Sperm - CMV Interactions: Implications for sperm donor recruitment

Human Cytomegalovirus (CMV) is a common herpesvirus found in 60% of the population. Normally, it poses no risk, however it can have consequences for unborn babies. This is of concern when donor sperm is used in assisted conception, as CMV is present in semen. The risk of transmission from a positive donor is unclear, as it is not known if sperm can act as a vector for transmission. Additionally, this raises questions about whether CMV might affect sperm function. The hypothesis for this study is that CMV will interact with human sperm and alter sperm function and that sperm will act as a vector for viral transmission. A survey was conducted to examine how fertility clinics were screening for CMV in sperm donors. This survey found that the majority of UK clinics are screening for CMV in sperm donors in the manner recommended by current guidelines but that the requirement to screen for CMV is causing problems in clinics with regards to sperm donor supply. Fortunately, this thesis has shown that sperm washing by density gradient centrifugation is mostly effective at removing CMV from semen samples infected in vitro, with CMV (AD169) grown in the laboratory, and in naturally infected samples. This presents a possible approach for alleviating some of the problems relating to CMV infection in sperm donors in UK fertility clinics. However, co-incubation with CMV has no effect on any of the sperm function parameters tested in this thesis, including, motility, viability, acrosome reaction, tyrosine phosphorylation and levels of DNA damage. In conclusion, this thesis has highlighted problems with the current approach to screening and managing CMV infection in sperm donors but has provided evidence to show that there could be a simple solution to the problem. No effect on sperm function was observed, but this does not rule out a direct interaction between CMV and sperm. Overall, this thesis shows that fertility clinics should be concerned about CMV infection in sperm donors, but that simple steps could be taken to alleviate the current problems clinics are experiencing.