Title: Biomarkers of semen exposure: Applications in Trials of HIV/STI Prevention
Authors: Mauck CK,1 Doncel GF2
1CONRAD, Eastern Virginia Medical School (EVMS), Arlington, VA, USA
2CONRAD, EVMS, Norfolk, VA, USA
Issues: Biomarkers can be useful in HIV/STI prevention in several settings: 1) in effectiveness trials of new microbicides, biomarkers can give evidence of unprotected intercourse and condom disinhibition among women who have been advised to use condoms; 2) in early microbicide safety studies in which women have been advised to refrain from intercourse in order to avoid the confounding effects of sex, biomarkers can give evidence of unprotected intercourse; and 3) in early studies of mechanical barriers such as condoms and cervical barriers, biomarkers can give evidence of whether the barrier has been breached by semen. Existing biomarkers, such as Prostate Specific Antigen (PSA) have been studied and are promising but have certain drawbacks including insufficient sensitivity in some circumstances. Better characterized existing biomarkers and new biomarkers could help assess compliance in clinical trials and allow faster triage of products early in development.
Descripion: Following a meeting on semen biomarkers convened by CONRAD, Ibis, and NIH in June 2004 which brought together experts in the field, a working group has been meeting bimonthly by teleconference. The group is outlining characteristics of an ideal biomarker, studying approaches to using biomarkers to measure protocol compliance, assisting in the interpretation of results of completed studies, standardizing collection techniques for upcoming studies, and identifying gaps in knowledge that could be addressed by new clinical studies.
Conclusion: A manuscript that reviews the field has been prepared. Several studies are already being conducted as a direct result of the group's discussions, including a study to assess whether microbicide candidates interfere with assays for PSA, and a study comparing rocket immunoelectrophoresis with an immunoassay test for PSA. It may be possible to design surrogate biomarkers of HIV itself that may be combined with semen biomarkers to assess chemical/mechanical barrier efficacy and protocol compliance. The development of surrogate biomarkers of semen exposure will be a significant contribution to microbicide and physical barrier developmental strategies in the near future.
This work was supported by CONRAD with funding provided by USAID and NIH.
