China News Service, Beijing, March 26 (Reporter Sun Zifa) A newly published virology research paper in Springer Nature's professional academic journal "Nature Microbiology" shows that extracellular vesicles found in semen and saliva ( A molecule on the surface of EVs can block infection by viruses such as Zika or dengue viruses. The findings help understand why direct human-to-human transmission of these viruses is low and why they are easily spread through body fluids that lack this molecule (such as blood) or through blood-sucking insects.

　　The paper explains that viruses such as dengue, Zika, chikungunya, Ebola or Lassa can infect many cell types. However, although these viruses are present in various body fluids (including semen and saliva), oral or sexual transmission routes are clearly limited. Previous studies have shown that EVs contained in semen and saliva can competitively block Zika virus binding to target cells and inhibit infection in laboratory experiments. However, the specific mechanism behind this has been unclear.

　　The corresponding author of the paper, Janis A. Müller of the University of Marburg-Philippines in Germany, together with colleagues and collaborators, isolated EVs from five different human body fluids, including semen, saliva, urine, breast milk and blood. They found that a molecule called phosphatidylserine (PS) was more common on the EV surface of semen than on the EV surface of blood. In laboratory experiments, it was found that PS on the EV surface can block Zika virus infection of cells because these EVs compete for the same PS receptors and interfere with virus attachment and invasion. Dengue, West Nile, Chikungunya, Ebola and herpetic stomatitis virus infections are all suppressed if EV concentrations similar to those found in vivo are achieved.

　　However, HIV, hepatitis C virus (HCV), severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), and herpes viruses are not inhibited because they use other invasion receptors. When the researchers used enzymes to "shave" the PS off the EVs, their effectiveness in blocking infection disappeared.

　　The authors concluded that their findings could be used to develop new antiviral drugs, but further research is needed. (over)