Fig. 8
Genotypic and phenotypic features of HIV-1 isolates acquired in utero are distinct from those acquired through breastfeeding. On the far left, the pool of viral variants present in the chronically-infected donor are represented by differently-colored virion cores, with heavily-glycosylated envelopes coated in blue and those with less glycosylation coated in red. Strong selection during or following transmission (red box, middle) results in either a single or a very small number of variants that ultimately establish acute infection in the new host (right). Genotypic and phenotypic signatures by route of MTCT are as shown. For subtype C variants, heterosexual transmission bears similarity to transmission in utero, as both transmission modes select for isolates with shorter and less-glycosylated variable regions. MTCT of HIV-1 takes place in the presence of HIV-specific maternal antibody, while heterosexual transmission does not