VIROLOGY

Virology Introduction

Morphology of Virus

• Definition: Virus is a submicroscopic infectious agent consisting of a nucleic acid (either DNA or RNA) surrounded by a protein coat called capsid.
• Structure:
  • Nucleocapsid: Made of protein and encloses the genetic material.
  • Envelope: Lipid layer derived from host cell membrane, some viruses have it.
• Types of viruses:
  • Helical: Tobacco mosaic virus
  • Icosahedral: Poliovirus
  • Complex: HIV
  • Filamentous: HIV

Viral Replication

• Step 1: Attachment → Virus binds to host cell receptors.

• Step 2: Penetration → Virus enters host cell through either fusion or endocytosis.

• Step 3: Uncoating → Viral capsid is removed.

• Step 4: Replication → Viral DNA or RNA is replicated inside host cell.

• Step 5: Transcription → Genetic material is transcribed into mRNA.

• Step 6: Translation → mRNA is translated into viral proteins.

• Step 7: Assembly → New viral particles are assembled.

• Step 8: Release → New viral particles are released from host cell.

• Rhyming memory trick: "Adequate parents punish only the rude."

Viral Inclusion Bodies

• Definition: Accumulations of viral proteins or genetic material within host cell.
• Types:
  • Amyloid bodies
  • Basophilic bodies
  • Basophilic intranuclear bodies
  • Basophilic intracytoplasmic bodies
  • Cowdry A bodies
  • Cowdry B bodies
  • Heterophile inclusions
  • Intranuclear inclusions
  • Intracytoplasmic inclusions
  • Lipofuscin

Pathogenesis of Viral Infections

• Pathogenesis is the process by which a virus causes disease in a host.
• Factors influencing pathogenesis:
  • Viral load
  • Virulence of the virus
  • Immune status of the host
  • Genetic factors of the host

Lab Diagnosis of Viral Infections

• Cultivation of viruses: Inoculation of tissue culture or cell lines with clinical specimens.
• Serological tests: Detecting antibodies or antigens using various methods.
• Molecular biology techniques: PCR, sequencing, etc.

Classification of Viruses

• Based on type of nucleic acid:
  • DNA viruses
  • RNA viruses
• Based on host range:
  • Animal viruses
  • Plant viruses
• Based on mode of transmission:
  • Airborne viruses
  • Arthropod-borne viruses
  • Contact viruses
  • Droplet viruses
  • Fecal-oral viruses
  • Food and waterborne viruses
  • Vector-borne viruses

Virus Host Interactions and its Significance in Homoeopathy

• Definition: Interaction between virus and host cell.
• Importance in homoeopathy:
  • To understand the pathogenesis of viral infections.
  • To select suitable remedies.

Bacteriophages

• Definition: Viruses that infect bacteria.

• Morphology:

  • Head: Protein coat containing genetic material.
  • Tail: Fiber structure used for attachment and penetration.

• Types:

  • T2 phage: Has a long tail and a head.
  • T4 phage: Has a short tail and a head.

• Significance in medical microbiology:

  • Used as indicators of water quality.
  • Used as tools for gene therapy.
  • Used as anti-bacterial agents.

• Rhyming memory trick for bacteriophage morphology: "Head is like a helmet, tail is like a feather."