Glycosylation and antigenic variation among Kunjin virus isolates

Abstract

Previous studies have found Kunjin (KUN) virus isolates from within Australia to be genetically homogenous and that the envelope protein of the type strain (MRM61C) was unglycosylated and lacked a potential glycosylation site. We investigated the extent of antigenic variation between KUN virus isolates from Australia and Sarawak using an immunoperoxidase assay and a panel of six monoclonal antibodies. The glycosylation status of the E protein of each virus was also determined by N glycosidase F (PNGase F) digestion and limited sequence analysis. The results showed that KUN viruses isolated within Australia oscillated between three antigenic types defined by two epitopes whose expression was influenced by passage history and host cell type. In contrast an isolate from Sarawak formed a stable antigenic type that was not influenced by passage history and was distinct from all Australian isolates. PNGase F digestions of KUN isolates indicated that 19 of the 33 viruses possessed a glycosylated E protein. Nucleotide sequence of the 5' third of the E gene of selected KUN isolates revealed that a single base change in PNGase F sensitive strains changed the tripeptide N-Y-F (amino acids 154-156 of the published sequence) to the potential glycosylation site N-Y-S. Further analysis revealed that passage history also had a significant influence on glycosylation.

Post-translational regulation and modifications of flavivirus structural proteins

“…Glycosylation of the E protein is more variable, usually occurring at residues 153/154 and at residue 67 in the four serotypes of DENV (Bryant et al, 2007;Lee et al, 2010). However, some strains of WNV (Beasley et al, 2005;Botha et al, 2008;Shirato et al, 2004b;Wengler et al, 1985), including KUNV (Adams et al, 1995), as well as strains of St Louis encephalitis virus (SLEV) (Vorndam et al, 1993), Alfuy virus (May et al, 2006) and YFV-17D (Post et al, 1992) lack any active carbohydrate modification in E. Therefore, such glycosylation is not absolutely required for flavivirus replication.…”

“…Increased virion secretion leads to higher viraemias in vertebrate hosts (Beasley et al, 2005;Murata et al, 2010;Shirato et al, 2004b;Totani et al, 2011) and thus may improve the likelihood that novel vector species become exposed to and infected with the virus. This may explain why North American (emergent) WNV is predominantly glycosylated (Beasley et al, 2005;Charrel et al, 2003), whereas isolates of WNV (including KUNV) that circulate in the Old World (with long-established vectorhost relationships) have been demonstrated to lack E glycosylation (Adams et al, 1995;Botha et al, 2008).…”

DNA vaccine coding for the full-length infectious Kunjin virus RNA protects mice against the New York strain of West Nile virus

“…KUN-specific antibody responses in unimmunized mice or mice receiving defective DNA could not be detected (ELISA titer Ͻ40). Neutralizing antibody to KUN virus was also detected in sera of mice immunized with pKUN1 DNA (titers of [10][11][12][13][14][15][16][17][18][19][20] or FLSD virus (titers of 40). Slightly higher levels of antibody as measured by ELISA and virus neutralization correlated with a longer period of viremia in FLSD-immunized mice (Table 1).…”

Requirement of Glycosylation of West Nile Virus Envelope Protein for Infection of, but Not Spread within, Culex quinquefasciatus Mosquito Vectors

“…Glycosylation of the E protein is not required for virion formation or infectivity because naturally non-glycosylated isolates of St. Louis encephalitis virus, yellow fever virus, and WNV have been identified. [8][9][10][11][12][13][14][15] However, the presence or absence of a glycan on the E protein can affect the viral phenotype. E protein glycosylation increases in vitro infectivity of DENV and WNV, although particle release is significantly inhibited.…”