No abstract

Serotype specific (non-immunoglobulin) inhibitors of rotavirus have been identified in normal mouse serum obtained from BALB/c, CBA, and BL10 mice. Sialic acid was essential for the neutralising activity sera treated with the neuraminidase from Vibrio cholerae failed to neutralise rotavirus. G serotypes 4, 5, 7, 8, 9, and 10 were unaffected by the inhibitor(s) while G serotypes 1, 2, 6 and two G3 strains were neutralised to significant titres. Assessment of neutralisation of reassortants suggested that VP7 is the virus protein involved in the interaction although it remains possible that VP7 is influencing VP4 binding. Analysis of the sera by Western blot followed by virus overlay confirmed that binding is dependent on the presence of sialic acid. The human strain tested, Wa, bound to two (glyco) proteins (50 and 80 kDa) while the bovine strains tested, NCDV and UK bound to one (55 kDa) and two (36 and 55 kDa) proteins respectively. This indicates that while the bovine rotaviruses may bind to a common element, the human strain binds to clearly distinct proteins. We propose that these inhibitors interact with animal rotaviruses in a manner analogous to that by which they attach to target cells. The glycoprotein to which NCDV bound was purified and identified by N-terminal sequencing as murine alpha-1-anti-trypsin (MuAAT) and was confirmed to possess both neutralisation and anti-trypsin activity. Since MuAAT is known to possess only three N-linked glycans, identification and analysis of the actual virus-binding structure should now be possible.

The Vp7 gene of the avian strain Ty-1, which is classified as G7 serotype, was sequenced and the amino acid sequence deduced. The gene is 1065 nucleotides long with a long open reading frame of 987 nucleotides producing a protein 329 amino acids in length. The amino acid homology of the Ty-1 Vp7 protein to that of the avian Ch-2 Vp7 was 70%. The A, B, and C variable epitope regions of Ty-1 were unique compared to those of Ch-2 and other strains representing the 14G serotypes. The low 53% homology of the A and C regions of Ty-1 and Ch-2 would suggest that Ty-1 may be of a different serotype to the G7 reference strain Ch-2.

A reassortant, TyRh, was isolated after coinfection of MA104 cells with avian Ty-1 and simian RRV rotaviruses. Hybridization and serological studies showed that the reassortant's 4th gene, which encodes Vp4, was derived from the simian RRV rotavirus parent, whereas the remaining 10 genes were derived from the avian Ty-1 rotavirus parent.

During the course of genome studies in a rural community in the South Indian state of Karnataka, DNA-based investigations and counselling for familial adenomatous polyposis (FAP) were requested via the community physician. The proposita died in 1940 and FAP had been clinically diagnosed in 2 of her 5 children, both deceased. DNA samples from 2 affected individuals in the third generation were screened for mutations in the APC gene, and a frame-shift mutation was identified in exon 15 with a common deletion at codon 1061. Predictive testing for the mutation was then organized on a voluntary basis. There were 11 positive tests, including confirmatory positives on 2 persons diagnosed by colonoscopy, and to date surgery has been successfully undertaken on 3 previously undiagnosed adults. The ongoing success of the study indicates that, with appropriate access to the facilities offered by collaborating centres, predictive testing is feasible for diseases such as FAP and could be of significant benefit to communities in economically less developed countries.