Vaginally delivered tenofovir disoproxil fumarate provides greater protection than tenofovir against genital herpes in a murine model of efficacy and safety.

Increased susceptibility to genital herpes in medroxyprogesterone-treated mice may provide a surrogate of increased HIV risk and a preclinical biomarker of topical preexposure prophylaxis safety. We evaluated tenofovir disoproxil fumarate (TDF) in this murine model because an intravaginal ring eluting this drug is being advanced into clinical trials. To avoid the complications of surgically inserting a ring, hydroxyethylcellulose (HEC)-stable formulations of TDF were prepared. One week of twice-daily 0.3% TDF gel was well tolerated and did not result in any increase in HSV-2 susceptibility but protected mice from herpes simplex virus 2 (HSV-2) disease compared to mice treated with the HEC placebo gel. No significant increase in inflammatory cytokines or chemokines in vaginal washes or change in cytokine, chemokine, or mitochondrial gene expression in RNA extracted from genital tract tissue was detected. To further evaluate efficacy, mice were treated with gel once daily beginning 12 h prior to high-dose HSV-2 challenge or 2 h before and after viral challenge (BAT24 dosing). The 0.3% TDF gel provided significant protection compared to the HEC gel following either daily (in 9/10 versus 1/10 mice, P < 0.01) or BAT24 (in 14/20 versus 4/20 mice, P < 0.01) dosing. In contrast, 1% tenofovir (TFV) gel protected only 4/10 mice treated with either regimen. Significant protection was also observed with daily 0.03% TDF compared to HEC. Protection was associated with greater murine cellular permeability of radiolabeled TDF than of TFV. Together, these findings suggest that TDF is safe, may provide substantially greater protection against HSV than TFV, and support the further clinical development of a TDF ring.

Zinc acetate/carrageenan gels exhibit potent activity in vivo against high-dose herpes simplex virus 2 vaginal and rectal challenge.

Topical microbicides that block the sexual transmission of HIV and herpes simplex virus 2 (HSV-2) are desperately needed to reduce the incidence of HIV infections worldwide. Previously we completed phase 3 testing of the carrageenan-based gel Carraguard. Although the trial did not show that Carraguard is effective in preventing HIV transmission during vaginal sex, it did show that Carraguard is safe when used weekly for up to 2 years. Moreover, Carraguard has in vitro activity against human papillomavirus (HPV) and HSV-2 and favorable physical and rheological properties, which makes it a useful vehicle to deliver antiviral agents such as zinc acetate. To that end, we previously reported that a prototype zinc acetate carrageenan gel protects macaques against vaginal challenge with combined simian-human immunodeficiency virus reverse transcriptase (SHIV-RT). Herein, we report the safety and efficacy of a series of zinc acetate and/or carrageenan gels. The gels protected mice (75 to 85% survival; P < 0.001) against high-dose (10(6)-PFU) HSV-2 vaginal or rectal challenge. In contrast, zinc acetate formulated in HEC (hydroxyethylcellulose; or the Universal Placebo) failed to protect mice against the high-dose vaginal HSV-2 challenge (similar to aqueous zinc acetate solution and the placebo controls). The gels were found to be effective spreading gels, exhibited limited toxicity in vitro, caused minimal damage to the architecture of the cervicovaginal and rectal mucosae in vivo, and induced no increased susceptibility to HSV-2 infection in a mouse model. Our results provide a strong rationale to further optimize and evaluate the zinc acetate/carrageenan gels for their ability to block the sexual transmission of HIV and HSV-2.

Calcium phosphate nanoparticles induce mucosal immunity and protection against herpes simplex virus type 2.

Previously we reported that calcium phosphate nanoparticles (CAP) represented a superior alternative to alum adjuvants in mice immunized with viral protein. Additionally, we showed that CAP was safe and elicited no detectable immunoglobulin E (IgE) response. In this study, we demonstrated that following mucosal delivery of herpes simplex virus type 2 (HSV-2) antigen with CAP, CAP adjuvant enhanced protective systemic and mucosal immunity versus live virus. Mice were immunized intravaginally and intranasally with HSV-2 protein plus CAP adjuvant (HSV-2+CAP), CAP alone, phosphate-buffered saline, or HSV-2 alone. HSV-2+CAP induced HSV-specific mucosal IgA and IgG and concurrently enhanced systemic IgG responses. Our results demonstrate the potency of CAP as a mucosal adjuvant. Furthermore, we show that systemic immunity could be induced via the mucosal route following inoculation with CAP-based vaccine. Moreover, neutralizing antibodies were found in the sera of mice immunized intranasally or intravaginally with HSV-2+CAP. Also, the results of our in vivo experiments indicated that mice vaccinated with HSV-2+CAP were protected against live HSV-2 infection. In conclusion, these preclinical data support the hypothesis that CAP may be an effective mucosal adjuvant that protects against viral infection.