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This study evaluated whether IgG avidity measured by chemiluminescent microparticle immunoassay (CMIA) compared with enzyme-linked immunosorbent assay (ELISA) was useful to detect primary T. gondii infection during pregnancy and to estimate the risk for congenital T. gondii infection. One hundred six women with positive tests for T. gondii IgG and T. gondii IgM, comprising 21 women (19.8%) with low (<30%), 6 (5.7%) with borderline (30%–35%), and 79 (74.5%) with high (>35%) IgG avidity measured by ELISA were selected. Their stored sera were used for T. gondii IgG avidity measurements by CMIA. In CMIA, 72 (67.9%) women had low (<50%), 12 (11.3%) had borderline (50%–59.9%), and 22 (20.8%) had high (≥60%) IgG avidity. The ratio of low T. gondii IgG avidity index in CMIA was more than three-fold than that in ELISA. Eighteen (85.7%) of 21 women with ELISA low avidity also had CMIA low avidity, and 26 (96.3%) of 27 women with ELISA low or borderline avidity corresponded to CMIA low or borderline avidity, whereas 21 (26.6%) of 79 women with ELISA high avidity were diagnosed with CMIA low avidity. All three cases with congenital T. gondii infection showed coincidentally low IgG avidity in both methods. A positive correlation in IgG avidity indices was found between of ELISA and CMIA. CMIA for T. gondii avidity measurements compared with ELISA was clinically useful to detect pregnant women at a high risk of developing congenital T. gondii infection. [ABSTRACT FROM AUTHOR]

Measles is a highly infectious illness requiring herd immunity of 95% to interrupt transmission. China has not reached elimination goals despite high vaccination coverage. We estimated the population susceptibility against measles in Tianjin, China and to tailor awareness raising activities in the measles elimination plan. Age-specific measles seroprevalence was evaluated by Enzyme-Linked Immunosorbent Assay (ELISA) on 12,164 individual aged 0–44 years in 2009–2018. Measles IgG avidity testing was performed to confirm the relationship of the waning immunity after vaccination and secondary vaccination failures (SVF) on 324 confirmed measles cases in 2013–2018. 11,108 samples (91.32%) tested positive for measles IgG, 239 (1.96%) tested as equivocal and 817 (6.72%) were negative. The age distribution of measles cases in Tianjin followed a U-shaped curve and was highest for those at <8 months and again at 20–39 years which correlated closely with the age distribution of measles susceptibility based on measles IgG antibody status (r = 0.72, P < 0.001). The seropositivity rate and antibody geometric mean concentration (GMC) for the 2018 study population were significantly lower (χ 2 = 7.45, P = 0.006 and t = 12.01, P < 0.001) compared to 2009. The multivariate stepwise logistic regression analysis showed that age and region were the risk factors for both measles seropositivity rate and GMC after vaccination. The proportion of high avidity cases increased with age, being significantly higher in 75.31% of cases in patients aged 30–34 years (χ 2 = 18.04, P = 0.003). High immunization coverage in children alone will not be adequate to realizing sufficient levels of population herd immunity, particularly given that the potential susceptibility window in adult. Implementation of supplemental immunization activity (SIA) targeted to appropriate group aged 30–34 years is recommended. [ABSTRACT FROM AUTHOR]

To identify measles vaccine failures in Tianjin, China using a measles virus IgG avidity assay. The China Information System for Disease Control and Prevention (CISDCP) was used to collect information about measles cases and blood specimens in Tianjin from 2013 to 2015. Measles-specific IgM and IgG antibodies were detected using Enzyme-Linked Immunosorbent Assay (ELISA). Avidity testing for measles IgG was performed using a commercial enzyme immunoassay (EIA). A total of 284 confirmed measles cases were identified. Of this total, 262 (92.25%) were in patients aged ≥ 20 years. High avidity was exhibited in 172 (60.56%) cases, while 80 (28.17%) cases demonstrated low avidity. High avidity was detected in only 21.43% of cases in patients aged < 1 year. The proportion of high avidity increased with age, and was significantly higher in patients aged 30–39 years at 70.07% (χ 2 = 17.27, P = 0.002). Of the 52 measles cases in patients with a history of vaccinations, 41 (78.85%) cases showed high avidity, indicating secondary vaccine failures (SVF). In these vaccinations, there was no significant difference (P > 0.05) in clinical severity between high avidity and low avidity cases. However, regardless of vaccination status, clinical severity was significantly lower in high avidity cases (P < 0.001) than in low avidity cases. The percentages of positive measles IgM results in high avidity and low avidity cases were 66.28% and 91.25%, respectively. Geometric Mean Concentration (GMC) was significantly lower in high avidity cases at 33.73 U/mL, compared to 166.07 U/mL in low avidity cases. Low clinical severity and inconclusive IgM antibody results are more likely in high avidity measles cases. Measles cases were more common in adults. Therefore, a further dose of vaccines should be recommended for 30–39 years in Tianjin. [ABSTRACT FROM AUTHOR]

Abstract: The preliminary diagnostic utility of two mixtures of Toxoplasma gondii recombinant antigens (rROP1+rSAG2 and rROP1+rGRA6) in IgG ELISA and IgG avidity test has been evaluated. A total of 173 serum samples from patients with toxoplasmosis and seronegative people were examined. The sensitivity of IgG ELISA for rROP1+rSAG2 and rROP1+rGRA6 was 91.1% and 76.7%, respectively, while the reactivity for sera from patients where acute toxoplasmosis was suspected was higher, at 100% and 95.4%, respectively, than for people with chronic infection, at 88.2% and 70.6%. In this study a different trend in avidity maturation of IgG antibodies for two mixtures of proteins in comparison with native antigen was observed. The results suggest that a new IgG avidity test using the mixtures of recombinant antigens may be useful for the diagnosis of difficult-to-identify phases of toxoplasmosis. For this reason, selected mixtures after the additional tests on groups of sera with well-defined dates of infection could be used as a better alternative to the native antigens of the parasite in the serodiagnosis of human T. gondii infection. [Copyright &y& Elsevier]

Abstract: A search for specific IgM antibodies was used for the detection of primary human cytomegalovirus (HCMV) infections, but the significance of the results is limited by the possible persistence of specific IgM over time, the fact that they are also produced during episodes of reactivation or reinfection, and possible cross-reactions with other viruses. Anti-HCMV antibody screening was carried out to assess the positive predictive value of detecting specific IgM antibodies using IgG and IgM enzyme-linked immunosorbent assays (ELISAs) in 6990 patients examined during the period 2005–2007. In comparison with IgG avidity, the positive predictive value of screening by IgM ELISA alone was 49.3%, which increased to 73% when the presence of IgM was confirmed by an enzyme-linked fluorescent assay (ELFA). The predictive values of highly or weakly positive IgM ELISA alone were respectively 68.8% and 16.4%, but increased to 83.1% and 39.1% if IgM was confirmed by ELFA. The positive predictive value of the IgM/IgG ratio ranged from 26.7% for a low ratio and the detection of IgM by ELISA alone, to 90.7% for a high ratio and ELFA-confirmed IgM detection. These findings indicate that a specimen in which highly positive IgM ELISA values are confirmed by ELFA, or which shows a high IgM/IgG ratio, is a good indicator of infection occurring within the previous three months. [Copyright &y& Elsevier]

Abstract: Background: The interpretation of a positive IgM antibody result to human cytomegalovirus (HCMV) in a pregnant woman is of major importance for the correct management of the pregnancy. Determination of HCMV-specific IgG avidity is considered an useful approach for distinguishing IgM antibody due to primary HCMV infection from IgM antibody elicited during non-primary infection. Objective: Comparative evaluation of eight commercial HCMV IgG avidity assays currently available in Europe. Study design: A panel of 198 sequential samples collected from 65 pregnant women at 0–90, 91–180, and >180 days after the onset of primary HCMV infection was retrospectively tested by Abbott, BioMérieux, Bio-Rad, DiaSorin, Diesse, Euroimmun, Radim, and Technogenetics HCMV IgG avidity assays according to the manufacturer''s instructions. Results: None of the 198 samples tested yielded identical scores by the kits under evaluation. The Euroimmun and Radim assays showed the best correlation with expected results in terms of low (0–90 days), intermediate (90–180 days) and high (>180 days) avidity results, respectively. The best accuracy in diagnosing a recent (<90 days after the onset) or non-recent (>180 days after the onset) primary HCMV infection was shown by Radim followed by Euroimmun and Diesse. The best correlation with a well established in-house developed HCMV IgG avidity assay was shown by Radim. Conclusions: HCMV IgG avidity kits need to be improved and standardized. In the meantime, highly specific IgM assays are preferable for screening purposes in pregnant women. [Copyright &y& Elsevier]

Abstract: The objective of this work was to carry out a study on caprine toxoplasmosis in the state of Minas Gerais, Brazil. To determine the prevalence of toxoplasmosis in goats in Minas Gerais, 767 sera from goats were tested by ELISA (enzyme-linked immunosorbent assay) and IFAT (indirect fluorescence antibody test). The prevalence of antibodies to Toxoplasma gondii was 43.0% and 46.0% by ELISA and IFAT, respectively. It was observed that 26.8% of the goats show low-avidity IgG to T. gondii. These results suggest the presence of animals in recent phase of toxoplasmosis in Minas Gerais. The risk factors for toxoplasmosis in goats were: age over 36 months (OR=1.21; IC 95% 1.02–1.44), use of pen (OR=1.83; IC 95%1.01–3.31) and pure breed animals (OR=2.49; IC 95% 1.11–5.59). [Copyright &y& Elsevier]

Abstract: Sheep are important domestic animals in the Northeast region of Brazil due to their minimal rearing and maintenance costs, and to their production of both meat and milk. In animals, Toxoplasma gondii infection results in significant reproductive and economic losses. The epidemiology of toxoplasmosis in sheep in the Northeast of Brazil has been little studied; particularly in Rio Grande do Norte State. Sera from 102 sheep intended for consumption in Lajes were subjected to the Toxoplasma-ELISA test to detect anti-T. gondii specific IgG confirming a past infection. Of the total tested, 30 (29.41%) sera were positive for IgG with an increasing number of positive animals with advancing age. We used IgG avidity ELISA in 30 positive samples and observed that 6 (20%) had low avidity antibodies and 24 (80%) had high avidity antibodies. Epidemiological studies are required in order to identify sources of infection for these hosts as well as their impact on animal breeding in the region and risk of transmission to humans. [Copyright &y& Elsevier]