Molecular analysis of non structural rotavirus group A enterotoxin gene of bovine origin from India

- Bovine rotavirus genotype E1 detected for the first time in India.
- Three variants among genotype E2 sequences identified.
- Rotaviral enterotoxin under strong negative selection.
- Unique pentameric structure of enterotoxin on homology modeling.

The rotavirus enterotoxin NSP4 (nonstructural protein 4), plays a pivotal role in viral morphogenesis as well as pathogenesis. In this study, the NSP4 gene of rotavirus group A (RVA) isolates of bovine origin isolated in several states of India from 2008 to 2011 were characterized. The complete open reading frame of 23 RVA strains were sequenced and analyzed phylogenetically. Genotype E1 was detected for the first time in bovines from India, in addition to the more common bovine genotype E2. Sequence similarity analysis of the E1 sequences showed a close genetic relatedness to human strains. Six of the bovine E2 genotypes strains clustered near bovine and unusual human strains (possible human animal reassortant) from Thailand, while the remaining E2 sequences clustered with Indian bovine strains. Analysis pointed out one positively selected site (154aa), believe to be part of an antigenic region and 123 negatively selected sites. Unexpectedly, a pentameric NSP4 structure of the coiled coil domain in the E1 carrying strains and a monomeric NSP4 in RVA strain P14 (E2) was predicted based on homology modeling, potentially affecting the biological properties of NSP4. The close relationship between bovine and human rotavirus strains further highlights the complex interaction among rotaviruses of different species.