Men infected with the high-risk form of the virus that causes cervical cancer (HPV) have been found to have higher levels of dead sperm, negatively affecting their fertility, according to a new study.
Human papillomavirus (HPV), a sexually transmitted infection, includes high-risk and low-risk viruses. While the former are known to pose a high risk for developing cancers, the latter are known to cause largely benign warts or spots, researchers explained in the study published in the journal Frontiers in Cellular and Infection Microbiology.
The researchers from Argentina, including those from the National University of Cordoba, examined the quality of the sperm of 205 adult men.
About a fifth of them, or 39, tested positive for HPV – 20 had the high-risk form of the virus, seven had the low-risk form, and the team could not determine whether 12 were high-risk or low-risk. The 39 HPV-positive men were compared with 43 HPV-negative men.
While the semen quality of the men in these groups did not differ, upon closer inspection the researchers found that the samples from the men infected with the high-risk virus contained significantly lower numbers of immune cells known to help fight the infection – white blood cells (CD45).
Lead author Virginia Rivero explained that the lower number of immune cells in these samples was due to HPV's known ability to evade an immune response.
This would result in fewer white blood cells migrating to the site of HPV infection, thereby compromising their ability to fight the infection, said Rivero, a professor at the National University of Córdoba.
The researchers also found evidence that the sperm of men infected with the high-risk version of HPV may be repeatedly damaged due to oxidative stress, as judged by the increased production of reactive oxygen species (ROS) in these men.
While low ROS levels are a consequence of normal sperm function, elevated levels can lead to damage to the cell outer shell, breaks in genetic material and cell death.
In line with this, the researchers found that HPV-positive men infected with the high-risk virus had more dead sperm.
“… a higher frequency of ROS-killed sperm was observed in HR-HPV-infected individuals than in individuals infected with LR-HPV genotypes,” the authors wrote.
“We concluded that men infected with high-risk HPV, but not men infected with low-risk HPV, have increased sperm death due to oxidative stress and a weakened local immune response in the urogenital tract,” Rivero said.
The results suggested that men infected with the high-risk form of the virus may have reduced fertility, Rivero said.
The high-risk form of HPV can be detected in almost all cervical cancers in women and in a high number of anal, genital, oral and throat cancers in women and men, the authors explained.
The low-risk form of HPV is typically found in abnormal but benign cells in the cervix of women and in warts on the surface of the larynx and genitals of men and women, but does not cause cancer, it said.