H. Johnson1, L. Gunder1, T. Moyer2, M. Ziolkowski1, P. Bertrang1, A. Bilger3, E. Carchman1 1University Of Wisconsin, Department Of Surgery, Madison, WI, USA 2University Of Wisconsin, Waisman Center, Madison, WI, USA 3University Of Wisconsin, School Of Medicine And Public Health, Madison, WI, USA
Introduction: The development of anal dysplasia is associated with infection of anal tissue with human papillomavirus (HPV). Anal dysplasia has the potential to progress to anal cancer without treatment. We have found that the topical application of the protease inhibitor, Saquinavir, prevents the progression of anal dysplasia to anal cancer in an immunocompetent transgenic mouse model. We hypothesized that topical Saquinavir would promote viral clearance in an immunocompromised NOD scid gamma (NSG) mouse model infected with Mus musculus papillomavirus (MmuPV1). This novel infectious mouse model allows us to study viral clearance.
Methods: Male and female NSG mice were infected in the anus with 10^8 viral genome equivalents of MmuPV1 and began treatment 140 days post-infection to allow time for progression to high-grade anal dysplasia. Mice were randomized into four treatment groups, which included: control (mock, infected with MmuPV1, but left untreated), 7,12 dimethylbenz(a)anthracene only (DMBA (0.12 μmol)), Saquinavir only (SQV (1%)) (dissolved in dimethyl sulfoxide), and Saquinavir with DMBA (SQV + DMBA). Mice were treated topically at the anus with Saquinavir, 5 days per week and DMBA once weekly, for 20 weeks. Prior to initial treatment and again immediately before sacrifice, mice anal tracts were lavaged with phosphate buffered saline and DNA was extracted from the lavages. MmuPV1 viral load was measured using qPCR. Viral load data was analyzed with one-way ANOVA and paired t-tests.
Results: All of the treatment groups showed no significant difference in initial viral loads prior to receiving treatment regardless of sex. There were no differences in female or male control mice when comparing initial to final viral load. However, female mice had a statistically significant decrease in mean viral load following treatment (initial versus final) in both the SQV (P = 0.0198) and SQV + DMBA groups (P = 0.0033). Male mice had an increase in mean viral load from initial to final lavage in the SQV + DMBA (P = 0.0219) treatment group. There was no difference in mean initial and final viral load found in male mice in the SQV alone group.
Conclusion: Female NSG mice infected with MmuPV1 and treated with topical Saquinavir had a significant decrease in mean viral load in final lavage compared to initial lavage. We suspect the increase in viral load seen in male mice following SQV+ DMBA may be related to the ability of male mice to re-infect cage mates via anal penetration and/or epithelial damage from DMBA or dimethyl sulfoxide (the diluent). Further experiments with singly housed male mice are needed to confirm this hypothesis and exclude sex differences. These results could have implications for determining treatment length and regimen when considering the possibility of viral re-infection in humans.