Deciphering the Enigma of Viral Transmission: A Breakthrough in Host Defense

Deciphering the Enigma of Viral Transmission: A Breakthrough in Host Defense


Recent research has revealed a new way that our bodies fight against certain viruses like Zika, dengue, and chikungunya.

  • These viruses are typically found in bodily fluids but don’t spread in the usual way from one person to another.

GS-03 (Science and technology)

What is the Issue?

  • Understanding viral transmission is critical for combating infectious diseases. But for viruses that do not follow conventional transmission pathways, it is difficulty.
  • For instance, like the Zika virus, despite being present in bodily fluids like saliva and semen, primarily spreads through mosquito bites.

Zika Virus:

  • The Zika virus, like several other pathogens, utilizes unique receptors on host cells for entry and infection.
  • One such receptor is phosphatidyl serine (PS), typically expressed by dying cells as a signal for immune clearance.
  • Viruses exploit this pathway by mimicking PS on their surfaces, allowing them to infect unsuspecting host cells.

New Type of Host Defense Against Zika:

  • Recent research conducted at the Institute of Molecular Virology at Ulm University Medical Centre, Germany, has uncovered a novel defense mechanism against Zika and related viruses.
  • Published in Nature Microbiology, the study elucidates how the human body employs extracellular vesicles to impede viral transmission via non-conventional routes.
  • Extracellular vesicles, small structures released by cells, were found to contain PS proteins on their surfaces, akin to those exploited by viruses for entry.
  • Importantly, these vesicles were abundant in bodily fluids like saliva and semen, where viral transmission occurs.
  • Through experiments, researchers demonstrated that PS-containing vesicles compete with viruses for entry receptors, effectively blocking viral infection.

Implications of the Discovery:

  • The significance of this discovery extends beyond Zika virus to encompass other pathogens that utilize the PS receptor for entry, including dengue, chikungunya, and Ebola viruses.
  • By elucidating a new avenue of host defense, this research opens doors for potential therapeutic interventions against a range of infectious diseases.
  • While the immediate therapeutic implications of this discovery remain uncertain, it offers promising prospects for future research.
  • Further investigation into the role of extracellular vesicles in immune defense may uncover novel strategies for combating viral infections and inform the development of targeted therapies.

About Viruses:

  • Viruses, unlike living organisms, are unique entities that straddle the boundary between the living and non-living world.
  • They consist of genetic material enclosed in a protein coat called capsid.
  • Their genome is either a RNA or a DNA.
  • Despite their reproductive capabilities, viruses cannot survive outside a host cell and lack essential cellular components like ribosomes. Instead, they rely on host cells for protein synthesis and energy production.

Structure of Virus:

  • A virus is essentially genetic material surrounded by either a protein shell, called a capsid, or by a membrane, called an envelope.
  • This envelope is made of lipids (fat or fat-like substances that can be broken down by soap and other detergents) derived from the host cell and proteins.
  • Viruses that infect bacteria are called bacteriophages.
  • These can have elaborate structures, such as tail fibers, that allow the virus to attach to cells and inject genetic material.

Difference between Virus and Bacteria:

  • In comparison to bacteria, viruses are acellular and much smaller in size. While bacteria are unicellular organisms with a defined cellular structure, viruses lack cellular components and rely on host cells for replication.
  • Viruses are responsible for a range of diseases, including COVID-19, influenza, HIV, and smallpox, while bacteria cause illnesses such as tuberculosis, pneumonia, and tetanus. Despite their differences, both viruses and bacteria play significant roles in human health and disease.