Hydroxychloroquine is associated with lower seroconversion upon 17DD-Yellow fever primovaccination in patients with primary Sjögren's syndrome.

The present study aimed at investigating whether the hydroxychloroquine (HCQ) treatment would impact the neutralizing antibody production, viremia levels and the kinetics of serum soluble mediators upon planned 17DD-Yellow Fever (YF) primovaccination (Bio-Manguinhos-FIOCRUZ) of primary Sjögren's syndrome (pSS). A total of 34 pSS patients and 23 healthy controls (HC) were enrolled. The pSS group was further categorized according to the use of HCQ (HCQ and Non-HCQ). The YF-plaque reduction neutralization test (PRNT ≥1:50), YF viremia (RNAnemia) and serum biomarkers analyses were performed at baseline and subsequent time-points (Day0/Day3-4/Day5-6/Day7/Day14-D28). The pSS group showed PRNT titers and seropositivity rates similar to those observed for HC (GeoMean = 238 vs 440, p = .11; 82% vs 96%, p = .13). However, the HCQ subgroup exhibited lower seroconversion rates as compared to HC (GeoMean = 161 vs 440, p = .04; 69% vs 96%, p = .02) and Non-HQC (GeoMean = 161 vs 337, p = .582; 69% vs 94%, p = .049). No differences in YF viremia were observed amongst subgroups. Serum biomarkers analyses demonstrated that HCQ subgroup exhibited increased levels of CCL2, CXL10, IL-6, IFN-γ, IL1-Ra, IL-9, IL-10, and IL-2 at baseline and displayed a consistent increase of several biomarkers along the kinetics timeline up to D14-28. These results indicated that HCQ subgroup exhibited a deficiency in assembling YF-specific immune response elicited by 17DD-YF primovaccination as compared to Non-HCQ subgroup. Our findings suggested that hydroxychloroquine is associated with a decrease in the humoral immune response after 17DD-YF primovaccination.

Plaque Reduction Neutralization Test (PRNT) Accuracy in Evaluating Humoral Immune Response to SARS-CoV-2.

Massive vaccination positively impacted the SARS-CoV-2 pandemic, being a strategy to increase the titers of neutralizing antibodies (NAbs) in the population. Assessing NAb levels and understanding the kinetics of NAb responses is critical for evaluating immune protection. In this study, we optimized and validated a PRNT50 assay to assess 50% virus neutralization and evaluated its accuracy to measure NAbs to the original strain or variant of SARS-CoV-2. The optimal settings were selected, such as the cell (2 × 105 cells/well) and CMC (1.5%) concentrations and the viral input (~60 PFU/well) for PRNT-SARS-CoV-2 with cut-off point = 1.64 log5 based on the ROC curve (AUC = 0.999). The validated PRNT-SARS-CoV-2 assay presented high accuracy with an intraassay precision of 100% for testing samples with different NAb levels (low, medium, and high titers). The method displays high selectivity without cross-reactivity with dengue (DENV), measles (MV), zika (ZIKV), and yellow fever (YFV) viruses. In addition, the standardized PRNT-SARS-CoV-2 assay presented robustness when submitted to controlled variations. The validated PRNT assay was employed to test over 1000 specimens from subjects with positive or negative diagnoses for SARS-CoV-2 infection. Patients with severe COVID-19 exhibited higher levels of NAbs than those presenting mild symptoms for both the Wuhan strain and Omicron. In conclusion, this study provides a detailed description of an optimized and validated PRNT50 assay to monitor immune protection and to subsidize surveillance policies applied to epidemiologic studies of COVID-19.

Timeline kinetics of protective immunity to SARS-CoV-2 upon primary vaccination and humoral response to variants after booster dose.

New variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have emerged, imposing the need for periodic booster doses. However, whether booster doses should be applied to the entire population or groups, and the booster doses interval, remains unclear. In this study, we evaluated humoral reactivity kinetics from before the first dose to 180 days after the third booster dose in different schedules in a well-controlled health worker cohort. Among the 2,506 employees, the first 500 vaccinated health workers were invited to participate. The third booster dose was administered 8 months after the first dose. Among the invited participants, 470 were included in the study; 258 received inactivated vaccine CoronaVac (VAC group) and 212 received viral vector vaccine ChAdOx1 (AZV group). The groups were homogeneous in terms of age and sex. 347 participants were followed up after the booster dose with AZV or BNT162b2 (Pfizer, BNT group): 63 with VAC/AZV, 117 with VAC/BNT, 72 with the AZV/AZV and 95 with AZV/BNT schedules. Blood samples were collected immediately before, 28 days after each dose and 180 days after the primary vaccination and booster dose. Anti-SARS-CoV-2 antibodies were measured by chemiluminescence and plaque reduction neutralization test (PRNT). Plasma immune mediators were quantified using a multiplex immunoassay. Geometric mean of antibodies increased 28 days after the second dose with 100 % seroconversion rate in both groups and decreased 180 days after the first dose. In the baseline-seropositive VAC group, the levels of plasma immune mediators increased after the second dose. Booster dose was applied at 4-6 months after the primary vaccination. Heterologous booster in VAC or AZV primary vaccinees were effective maintaining the titers of anti-SARS-CoV-2 antibodies even after 6 months of follow-up. The heterologous schedule induced higher and stable antibody reactivity, even after 180 days, protecting to ancestral (Wuhan), Delta, and Omicron variants.