Modeling the evolution of SIV sooty mangabey progenitor virus towards HIV-2 using humanized mice.

HIV-2 is thought to have originated from an SIV progenitor native to sooty mangabeys. To model the initial human transmission and understand the sequential viral evolution, humanized mice were infected with SIVsm and serially passaged for five generations. Productive infection was seen by week 3 during the initial challenge followed by chronic viremia and gradual CD4+ T cell decline. Viral loads increased by the 5th generation resulting in more rapid CD4+ T cell decline. Genetic analysis revealed several amino acid substitutions that were nonsynonymous and fixed in multiple hu-mice across each of the 5 generations in the nef, env and rev regions. The highest rate of substitution occurred in the nef and env regions and most were observed within the first two generations. These data demonstrated the utility of hu-mice in modeling the SIVsm transmission to the human and to evaluate its potential sequential evolution into a human pathogen of HIV-2 lineage.