients with immune-mediated inflammatory diseases (IMIDs) on immunosuppressive therapy is not known. The aim of this study was to compare the persistence of anti-Spike antibodies following two-dose SARS-CoV-2 vaccination between IMID patients and healthy controls and to identify factors associated with antibody decline.Methods: IMID patients on immunosuppressive medication enrolled in the prospective observational Nor-vaC study were included. Participants received two-dose SARS-CoV-2 vaccination. Serum collected at two time points following vaccination (first assessment within 6-48 days, second within 49-123 days) were analyzed for antibodies binding the receptor-binding domain (RBD) of the SARS-CoV-2 Spike protein. Multivariable regression models estimated percent reduction in anti-RBD over 30 days and factors associated with reduction.Results: A total of 1108 patients (403 rheumatoid arthritis, 195 psoriatic arthritis, 195 spondyloarthritis, 124 ulcerative colitis, 191 Crohn's disease) and 134 controls provided blood samples within the defined intervals (median 19 days [IQR 15-24] and 97 days [87-105] after second vaccine dose). Antibody levels were lower in patients compared to controls at both time points, with median anti-RBD 2806 BAU/ml [IQR 1018-6068] in patients and 6187 BAU/ml [4105-7496] in controls (p<0.001) at first assessment, and 608 BAU/ml [IQR 58-1053] in patients and 1520 BAU/ml [979-3766] in controls (p<0.001) at second assessment. At second assessment, low anti-RBD antibody levels (defined as <200 BAU/ml) were found in 449 (41%) patients, and 6 (5%) controls (p<0.001). The change was - 83% in patients and - 66% in controls (p<0.001). Patients had a greater estimated 30 days percent reduction in anti-RBD levels compared to controls - 4.9 (95% CI - 7.4 to - 2.4), (p<0.05). Among therapies, mono- or combination treatment with tumor necrosis factor inhibitors was associated with the greatest decline.Conclusions: Within 4 months after vaccination, antibody levels declined considerably in both IMID patients and controls. Patients had lower initial antibody levels and a more pronounced decline compared to healthy controls and were therefore more likely to decline to low antibody levels. These results support that IMID patients need additional vaccine doses at an earlier stage than healthy individuals. [ABSTRACT FROM AUTHOR]

Objective: Immunogenicity and safety following receipt of the standard SARS–CoV‐2 vaccination regimen in patients with immune‐mediated inflammatory diseases (IMIDs) are poorly characterized, and data after receipt of the third vaccine dose are lacking. The aim of the study was to evaluate serologic responses and adverse events following the standard 2‐dose regimen and a third dose of SARS–CoV‐2 vaccine in IMID patients receiving immunosuppressive therapy. Methods: Adult patients receiving immunosuppressive therapy for rheumatoid arthritis, spondyloarthritis, psoriatic arthritis, Crohn's disease, or ulcerative colitis, as well as healthy adult controls, who received the standard 2‐dose SARS–CoV‐2 vaccination regimen were included in this prospective observational study. Analyses of antibodies to the receptor‐binding domain (RBD) of the SARS–CoV‐2 spike protein were performed prior to and 2–4 weeks after vaccination. Patients with a weak serologic response, defined as an IgG antibody titer of ≤100 arbitrary units per milliliter (AU/ml) against the receptor‐binding domain of the full‐length SARS–Cov‐2 spike protein, were allotted a third vaccine dose. Results: A total of 1,505 patients (91%) and 1,096 healthy controls (98%) had a serologic response to the standard regimen (P < 0.001). Anti‐RBD antibody levels were lower in patients (median 619 AU/ml interquartile range [IQR] 192–4,191) than in controls (median 3,355 AU/ml [IQR 896–7,849]) (P < 0.001). The proportion of responders was lowest among patients receiving tumor necrosis factor inhibitor combination therapy, JAK inhibitors, or abatacept. Younger age and receipt of messenger RNA–1273 vaccine were predictors of serologic response. Of 153 patients who had a weak response to the standard regimen and received a third dose, 129 (84%) became responders. The vaccine safety profile among patients and controls was comparable. Conclusion: IMID patients had an attenuated response to the standard vaccination regimen as compared to healthy controls. A third vaccine dose was safe and resulted in serologic response in most patients. These data facilitate identification of patient groups at risk of an attenuated vaccine response, and they support administering a third vaccine dose to IMID patients with a weak serologic response to the standard regimen. [ABSTRACT FROM AUTHOR]

The SARS-CoV-2 Omicron variant has more than 15 mutations in the receptor binding domain of the Spike protein enabling increased transmissibility and viral escape from antibodies in vaccinated individuals. It is unclear how vaccine immunity protects against Omicron infection. Here we show that vaccinated participants at a super-spreader event have robust recall response of humoral and pre-existing cellular immunity induced by the vaccines, and an emergent de novo T cell response to non-Spike antigens. Individuals with Omicron SARS-CoV-2 breakthrough infections have significantly increased activated SARS-CoV-2 wild type Spike-specific cytotoxic T cells, activated follicular helper (TFH) cells, functional T cell responses, boosted humoral responses, and rapid release of Spike and RBD-specific IgG+ B cell plasmablasts and memory B cells into circulation. Omicron breakthrough infection affords significantly increased de novo memory T cell responses to non-Spike viral antigens. Concerted T and B cell responses may provide durable and broad immunity. The SARS-CoV-2 Omicron variant possess many mutations within the receptor binding domain of the Spike protein, which confer increased transmissibility and higher antibody escape. Here, the authors carry out analysis of the serological and cellular immune responses of individuals with Omicron breakthrough infection. [ABSTRACT FROM AUTHOR]

Seasonal influenza causes substantial numbers of hospitalizations annually. We have characterized the clinical picture and treatment practice in hospitalized adult influenza patients and assessed whether clinical risk scores on admission or influenza type were associated with severe outcomes. Clinical characteristics and risk scores on admission (CRB65, CRB, SIRS and quick Sequential Organ Failure Assessment [qSOFA]), treatment and severe outcomes (defined as: stay in intensive care unit (ICU), receiving oxygen supplementation or staying ≥5 days in hospital), were recorded in patients hospitalized with influenza at Oslo University Hospital, Norway, between 2014 and 2018. Among the 156 included patients, 52.6% had influenza A(H3N2), 32.6% influenza B and 12.8% influenza A(H1N1). Median age was 70 years and 59.6% of patients were ≥65 years. Nine (5.8%) of the patients were treated in ICU, 43.0% received oxygen and 47.4% stayed ≥5 days in hospital. Overall, 34.6% of the patients had a high CRB score on admission which was associated with stay in ICU and oxygen supplementation. Multivariate analyses identified age, and pneumonia (46.8%), but not influenza type, to be associated with severe outcomes. Antiviral treatment was given to 37.2% of the patients, while 77.6% received antibiotics. Only 25.5% of patients with influenza B received antiviral therapy. The influenza patients were mostly elderly, and few patients were treated in ICU. A high CRB score was associated with severe outcomes with possible implications for patient monitoring. Less than 40% of the patients received antiviral therapy, whereas the majority were treated with antibiotics, indicating potential for optimising treatment strategies. [ABSTRACT FROM AUTHOR]

Background: In 2009, a new influenza A H1N1 virus emerged causing a global pandemic. A range of monovalent influenza A H1N1pdm09 vaccines with or without adjuvants were developed. After the mass vaccination campaigns safety concerns related to H1N1pdm09 vaccines were reported. More than a decade later, reported AEFIs are still under scrutiny. We performed a systematic review aiming to synthesize the evidence on the safety of the H1N1pdm09 vaccines on reported outcomes from existing systematic reviews. Methods: Four electronic databases, PubMed, EMBASE, Epistimonikos and the Cochrane Database of Systematic Reviews were searched for articles on H1N1pdm09 vaccination published from 2009 to January 2021. Systematic reviews assessing short- or long-term adverse events after H1N1pdm09 vaccination were considered for inclusion. Data was extracted from all selected reviews. Outcomes were grouped and results from each included review were presented narratively and in tables. Results: 16 systematic reviews met the inclusion criteria. Reported outcomes were short-term events (3 reviews), fetal/pregnancy outcomes (8 reviews), Guillain-Barré syndrome (GBS) (4 reviews), narcolepsy (2 reviews) demyelinating diseases (1 review based on one study only) and inflammatory bowel disease (IBD) (1 review). Short-term serious adverse events were rare, 3 cases amongst 16725 subjects in 18 randomized controlled trials (0.018%). No deaths were reported. The risks of local events were generally higher for adjuvanted vaccines as compared to unadjuvanted vaccines. Maternal H1N1pdm09 vaccination in any trimester was not associated with an increase in preterm birth, small for gestational age, congenital malformations or fetal death. For GBS, results were conflicting. The main systematic review on narcolepsy found a 5-14-fold increased risk in children, and a 2-7- fold increased risk in adults after vaccination with Pandemrix. The attributable risk of narcolepsy one year after vaccination was 1 case per 18 400 vaccine doses in children/adolescents, and 1 case per 181 000 vaccine doses in adults. Conclusion: Adjuvanted vaccines had more local but not serious adverse events compared to unadjuvanted vaccines. Vaccination with Pandemrix was strongly associated with narcolepsy, particularly in children. No increased risks of pregnancy outcomes were seen after pandemic vaccination. The findings on GBS were inconclusive. [ABSTRACT FROM AUTHOR]

Aims We recently reported five cases of vaccine-induced immune thrombotic thrombocytopenia (VITT) 7–10 days after receiving the first dose of the ChAdOx1 nCoV-19 adenoviral vector vaccine against corona virus disease 2019 (COVID-19). We aimed to investigate the pathogenic immunological responses operating in these patients. Methods and results We assessed circulating inflammatory markers by immune assays and immune cell phenotyping by flow cytometry analyses and performed immunoprecipitation with anti-platelet factor (PF)4 antibody in plasma samples followed by mass spectrometry from all five patients. A thrombus was retrieved from the sinus sagittal superior of one patient and analysed by immunohistochemistry and flow cytometry. Precipitated immune complexes revealed multiple innate immune pathway triggers for platelet and leucocyte activation. Plasma contained increased levels of innate immune response cytokines and markers of systemic inflammation, extensive degranulation of neutrophils, and tissue and endothelial damage. Blood analyses showed activation of neutrophils and increased levels of circulating H3Cit, dsDNA, and myeloperoxidase–DNA complex. The thrombus had extensive infiltration of neutrophils, formation of neutrophil extracellular traps (NETs), and IgG deposits. Conclusions The results show that anti-PF4/polyanion IgG-mediated thrombus formation in VITT patients is accompanied by a massive innate immune activation and particularly the fulminant activation of neutrophils including NETosis. These results provide novel data on the immune response in this rare adenoviral vector-induced VITT. [ABSTRACT FROM AUTHOR]

The 2009 "swine flu" pandemic outbreak demonstrated the limiting capacity for egg-based vaccines with respect to global vaccine supply within a timely fashion. New vaccine platforms that efficiently can quench pandemic influenza emergences are urgently needed. Since 2009, there has been a profound development of new vaccine platform technologies with respect to prophylactic use in the population, including DNA vaccines. These vaccines are particularly well suited for global pandemic responses as the DNA format is temperature stable and the production process is cheap and rapid. Here, we show that by targeting influenza antigens directly to antigen presenting cells (APC), DNA vaccine efficacy equals that of conventional technologies. A single dose of naked DNA encoding hemagglutinin (HA) from influenza/A/California/2009 (H1N1), linked to a targeting moiety directing the vaccine to major histocompatibility complex class II (MHCII) molecules, raised similar humoral immune responses as the adjuvanted split virion vaccine Pandemrix, widely administered in the 2009 pandemic. Both vaccine formats rapidly induced serum antibodies that could protect mice already 8 days after a single immunization, in contrast to the slower kinetics of a seasonal trivalent inactivated influenza vaccine (TIV). Importantly, the DNA vaccine also elicited cytotoxic T-cell responses that reduced morbidity after vaccination, in contrast to very limited T-cell responses seen after immunization with Pandemrix and TIV. These data demonstrate that DNA vaccines has the potential as a single dose platform vaccine, with rapid protective effects without the need for adjuvant, and confirms the relevance of naked DNA vaccines as candidates for pandemic preparedness. [ABSTRACT FROM AUTHOR]

Background: Chronic fatigue syndrome/myalgic encephalomyelitis (CFS/ME) is understood as a complex condition, likely triggered and sustained by an interplay of biological, psychological, and social factors. Little oversight exists of the field of causal research. This systematic scoping review explores potential causal factors of CFS/ME as researched by primary studies.Methods: We searched eight databases for primary studies that examined potential causal factors of CFS/ME. Based on title/abstract review, two researchers independently sorted each study's factors into nine main categories and 71 subordinate categories, using a system developed with input given during a 2018 ME conference, specialists and representatives from a ME patient advocacy group, and using BMJ Best Practice's description of CFS/ME etiology. We also extracted data related to study design, size, diagnostic criteria and comparison groups.Results: We included 1161 primary studies published between January 1979 and June 2019. Based on title/abstract analysis, no single causal factor dominated in these studies, and studies reported a mean of 2.73 factors. The four most common factors were: immunological (297 studies), psychological (243), infections (198), and neuroendocrinal (198). The most frequent study designs were case-control studies (894 studies) comparing CFS/ME patients with healthy participants. More than half of the studies (that reported study size in the title/abstract) included 100 or fewer participants.Conclusion: The field of causal hypotheses of CFS/ME is diverse, and we found that the studies examined all the main categories of possible factors that we had defined a priori. Most studies were not designed to adequately explore causality, rather to establish hypotheses. We need larger studies with stronger study designs to gain better knowledge of causal factors of CFS/ME. [ABSTRACT FROM AUTHOR]

Background: The underlying cellular mechanisms causing adverse reactions to food are complex and still not fully understood. Therefore, in this study we aimed to identify functional and/or phenotypical immune cell signatures characteristic for adult patients reporting adverse reactions to food. By mass cytometry, we performed high-dimensional profiling of peripheral blood mononuclear cells (PBMC) from adult patients reporting adverse reactions to food and healthy controls. The patients were grouped according to sIgE-positive or sIgE-negative serology to common food and inhalant allergens. Two broad antibody panels were used, allowing determination of major immune cell populations in PBMC, as well as activation status, proliferation status, and cytokine expression patterns after PMA/ionomycin-stimulation on a single cell level. Results: By use of data-driven algorithms, several cell populations were identified showing significantly different marker expression between the groups. Most striking was an impaired frequency and function of polyfunctional CD4+ and CD8+ T cells in patients reporting adverse reactions to food compared to the controls. Further, subpopulations of monocytes, T cells, and B cells had increased expression of functional markers such as CD371, CD69, CD25, CD28, and/or HLA-DR as well as decreased expression of CD23 in the patients. Most of the differing cell subpopulations were similarly altered in the two subgroups of patients. Conclusion: Our results suggest common immune cell features for both patient subgroups reporting adverse reactions to food, and provide a basis for further studies on mechanistic and diagnostic biomarker studies in food allergy. [ABSTRACT FROM AUTHOR]

Background: Reliable exposure information is crucial for assessing health outcomes of influenza infection and vaccination. Current serological methods are unable to distinguish between anti‐hemagglutinin (HA) antibodies induced by infection or vaccination. Objectives: We aimed to explore an alternative method for differentiating influenza infection and vaccination. Methods: Sera from animals inoculated with influenza viruses or purified H1N1pdm09 HA were obtained. Human samples were selected from a pregnancy cohort established during the 2009 H1N1 pandemic. Unvaccinated, laboratory‐confirmed cases (N = 18), vaccinated cases without influenza‐like‐illness (N = 18) and uninfected, unvaccinated controls (N = 18) were identified based on exposure data from questionnaires, national registries and maternal hemagglutination inhibition (HI) titres at delivery. Animal and human samples were tested for antibodies against the non‐structural protein 1 (NS1) and HA from H1N1pdm09, using a Luciferase Immunoprecipitation System (LIPS). Results: Anti‐NS1 H1N1pdm09 antibodies were detected in sera from experimentally infected, but not from vaccinated, animals. Anti‐HA H1N1pdm09 antibodies were detectable after either of these exposures. In human samples, 28% of individuals with laboratory‐confirmed influenza were seropositive for H1N1pdm09 NS1, whereas vaccinated cases and controls were seronegative. There was a trend for H1N1pdm09 NS1 seropositive cases reporting more severe and longer duration of symptomatic illness than seronegative cases. Anti‐HA H1N1pdm09 antibodies were detected in all cases and in 61% of controls. Conclusions: The LIPS method could differentiate between sera from experimentally infected and vaccinated animals. However, in human samples obtained more than 6 months after the pandemic, LIPS was specific, but not sufficiently sensitive for ascertaining cases by exposure. [ABSTRACT FROM AUTHOR]

Background: A population‐based pregnancy cohort was established in Norway to study potential effects of exposure to the 2009 influenza pandemic or pandemic vaccination during pregnancy. Objectives: We studied maternal A(H1N1)pdm09‐specific hemagglutination inhibition (HI)‐titer levels and waning in women with influenza‐like illness (ILI) in pregnancy compared to vaccinated women. Moreover, we studied the association between HI‐titers and self‐reported severity and duration of ILI. Methods: HI‐titers against the pandemic virus were measured in maternal blood samples obtained at birth, 3‐9 months after exposure, and linked with information about pregnancy, influenza and vaccination from national registries and a cohort questionnaire. Results: Among 1821 pregnant women included, 43.7% were unvaccinated and 19.3% of these had ILI. HI‐titers were low (geometric mean titer (GMT) 11.3) in the unvaccinated women with ILI. Higher HI‐titers (GMT 37.8) were measured in the vaccinated women. Estimated HI‐titer waning was similar for vaccinated women and women with ILI. Most ILI episodes were moderate and lasted 3‐5 days. Women with ILI reporting specific influenza symptoms such as fever or cough had higher HI‐titers than women without these symptoms. Women who reported being "very ill" or illness duration of >5 days had higher HI‐titers than women reporting less severe illness or illness of shorter duration, respectively. Conclusions: Antibody waning was similar in vaccinated women and women with ILI. More severe ILI or longer duration of illness was associated with higher HI‐titers. Most unvaccinated pregnant women with ILI had low HI‐titers, probably due to moderate illness and HI‐titer waning between exposure and sampling. [ABSTRACT FROM AUTHOR]

Maternal influenza infection during pregnancy is associated with increased risk of morbidity and mortality. However, the link between the anti-influenza immune responses and health-related risks during infection is not well understood. We have analyzed memory T and NK cell mediated immunity (CMI) responses in pandemic influenza A(H1N1)pdm09 (pdm09) virus infected non-vaccinated pregnant women participating in the Norwegian Influenza Pregnancy Cohort (NorFlu). The cohort includes information on immunization, self-reported health and disease status, and biological samples (plasma and PBMC). Infected cases (N = 75) were defined by having a serum hemagglutination inhibition (HI) titer > = 20 to influenza pdm09 virus at the time of delivery, while controls (N = 75) were randomly selected among non-infected pregnant women (HI titer <10). In ELISpot assays cases had higher frequencies of IFNγ+ CD8+ T cells responding to pdm09 virus or conserved CD8 T cell-restricted influenza A virus epitopes, compared to controls. Within this T cell population, frequencies of CD95+ late effector (CD45RA+CCR7-) and naive (CD45RA+CCR7+) CD8+ memory T cells correlated inversely with self-reported influenza illness (ILI) symptoms. ILI symptoms in infected women were also associated with lower numbers of poly-functional (IFNγ+TNFα+, IL2+IFNγ+, IL2+IFNγ+TNFα+) CD4+ T cells and increased frequencies of IFNγ+CD3-CD7+ NK cells compared to asymptomatic cases, or controls, after stimulation with the pdm09 virus. Taken together, virus specific and functionally distinct T and NK cell populations may serve as cellular immune correlates of clinical outcomes of pandemic influenza disease in pregnant women. Our results may provide information important for future universal influenza vaccine design. [ABSTRACT FROM AUTHOR]

Background: Annual vaccination for healthcare workers and other high-risk groups is the mainstay of the public health strategy to combat influenza. Inactivated influenza vaccines confer protection by inducing neutralizing antibodies efficiently against homologous and closely matched virus strains. In the absence of neutralizing antibodies, cross-reactive T cells have been shown to limit disease severity. However, animal studies and a study in immunocompromised children suggested that repeated vaccination hampers CD8+ T cells. Yet the impact of repeated annual influenza vaccination on both cross-reactive CD4+ and CD8+ T cells has not been explored, particularly in healthy adults.Methods: We assembled a unique cohort of healthcare workers who received a single AS03-adjuvanted H1N1pdm09 vaccine in 2009 and subsequently either repeated annual vaccination or no further vaccination during 2010-2013. Blood samples were collected before the influenza season or vaccination to assess antibody and T-cell responses.Results: Antibody titers to H1N1pdm09 persisted above the protective level in both the repeated- and single-vaccination groups. The interferon γ+ (IFN-γ+) and multifunctional CD4+ T-cell responses were maintained in the repeated group but declined significantly in the single-vaccination group. The IFN-γ+CD8+ T cells remained stable in both groups.Conclusions: This study provides the immunological evidence base for continuing annual influenza vaccination in adults. [ABSTRACT FROM AUTHOR]

Correction to: I npj Vaccines i https://doi.org/10.1038/s41541-022-00586-7, published online 30 December 2022 In this article the author name Marte Lie Høivik was incorrectly written as Marte Lie Høivk. The original article can be found online at https://doi.org/10.1038/s41541-022-00586-7. [Extracted from the article]

Pre-existing human CD4+ and CD8+ T-cell-mediated immunity may be a useful correlate of protection against severe influenza disease. Identification and evaluation of common epitopes recognized by T cells with broad cross-reactivity is therefore important to guide universal influenza vaccine development, and to monitor immunological preparedness against pandemics. We have retrieved an optimal combination of MHC class I and class II restricted epitopes from the Immune Epitope Database (), by defining a fitness score function depending on prevalence, sequence conservancy and HLA super-type coverage. Optimized libraries of CD4+ and CD8+ T-cell epitopes were selected from influenza antigens commonly present in seasonal and pandemic influenza strains from 1934 to 2009. These epitope pools were used to characterize human T-cell responses in healthy donors using interferon- γ ELISPOT assays. Upon stimulation, significant CD4+ and CD8+ T-cell responses were induced, primarily recognizing epitopes from the conserved viral core proteins. Furthermore, the CD4+ and CD8+ T cells were phenotypically characterized regarding functionality, cytotoxic potential and memory phenotype using flow cytometry. Optimized sets of T-cell peptide epitopes may be a useful tool to monitor the efficacy of clinical trials, the immune status of a population to predict immunological preparedness against pandemics, as well as being candidates for universal influenza vaccines. [ABSTRACT FROM AUTHOR]

Increased understanding of immune responses influencing clinical severity during pandemic influenza infection is important for improved treatment and vaccine development. In this study we recruited 46 adult patients during the 2009 influenza pandemic and characterized humoral and cellular immune responses. Those included were either acute hospitalized or convalescent patients with different disease severities (mild, moderate or severe). In general, protective antibody responses increased with enhanced disease severity. In the acute patients, we found higher levels of TNF-α single-producing CD4+T-cells in the severely ill as compared to patients with moderate disease. Stimulation of peripheral blood mononuclear cells (PBMC) from a subset of acute patients with peptide T-cell epitopes showed significantly lower frequencies of influenza specific CD8+ compared with CD4+ IFN-γ T-cells in acute patients. Both T-cell subsets were predominantly directed against the envelope antigens (HA and NA). However, in the convalescent patients we found high levels of both CD4+ and CD8+ T-cells directed against conserved core antigens (NP, PA, PB, and M). The results indicate that the antigen targets recognized by the T-cell subsets may vary according to the phase of infection. The apparent low levels of cross-reactive CD8+ T-cells recognizing internal antigens in acute hospitalized patients suggest an important role for this T-cell subset in protective immunity against influenza. [ABSTRACT FROM AUTHOR]

Targeting antigens to cross-presenting dendritic cells (DCs) is a promising method for enhancing CD8+ T-cell responses. However, expression patterns of surface receptors often vary between species, making it difficult to relate observations in mice to other animals. Recent studies have indicated that the chemokine receptor Xcr1 is selectively expressed on cross-presenting murine CD8α+ DCs, and that the expression is conserved on homologous DC subsets in humans (CD141+ DCs), sheep (CD26+ DCs), and macaques (CADM1+ DCs). We therefore tested if targeting antigens to Xcr1 on cross-presenting DCs using antigen fused to Xcl1, the only known ligand for Xcr1, could enhance immune responses. Bivalent Xcl1 fused to model antigens specifically bound CD8α+ DCs and increased proliferation of antigen-specific T cells. DNA vaccines encoding dimeric Xcl1-hemagglutinin (HA) fusion proteins induced cytotoxic CD8+ T-cell responses, and mediated full protection against a lethal challenge with influenza A virus. In addition to enhanced CD8+ T-cell responses, targeting of antigen to Xcr1 induced CD4+ Th1 responses and highly selective production of IgG2a antibodies. In conclusion, targeting of dimeric fusion vaccine molecules to CD8α+ DCs using Xcl1 represents a novel and promising method for induction of protective CD8+ T-cell responses. [ABSTRACT FROM AUTHOR]

Different diseases require different immune responses for efficient protection. Thus, prophylactic vaccines should prime the immune system for the particular type of response needed for protection against a given infectious agent. We have here tested fusion DNA vaccines which encode proteins that bivalently target influenza hemagglutinins (HA) to different surface molecules on antigen presenting cells (APC). We demonstrate that targeting to MHC class II molecules predominantly induced an antibody/Th2 response, whereas targeting to CCR1/3/5 predominantly induced a CD8+/Th1 T cell response. With respect to antibodies, the polarizing effect was even more pronounced upon intramuscular (i.m) delivery as compared to intradermal (i.d.) vaccination. Despite these differences in induced immune responses, both vaccines protected against a viral challenge with influenza H1N1. Substitution of HA with ovalbumin (OVA) demonstrated that polarization of immune responses, as a consequence of APC targeting specificity, could be extended to other antigens. Taken together, the results demonstrate that vaccination can be tailor-made to induce a particular phenotype of adaptive immune responses by specifically targeting different surface molecules on APCs. [ABSTRACT FROM AUTHOR]

Background: Cell lines from Atlantic salmon kidney have made it possible to culture and study infectious salmon anemia virus (ISAV), an aquatic orthomyxovirus affecting farmed Atlantic salmon. However, transfection of these cells using calcium phosphate precipitation or lipid-based reagents shows very low transfection efficiency. The Amaxa Nucleofector technology™ is an electroporation technique that has been shown to be efficient for gene transfer into primary cells and hard to transfect cell lines. Findings: Here we demonstrate, enhanced transfection of the head kidney cell line, TO, from Atlantic salmon using nucleofection and subsequent flow cytometry. Depending on the plasmid promoter, TO cells could be transfected transiently with an efficiency ranging from 11.6% to 90.8% with good viability, using Amaxa's cell line nucleofector solution T and program T-20. A kill curve was performed to investigate the most potent antibiotic for selection of transformed cells, and we found that blasticidin and puromycin were the most efficient for selection of TO cells. Conclusions: The results show that nucleofection is an efficient way of gene transfer into Atlantic salmon cells and that stably transfected cells can be selected with blasticidin or puromycin. [ABSTRACT FROM AUTHOR]

Immunization of rats with haptenized monoclonal antibodies (mAbs) against accessory cells enhances anti-hapten antibody responses. To see whether the mAb-conjugates really targetted the antigen (hapten) to the antigen presenting cells, we have investigated the lymph node distribution of locally injected radiolabelled conjugates. Compared with control conjugates, i.e. haptenized non-binding mAbs, a much larger proportion of the specific conjugates were retained in the draining lymph nodes. Whereas control conjugates were rapidly phagocytosed and degraded by macrophages, the specific conjugates were associated with the targetted accessory cells, which were radiolabelled for extended periods. Haptenated MRC 0X6 (anti-MHC class II) gave strong labelling of interdigitating cells (IDC) in the paracortex with 70% of IDC still labelled by 4 days and 15% by 16 days following injection. By Western blots intact 0X6 conjugates were still detected in the draining lymph node as long as 3 days after injections, whereas control conjugates were hardly detectable even by 24 h. The findings substantiate the idea that mAbs can be exploited for vectorial transport of antigens to accessory cells. [ABSTRACT FROM PUBLISHER]

Preschool children in Addis Ababa, Ethiopia, are highly exposed to influenza viruses. Factors related to infections, nutrition, and environmental conditions that might explain the burden of influenza among these children were investigated. Ninety-five preschool children, 48 girls and 47 boys, were followed clinically for 12 months. Illness and immune responses to influenza; three other respiratory viruses; five airway pathogenic bacteria; and levels of vitamins D, A, and B12 were assessed. Most of the children had antibodies to numerous respiratory viral and bacterial agents at study start, and many were infected during follow-up. Twenty-five girls and 25 boys fell ill during the study, and were treated with one or more courses of systemic antimicrobials. Ninety percent of both girls and boys had 25-hydroxyvitamin D [25(OH)D] levels below the recommended levels. While there was no overall difference in the levels of vitamins D, A, and B12 between girls and boys, treated girls had significantly lower 25(OH)D levels than non-treated girls and treated boys. There was a considerable number of short for age children, but only the short treated girls had significantly lower 25(OH)D levels than the non-treated children. Preschool girls with low 25(OH)D levels were more vulnerable to pathogenic microbes than boys. [ABSTRACT FROM AUTHOR]

In the original published version of this Article, the text for the Editorial Summary was mistakenly incorporated at the end of the abstract. The HTML and PDF versions of the paper have been corrected. [ABSTRACT FROM AUTHOR]

Annual seasonal influenza vaccination is recommended for high-risk populations and often occupational groups such as healthcare workers (HCWs). Repeated annual vaccination has been reported to either have no impact or reduce antibody responses or protection. However, whether repeated vaccination influences T-cell responses has not been sufficiently studied, despite the increasing evidence of the protective roles of T-cell immunity. Here, we explored the impact of repeated annual vaccination with the same vaccine strain (H1N1pdm09) over multiple seasons in the post-2009 pandemic era and showed that repeated vaccination increased both T-cell and humoral responses. Using the T-cell FluroSpot and intracellular cytokine-staining, the hemagglutination inhibition (HI), and the memory B-cell (MBC) ELISpot assays, we investigated pre- and postvaccination T cells, antibodies, and MBCs in a cohort of HCWs repeatedly vaccinated with H1N1pdm09 for 5 years (pandemic vaccination in 2009 and subsequently annual seasonal vaccination containing H1N1pdm09 during 2010–2013). We found that the prevaccination H1N1pdm09-specific T cells, antibodies, and MBCs were significantly increased after 3–4 repeated vaccinations and maintained at high levels throughout seasons 2012 and 2013. The cross-reactive IFN-γ-secreting CD4+ cells recognizing conserved viral external or internal epitopes were also maintained throughout 2012 and 2013. Repeated vaccination improved the multifunctional memory CD4+ responses. Particularly, the IFN-γ+TNF-α+CD4+ T cells were boosted following each vaccination. HI antibodies were significantly induced after each vaccination over 5 years. Our findings indicate a broad impact of repeated annual vaccination, even with the same vaccine component, on the influenza-specific T-cell and humoral immunity and support the continuing recommendation of annual influenza vaccination. Influenza vaccination: Repeat vaccination augments human immune responses Despite the widespread implementation of annual influenza vaccination, the effect of repeated vaccinations on the immune response in subsequent seasons is poorly understood. A team lead by Rebecca Jane Cox at the University of Bergen examine the humoral and T cell response elicited by 2009's H1N1pdm09 seasonal vaccine. Since the H1N1pdm09 strain continued to circulate in subsequent years it was included in later vaccine formulations and the authors could therefore examine the effects of repeated annual vaccination over multiple seasons. They observed that H1N1pdm09-specific polyfunctional T cell responses and antibodies were enhanced by multiple annual vaccinations. In particular, T cells showed progressive skewing to IFN-γ+TNF+ double producers but the magnitude of the T cell response tended to plateau after 3–4 repeated vaccinations. The findings suggest that including the same component in subsequent annual vaccines can significantly impact the influenza immune response. [ABSTRACT FROM AUTHOR]

Background: The effects of maternal influenza infection on the fetus remain unclear. We studied mild influenza and influenza antibodies in relation to birth weight and risks of pre-eclampsia, preterm birth (PTB), and small for gestational age (SGA) birth among the unvaccinated participants in the Norwegian Influenza Pregnancy Cohort.Methods: Pregnant women attending a routine ultrasound were recruited from four hospitals in Norway shortly after the 2009 A(H1N1) pandemic. The present study was restricted to unvaccinated participants who were pregnant during the pandemic. Information on the participants was obtained through questionnaires and linkage with national registries. Maternal blood samples were collected at delivery. Women with laboratory-confirmed A(H1N1)pdm09 influenza, a clinical diagnosis of influenza, or self-reported influenza during the pandemic were classified as having had influenza. A(H1N1)pdm09-specific antibodies in serum were detected with the hemagglutination-inhibition assay. Detection of antibodies was considered an indicator of infection during the pandemic in the unvaccinated participants. Odds ratios were estimated with logistic regression. Quantile regression was used to estimate differences in the distribution of birth weight.Results: Among the 1258 women included in this study, there were 37 cases of pre-eclampsia, 41 births were PTB, and 103 births were SGA. 226 women (18.0%) had influenza during the pandemic. The majority of cases did not receive medical care, and only a small proportion (1.3%) of the cases were hospitalized. Thus, the cases consisted primarily of women with mild illness. No significant associations between influenza and risk of pre-eclampsia, PTB, or SGA birth were observed. Detection of A(H1N1)pdm09-specific antibodies was associated with a lower 10th percentile of birth weight, β = - 159 g (95% CI - 309, - 9).Conclusions: Mild influenza illness during pregnancy was not associated with increased risk of pre-eclampsia, PTB or SGA birth. However, influenza infection during pregnancy may reduce the birth weight of the smallest children. [ABSTRACT FROM AUTHOR]