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Chikungunya virus (CHIKV) infection is endemic in many different countries. CHIKV outbreaks are emerging in new areas and re-emerging in previously exposed geographical regions, thus making it a significant public health concern. CHIKV infections are often clinically inapparent, especially in children, which poses a challenge to testing and evaluating any vaccine. During CHIKV infection, CHIKV-specific antibodies are produced, and some of these antibodies can neutralize viruses released from infected cells before they can enter uninfected cells. In this study, we evaluated IgG binding and neutralizing antibody responses in paired serum samples from CHIKV-infected children and those with other febrile illness, using a recombinant truncated E2 protein and whole CHIKV particles as test antigens. Antibody detection using the truncated E2 protein showed a significant overlap between CHIKV-infected subjects and those with other febrile illnesses. This overlap was greater when binding antibody titers were determined using fixed CHIKV particles as the test antigen. Acute- and convalescent-phase sera collected from children after CHIKV infection showed significant differences in their neutralizing capacity. The neutralizing and binding antibody response showed a significant positive correlation. We detected IgG antibodies in most cases during the acute phase of infection. This was observed at two different geographical locations, one of which is not considered highly endemic. Conventional wisdom would suggest this to be a marker of re-infection (secondary infection). However, dissenting opinions have been voiced in other viral diseases (such as Ebola) where studies have detected IgG in acute illness. In the absence of any significant body of work documenting secondary CHIKV infections, we believe further work is needed to understand the early IgG response that we observed.

India is one of the most affected countries by COVID-19 pandemic; but little is understood regarding immune responses to SARS-CoV-2 in this region. Herein we examined SARS-CoV-2 neutralizing antibodies, IgG, IgM, IgA and memory B cells in COVID-19 recovered individual from India. While a vast majority of COVID-19 recovered individuals showed SARS-CoV-2 RBD-specific IgG, IgA and IgM antibodies (38/42, 90.47%; 21/42, 50%; 33/42, 78.57% respectively), only half of them had appreciable neutralizing antibody titers. RBD-specific IgG, but not IgA or IgM titers, correlated with neutralizing antibody titers and RBD-specific memory B cell frequencies. These findings have timely significance for identifying potential donors for plasma therapy using RBD-specific IgG assays as surrogate measurement for neutralizing antibodies in India. Further, this study provides useful information needed for designing large-scale studies towards understanding of inter-individual variation in immune memory to SARS CoV-2 natural infection for future vaccine evaluation and implementation efforts., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Chikungunya virus (CHIKV) infection causes acute febrile illness in humans, and some of these individuals develop a debilitating chronic arthritis that can persist for months to years for reasons that remain poorly understood. In this study from India, we characterized antibody response patterns in febrile chikungunya patients and further assessed the association of these initial febrile-phase antibody response patterns with protection versus progression to developing chronic arthritis. We found 5 distinct patterns of the antibody responses in the febrile phase: no CHIKV binding or neutralizing (NT) antibodies but PCR positive, IgM alone with no NT activity, IgM alone with NT activity, IgM and IgG without NT activity, and IgM and IgG with NT activity. A 20-month follow-up showed that appearance of NT activity regardless of antibody isotype or appearance of IgG regardless of NT activity during the initial febrile phase was associated with a robust protection against developing chronic arthritis in the future. These findings, while providing potentially novel insights on correlates of protective immunity against chikungunya-induced chronic arthritis, suggest that qualitative differences in the antibody response patterns that have evolved during the febrile phase can serve as biomarkers that allow prediction of protection or progression to chronic arthritis in the future.

Background: The Indian population is facing highest dengue burden worldwide supporting an urgent need for vaccines. For vaccine introduction, evaluation and interpretation it is important to gain a critical understanding of immune memory induced by natural exposure. However, immune memory to dengue remains poorly characterized in this region., Methods: We enumerated levels of dengue specific memory B cells (MBC), neutralizing (NT) and binding antibodies in healthy adults (n=70) from New Delhi., Results: NT-antibodies, binding antibodies and MBC were detectable in 86%, 86.56% and 81.63% of the subjects respectively. Among the neutralizing positive subjects, 58%, 27%, 5% and 10% neutralized all four, any three, any two and any one dengue serotypes respectively. The presence of the neutralizing antibodies was associated with the presence of the MBC and binding antibodies. However, a massive interindividual variation was observed in the levels of the neutralizing antibodies (range, <1:50-1:30,264), binding antibodies (range, 1:3,000-1:134,000,) as well as the MBC (range=0.006%-5.05%)., Conclusion: These results indicate that a vast majority of the adults are immune to multiple dengue serotypes and show massive interindividual variation in neutralizing/binding antibodies and MBCs - emphasizing the importance of monitoring multiple parameters of immune memory in order to properly plan, evaluate and interpret dengue vaccines., (Copyright © 2019. Published by Elsevier Ltd.)

The catastrophic rise in dengue infections in India and globally has created a need for an accurate, validated low-cost rapid diagnostic test (RDT) for dengue. We prospectively evaluated the diagnostic performance of NS1/IgM RDT (dengue day 1) using 211 samples from a pediatric dengue cohort representing all 4 serotypes in southern India. The dengue-positive panel consisted of 179 dengue real-time polymerase chain reaction (RT-PCR) positive samples from symptomatic children. The dengue-negative panel consisted of 32 samples from dengue-negative febrile children and asymptomatic individuals that were negative for dengue RT-PCR/NS1 enzyme-linked immunosorbent assay/IgM/IgG. NS1/IgM RDT sensitivity was 89.4% and specificity was 93.8%. The NS1/IgM RDT showed high sensitivity throughout the acute phase of illness, in primary and secondary infections, in different severity groups, and detected all 4 dengue serotypes, including coinfections. This NS1/IgM RDT is a useful point-of-care assay for rapid and reliable diagnosis of acute dengue and an excellent surveillance tool in our battle against dengue., (Copyright © 2016. Published by Elsevier Inc.)

Disease caused by Chikungunya virus (CHIKV) is clinically characterized by sudden-onset of fever and severe arthralgia, which may persist for weeks, months, or years after acute phase of the infection. CHIKV is spreading globally; in India it first appeared in the 1960s followed by a quiescent period and then a full-blown remergence in 2006 and sporadic persistence since then. Despite a large number of commercially available diagnostic kits for CHIKV, clinical preparedness and diagnostics suffer from sub-optimal assays. An international diagnostic laboratory survey suggested that there is a critical need for improved CHIKV diagnostics especially in the early acute phase of illness. With the recent studies indicating that a vast majority of human humoral response in CHIKV infection is directed against E2 protein, this supports strong interest to develop CHIKV E2 based serological tests. However, methods to produce large amounts of CHIKV protein are limited. Here we report cloning, expression and purification methods for obtaining a truncated 37kDa Chikungunya E2 protein at a high yield of 65-70mg/l. We found that this purified protein can be reliably used in ELISA and western blot to detect CHIKV specific antibodies in sera from patients who were PCR or IgM positive. Thus, using this protocol, laboratories can make large quantities of purified protein that can be potentially used in CHIKV serological analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)