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Syphilis increased risk for HIV in MSM
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Syphilis infection was associated with HIV acquisition among HIV-negative men and transgender women who have sex with men in a pre-exposure prophylaxis trial, according to data published in Clinical Infectious Diseases.
“Despite this increased risk, syphilis did not reduce the protective effect of pre-exposure prophylaxis (PrEP) with tenofovir/emtricitabine,” Marc M. Solomon, MD, MPH, clinical and research fellow in the division of infectious diseases at the University of California, San Francisco, told Infectious Disease News. “HIV-negative individuals presenting with syphilis should be offered PrEP unless otherwise contraindicated.”
Marc M. Solomon
This is a substudy of the Pre-exposure Prophylaxis Initiative (iPrEx) trial, which evaluated the safety and efficacy of tenofovir/emtricitabine (Truvada, Gilead Sciences) as PrEP for MSM and transgender women. In the iPrEx study, patients were tested at screening and in 24-week intervals for syphilis and other asymptomatic STIs. For this study, Solomon and colleagues evaluated rates of prevalent and incident syphilis and whether incident syphilis was associated with HIV acquisition.
Among the 2,499 individuals, 360 were positive for syphilis by rapid plasma reagin (RPR) at screening and 333 had a positive confirmatory test. Overall, the incidence of syphilis during the trial was 7.3 cases per 100 person-years. The incidence did not differ between the PrEP and placebo arms.
There were 129 incident HIV infections. There were 2.8 cases per 100 person-years among patients without incident syphilis and eight cases per 100 person-years among patients without syphilis (HR=2.6; 95% CI, 1.6-4.4). The researchers found no interaction between syphilis and randomization to the PrEP arm on HIV incidence.
“PrEP uptake has been slow due to lack of provider familiarity and comfort with prescribing ART and a heightened concern about risk compensation despite evidence showing that it did not occur in the iPrEx study and other large PrEP trials,” Solomon said. “We hope that these data will trigger physicians to offer PrEP to MSM with a new diagnosis of syphilis, unless there are contraindications present.”
Solomon said that future research will continue to evaluate novel approaches to HIV prevention, including additional strategies for PrEP delivery that can be offered to individuals who find it challenging to take pills regularly. — by Emily Shafer
Disclosure: The researchers report no relevant financial disclosures.
Perspective
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Edward Hook III, MD
This study converges with the changing epidemiology of syphilis in developed nations. We know that syphilis lesions facilitate the risk for acquiring HIV. This occurs in several ways. First is the behaviors: the behaviors that lead syphilis infection are similar to those lead to HIV infection. But, more importantly, syphilis acts biologically to enhance the risk for HIV. The way the host responds to syphilis lesions represents a portal of entry for HIV. These lesions typically have many CD4 lymphocytes, the target cells of HIV, present in the base of the lesions. When people with syphilis are sexually exposed to HIV, they have this whole target area of readily accessible, easily infected CD4 lymphocytes (the syphilis lesion), thereby increasing the risk of acquiring HIV.
This relationship is something that people have realized for more than 20 years, but showing its presence and importance in a prospective study, as opposed to case reviews and retrospective studies, adds an important degree of rigor to our understanding of this process. It also reaffirms important point that sexually-transmitted infection control is a mechanism for HIV prevention. People with STIs, syphilis and otherwise, are at increased risk for HIV. If we can reduce the STI rate, we can put the brakes on the HIV epidemic. We know that persons who don’t have STIs can also get HIV. But we know that the presence of coexisting STIs accelerates and enhances that risk for infection.
We are now in an era where there are many ways to prevent HIV. No single measure is sufficient. But if you add up the potential of improved STI control, pre-exposure prophylaxis and post-exposure prophylaxis, and continue to encourage people to choose their partners carefully and practice safe sex with unknown partners, we really can begin to slow this epidemic.
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