Cytomegalovirus (CMV) is More Common in Semen Than Generally Thought, According to a New Study

Cytomegalovirus (CMV) is more common in semen than generally thought, according to a new study by Bedford Research Foundation scientists.

CMV is a common herpes virus that causes a minor disease in children and adults, but can also infect fetuses in utero and causes permanent problems in 1 out of 750 children born in the U.S.

In the February issue of Fertility and Sterility, the official journal of the American Society for Reproductive Medicine (ASRM), Bedford Research scientists report two surprising findings: First, nearly half (45%) of the semen specimens from 68 men without and with HIV co-infection had detectable CMV, including specimens from two men who initially tested negative for antibody against CMV in their blood. Second, men with even mild suppression of their immune system were twice as likely (57%) to have CMV in their semen as men with normal immunity (28%).

The first finding calls into question the ASRM guidelines for sperm banks based on the notion that CMV antibody-positive men are “…at low risk for shedding virus into semen” and the second finding calls into question one of the guidelines for starting HIV infected men on antiretroviral therapy, which is to wait until there is evidence of suppression of their immune system. HIV infects an important cell in the immune system termed “CD4+ T-Cell” and causes them to die. A common guideline for starting anti-retroviral therapy is when the number of CD4+T-Cells has decreased to 500/ul of blood. Bedford Research scientists discovered a sharp increase in CMV in semen from men whose CD4+T-cells had fallen to 700/ul of blood, suggesting a new benchmark for immune suppression and initiating antiretroviral therapy.

CMV is a common human infection, usually occurring in childhood, as a mild disease with minor symptoms. Approximately 60% of the U.S. population has antibody against CMV in their bloodstream, which has historically been thought to confer immunity to new CMV infection. Therefore, women testing positive for CMV antibody before pregnancy have been considered not at risk for a new CMV infection that could be transmitted to their developing fetus during pregnancy. And men testing positive for prior CMV infection were considered to be at low risk of having CMV in their semen.

More recent studies from other investigators have shed doubt on these assumptions. Reappearance of serious CMV infections in organ transplant recipients has spurred efforts to develop a protective vaccine against CMV.  Results to date have revealed vaccination is only partially protective. Moreover, whereas CMV is transmitted to the fetuses of 40% of women newly infected during early pregnancy, women testing positive for CMV before pregnancy, or that received the CMV vaccine, still developed new CMV infections that were transmitted to up to 2% of their fetuses. Therefore, anti-CMV antibodies, either following infection or vaccination, only partially protect against new CMV infection.

The results reported by Bedford Research scientists this month confirm and extend recent reports from CMV-screening studies conducted in Europe on semen specimens in sperm banks. Bedford Research scientists detected CMV in nearly half of semen specimens from a cohort of gay men who were selected for the study because gay men are more uniformly positive (>90%) for antibody to CMV in their blood than the general population (ca 60%). Taken together, the data suggest that the assumption that men testing positive for CMV antibody in their blood are at low risk for CMV in their semen is in error, the actual risk is somewhere between 5% and 50%. Moreover, women testing positive for CMV antibody in their blood are not fully immune against a new CMV infection that could be transmitted to their fetus during early pregnancy.

According to Dr. Ann Kiessling, Bedford Research Foundation Director, “Our new report impacts two areas of clinical care, antiretroviral therapy decisions, and infertility treatment. The appearance of CMV in the semen of HIV infected men with fewer than 700 CD4+T-Cells/ul blood may be a useful new benchmark for initiation of anti-retroviral therapy. Secondly, there is an urgent need for larger studies of semen CMV, including sperm bank specimens, to establish risks of CMV transmission to women seeking pregnancy, including gestational carriers who are otherwise not exposed to the sperm donor.

Dr. Robert Kaufmann, a reproductive endocrinologist at Fort Worth Fertility in Fort Worth, TX says: “The recent paper by the Bedford Research Foundation may have a significant impact on the way we consider using donor sperm and embryos being placed into surrogates. Until now most physicians in the US have used donor specimens positive for CMV in both patients that were CMV positive and in some cases CMV negative. Given the findings in this study I think physicians reevaluate these recommendations. As physicians our job is to protect our patients in a responsible manner. Hopefully, our guideline from the American Society for Reproductive Medicine regarding use of sperm from sperm banks that are CMV positive will be updated given this information as the French did given the existing information even in the 1990’s.”

Bedford Research Foundation is a not for profit research institute currently developing stem cell therapy approaches to incurable diseases such as HIV/AIDS, spinal cord injury, Parkinson’s disease, and diabetes.

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