Development of a genetically engineered vaccine against feline leukemia virus infection.

A genetically engineered subunit vaccine against FeLV infection was developed. The protective immunogen in the vaccine was a purified recombinant protein containing the entire amino acid sequence of FeLV subgroup A gp70 envelope protein. The optimal adjuvant was determined to be a highly purified saponin, QS-21, derived from Quillaja saponaria Molina. A vaccine formulation containing the recombinant protein, QS-21, and aluminum hydroxide was tested in specific-pathogen-free kittens and was shown to induce neutralizing antibodies as well as appreciable antibody responses to native gp70 by enzyme immunoassay and protein (western) immunoblot analysis and of whole virus preparations.