Write a brief account of the different types of cytopathic effects you have studied. List the cell types used for virus culture. Explain virus culture methods that involve the use of cell lines and animal models.

Biology
Write a brief account of the different types of cytopathic effects you have studied. List the cell types used for virus culture. Explain virus culture methods that involve the use of cell lines and animal models.

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mRNA (e.g., SARS-CoV-2).

Section A

1a. Different types of cytopathic effects (CPE):

Step 1: Cell rounding and detachment – Cells shrink, become rounded, and detach from monolayer (e.g., enteroviruses like coxsackievirus).

Step 2: Syncytium formation – Fusion of infected cells forming multinucleated giant cells (e.g., respiratory syncytial virus (RSV), herpes simplex virus (HSV)).

Step 3: Inclusion bodies – Intranuclear or cytoplasmic inclusions (e.g., nuclear in CMV, cytoplasmic in rabies).

Step 4: Cell lysis and ballooning – Cells swell and lyse (e.g., poliovirus).

Step 5: No CPE or minimal – Some viruses require assays (e.g., hepatitis viruses).

1b. Cell types used in virus isolation:

  • Primary monkey kidney cells (PMK)
  • Vero cells (African green monkey kidney)
  • Human diploid fibroblasts (MRC-5, WI-38)
  • HEp-2 cells
  • MDCK cells (for influenza)

2. Serological methods of virus identification:

Serological methods detect specific antibody-antigen reactions for virus ID.

Step 1: Hemagglutination Inhibition (HI) assay
Virus causes RBC agglutination; specific Ab inhibits.
E.g., measure Ab titer against influenza HA.

Step 2: Complement Fixation (CF) test
Ag + Ab fix complement; indicator lysis absent if positive.
Used for many viruses like varicella.

Step 3: Virus Neutralization (NT) test
Ab prevents virus infection in cell culture; plaques/CPE measured.
Gold standard for specificity (e.g., polio).

Step 4: ELISA (Enzyme-Linked Immunosorbent Assay)
Capture Ag/Ab, enzyme-linked detection. IgM for acute (e.g., dengue).
Indirect: Ab detection; Capture: Ag detection.

Step 5: Immunofluorescence (IF)
Ab with fluorescent dye binds Ag in cells/tissues. Direct/indirect.
Rapid for RSV in nasopharyngeal smears.

Step 6: Western Blot
Confirmatory for HIV (gp120, p24 bands).

Advantages: Specific, no live virus needed. Disadvantages: Time (2-7 days), cross-reactivity.

Section B

3a. Stepwise general overview of viral infection:

Step 1: Attachment – Viral attachment proteins bind host receptors (e.g., SARS-CoV-2 spike to ACE2).

Step 2: Penetration/Entry – Fusion or endocytosis (e.g., HIV CD4/CCR5).

Step 3: Uncoating – Release genome from capsid.

Step 4: Replication – Genome synthesis and protein translation.

Step 5: Assembly – New virions form.

Step 6: Release – Budding or lysis.

3b. Two general factors for successful viral infection:

Factor 1: Host cell receptor availability – Specific receptors determine tropism (e.g., sialic acid for influenza).

Factor 2: Viral enzymes and evasion – Polymerases, proteases; evade IFN (e.g., NS proteins in flaviviruses).

3c. Viral infections causing exanthems and CNS involvement:

Exanthems (3):

  1. Measles (rubeola)
  2. Rubella
  3. Varicella-zoster (chickenpox)

CNS (2):

  1. Poliovirus
  2. Rabies virus

4a. Agents causing viral hepatitis with modes of transmission:

  1. Hepatitis A (HAV): Fecal-oral (contaminated water/food)
  2. Hepatitis B (HBV): Percutaneous (blood, sex), perinatal
  3. Hepatitis C (HCV): Blood (needles, transfusion)
  4. Hepatitis D (HDV): Blood (co/super with HBV)
  5. Hepatitis E (HEV): Fecal-oral (water)
  6. Yellow fever virus: Mosquito
  7. Dengue: Mosquito
  8. CMV/EBV (in immunocompromised): Saliva, transplant

4b. Diagnostic methods for viral hepatitis:

  1. Serology:

    • HAV: Anti-HAV IgM (acute)
    • HBV: HBsAg, anti-HBc IgM, HBeAg
    • HCV: Anti-HCV, HCV-RNA PCR
    • HEV: Anti-HEV IgM

  2. Molecular (PCR): Detect viral RNA/DNA (e.g., HCV RNA quantitative).

  3. Liver biopsy: Histology (ground glass for HBV).

Etiology: HAV/HEV enterovirus-like, fecal-oral; HBV/D DNA RT hepadnavirus, bloodborne; HCV flavivirus RNA.

Section C

5a. Types of viral genomes with examples:

  1. dsDNA: Herpesviruses (HSV)
  2. ssDNA: Parvovirus B19
  3. dsRNA: Reovirus (rotavirus)
  4. (+)ssRNA: Picornavirus (poliovirus)
  5. (-)ssRNA: Rhabdovirus (rabies)
  6. (+)ssRNA-RT: Retrovirus (HIV)
  7. dsDNA-RT: Hepadnavirus (HBV)

Positive-sense RNA: Acts as mRNA, direct translation.
Negative-sense RNA: Complementary to mRNA, requires viral RdRp to transcribe +sense first.

5b (A). Basic structure, three components:

Nucleic acid genome (DNA/RNA).
Protein capsid (protects, icosahedral/helical).
Envelope (lipid bilayer with glycoproteins for attachment/entry; absent in non-enveloped).

Diagram:

Nucleocapsid (genome + capsid)
     |
   Envelope (GPs)

5b (B). Baltimore classification (three examples):

Groups based on genome type/mRNA synthesis:

  1. Group I: dsDNA – Host Pol transcribes mRNA (e.g., adenovirus).
  2. Group IV: (+)ssRNA – Genome = mRNA (e.g., SARS-CoV-2).
  3. Group V: (-)ssRNA – Viral RdRp makes +mRNA (e.g., influenza).

6a. Role of ICTV:

International Committee on Taxonomy of Viruses.
Classifies: Orders, families, genera, species based on genome, structure, replication.
Nomenclature: Binomial (e.g., Orthohantavirus hantaan).
Hierarchical: Realm > Kingdom > ... > Species.
Updates via proposals, publishes reports.

6b. Criteria: Lytic vs. lysogenic cycles (bacteriophages):

Lytic (virulent):

  1. Attachment/injection.
  2. Immediate replication (early/late genes).
  3. Assembly.
  4. Lysis (holin/endolysin).

Lysogenic (temperate):

  1. Attachment/injection.
  2. Circularize/integrate as prophage.
  3. Replicate with host (no lysis).
  4. Induce to lytic (SOS response).
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Quick Answer
  1. Serological methods of virus identification: Serological methods detect specific antibody-antigen reactions for virus ID.
  2. E.g., measure Ab titer against influenza HA.
  3. Used for many viruses like varicella.
  4. Gold standard for specificity (e.g., polio).
Write a brief account of the different types of cytopathic effects you have studied. List the cell types used for virus culture. Explain virus culture methods that involve the use of cell lines and animal models.
Biology

This biology question covers important biological concepts and processes. The step-by-step explanation below helps you understand the underlying mechanisms and reasoning.

ScanSolve AI Answer
Section A 1a. Different types of cytopathic effects (CPE): Step 1: Cell rounding and detachment – Cells shrink, become rounded, and detach from monolayer (e.g., enteroviruses like coxsackievirus). Step 2: Syncytium formation – Fusion of infected cells forming multinucleated giant cells (e.g., respiratory syncytial virus (RSV), herpes simplex virus (HSV)). Step 3: Inclusion bodies – Intranuclear or cytoplasmic inclusions (e.g., nuclear in CMV, cytoplasmic in rabies). Step 4: Cell lysis and ballooning – Cells swell and lyse (e.g., poliovirus). Step 5: No CPE or minimal – Some viruses require assays (e.g., hepatitis viruses). 1b. Cell types used in virus isolation: Primary monkey kidney cells (PMK) Vero cells (African green monkey kidney) Human diploid fibroblasts (MRC-5, WI-38) HEp-2 cells MDCK cells (for influenza) 2. Serological methods of virus identification: Serological methods detect specific antibody-antigen reactions for virus ID. Step 1: Hemagglutination Inhibition (HI) assay Virus causes RBC agglutination; specific Ab inhibits. E.g., measure Ab titer against influenza HA. Step 2: Complement Fixation (CF) test Ag + Ab fix complement; indicator lysis absent if positive. Used for many viruses like varicella. Step 3: Virus Neutralization (NT) test Ab prevents virus infection in cell culture; plaques/CPE measured. Gold standard for specificity (e.g., polio). Step 4: ELISA (Enzyme-Linked Immunosorbent Assay) Capture Ag/Ab, enzyme-linked detection. IgM for acute (e.g., dengue). Indirect: Ab detection; Capture: Ag detection. Step 5: Immunofluorescence (IF) Ab with fluorescent dye binds Ag in cells/tissues. Direct/indirect. Rapid for RSV in nasopharyngeal smears. Step 6: Western Blot Confirmatory for HIV (gp120, p24 bands). Advantages: Specific, no live virus needed. Disadvantages: Time (2-7 days), cross-reactivity. Section B 3a. Stepwise general overview of viral infection: Step 1: Attachment – Viral attachment proteins bind host receptors (e.g., SARS-CoV-2 spike to ACE2). Step 2: Penetration/Entry – Fusion or endocytosis (e.g., HIV CD4/CCR5). Step 3: Uncoating – Release genome from capsid. Step 4: Replication – Genome synthesis and protein translation. Step 5: Assembly – New virions form. Step 6: Release – Budding or lysis. 3b. Two general factors for successful viral infection: Factor 1: Host cell receptor availability – Specific receptors determine tropism (e.g., sialic acid for influenza). Factor 2: Viral enzymes and evasion – Polymerases, proteases; evade IFN (e.g., NS proteins in flaviviruses). 3c. Viral infections causing exanthems and CNS involvement: Exanthems (3): 1. Measles (rubeola) 2. Rubella 3. Varicella-zoster (chickenpox) CNS (2): 1. Poliovirus 2. Rabies virus 4a. Agents causing viral hepatitis with modes of transmission: 1. Hepatitis A (HAV): Fecal-oral (contaminated water/food) 2. Hepatitis B (HBV): Percutaneous (blood, sex), perinatal 3. Hepatitis C (HCV): Blood (needles, transfusion) 4. Hepatitis D (HDV): Blood (co/super with HBV) 5. Hepatitis E (HEV): Fecal-oral (water) 6. Yellow fever virus: Mosquito 7. Dengue: Mosquito 8. CMV/EBV (in immunocompromised): Saliva, transplant 4b. Diagnostic methods for viral hepatitis: 1. Serology: HAV: Anti-HAV IgM (acute) HBV: HBsAg, anti-HBc IgM, HBeAg HCV: Anti-HCV, HCV-RNA PCR HEV: Anti-HEV IgM 2. Molecular (PCR): Detect viral RNA/DNA (e.g., HCV RNA quantitative). 3. Liver biopsy: Histology (ground glass for HBV). Etiology: HAV/HEV enterovirus-like, fecal-oral; HBV/D DNA RT hepadnavirus, bloodborne; HCV flavivirus RNA. Section C 5a. Types of viral genomes with examples: 1. dsDNA: Herpesviruses (HSV) 2. ssDNA: Parvovirus B19 3. dsRNA: Reovirus (rotavirus) 4. (+)ssRNA: Picornavirus (poliovirus) 5. (-)ssRNA: Rhabdovirus (rabies) 6. (+)ssRNA-RT: Retrovirus (HIV) 7. dsDNA-RT: Hepadnavirus (HBV) Positive-sense RNA: Acts as mRNA, direct translation. Negative-sense RNA: Complementary to mRNA, requires viral RdRp to transcribe +sense first. 5b (A). Basic structure, three components: Nucleic acid genome (DNA/RNA). Protein capsid (protects, icosahedral/helical). Envelope (lipid bilayer with glycoproteins for attachment/entry; absent in non-enveloped). Diagram: ` Nucleocapsid (genome + capsid) | Envelope (GPs) ` 5b (B). Baltimore classification (three examples): Groups based on genome type/mRNA synthesis: 1. Group I: dsDNA – Host Pol transcribes mRNA (e.g., adenovirus). 2. Group IV: (+)ssRNA – Genome = mRNA (e.g., SARS-CoV-2). 3. Group V: (-)ssRNA – Viral RdRp makes +mRNA (e.g., influenza). 6a. Role of ICTV: International Committee on Taxonomy of Viruses. Classifies: Orders, families, genera, species based on genome, structure, replication. Nomenclature: Binomial (e.g., Orthohantavirus hantaan). Hierarchical: Realm > Kingdom > ... > Species. Updates via proposals, publishes reports. 6b. Criteria: Lytic vs. lysogenic cycles (bacteriophages): Lytic (virulent): 1. Attachment/injection. 2. Immediate replication (early/late genes). 3. Assembly. 4. Lysis (holin/endolysin). Lysogenic (temperate): 1. Attachment/injection. 2. Circularize/integrate as prophage. 3. Replicate with host (no lysis). 4. Induce to lytic (SOS response).