Background: HIV-1 variants carrying non-macrophage-tropic HIV-1 R5 envelopes (Envs) are predominantly trans‑
mitted and persist in immune tissue even in AIDS patients who have highly macrophage-tropic variants in the brain.
Non-macrophage-tropic R5 Envs require high levels of CD4 for infection contrasting with macrophage-tropic Envs,
which can efficiently mediate infection of cells via low CD4. Here, we investigated whether non-macrophage-tropic
R5 Envs from the acute stage of infection (including transmitted/founder Env) mediated more efficient infection of
ectocervical explant cultures compared to non-macrophage-tropic and highly macrophage-tropic R5 Envs from late
disease.
Results: We used Env+ pseudovirions that carried a GFP reporter gene to measure infection of the first cells targeted
in ectocervical explant cultures. In straight titrations of Env+ pseudovirus supernatants, mac-tropic R5 Envs from late
disease mediated slightly higher infectivities for ectocervical explants although this was not significant. Surprisingly,
explant infection by several T/F/acute Envs was lower than for Envs from late disease. However, when infectivity for
explants was corrected to account for differences in the overall infectivity of each Env+ pseudovirus (measured on
highly permissive HeLa TZM-bl cells), non-mac-tropic early and late disease Env+ pseudoviruses mediated signifi‑
cantly higher infection. This observation suggests that cervical tissue preferentially supports non-mac-tropic Env+
viruses compared to mac-tropic viruses. Finally, we show that T-cells were the main targets for infection regardless of
whether explants were stimulated with T-cell or monocyte/macrophage cytokines. There was no evidence of mac‑
rophage infection even for pseudovirions carrying highly mac-tropic Envs from brain tissue or for the highly mactropic,
laboratory strain, BaL, which targeted T-cells in the explant tissue.
Conclusions: Our data support ectocervical tissue as a favorable environment for non-mac-tropic HIV-1 R5 variants
and emphasize the role of T-cells as initial targets for infection even for highly mac-tropic variants.