Treating STIs – does it work to reduce HIV transmission?

Published: 07 April 2009

Due to the associations between STIs and HIV risk, there is a clear and plausible argument that successfully treating STIs should result in reduced risk of HIV infection. However, studies of this strategy have produced largely disappointing results thus far.1

Studies have predominantly focused on treating HSV-2 infection. Studies have looked at two outcomes: the effects of antiviral treatment for HSV-2 (aciclovir and valaciclovir) on genital shedding of HIV and HSV-2, and the effects of treatment on HIV transmission rates.

In men and women who are not on antiretroviral treatment, treating HSV-2 has generally decreased the amount and/or frequency of HIV shed from the genitals or from herpes lesions,2 3 4 although some studies have shown mixed results.5 Some studies have found that suppressive treatment with valaciclovir significantly reduced HSV-2 genital shedding,6 but larger studies using aciclovir7 8 found mixed results.

The key question, however, is whether HSV-2 treatment has actually lowered HIV incidence rates. It has failed to do so in most clinical trials,9 10 including the largest such trial so far, which studied nearly 1400 African women and over 1800 North and South American MSM.8 The reasons are not clearly understood, but may include poor adherence, too low a dose of aciclovir, or the direct effect of aciclovir on HIV levels being too modest to have a significant impact on HIV transmission.

Other studies have looked at treating STIs other than HSV-2. Treating bacterial STIs such as gonorrhoea and chlamydia has been found to reduce genital HIV shedding, making a theoretical argument for reduced infectiousness.11

References

  1. Kaul R et al. The genital tract immune milieu: an important determinant of HIV susceptibility and secondary transmission. Journal of Reproductive Immunology 77: 32-40, 2008
  2. Nagot N et al. Reduction of HIV-1 RNA levels with therapy to suppress herpes simplex virus. N Engl J Med 356: 790-799, 2007
  3. Paz-Bailey G et al. Improvement in healing and reduction on HIV shedding following addition of episodic acyclovir therapy to the syndromic management of genital ulceration: a randomized controlled trial. Seventeenth International AIDS Conference, Mexico City, abstract MOAX0103, 2008
  4. Zuckerman RA et al. Herpes simplex virus (HSV) suppression with valaciclovir reduces rectal and blood plasma HIV-1 levels in HIV-1/HSV-2-seropositive men: a randomised, double blind, placebo-controlled crossover trial. J Infect Dis 196: 1500-1508, 2007
  5. Phiri S et al. Impact of acyclovir on ulcer healing and HIV-1 lesional and genital shedding among patients with genital ulcer disease in Malawi: a randomised controlled trial. Seventeenth International AIDS Conference, Mexico City, abstract THAC0303, 2008
  6. Baeten J et al. Herpes simplex virus suppressive treatment decreases plasma and genital HIV-1 viral loads in HSV-2/HIV-1 co-infected women: a randomized, placebo-controlled, cross-over trial. Fifteenth Conference on Retroviruses and Opportunistic Infections, Boston, abstract 676, 2008
  7. Tanton C et al. A randomized controlled trial in Tanzania to assess the impact of HSV-2 suppressive therapy on genital HIV viral load among HSV-2 and HIV-1 seropositive women. Fourth International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention, abstract TUPEC011, Sydney, 2007
  8. Sanchez J et al. Incidence of genital ulcers and HSV+ genital ulcers in trial of HSV-2 suppression to prevent HIV acquisition (HPTN 039). Seventeenth International AIDS Conference, Mexico City, abstract THAC0302, 2008
  9. Watson-Jones D et al. Impact of HSV-2 suppressive therapy on HIV incidence in HSV-2 seropositive women: a randomised controlled trial in Tanzania. Fourth International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention, abstract MOAC104, Sydney, 2007
  10. Celum C et al. HSV-2 suppressive therapy for prevention of HIV acquisition: results of HPTN 039. Fifteenth Conference on Retroviruses and Opportunistic Infections, Boston, abstract 32LB, 2008
  11. McClelland RS and Baeten JM Reducing HIV-1 transmission through prevention strategies targeting HIV-1-seropositive individuals. J Antimicrob Chemo 57:163-166, 2006
This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.
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This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.