HLA allele selection for designing peptide vaccines.

A central problem in developing vaccines against rapidly evolving viruses such as HIV and Influenza is the mutability of their antigens. In principle, the problem can be mitigated by using peptides from conserved portions of viral proteins. However, because cytotoxic T lymphocytes (CTLs), which such vaccines would stimulate, recognize pathogenic peptides only in association with class I products of the Major Histocompatibility Complex (MHC), and because human leukocyte antigen genes (HLA; the human MHC) are highly polymorphic, a peptide vaccine would have to bind a number of different HLA products. A natural question then, which is pertinent to the safety of the vaccine is, which HLA molecules should be targeted to achieve a prespecified coverage (say 90%) of a population. Taking account of disequilibrium between linked HLA loci, we identify 3-6 class I HLA alleles, depending on ethnic group, which cover about 90% of the population. While this leaves large numbers of individuals uncovered, a high level of herd immunity, and hence eradication of the virus, can be achieved through such a vaccine.