In vitro comparison of topical microbicides for prevention of human immunodeficiency virus type 1 transmission

Abstract

A standardized protocol was used to compare cellular toxicities and anti-human immunodeficiency virus type 1 (HIV-1) activities of candidate microbicides formulated for human use. The microbicides evaluated were cellulose acetate phthalate (CAP), Carraguard, K-Y plus nonoxynol-9 (KY-N9), PRO 2000 (0.5 and 4%), SPL7013 (5%), UC781 (0.1 and 1%), and Vena Gel, along with their accompanying placebos. Products were evaluated for toxicity on cervical and colorectal epithelial cell lines, peripheral blood mononuclear cells (PBMCs), and macrophages (MPhi) by using an ATP release assay, and they were tested for their effect on transepithelial resistance (TER) of polarized epithelial monolayers. Anti-HIV-1 activity was evaluated in assays for transfer of infectious HIV-1 from epithelial cells to activated PBMCs and for PBMC and MPhi infection. CAP, Carraguard, PRO 2000, SPL7013, and UC781 along with their placebos were 20- to 50-fold less toxic than KY-N9 and Vena Gel. None of the nontoxic product concentrations disrupted the TER. Transfer of HIV-1(Ba-L) from epithelial cells to PBMCs and PBMC and MPhi infection with laboratory-adapted HIV-1(Ba-L) and HIV-1(LAI) isolates were inhibited by all products except Carraguard, KY-N9, and Vena Gel. KY-N9, Vena Gel, and Carraguard were not effective in blocking PBMC infection with primary HIV-1(A), HIV-1(C), and HIV-1(CRF01-AE) isolates. The concordance of these toxicity results with those previously reported indicates that our protocol may be useful for predicting toxicity in vivo. Moreover, our systematic anti-HIV-1 testing provides a rational basis for making better informed decisions about which products to consider for clinical trials.

FIG. 1.

Effect of microbicide product and placebo formulations on Caco-2 epithelial monolayer integrity. Caco-2 cells were grown on transwell supports and allowed to form intact monolayers (7 to 11 days). Nontoxic and toxic concentrations of each product (Table 2) were added to the apical side of the transwell, and epithelial integrity was measured at 30 min and 1, 2, 4, 8, and 24 h by using a Millicell-ERS instrument. The data shown are the averages from duplicate wells ± standard errors of the means after product addition and are representative of two independent experiments.

FIG. 2.

Ability of microbicide product and placebo formulations to block HIV-1_Ba-L transfer from colorectal and urogenital epithelial cell lines to activated PBMCs. Epithelial cell lines were cultured with virus and nontoxic epithelial concentrations of product or placebo (Table 2) overnight or with virus alone. The cells were washed, and activated PBMCs were added alone or with product or placebo. Virus infection was followed by using the HIV-1 p24gag ELISA. The data presented are the averages ± standard errors of the means for the combined Caco-2, SW837, HEC-1-A, and ME-180 cultures. Cultures that were positive for HIV infection had HIV-1 p24 levels of >1 ng/ml. D, during; A, after.

FIG. 3.

The capacity of the microbicide product and placebo formulations to prevent infection of PBMCs. Virus representing different HIV-1 clades as well as laboratory-adapted and primary isolates were cultured with PBMCs in the presence or absence of nontoxic concentrations of product and placebo (Table 2). The product and placebo formulations were tested in triplicate. Virus infection was measured by the release of p24gag in the supernatants from day 4 or 7 of culture. The data presented are the log₁₀ reductions versus the untreated controls and are representative of two independent experiments.

FIG. 4.

The ability of the microbicide product and placebo formulations to prevent infection of MΦs. HIV-1 was cultured with the MΦs in the presence or absence of nontoxic concentrations of product and placebo (Table 2). The product and placebo formulations were tested in duplicate. Virus infection was measured by the release of p24gag on day 7 or 9 of culture. The data presented are the log₁₀ reductions versus the untreated controls and are representative of two independent experiments.