SUMMARYMonoclonal antibodies (MAb) specific for citrus tristeza virus (CTV) were obtained from hybrid cells produced by fusion of a non-secreting myeloma cell line with spleen cells from BALB/c mice immunized with isolate T-308 of CTV. Three MAb were characterized for their immunoglobulin isotype and their titres in cell culture and ascites fluids. Each MAb was conjugated with alkaline phosphatase and used in a double-antibody sandwich enzyme-linked immunosorbent assay for CTV. When tested against 23 strains of CTV, each MAb recognized all the strains with uniform reactions and low background.

A synthetic peptide vaccine which protects dogs against challenge with virulent canine parvovirus is described. The amino acid sequence used was discovered in previous studies on the immunogenic properties of previously mapped antigenic sites and represents the amino-terminal region of viral protein VP2. As with marker vaccines, it is possible to discriminate between vaccinated dogs that have not been exposed to the virus and dogs that have been infected with the virus. The protective mechanism can be explained by a humoral response against the peptide aided by T-cell epitopes contained in the carrier protein used for peptide coupling. This is the first example of a synthetic peptide vaccine that induces protection in target animals.

No abstract

In this report we describe the topological mapping of neutralizing domains of canine parvovirus (CPV). We obtained 11 CPV-specific monoclonal antibodies (MAbs), six of which are neutralizing. The reactivities were as determined by ELISA and Western blot (immunoblot) analysis. VP2, the most abundant protein of the CPV capsid, seemed to contain all the neutralization sites. Also, an almost full-length genomic clone of CPV was constructed in the bacterial plasmid pUC18 to enable expression of CPV proteins. All the neutralizing MAbs recognized recombinant VP2 when it was expressed as a free protein in Escherichia coli but not when expressed as a fusion protein with glutathione-S-transferase. When two large fragments containing about 85 % and 67 % of the C terminus of VP2 were expressed, no neutralization sites were detected. When fusion proteins containing the N terminus were expressed, two linear determinants were mapped, one between residues 1 to 10 of VP2, and the other between amino acids 11 and 23. The peptide 11 GQPAVRNERATGS 23, recognized by MAb 3C9, was synthesized chemically and checked for immunogenicity, not being able to induce neutralizing activity. Although the antibody response in rabbits to all the fusion proteins was uniformly high, the anti-CPV response was very variable. Protein from pCPVExl 1, which contains a T cell epitope (peptide PKIFINLAKKKKAG) present in the VPl-specific region as well as the B cell epitopes, seemed to be the most effective in inducing virus neutralization.

No abstract