Risk of vertical HIV transmission combines the 'B35-Cw4 disadvantage' and the 'pattern of inheritance' theories of progression.

Mother-to-child transmission during pregnancy provides a unique system for studying the correlation between HLA phenotype and susceptibility to HIV infection. We studied this relationship in a Spanish cohort. We determined frequencies of HLA class I and II alleles in 120 infants born to HIV-infected mothers and 67 HIV-infected mothers. Although there was no statistical difference in the frequency of HLA-B35 between transmitting and non-transmitting mothers, the allele was more frequent in infected children than in uninfected children. HLA-B35 has been consistently reported as a risk factor in the progression to AIDS. In addition, it has been proposed that whether a given allele can confer susceptibility to, or protection against, progression depends on maternal versus paternal inheritance patterns, since the child inherits a virus that reflects the history of CTL encounters of the mother. Our results on vertical HIV transmission combine for the first time the 'HLA-B35 disadvantage' and the 'pattern of inheritance' theories.