Pharmacological evaluation of an ex vivo cervicovaginal HIV prevention model

The female genital tract (FGT) is a unique compartment with physiologically distinct properties complicating the extrapolation of drug efficacy; critical gaps remain in understanding regional variability within the FGT itself. We performed an in-depth investigation across endo- and ectocervical tissues on the utility of the cervical explant model to evaluate pre-exposure prophylaxis (PrEP) efficacy.

Using normal cervical tissues, we evaluated gene expression of relevant drug metabolizing enzymes and transporters (DMETs) via qRT-PCR and compared ecto- and endocervix. To determine differences in drug phosphorylation and to assess antiretroviral (ARV) efficacy, we incubated explants in tenofovir and emtricitabine then measured intracellular metabolites. Viral infectivity and dose-response with ARVs was measured using viral RNA and p24 following HIV-1JR-CSF challenge.

ABCC4 expression was 3-fold lower in ectocervical tissues compared with endocervical, whereas CYP3A5 was 2-fold higher. IL-6 was correlated with ABCB1 (r = 0.52, P = 0.01) and ABCG2 (r = 0.56, P =0.005). Dose-normalized phosphorylation did not differ between endo- and ectocervix (P > 0.5). Infectivity of explants was low (53%) but did not differ by compartment. Intracellular tenofovir diphosphate concentrations were associated with a decrease in ectocervical viral replication (r =0.39, P < 0.05). There was a strong relationship between the proportion of explants infected and emtricitabine dose (P =0.02) but no relationship between intracellular emtricitabine triphosphate and protection.

We identified differences in DMET expression and ARV metabolism between ecto- and endocervical tissues, as well as correlations between DMET and IL-6. Ectocervical explants demonstrated consistent viral infectivity and dose-dependent inhibition. The model is useful in determining tenofovir diphosphate targets.