Feature story

Overview of this year’s Conference on Retroviruses and Opportunistic Infections (CROI)

18 February 2008

15th Conference on Retroviruses
and Opportunistic Infections took place in
Boston 4-6 February 2008. Credit: CROI

The annual Conference on Retroviruses and Opportunistic Infections (CROI) began in 1994 as a small meeting of scientists studying HIV and clinicians treating people with HIV. It is now one of the most important annual HIV gatherings and provides a forum for basic scientists, clinical investigators, and global health researchers to present, discuss, and critique their investigations into the epidemiology and biology of human retroviruses and the diseases they produce.

The 15th CROI concluded in Boston on 6 February and while announced trial results were not encouraging, many significant topics were discussed. The absence of a scientific breakthrough in HIV vaccine development underscores the need to scale-up existing prevention and treatment strategies.

HSV-2 trial - No observed reduction in risk

Disappointing results were announced from trials to see if ongoing treatment of the virus that causes herpes in humans, herpes simplex virus type 2 (HSV-2), would reduce the risk of HIV transmission. HIV-negative people with HSV-2 were asked to take medication to suppress outbreaks of herpes. However, the trial results showed no difference in rates of HIV infection between individuals who had taken the medication and those who hadn’t.

Scientific data shows a link between HSV-2 infection and susceptibility to acquiring HIV infection and there are other on-going trials exploring different aspects of this link, so researchers remain cautiously hopeful about this avenue of research.

Male circumcision

Previously-released data from the studies of male circumcision in Uganda which were stopped in December 2006 were presented by trial investigator Maria Wawer. One trial explored whether circumcising a HIV-positive man reduced the risk of HIV transmission to his HIV-negative female partner. Results showed a trend towards increased HIV transmission from men to their female partners. This trend was more notable, although still not statistically significant, when the men resumed sex before their wound had healed completely.

While this data is not new, its presentation at CROI gave an opportunity for discussion and analysis of its implications. Advocates stressed the necessity for all male circumcision programmes to directly address women’s increased vulnerability to infection by sex with a recently-circumcised, HIV-positive man.

UNAIDS Chief Scientific Adviser Dr Catherine Hankins said, “This underlines the importance of considering male circumcision as part of a comprehensive prevention package which includes couple counselling and post-surgery advice involving both partners. Couples should consider a mutual commitment to abstinence until the wound is healed completely.”

UNAIDS guidelines recommend that all men undergoing male circumcision should be clearly instructed and supported to abstain from sexual intercourse until certified wound healing, which normally can take up to six weeks, to avoid increasing the risk of both acquiring and transmitting HIV.

Most importantly, individuals must understand that male circumcision does not afford complete protection against HIV infection and that it must not replace other prevention strategies such as correct and consistent use of male and female condoms, reduction in the number of sexual partners, avoidance of penetration, and treatment of sexually transmitted infections.


Last September there was a disappointing failure in Merck’s adenovirus- based HIV vaccine candidate. The consensus from experts at CROI was that it was important for scientists to go back to the drawing board of basic science to get a better understanding of the workings of the virus and the responses of the human immune system. There was a call for increased investment into basic scientific research and less emphasis on expensive clinical trials, although clearly both are needed.

There is a growing acceptance that the search for the elusive HIV vaccine is set to continue for some time. This underscores the need to scale-up existing prevention and treatment strategies and highlights the importance of improving people’s access to sexual health information, access to HIV testing and counselling services and to male and female condoms.

Other interesting topics under discussion at CROI included improved screening for TB, ensuring adequate representation of women in HIV trials, aging and AIDS, and paediatric and adolescent HIV care.