Clinical isolates of Treponema pallidum subspecies pallidum (T. pallidum) would facilitate study of prevalent strains. We describe the first successful rabbit propagation of T. pallidum from cryopreserved ulcer specimens. Fresh ulcer exudates were collected and cryopreserved with consent from syphilis-diagnosed patients (N = 8). Each of eight age-matched adult male rabbits were later inoculated with a thawed specimen, with two rabbits receiving 1.3 ml intratesticularly (IT), and six receiving 0.6 ml intravenously (IV) and IT. Monitoring of serology, blood PCR and orchitis showed that T. pallidum grew in 2/8 rabbits that were inoculated IV and IT with either a penile primary lesion specimen (CDC-SF003) or a perianal secondary lesion specimen (CDC-SF007). Rabbit CDC-SF003 was seroreactive by T. pallidum Particle Agglutination (TP-PA) and Rapid Plasma Reagin (RPR) testing, PCR+, and showed orchitis by week 6. Euthanasia was performed in week 7, with treponemal growth in the testes confirmed and quantified by qPCR and darkfield microscopy (DF). Serial passage of the extract in a second age-matched rabbit also yielded treponemes. Similarly, rabbit CDC-SF007 showed negligible orchitis, but was seroreactive and PCR+ by week 4 and euthanized in week 6 to yield T. pallidum, which was further propagated by second passage. Using the 4-component molecular typing system for syphilis, 3 propagated strains (CDC-SF003, CDC-SF007, CDC-SF008) were typed as 14d9f, 14d9g, and 14d10c, respectively. All 3 isolates including strain CDC-SF011, which was not successfully propagated, had the A2058G mutation associated with azithromycin resistance. Our results show that immediate cryopreservation of syphilitic ulcer exudate can maintain T. pallidum viability for rabbit propagation.

Objectives To advance the initiative of ending the global epidemic, long-lasting HIV protection is needed through sustained release of antiretroviral drugs for months to years. We investigated in macaques the safety and efficacy of biodegradable polycaprolactone implants releasing tenofovir alafenamide for HIV pre-exposure prophylaxis (PrEP). Methods Implants were administered subcutaneously in the arm using a contraceptive trocar. Efficacy against vaginal simian-HIV (SHIV) infection was investigated in six pigtailed macaques that received two tenofovir alafenamide implants (0.35 mg/day), one in each arm, for a total release rate of tenofovir alafenamide at 0.7 mg/day. Macaques were exposed to SHIV twice weekly for 6 weeks. Statistical analyses were used to compare outcome with eight untreated controls. Histological assessments were performed on skin biopsies collected near implantation sites. Results Median (range) tenofovir diphosphate level in PBMCs was 1519 (1068–1898) fmol/106 cells. All macaques with tenofovir alafenamide implants were protected against vaginal SHIV infection. In contrast, 7/8 controls were infected after a median of 4 SHIV exposures (P = 0.0047). Histological assessment of tissues near tenofovir alafenamide implant sites showed inflammation and necrosis in 5/6 animals, which were not evident by visual inspection. Conclusions We demonstrated complete protection against vaginal SHIV infection with two implants releasing a total of 0.7 mg of tenofovir alafenamide per day. We also identified tenofovir diphosphate concentrations in PBMCs associated with complete vaginal protection. Consistent with previous findings, we observed adverse local toxicity and necrosis near the tenofovir alafenamide implant site. Improved tenofovir alafenamide implants that are safe and maintain high efficacy have the potential to provide long-lasting protection against vaginal HIV infection.

Background Daily oral pre- or post-exposure prophylaxis (PrEP or PEP) is highly effective in preventing HIV infection. However, many people find it challenging to adhere to a daily oral regimen. Chemoprophylaxis with single oral doses of antiretroviral drugs taken before or after sex may better adapt to changing or unanticipated sexual practices and be a desirable alternative to daily PrEP or PEP. We investigated willingness to use a single oral pill before or after sex among men who have sex with men (MSM) and assessed the biological efficacy of a potent antiretroviral combination containing elvitegravir (EVG), emtricitabine (FTC), and tenofovir alafenamide (TAF). Methods Data on willingness to use single-dose PrEP or PEP were obtained from the 2017 cycle of the American Men's Internet Survey (AMIS), an annual online behavioral surveillance survey of MSM in the United States. Antiretroviral drug levels were measured in humans and macaques to define drug distribution in rectal tissue and identify clinically relevant doses for macaque modeling studies. The biological efficacy of a single dose of FTC/TAF/EVG as PrEP or PEP was investigated using a repeat-challenge macaque model of rectal HIV infection. Findings Through pharmacokinetic assessment in humans and macaques we found that EVG penetrates and concentrates in rectal tissues supporting its addition to FTC/TAF to boost and extend chemoprophylactic activity. Efficacy estimates for a single oral dose given to macaques 4h before or 2h after SHIV exposure was 91•7%[35•7%-98•9%] and 100%, respectively, compared to 80•1%[13•9%-95•4%] and 64•6%[-19•4%-89•5%] when single doses were given 6 and 24h post challenge, respectively. A two-dose regimen at 24h and 48h after exposure was also protective [77•1%[1•7%-94•7%]. Interpretation Informed by user willingness, human and macaque pharmacokinetic data, and preclinical efficacy we show that single-dose prophylaxis before or after sex is a promising HIV prevention strategy. Carefully designed clinical trials are needed to determine if any of these strategies will be effective in humans. Funding Funded by CDC intramural funds, CDC contract HCVJCG2-2016-03948 (to CFK), and a grant from the MAC AIDS Fund and by the National Institutes of Health [P30AI050409] – the Emory Center for AIDS Research (to MZ and TS).