An equine rotavirus (FI-14 strain) which bears both subgroup I and subgroup II specificities on its VP6.

This study identified a new equine rotavirus strain (FI-14) which reacts with both subgroup I and II monoclonal antibodies, making it the first of its kind. The research involved producing antibodies and testing them on various animal species which suggest that human rotaviruses may have two ancestral lineages. The strain doesn’t show homology with known human rotavirus serotypes.

Research Methodology

In this study, students used different established methods to identify and understand the novel rotavirus strain.

• An equine rotavirus strain, referred to as FI-14, was isolated from a foal diagnosed with diarrhea in New York. The neutralization assay determined that the strain belongs to serotype 3.
• This FI-14 strain was then found to react with monoclonal antibodies from both subgroup I and subgroup II when tested through an enzyme-linked immunosorbent assay (ELISA), revealing the unique subgroup specificities of this strain.
• Using hybridoma technology, the researchers generated monoclonal antibodies targeted toward the major inner capsid protein VP6 of the FI-14 virus.

Findings

Specific findings of the research were:

• The antibodies were specific to either subgroup I or subgroup II rotaviruses. This validated that the VP6 of the FI-14 virus holds both subgroup I- and subgroup II-specific epitopes, which is a novel observation.
• Additional monoclonal antibodies (monoclones) produced and tested with a panel of 49 rotavirus strains from different animal and avian species showed diverse reactions.
• This diversity in reactions revealed at least six different antigenic sites on the VP6 of the FI-14 virus.
• The rotaviruses, classified based on their reactivity patterns with the six representative monoclones, fell into one of eight reactivity groups.
• To gain insight into the origin of rotaviruses, analysis of reactivity patterns of rotaviruses from various animal species was conducted. This suggested that human rotaviruses might have two ancestral lineages: one with pig-human lineage for subgroup II, serotype 1, 3, and 4; and another with bovine-simian-human lineage for subgroup I, serotype 2.
• When analyzed by radioimmunoprecipitation, it was observed that the molecular weight of the FI-14 virus VP6 appeared to be more significant than those of the rhesus monkey MMU18006 virus VP6 or the human Wa virus VP6.
• Using RNA-RNA hybridization analysis, it was determined that the FI-14 virus did not show significant homology with viruses from the known four human rotavirus serotypes, making it distinctly different.

Implication

This study’s outcomes contribute significant insights into the complexity of rotaviruses and their diverse nature. The unique dual specificity of the FI-14 strain to both subgroup I and II antibodies adds a new layer of understanding to rotavirus taxonomy. Furthermore, the possibility of two distinct ancestral lineages of human rotaviruses alludes to the multifaceted nature of rotaviral evolution. Hence, these findings can enrich future research into rotavirus diversity, evolution, and phylogenetics.