Immune defense of the female lower reproductive tract and the use of monoclonal antibody-based topical microbicide films to protect against HIV infection
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Research on the human-immunodeficiency virus (HIV) and HIV transmission prevention methods is extensive, yet a female-controlled prevention method still does not exist. In many cultures where HIV prevalence is highest there are many social and cultural barriers to the prevention options currently available, specifically around the use of condoms. Topical microbicides could potentially offer a viable solution. In heterosexually transmitted HIV, the epithelium of the lower female genital tract is the first place of contact with invading pathogens. A topical microbicide that could protect against infection across this barrier, without causing inflammation, would be an ideal product to protect women against infection. In previous studies, several microbicides were shown to cause inflammation and increase the risk of HIV infection; therefore, it is vitally important that any new topical microbicide products developed do not have the same effect. Our laboratory is collaborating with Mapp Biopharmaceuticals in the development of a new vaginal microbicide product based on human monoclonal antibodies produced in plants. Our prototype microbicide, MB66, is a film containing two antibodies: VRC01 (anti-HIV) and HSV-8 (anti HSV-2). We hypothesize that the new MB66 topical microbicide film will provide protection against these sexually transmitted viruses without inducing inflammation in the vaginal epithelium, and will prove to be a viable topical microbicide product that does not cause inflammation and increase the risk of HIV infection. MatTek vaginal epithelium models were used to test for any potential inflammation by the MB66 film. Active MB66 and placebo films were placed on the MatTek models. Vaginal tissue models grown in the presence of estradiol were also exposed to the active film. After being exposed to the active MB66 film, apical and basal supernatants were collected and analyzed for proinflammatory cytokines; IL-6, IL-8, MCP-1, and TNF-alpha. There were no significant increases in IL-6 or IL-8 expression in vaginal epithelium when exposed to the MB66 film. There was a significant decrease in the expression of TNF-alpha in the apical supernatant of the film-treated cultures at the 24 hour time point, and a very small (<1%) but statistically significant increase in the expression of MCP-1 in the basal supernatant of the film and the placebo after 24 hours. These results indicate that the active MB66 film did not induce a significant amount of inflammation in the vaginal epithelium. Immunohistochemistry was used to ensure that the MatTek vaginal models are a valid representation of the native vaginal-ectocervical epithelium. Expression of toll-like receptors (TLRs) 2, 3, 4, 5, and 9 was compared in the MatTek models (partial and full thickness), as well as native vaginal and ectocervical tissue. Results show similar expression of all the TLR's in the native tissue and the partial and full thickness MatTek models. There was a greater degree of similarity between the native tissue and the full thickness MatTek models. Namely, there was a lack of expression with TLR 5 and TLR 9, and positive expression of TLRs 2, 4, and 9. Overall, the TLR expression validated the use of these models in testing current and future topical microbicides in order to find an effective female-controlled prevention method. In addition, cytokine analysis provided evidence that the new Mapp MB66 topical microbicide films do not cause significant inflammation to the vaginal-ectocervical tissue. Our data indicate that there should be further development of the MB66 film as a vaginal topical microbicide.