Genetic characterization of the glycoprotein G of Chandipura viruses in India with emphasis on an outbreak of 2015.

Chandipura virus (CHPV) is found to be associated with sporadic encephalitis outbreaks in humans in India since 1965. We report here, the investigation of CHPV activity during the period of June-August 2015 in the state of Gujarat, which revealed 24.44% positivity among 45 referred encephalitis cases. Phylogenetic study of the G gene sequences of strains from Gujarat 2015 along with available sequences of additional strains from different geographical locations and isolation years (1965-2015), indicated the relatedness of the 2015 strain to a group of the CHPV prototype strain of 1965 and the earliest outbreak strains of 2003. Analyses of selection pressure in the G gene revealed positively selected sites within the signal peptide region and a putative CHPV epitope. These results indicate a probable role of G protein-based immune selection and underline the need for continued surveillance to monitor genetic and antigenic variations in the CHPV.

Neutralization escape variant of West Nile virus associated with altered peripheral pathogenicity and differential cytokine profile.

In order to understand the factors influencing pathogenicity of a virus, two neutralization escape (NE) variants were selected from wild type lineage 1 West Nile virus (WNV) 68856 strain pathogenic by intra-peritoneal (i.p.) route using monoclonal antibodies (MAbs) against envelope (E) protein. Both NE IF1A7 1.1 and NE IVC3F10 1.2 were resistant to neutralization and were neurovirulent by intra-cranial (i.c.) inoculation. Growth kinetics in porcine stable (PS) kidney and baby hamster kidney (BHK) cells was unchanged. In contrast to parent WNV only NE IF1A7 1.1 failed to cause lethal encephalitis on i.p. inoculation and was non pathogenic. NE IF1A7 1.1 variant showed delayed replication kinetics in murine peritoneal exudate cells (PEC) and Neuro 346 cells in vitro. In comparison with parent WNV and NE IVC3F10 1.2 variant, non pathogenic variant exhibited significantly reduced tumour necrosis factor α (TNF-α) induction in infected animals and PEC. Other cytokines like Interleukin (IL)-10, IL-6 and Interferon (IFN)-ß remained unchanged. However, IL-1ß did not follow the pattern and was higher only in parent WNV-infected PEC. The E gene sequences of these NE variants showed three common amino acid substitutions at residues E50, E89 and E242. A unique E156 (ser→pro) substitution in NE IF1A7 1.1, was absent in NE IVC3F10 1.2 variant suggested probable virulence marker. Our data indicates possible role of WNV E protein in induction of TNF-α and IL-1ß and its association with WNV pathogenesis.

Japanese encephalitis virus produces a CD4+ Th2 response and associated immunoprotection in an adoptive-transfer murine model.

Japanese encephalitis is an acute infection of the central nervous system caused by Japanese encephalitis virus (JEV). The importance of an effective humoral response in preventing JEV infection has already been established, although the contribution of cellular immunity remains unclear. This study used an experimental murine model to understand the protective effects of cell-mediated immunity in JEV infection. Fourteen-day-old mice adoptively transferred with JEV-immune splenocytes were found to be protected from peripheral JEV challenge. The survival rate was reduced when transferred cells were depleted of their CD4(+) T-cell population. Correspondingly, increased protection was observed when JEV-primed isolated CD4(+) T cells were transferred compared with isolated CD8(+) T cells. Mice protected from JEV infection by the adoptive transfer of JEV-immune splenocytes had higher levels of immunomodulatory cytokines and decreased expression of pro-inflammatory cytokines. Concurrent with the increase in Th2 cytokines, JEV-specific IgM and IgG1 antibody titres were found to be elevated in protected mice. Taken together, these data indicate a definite role for CD4(+) T cells in protection from lethal JEV infection in naïve 14-day-old mice. Induction of a Th2 cytokine response and IgG1 antibody probably achieves an immunomodulatory effect that results in the enhanced survival of these animals.