Virus linked to infertility

Men with abnormal sperm tested positive for the virus

A virus previously thought to have no ill-effect on human health may have a role in male infertility, German scientists have suggested.

However, they say their work needs to be reproduced by others before the infection is considered a serious threat.

The virus - called adeno-associated virus (AAV) - was found in samples of testicular tissue taken from men whose semen was abnormal.

The virus was found in these men far more frequently than in those with normal semen.

Dr Jorg Schlehofer, from the Deutsches Krebsforschungszentrum in Heidelberg, which conducted the research, said the virus should be assessed further to see whether it is a cause of infertility.

"It raises the issue, for example, of whether sperm cells used in ICSI or other reproductive techniques should be checked for AAV or other viruses prior to fertilisation.

Common virus

"At the least, we think there should be research on the consequences of an infected sperm infecting an 'innocent' egg."

It raises the issue, for example, of whether sperm cells used in ICSI or other reproductive techniques should be checked for AAV or other viruses prior to fertilisation

Dr Jorg Schlehofer, Heidelberg

AAV is a relatively common virus which can often be detected in genital tissues - infection appears to take place when a child is in the womb, during childhood, or young adulthood.

In the German experiments, 73 men with semen abnormalities were tested for traces of AAV.

These were found in 28 of them - compared to only one out of 22 in the group of men with normal semen.

The exact role of the virus is unclear

The researchers also analysed samples taken from the testicles of 38 men taking part in fertility treatment because their semen contained no sperm.

Ten of these contained traces of AAV.

While this research raises the possibility that AAV might play a role in infertility, it certainly does not prove it.

It is possible that the presence of AAV may simply be a separate result of the underlying defect causing the subfertility.

'Confirmation needed'

Dr Simon Fishel, a fertility expert who runs the Care clinic in Nottingham, said that scientists investigating infertility in men had found many "links" such as these over the years, although no further supporting evidence had been uncovered subsequently.

He told BBC News Online: "It's an interesting paper, but it doesn't yet show that this virus has a role."

Any suspicion of a more sinister role for AAV - could be of interest to many groups working on ways of carrying out gene therapy on humans.

These scientists use viruses to carry modified genes into human cells, and one prime candidate is AAV, as it is thought to cause no disease - and does not provoke any reaction from the immune system.

Any stronger evidence of AAV as a factor in male subfertility may be of crucial importance to the safety of their techniques.