Genetic and antigenic features of the transmitted virus

Methodological and analytical advances in obtaining genetic information during acute HIV infection have provided an unprecedented view into viral transmission and early immune evasion. The findings suggest that a better understanding of the restricted viral diversity that follows mucosal transmission could lead to novel strategies for vaccine, microbicide or other therapeutic interventions.

During sexual transmission of HIV-1, viral diversity is reduced presumably due to obstacles an infectious virion must overcome to establish infection within a new host. Recently, single-genome amplification followed by direct sequencing from samples obtained during acute infection has been utilized to quantify the actual number of infecting variants. Overall, the vast majority (over 75%) of new infections were initiated by a single genetic variant. Transmission of multiple variants from a single donor (between two and five) was also observed and is associated with factors that compromise the genital mucosa. These analyses included over 200 patients representing subtypes A, B, C, D and have been reproduced in nonhuman primate model systems.

During acute infection, there is limited viral diversity in most patients, which provides a window of opportunity for vaccines or therapies to inhibit or prevent infection. Identifying the common genetic and antigenic properties of newly transmitted viruses will be necessary to advance vaccine design.