Evaluating Humoral Immunity against SARS-CoV-2: Validation of a Plaque-Reduction Neutralization Test and a Multilaboratory Comparison of Conventional and Surrogate Neutralization Assays

SARS-CoV-2, the causal agent of COVID-19, has infected over 150 million people and led to 3.8 million deaths worldwide. With the approval of several efficacious COVID-19 vaccines, methods to evaluate protective immune responses will be crucial for the understanding of long-term immunity in the rapidly growing vaccinated population.

Neutralization of UK-variant VUI-202012/01 with COVAXIN vaccinated human serum

We performed the plaque reduction neutralization test (PRNT50) using sera collected from the recipients of BBV152/COVAXIN™ against hCoV-19/India/20203522 (UK-variant) and hCoV27 19/India/2020Q111 (heterologous strain). A comparable neutralization activity of the vaccinated individuals sera showed against UK-variant and the heterologous strain with similar efficiency, dispel the uncertainty of possible neutralization escape.

Immunobridging efficacy of a tetravalent dengue vaccine against dengue and against hospitalized dengue from children/adolescents to adults in highly endemic countries

Background CYD-TDV demonstrated vaccine efficacy (VE) against symptomatic, virologically confirmed dengue of any serotype from month 13 to month 25 (VCD-DENV-AnyM13→M25) in the CYD14 (2–14-y-olds) and CYD15 (9–16-y-olds) phase 3 trials. Fifty percent plaque reduction neutralization test (PRNT50) titers are a potential surrogate for immunobridging VE to adults. Methods Using PRNT50 calibration datasets, we applied immunobridging approaches using baseline and/or M13 PRNT50 titers to estimate VE against VCD-DENV-AnyM0→M25 and against hospitalized VCD (HVCD)-DENV-AnyM0→M72 in hypothetical 18–45-y-old and 46–50-y-old CYD14 and CYD15 cohorts. Results Baseline and M13 geometric mean PRNT50 titers were greater in 18–45-y-olds and in 46–50-y-olds vs 9–16-y-olds for most comparisons. Estimated VE (95% CIs against VCD-DENV-AnyM0→M25 ranged from 75.3% to 90.9% (52.5% to 100%) for 18–45-y-olds and 74.8% to 92.0% (53.4% to 100%) for 46–50-y-olds. Estimated VE (95% CIs) against HVCD-DENV-AnyM0→M72 ranged from 58.8% to 78.1% (40.9 to 98.9%) for 18–45-y-olds and 57.2% to 78.4% (40.5 to 97.6%) for 46–50-y-olds. Corresponding predictions among baseline-seropositive individuals yielded comparable or higher VE estimates. Conclusions VE M0→M25 against DENV-Any and VE against HVCD-DENV-AnyM0→M72 are both expected to be higher in 18–45 and 46–50-y-olds vs CYD14 and CYD15 9–16-y-olds.

Plaque Reduction Neutralization Test (PRNT) in the Congenital Zika Syndrome: Positivity and Associations with Laboratory, Clinical, and Imaging Characteristics

The short duration of viremia, low blood viral load, inaccessibility to timely specific diagnostic tests, and cross-reactions with other flaviviruses have hindered laboratory confirmation of Congenital Zika Syndrome (CZS). This study analyzes the positivity of the plaque reduction neutralization test (PRNT) in children with clinical or imaging characteristics of CZS and its association with laboratory, clinical, and imaging characteristics. The 94 clinical cases of CZS submitted to the ZIKV PRNT90 test were followed from 2016 to 2018. The mean age of children at PRNT90 collection was 22 ± 6 months Standard Deviation. The ZIKV PRNT90 was positive (titer ≥ 10) in 40 (42.5%) children. ZIKV PRNT90 positivity was associated with severe microcephaly in newborns (p = 0.016), lower head circumference z-score at birth (p = 0.043) and 24 months of age (p = 0.031), and severe reduction of the cerebral parenchyma volume (p = 0.021), expressing greater disease severity. Negative PRNT90 in children with characteristic signs of CZS may be due to false-negative results, indicating that the diagnosis of CZS should be primarily syndromic.

Independent side-by-side validation and comparison of four serological platforms for SARS-CoV-2 antibody testing

Highly sensitive and specific platforms for the detection of anti-SARS-CoV-2 antibodies are becoming increasingly important for (1) evaluating potential SARS-CoV-2 convalescent plasma donors, (2) studying the spread of SARS-CoV-2 infections and (3) identifying individuals with seroconversion. This study provides a comparative validation of four anti-SARS-CoV-2 platforms. Unique feature of this study is the use of a representative cohort of COVID-19-convalescent patients with mild-to-moderate disease course. All platforms showed significant correlations with a SARS-CoV-2 plaque-reduction-neutralization test, with highest sensitivities for the Euroimmun and the Roche platforms, suggesting their preferential use for screening of persons at increased risk of SARS-CoV-2 infections.

Public Health Response to Zika Virus Exposure of Air Force Members Deployed to Caribbean Islands, 2016

Introduction The emergence of Zika virus disease (ZVD) in areas of military operations provided a new opportunity for force health protection. ZVD infection had an estimated 4:1 asymptomatic-to-symptomatic ratio and can cause neurologic sequelae. Materials and Methods We provide a brief report of a field investigation utilizing laboratory-based surveillance and survey instruments to characterize ZVD risk among personnel deployed to the Dominican Republic in support of Operation NEW HORIZONS (NH). Additionally, we describe a cluster of 3 ZVD cases among 8 aircrew on a short mission to St. Croix (U.S. Virgin Islands). Results Following Operation NH, 6 of a total 189 deployed cohort members tested positive for ZVD by immunoglobulin M and confirmatory plaque reduction neutralization test (3.2%). Reverse transcription polymerase chain reaction testing in urine or serum was positive in 4 of those 6 cases. All 6 cases reported at least one symptom, with 5 reporting subjective fever and arthralgia and 4 reporting rash. Cases were less likely to have air-conditioned living quarters (odds ratio = 0.1; 95% confidence interval 0.02–0.77; P < 0.03), but were otherwise similar to non-cases. Likewise, in St. Croix, 3/8 tested positive by immunoglobulin M and plaque reduction neutralization test for an attack rate of 38%. Similar to Operation NH, all three cases were symptomatic with subjective fever (67%), arthralgia (67%), and/or rash (100%). Conclusions This field investigation identified differing, mission location-dependent ZVD attack rates and a 0:9 asymptomatic-to-symptomatic case ratio. As this was unexpected based on a previous report of a 4:1 ratio, it emphasizes the need to be cautious before generalizing outbreak characteristics between populations while also offering additional practical experience for force health protection.