Safety and anti-HIV assessments of natural vaginal cleansing products in an established topical microbicides in vitro testing algorithm

Natural lime and lemon juice and household vinegar demonstrated anti-HIV-1 activity and cytotoxicity in transformed cell lines. Neutralization of the products reduced both anti-HIV-1 activity and cytotoxicity, resulting in a low therapeutic window for both acidic and neutralized formulations. For the natural juices and vinegar, the IC50 was ≤ 3.5 (0.8-3.5)% and the TC50 ≤ 6.3 (1.0-6.3)%. All three liquid products inhibited viability of beneficial Lactobacillus species associated with vaginal health. Comparison of three different toxicity endpoints in the cervical HeLa cell line revealed that all three products affected membrane integrity, cytosolic enzyme release, and dehydrogenase enzyme activity in living cells. The juices and vinegar also exerted strong cytotoxicity in cervico-vaginal cell lines, mainly due to their acidic pH. In human cervical explant tissues, treatment with 5% lemon or lime juice or 6% vinegar induced toxicity similar to application of 100 μg/ml nonoxynol-9, and exposure to 10% lime juice caused tissue damage comparable to treatment with 5% Triton-X-100.Lemon and lime juice and household vinegar do not fulfill the safety criteria mandated for a topical microbicide. As a result of their unphysiological formulation for the vaginal tract, they exhibit cytotoxicity to human cell lines, human vaginal tissues, and beneficial vaginal Lactobacillus species.Human immunodeficiency virus (HIV) infection and the resulting clinical disease, AIDS, has continued to be a world-wide epidemic since its discovery in 1982 [1,2]. Despite extensive international research efforts and funding support, no effective preventive measures for HIV apart from behavioral modifications and condom use have been shown fully effective to date [3]. Some of the research community has shifted its attention to the development of topical microbicides, defined as substances that prevent the sexual transmission of infectious agents [4]. Five chemical products were advanced to Phase III