Differential pathogenicity of SHIV_{SF162 P4} infection in pig-tailed and rhesus macaques

Background: Differential pathogenicity has been observed in cynomolgus and rhesus macaques following primate lentivirus infection. However, little is known about the comparative susceptibility of pig-tailed macaques to lentivirus infection and diseases. Methods: We compared thein vivo infectivity and pathogenicity of a CCR5-tropic SHIV_{SF162 P4} after intravenous, intravaginal or intrarectal inoculation in rhesus and pig-tailed macaques. Plasma viral load, peripheral blood CD4⁺ T cell counts and clinical signs were monitored. Results: Both rhesus and pig-tailed macaques are similarly susceptible to SHIV_{SF162 P4} infection by intravenous and mucosal routes. However, infection was significantly more robust in pig-tailed macaques than in rhesus, resulting in persistent viremia in 9/21 pig-tails vs. 2/24 rhesus (P < 0.013) and severe CD4⁺ T-cell depletion in 2/21 pig-tails (vs. none in rhesus). Conclusions: Together with earlier observations, our findings underscore the importance of considering host genetic and immunological factors when comparing vaccine efficacy in different macaque species.