Low level of HIV-1 evolution after transmission from mother to child

Mother-to-child HIV-1 transmission pairs represent a good opportunity to study the dynamics of CTL escape and reversion after transmission in the light of shared and non-shared HLA-alleles. Mothers share half of their HLA alleles with their children, while the other half is inherited from the father and is generally discordant between mother and child. This implies that HIV-1 transmitted from mother to child enters a host environment to which it has already partially adapted. Here, we studied viral evolution and the dynamics of CTL escape mutations and reversion of these mutations after transmission in the context of shared and non-shared HLA alleles in viral variants obtained from five mother-to-child transmission pairs. Only limited HIV-1 evolution was observed in the children after mother-to-child transmission. Viral evolution was mainly driven by forward mutations located inside CTL epitopes restricted by HLA alleles inherited from the father, which may be indicative of CTL pressure.