Antiviral antibodies constitute an important component of the host immune response against viral infections and serve to neutralize and reduce infectivity of the virus. However, these antibodies, intended to protect the host, may sometimes prove beneficial to the virus, by facilitating viral entry and replication in the target cell. This phenomenon, known as antibody-dependent enhancement (ADE) of infection, is a result of interaction of virus-antibody immune complexes with Fcγ and/or complement receptors on certain types of host cells and promotes viral entry into the host cells. The internalized immune complexes then modulate host immune response so as to enhance viral replication and aggravate disease severity. The possibility of induction of ADE remains a concern in the development and implementation of viral vaccines and immunotherapeutics.

The majority of human group A rotaviruses possess the P[8] VP4 genotype. Recently, a genetically distinct subtype of the P[8] genotype, also known as OP354-like P[8] or lineage P[8]-4, emerged in several countries. However, it is unclear for how long the OP354-like P[8] gene has been circulating in humans and how it has spread. In a global collaborative effort 98 (near-)complete OP354-like P[8] VP4 sequences were obtained and used for phylogeographic analysis to determine the viral migration patterns. During the sampling period, 1988-2012, we found that South and East Asia acted as a source from which strains with the OP354-like P[8] gene were seeded to Africa, Europe, and North America. The time to the most recent common ancestor (TMRCA) of all OP354-like P[8] genes was estimated at 1987. However, most OP354-like P[8] strains were found in three main clusters with TMRCAs estimated between 1996 and 2001. The VP7 gene segment of OP354-like P[8] strains showed evidence of frequent reassortment, even in localized epidemics, suggesting that OP354-like P[8] genes behave in a similar manner on the evolutionary level as other P[8] subtypes. The results of this study suggest that OP354-like P[8] strains have been able to disperse globally in a relatively short time period. This, in combination with a relatively large genetic distance to other P[8] subtypes, might result in a lower vaccine effectiveness, underscoring the need for a continued surveillance of OP354-like P[8] strains, especially in countries where rotavirus vaccination programs are in place.

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The differences between the G1P[8] strains in Pune and the G1 and P[8] components of the vaccine strains need to be described for appropriate evaluation of vaccine shedding. Continuous monitoring of the G1P[8] subgenotypic lineages would be necessary to study any long term impact of vaccine use on G1P[8] strain evolution.

Summary The degree of transmission of hepatitis A virus (HAV) is inversely proportional to the socioeconomic status of a community. Serosurveys conducted at Pune, India during 1982‐98 documented significant reduction in HAV exposure of paediatric, higher socioeconomic status (HSS) population. Anti‐HAV positivity (ELISA) in age‐stratified Pune population representing HSS and lower middle socioeconomic status (LMSS) (n = 1065) and infants till the age of 15 months (n = 690) was determined in 2017. Anti‐HAV positivity in the LMSS population decreased significantly in 2017 while an increase was seen in the HSS category. The surprising rise in anti‐HAV positivity in the HSS population reflected vaccine‐ and infection‐induced antibodies while only infection‐induced antibodies were present in the LMSS category. Lowest antibody prevalence in infants was at 12 months, the recommended age for hepatitis A vaccination. Improved hygiene and selective immunization practices impacted HAV exposure of the LMSS population. The data emphasize the need for hepatitis A vaccination irrespective of socioeconomic status.