Abstract
Sera obtained from gnotobiotic calves infected with bovine rotavirus strain NCDV (G6) or B223 (G10) were compared for their neutralization (NT) properties to a number of rotaviruses (representing G serotypes 1-6, 8-10). Two distinct patterns of neutralization were identified. NCDV GC antisera neutralized only SA11-4F and B641 to a relatively high titer compared with the homologous titer, implying a narrow pattern of NT response. In contrast, B223 GC antisera neutralized most of the G serotypes tested to titers close to the homologous titer, demonstrating a broad pattern of NT response. The calves immunized with NCDV responded optimally to the VP4 antigen shared by NCDV and SA11-4F. This was confirmed by the use of B641/NCDV reassortants. Using reassortants, it was determined that the immunodominant neutralizing antigen of B223 during primary immune response in calves is VP7 and heterologous response is probably directed at VP4. MAB B223-N6 identified a shared epitope among B223, B641 and various G serotype rotaviruses. These data support the conclusion that VP4 is an important antigen for G10 as well as G6 rotavirus immunity. The B223/69M reassortants were assayed with two cross-reactive VP4 MABs B223-N6 and 2G4. B223 VP7 was found to enhance the neutralization titers of the MABs with rotaviruses containing either homologous (B223) VP4 or the heterologous (69M) VP4. B223 VP7 gene was selected non-randomly (93.4% frequency) in the reassortants derived from B223/69M coinfection. The studies on the growth curves of B223, 69M and their reassortants indicate that B223 VP7 provided replication advantages. B223 was cultured as coinfections with each of the following viruses: Wa, 69M, H-2, SA11-4F and NCDV followed by 20 subpassages. For coinfections with Wa, 69M, H-2 and SA11-4F, B223 VP7 gene was selected, in contrast to the B223/NCDV coinfection, when NCDV VP7 gene was selected. Other genes were also selected non-randomly, but varied among the five coinfection pairs. These data suggest that B223 or NCDV VP7 protein can provide replication advantages to reassortant viruses, possibly by modifying VP4 to make it absorb more efficiently to the cell receptors.
Xu, Zhichang (1993). Immunological and genetic studies of bovine rotaviruses. Texas A&M University. Texas A&M University. Libraries. Available electronically from
https : / /hdl .handle .net /1969 .1 /DISSERTATIONS -1531374.