Claflin University ,Usa
Study Qustion: What is the mechanism of sexual transmission of Zika Virus?
Summary Answer: By utilizing exquisite reverse-transcriptase-initiated in situ PCR (RT-in situ PCR), which enables an improved visualization of spermatozoa’s subcellular compartments; we precisely localized the mid-piece of sperm that carry receptors for Zikv.
What is already known: Zikv is transmitted sexually and recent studies have verified Zikv presence in semen of previously Zika-infected patients for more than 6-months post-infection when Zikv had disappeared from blood, saliva and urine. Strong serial analyses of various body fluids suggest that Zikv can be transmitted between sexual partners. Currently, there is limited information on the association of the virus with human semen cell types that may carry the virus.
Study design, size, duration: Analyses were carried out to localize Zikv for subcellular localization of Zikv on cell types. The Tyro3 receptor for Zikv was co-localized by dual immunocytochemistry with specific monoclonal antibodies.
Participants/Materials, setting, Methods: Three semen specimens were purchased from a commercial sperm bank. Motile sperm was separated from non-motile cells by the ‘swim up’ technique. Each of the semen fractions was infected with Zikv at the multiplicity of infection (moi) of 0.1.0 and 1.0 and evaluated for the primary targets of Zikv in the semen cells by RT-in situ PCR and confirmed by real time RT-PCR.
Main results and the role of chance: Zikv was present primarily at the mid-piece of mature spermatozoa in about 30% of the sperm. In addition, we determined that Tyro3 receptors, primarily expressed on mid-piece of human spermatozoa, play a role in Zikv binding and entry into spermatozoa, Conclusions: Our data strongly suggest a potential sexual/horizontal route of transmission for Zikv primarily via infected sperms; most likely Zikv enters the sperm via the Tyro3 receptor found at the mid-piece of the mature spermatozoa.
Limations, reasons for Caution: We are uncertain as to what phase of spermatogenesis, that in human takes about 120 days, sperms are permissive to Zikv. If permissiveness was very early during spermatogenesis males could be infectious for ~120 days after the disappearance of viremia in an infected man.
Wider Implication of the findings: Our findings bring a new focus on the current affords to develop Zikv vaccine. Why in the presence of anti-Zikv Abs infected men are still able to transmit the virus sexually? We suggest that only certain subclass of IgG (i.e., IgG4) can cross the blood-Sertoli barrier therefore, a successful vaccine must provoke a subclass of IgG can quell Zikv inside the seminiferous tubules.
Study funding/competing interest:These studies were not funded by any governmental or private funding. The authors declare that there are no conflicts of interest.