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Immune imprinting is a phenomenon in which prior antigenic experiences influence responses to subsequent infection or vaccination 1,2 . The effects of immune imprinting on serum antibody responses after boosting with variant-matched SARS-CoV-2 vaccines remain uncertain. Here we characterized the serum antibody responses after mRNA vaccine boosting of mice and human clinical trial participants. In mice, a single dose of a preclinical version of mRNA-1273 vaccine encoding Wuhan-1 spike protein minimally imprinted serum responses elicited by Omicron boosters, enabling generation of type-specific antibodies. However, imprinting was observed in mice receiving an Omicron booster after two priming doses of mRNA-1273, an effect that was mitigated by a second booster dose of Omicron vaccine. In both SARS-CoV-2-infected and uninfected humans who received two Omicron-matched boosters after two or more doses of the prototype mRNA-1273 vaccine, spike-binding and neutralizing serum antibodies cross-reacted with Omicron variants as well as more distantly related sarbecoviruses. Because serum neutralizing responses against Omicron strains and other sarbecoviruses were abrogated after pre-clearing with Wuhan-1 spike protein, antibodies induced by XBB.1.5 boosting in humans focus on conserved epitopes targeted by the antecedent mRNA-1273 primary series. Thus, the antibody response to Omicron-based boosters in humans is imprinted by immunizations with historical mRNA-1273 vaccines, but this outcome may be beneficial as it drives expansion of cross-neutralizing antibodies that inhibit infection of emerging SARS-CoV-2 variants and distantly related sarbecoviruses., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Chikungunya fever is a viral disease transmitted to humans by the bite of infected mosquitoes. The disease is characterized by fever, headache, rash, severe joint, and muscle pain. To evaluate the disease burden in the population and the effectiveness of public health measures, periodic seroprevalence surveys are essential. Chikungunya outbreaks were reported from many Asian countries since 2005, after more than three decades of disappearance. The study aimed to estimate the seroprevalence of the chikungunya virus in southern parts of Karnataka state, through demonstrating chikungunya virus-specific neutralizing antibodies. A cross-sectional study was carried out using 509 archived blood samples from a hospital-based acute febrile illness surveillance project, representative of the period between June 2014 and 2018. The study reported a 3.7% seroprevalence of chikungunya virus-neutralizing antibodies in Thirthahalli and Hosanagara taluks of South Karnataka. The low prevalence of chikungunya-neutralizing antibodies indicates that a major population is unexposed and prone to future outbreaks., (© 2019 Wiley Periodicals, Inc.)

Influenza viruses are major respiratory pathogens that cause seasonal epidemics and occasional pandemics. Immune response to influenza viruses is majorly targeted against the hemagglutinin antigen. A laboratory-based retrospective cross-sectional study was conducted on 50 acute and 50 follow-up samples to assess the immune response to influenza A(H1N1)pdm09 virus after natural infection and detect the presence of pre-existing antibodies against influenza A(H3N2) and influenza B viruses. Two-fourfold rise in hemagglutination-inhibition (HAI) titer was observed in 100% of the follow-up samples for influenza A(H1N1)pdm09 virus. No change in HAI titers for influenza A(H3N2) and influenza B viruses was observed.

Background & Objectives: Dengue virus infection is endemic in India with all the four serotypes of dengue virus in circulation. This study was aimed to determine the geographic distribution of the primary and secondary dengue cases in India., Methods: A multicentre cross-sectional study was conducted at Department of Health Research / Indian Council of Medical Research (DHR)/(ICMR) viral research and diagnostic laboratories (VRDLs) and selected ICMR institutes located in India. Only laboratory-confirmed dengue cases with date of onset of illness less than or equal to seven days were included between September and October 2017. Dengue NS1 antigen ELISA and anti-dengue IgM capture ELISA were used to diagnose dengue cases while anti-dengue IgG capture ELISA was used for identifying the secondary dengue cases., Results: Of the 1372 dengue cases, 897 (65%) were classified as primary dengue and 475 (35%) as secondary dengue cases. However, the proportion varied widely geographically, with Theni, Tamil Nadu; Tirupati, Andhra Pradesh and Udupi-Manipal, Karnataka reporting more than 65 per cent secondary dengue cases while Srinagar, Jammu and Kashmir reporting as low as 10 per cent of the same. The median age of primary dengue cases was 25 yr [interquartile range (IQR 17-35] while that of secondary dengue cases was 23 yr (IQR 13.5-34). Secondary dengue was around 50 per cent among the children belonging to the age group 6-10 yr while it ranged between 20-43 per cent among other age groups., Interpretation & Conclusions: Our findings showed a wide geographical variation in the distribution of primary and secondary dengue cases in India. It would prove beneficial to include primary and secondary dengue differentiation protocol in the national dengue surveillance programme., Competing Interests: None

Protection from influenza virus infection is canonically associated with antibodies that neutralize the virus by blocking the interaction between the viral hemagglutinin and host cell receptors. However, protection can also be conferred by other mechanisms, including antibody-mediated effector functions. Here, we report the characterization of 22 broadly cross-reactive, nonneutralizing antibodies specific for influenza B virus hemagglutinin. The majority of these antibodies recognized influenza B viruses isolated over the period of 73 years and bind the conserved stalk domain of the hemagglutinin. A proportion of the characterized antibodies protected mice from both morbidity and mortality after challenge with a lethal dose of influenza B virus. Activity in an antibody-dependent cell-mediated cytotoxicity reporter assay correlated strongly with protection, suggesting that Fc-dependent effector function determines protective efficacy. The information regarding mechanism of action and epitope location stemming from our characterization of these antibodies will inform the design of urgently needed vaccines that could induce broad protection against influenza B viruses. IMPORTANCE While broadly protective antibodies against the influenza A virus hemagglutinin have been well studied, very limited information is available for antibodies that broadly recognize influenza B viruses. Similarly, the development of a universal or broadly protective influenza B virus vaccine lags behind the development of such a vaccine for influenza A virus. More information about epitope location and mechanism of action of broadly protective influenza B virus antibodies is required to inform vaccine development. In addition, protective antibodies could be a useful tool to treat or prevent influenza B virus infection in pediatric cohorts or in a therapeutic setting in immunocompromised individuals in conjugation with existing treatment avenues., (Copyright © 2019 American Society for Microbiology.)

Coxsackievirus A6 (CV-A6) has recently emerged as an enterovirus causing Hand Foot and Mouth Disease with severe complications. The pathogenic mechanisms of CV-A6- associated Hand foot and Mouth disease are largely unknown. In this study, it was investigated whether serum and IgG from patients with CV-A6 infection can enhance the infection of PBMC with the virus. Serum samples were obtained from five children with CV-A6 infection confirmed by RT-PCR and seven controls. IgG was isolated from serum by using affinity chromatography columns. CV-A6 was incubated with serum or IgG from controls and patients then the mixtures were added to PBMC cultures. The levels of IFNα in supernatants were measured by ELISA, and the levels of intracellular viral RNA were measured by RT-qPCR. It has been observed that there is an anti-CV-A6 enhancing activity in serum and serum-derived immunoglobulin G of children with CV-A6 infection but not in those of uninfected controls. Whether this activity has implications in the pathogenesis of CV-A6 associated diseases should be investigated., (Copyright © 2018 Elsevier Ltd. All rights reserved.)

Fairly large number of mumps virus infections present atypically without parotitis leading to delay in diagnosis and increased morbidity. Awareness of such presentations and inclusion of serological test for detecting IgM-specific antibodies could help in solving diagnostic dilemma, especially in unvaccinated individuals from developing countries.