Rotavirus neutralizing protein VP7: antigenic determinants investigated by sequence analysis and peptide synthesis

Abstract

The rotavirus neutralizing antigen, VP7, is a 37,000-molecular-weight glycoprotein which is a major component of the outer shell of the virion. The amino acid sequence of VP7 for strain S2 (human serotype 2) and Nebraska calf diarrhea virus (bovine serotype) has been inferred from the nucleic acid sequence of cloned copies of genomic segment nine. Comparison of the amino acid sequences of these two VP7 proteins with those already determined for other rotavirus strains reveals extensive sequence conservation between serotypes with clusters of amino acid differences sited predominantly in hydrophilic domains of the protein. Six peptides have been synthesized that span the hydrophilic regions of the molecule. Antisera to these peptides both recognize the respective homologous peptides in a solid-phase radioimmunoassay and bind to denatured VP7 in a Western blot. However, none of the antisera either recognize virus or exhibit significant neutralizing activity, indicating that these peptide sequences are not available on the surface of the virus.

Processing of rotavirus glycoprotein VP7: implications for the retention of the protein in the endoplasmic reticulum.

“…The major cleavage site producing amino-terminal Gln appears to be a typical substrate for signal peptidase (Fig. 1) (24,25) and is conserved in all VP7 serotypes (8,9). However, cleavage by signal peptidase to produce amino-terminal Arg49 or Ala50 is much less likely (25) and these residues are not conserved in other VP7 proteins (8,9).…”

Deletions into an NH2-terminal hydrophobic domain result in secretion of rotavirus VP7, a resident endoplasmic reticulum membrane glycoprotein.

“…The complete sequence of genomic segment nine of Simian 11 rotavirus was obtained previously using a partial length cDNA clone that lacked 5'terminal sequences (7). A full-length clone was isolated using a modified cloning strategy (20). This yielded a VP7 clone inserted in the Pst I site of pBR322 which was confirmed as full length by terminal sequence analysis (30 revealed that pJC 16 nevertheless contained residual homopolymeric sequences (15G residues) at the 5'-end of the gene.…”

Prospects for vaccines against rotaviruses

“…VP7) from E. coli-or Salmonella-specific plasmids, or from vaccinia virus recombinants were on the whole disappointing [85][86][87] as was the use of smaller antigens, namely synthetic peptides. [88][89][90] Microencapsidation of rotavirus vaccine allows the release of replication-competent virus to be delayed and in children has led to persistence of virus in gutassociated lymphoid tissues and to greatly enhanced virus-specific immune responses. 91 Similarly, the immunogenicity of a RRV/human reassortant rotavirus vaccine could be improved by co-administration with Lactobacillus casei GG strain.…”