Human sperm inhibits Zika, Dengue and West Nile viruses
In a man infected with Zika viruses, the sperm contains up to a hundred million Zika viruses. Nevertheless, the risk of sexual transmission is relatively low. The virus is transmitted by mosquitoes in most cases. An international team of researchers investigated why Zika cannot be transmitted so well via sperm and found that certain substances in the sperm inhibit the Zika virus. So-called vesicles are responsible for the effect. These are small bubbles surrounded by a membrane. They make it difficult for viruses to dock onto other cells.
These results come from a current study by the research team led by virologist Professor Jan Münch from the University of Ulm. In previous work, sperm had already been noticed due to its antimicrobial effect. The scientists have now clarified how the seminal fluid inhibits the Zika virus and which biochemical components are responsible for these effects. The study results were recently published in the journal "Nature Communications".
Sperm as a natural protection against Zika
"We were very surprised when we found that the sperm inhibits the Zika virus infection and not - as with HIV-1 - does not increase it even further," explains the lead author of the study, Dr. Janis Müller in a press release on the study results. The researchers showed that the viruses were less able to spread through the sperm both in the vaginal and anal tract and in the uterus.
Sperm affects the transferability of sexual diseases
"The semen is rich in bioactive substances," reports Sudienleiter Münch. These include, for example, proteins, enzymes, cytokines, hormones and ions. These can affect the vaginal milieu, which in turn affects the transferability of sexual diseases. With HIV viruses, the risk of transmission from sperm increases, with Zika viruses, it decreases.
Where does the protective effect against Zika, Dengue and West Nile viruses come from?
"Extracellular vesicles, which are present in large numbers in the sperm, reduce the attachment of the viruses to the cells and thus prevent the infection," explains Münch. The vesicles are vesicular particles that are abundant in the sperm. You are responsible for the storage and transport of certain substances at the cellular level. The same protective effect was also found in dengue and West Nile viruses, which can cause dangerous tropical diseases. The findings can be used to explain why, despite large amounts of virus particles in the sperm, sexual transmission of Zika rarely occurs, the researchers said.
Do not do without condoms
Even though sperm may offer some protection against these diseases, the researchers warn that they should not do without condoms. Anyone traveling to Zika danger zones should protect themselves against mosquitoes and use a condom during sex. Not least because numerous other sexual diseases such as HIV can also be transmitted through unprotected sexual intercourse.
Protection against mosquito bites
The Aedes mosquito is the number one infection spreader for Zika, Dengue and West Nile viruses. Recent studies by another research group have shown that this type of mosquito is increasingly spreading in Europe and that tropical diseases such as yellow fever, dengue and zika will soon also be conceivable in Germany.
The Zika virus is particularly common in countries in Central and South America and on the Pacific Islands. Infection is usually not fatal, but it can cause severe cases of meningitis. Pregnant women in particular have to beware of the virus because the infection is linked to skull malformations. For example, unborn babies can be affected by microcephaly, in which the embryos develop a very small head. (vb)