Novel Defense Mechanism Against Zika and Dengue Viruses
GS PAPER 3
SCIENCE AND TECHNOLOGY
- Understanding Viral Transmission: The presence of viruses in bodily fluids doesn't necessarily mean transmission through those routes, puzzling scientists for years.
- Challenges in Studying Viral Transmission: The complexity of viral transmission is highlighted by examples like the misinformed tweet from WHO regarding COVID-19 being airborne, emphasizing the difficulties in understanding how viruses spread.
- Viral Tropism and Receptors: Viruses infect specific cells through receptors on their surface; for example, HIV targets cells expressing the CD4 protein, while SARS-CoV-2 uses the ACE2 receptor.
- The Role of PS Receptor: Viruses like Zika and others exploit the phosphatidyl serine (PS) receptor, typically expressed by dying cells, to gain entry into host cells, a process known as apoptotic mimicry.
- Defense Mechanism Using Extracellular Vesicles: Researchers discovered that extracellular vesicles abundant in bodily fluids like saliva and semen contain PS proteins on their surface, competing with viruses for entry receptors.
- Inhibition of Viral Infection: Through experiments, it was demonstrated that these PS-containing vesicles can effectively inhibit viruses that utilize the PS receptor for entry, including dengue, chikungunya, and others.
- Specificity of Defense Mechanism: The presence of these vesicles doesn't affect the infectivity of viruses like HIV and SARS-CoV-2, which don't use the PS receptor for entry.
- Implications and Further Research: While the therapeutic implications of this discovery are yet to be fully understood, it opens avenues for further exploration into novel host defense mechanisms against viral infections.
- Potential Evolutionary Impact: There's speculation that the presence of PS-containing vesicles in humans might have influenced the evolution of mosquito-borne viruses, leading to alternative transmission routes.