Virology Practice Questions

Q: All of the following are true about HIV infection except?

Increased release of acid labile interferon. **Explanation:** The correct answer is **C (Increased release of acid-labile interferon)** because HIV infection is actually associated with the production of **acid-labile Interferon-alpha (IFN-α)**, not its increased release as a protective mechanism. In HIV patients, the presence of acid-labile IFN-α is a marker of disease progression and is often found in the serum of those with AIDS or symptomatic HIV, rather than being a standard physiological response to the virus. **Analysis of Options:** * **Option A (Enveloped RNA virus):** This is **true**. HIV is a member of the *Lentivirus* genus within the *Retroviridae* family. It possesses a lipid envelope derived from the host cell membrane and contains two copies of single-stranded positive-sense RNA. * **Option B (Rate of killing vs. T4 molecules):** This is **true**. The HIV gp120 envelope glycoprotein binds specifically to the **CD4 (T4) molecule**. Cells with higher densities of CD4 receptors on their surface are more susceptible to viral entry and subsequent cytopathic destruction. * **Option D (Decreased delayed hypersensitivity):** This is **true**. HIV causes a profound depletion of CD4+ T cells, leading to a defect in cell-mediated immunity. This results in **anergy**, manifested as a decreased or absent delayed-type hypersensitivity (DTH) skin test response (e.g., to Tuberculin). **High-Yield Clinical Pearls for NEET-PG:** * **Primary Receptor:** CD4 molecule. * **Co-receptors:** **CCR5** (macrophages/early infection) and **CXCR4** (T-cells/late infection). Individuals with a homozygous **CCR5-Δ32 mutation** are resistant to HIV-1 infection. * **Hallmark Immunological Defect:** Inversion of the CD4:CD8 ratio (normal is ~2:1; in AIDS it is <1:1). * **Acid-labile IFN-α:** Its presence in HIV is unusual because IFN-α is typically acid-stable; its appearance in HIV/SLE is a specific diagnostic nuance.

Q: Which of the following conditions is caused by HHV-8?

Kaposi sarcoma. **Explanation:** **Human Herpesvirus 8 (HHV-8)**, also known as **Kaposi Sarcoma-associated Herpesvirus (KSHV)**, is a gamma-herpesvirus that primarily infects vascular endothelial cells. It carries oncogenes (like viral cyclin and v-FLIP) that promote cell proliferation and inhibit apoptosis. In immunocompromised states, particularly HIV/AIDS, HHV-8 leads to the development of **Kaposi Sarcoma**, a multicentric vascular tumor characterized by spindle cells and slit-like neovascular spaces. **Analysis of Incorrect Options:** * **A & B (Burkitt's Lymphoma & Nasopharyngeal Carcinoma):** Both are strongly associated with **Epstein-Barr Virus (EBV)**, also known as HHV-4. EBV is a gamma-herpesvirus that infects B-cells and epithelial cells. * **D (Hepatic Carcinoma):** Hepatocellular carcinoma is primarily linked to chronic infections with **Hepatitis B Virus (HBV)** and **Hepatitis C Virus (HCV)**, as well as aflatoxin exposure. **High-Yield Clinical Pearls for NEET-PG:** * **HHV-8 Spectrum:** Besides Kaposi Sarcoma, HHV-8 is also the causative agent of **Primary Effusion Lymphoma (PEL)** and **Multicentric Castleman Disease**. * **Transmission:** HHV-8 is most commonly transmitted through saliva and sexual contact. * **Histopathology:** Look for "spindle-shaped cells" and "extravasated RBCs" in biopsy descriptions of Kaposi Sarcoma. * **Classification:** Remember the "Rule of 8"—HHV-8 causes Kaposi Sarcoma (the 8th virus causes the sarcoma starting with 'K', the 11th letter, but often associated with AIDS/Advanced stages).

Q: Influenza pandemics are primarily caused by which type of influenza virus?

Type A. **Explanation:** **Influenza Type A** is the primary cause of pandemics due to its unique ability to undergo **Antigenic Shift**. This process involves a major genetic recombination (reassortment) between different viral strains, resulting in a completely new subtype with novel Hemagglutinin (H) or Neuraminidase (N) surface antigens. Because the human population has little to no pre-existing immunity to these new subtypes, the virus spreads globally, leading to a pandemic. Type A also has a broad host range, infecting humans, birds, and pigs, which facilitates this genetic mixing. **Why other options are incorrect:** * **Type B:** While it causes significant seasonal epidemics, it does not cause pandemics. This is because Type B undergoes **Antigenic Drift** (minor point mutations) but not Shift, and it lacks an animal reservoir to facilitate reassortment. * **Type C:** This type generally causes only mild respiratory illness or sporadic cases and does not lead to epidemics or pandemics. * **Type D:** Primarily affects cattle and is not known to infect or cause disease in humans. **High-Yield NEET-PG Pearls:** * **Antigenic Shift:** Sudden, major change; causes **Pandemics** (Only Type A). * **Antigenic Drift:** Gradual, minor mutations; causes **Epidemics** (Types A and B). * **Nomenclature:** The most common subtypes currently circulating in humans are H1N1 and H3N2. * **Vaccine:** The influenza vaccine is updated annually to match the predicted circulating strains (usually quadrivalent, covering two Type A and two Type B strains).

Q: What is antigenic shift?

Results from genetic recombination. ### Explanation **Antigenic Shift** is a sudden, major change in the surface antigens (Hemagglutinin and/or Neuraminidase) of the Influenza virus. **Why Option C is Correct:** Antigenic shift occurs due to **genetic reassortment** (recombination). When two different strains of Influenza A virus infect the same host cell (e.g., in a pig or bird), their segmented RNA genomes mix during assembly. This results in a completely new subtype (e.g., H1N1 shifting to H2N2) to which the human population has little to no immunity. This is the primary driver of **Pandemics**. **Why Other Options are Incorrect:** * **Option A:** Antigenic shift is unpredictable and occurs at irregular, long intervals (typically decades), not every 2–3 years. * **Option B:** Gradual changes over time describe **Antigenic Drift**, which results from point mutations during viral replication. * **Option D:** Antigenic shift occurs **only in Influenza A** because it has a wide host range (humans, birds, swine). Influenza B and C undergo only antigenic drift, as they primarily infect humans, limiting the opportunity for reassortment. **High-Yield Clinical Pearls for NEET-PG:** * **Segmented Genome:** Influenza virus has 8 RNA segments. This segmentation is the structural prerequisite for reassortment/shift. * **Drift vs. Shift:** * **Drift:** Point mutations $\rightarrow$ Epidemics $\rightarrow$ Seen in A and B. * **Shift:** Reassortment $\rightarrow$ Pandemics $\rightarrow$ Seen only in A. * **Mixing Vessel:** Pigs are often called "mixing vessels" because they possess receptors for both avian and human influenza viruses.

Q: Which virus is the leading cause of bronchiolitis and community-acquired pneumonia in infants?

Respiratory syncytial virus. **Explanation:** **Respiratory Syncytial Virus (RSV)** is the most common cause of lower respiratory tract infections (LRTIs), specifically **bronchiolitis** and **pneumonia**, in infants and children under the age of two. The underlying medical concept involves the virus causing inflammation and edema of the small airways (bronchioles), leading to obstruction, wheezing, and air trapping. In infants, the narrow caliber of the airways makes them particularly susceptible to significant clinical distress from this inflammation. **Analysis of Incorrect Options:** * **Measles Virus:** While it can cause Giant Cell Pneumonia (Hecht’s pneumonia), it is primarily a systemic febrile illness characterized by Koplik spots and a maculopapular rash. It is not the leading cause of bronchiolitis. * **Influenza Virus:** Though a major cause of pneumonia across all age groups, it typically presents with high fever, myalgia, and systemic symptoms. It is less frequently associated with the specific clinical syndrome of bronchiolitis compared to RSV. * **Parainfluenza Virus:** This is the leading cause of **Croup (Laryngotracheobronchitis)**, characterized by a "barking" cough and inspiratory stridor, rather than the lower airway wheezing seen in bronchiolitis. **High-Yield Clinical Pearls for NEET-PG:** * **RSV Morphology:** A pleomorphic, enveloped, negative-sense ssRNA virus (Paramyxoviridae family). * **Cytopathology:** Characterized by the formation of **syncytia** (multinucleated giant cells) due to the "F" (fusion) protein. * **Diagnosis:** Rapid antigen detection tests or RT-PCR from nasopharyngeal aspirates. * **Prophylaxis:** **Palivizumab**, a monoclonal antibody against the F protein, is used for high-risk premature infants. * **Seasonality:** Typically peaks during winter months.

Q: An 18-year-old lady presents with severe sore throat, fever, and malaise. She has cervical lymphadenopathy, splenomegaly, and scattered petechiae on the soft palate with enlarged tonsils covered with white exudates. Which of the following investigations is most likely to help guide your management?

Heterophile antibody test. ### Explanation The clinical presentation of **fever, sore throat (exudative pharyngitis), cervical lymphadenopathy, and splenomegaly** in a young adult is the classic triad of **Infectious Mononucleosis (IM)**, primarily caused by the **Epstein-Barr Virus (EBV)**. **1. Why Heterophile Antibody Test is Correct:** The Heterophile antibody test (e.g., **Monospot test**) is the screening investigation of choice. It detects IgM antibodies that agglutinate sheep or horse red blood cells. These antibodies are produced during the acute phase of EBV infection due to polyclonal B-cell activation. In a patient with palatal petechiae and splenomegaly, this test confirms the diagnosis of IM, guiding management toward supportive care and avoidance of contact sports (to prevent splenic rupture). **2. Why Other Options are Incorrect:** * **Fine needle aspiration (FNA):** While lymphadenopathy is present, FNA is unnecessary and typically reserved for suspected malignancy (lymphoma). In IM, nodes are reactive and tender. * **Hepatitis B surface antigen:** While EBV can cause mild hepatitis, the primary symptoms (pharyngitis, tonsillar exudates) are not characteristic of HBV. * **HIV test:** Acute Retroviral Syndrome can mimic IM (mononucleosis-like illness), but the presence of **exudative tonsillitis** and **splenomegaly** strongly favors EBV over HIV. **Clinical Pearls for NEET-PG:** * **Atypical Lymphocytes:** Peripheral smear shows "Downey cells" (activated T-cells/CD8+). * **Ampicillin Rash:** Administration of Ampicillin or Amoxicillin in a patient with IM often triggers a characteristic maculopapular rash. * **Specific Serology:** If the heterophile test is negative but IM is suspected, test for **Anti-VCA (Viral Capsid Antigen) IgM**. * **Complication:** Splenic rupture is a rare but life-threatening complication; patients must avoid heavy lifting for 3–4 weeks.

Question 1

All of the following are true about HIV infection except?

Accepted Answer

Increased release of acid labile interferon

Answer

Caused by an enveloped RNA virus

Answer

Rate of killing is directly proportional to T4 molecules on the cell surface

Answer

Decreased delayed hypersensitivity activity reaction

Question 2

Which of the following conditions is caused by HHV-8?

Accepted Answer

Kaposi sarcoma

Answer

Burkitt's lymphoma

Answer

Nasopharyngeal carcinoma

Answer

Hepatic carcinoma

Question 3

Influenza pandemics are primarily caused by which type of influenza virus?

Accepted Answer

Type A

Answer

Type B

Answer

Type C

Answer

All types

Question 4

What is antigenic shift?

Accepted Answer

Results from genetic recombination

Answer

Occurs every 2-3 years

Answer

Gradual change over time

Answer

Occurs in all influenza viruses

Question 5

A 6-year-old girl presents with a blotchy, reddish-brown rash on her face, trunk, and proximal extremities that developed over 3 days. Physical examination reveals 0.2-cm to 0.5-cm ulcerated lesions on the oral mucosa and generalized tender lymphadenopathy. A cough with minimal sputum production worsens over the next 3 days. Which of the following viruses is most likely to produce these findings?

Accepted Answer

Rubeola virus

Answer

Epstein-Barr virus

Answer

Mumps virus

Answer

Rubella virus

Question 6

Which of the following is the first stage in the life cycle of a bacteriophage?

Accepted Answer

Lytic cycle

Answer

Lysogenic cycle

Answer

Maturation

Answer

Eclipse phase

Question 7

All of the following are true about HIV except?

Accepted Answer

Mostly spread by heterosexual contact.

Answer

A DNA virus belonging to the retrovirus family.

Answer

Attacks CD4 lymphocytes.

Answer

The CD4:CD8 ratio is reversed.

Question 8

Which virus is the leading cause of bronchiolitis and community-acquired pneumonia in infants?

Accepted Answer

Respiratory syncytial virus

Answer

Measles virus

Answer

Influenza virus

Answer

Parainfluenza virus

Question 9

Which of the following statements about Coronaviruses is false?

Accepted Answer

It does not spread through coughing, sneezing, or direct contact.

Answer

These viruses have club-shaped peplomers on their surface.

Answer

SARS spreads mainly by inhalation.

Answer

The SARS virus is highly mutable.

Question 10

An 18-year-old lady presents with severe sore throat, fever, and malaise. She has cervical lymphadenopathy, splenomegaly, and scattered petechiae on the soft palate with enlarged tonsils covered with white exudates. Which of the following investigations is most likely to help guide your management?

Accepted Answer

Heterophile antibody test

Answer

Fine needle aspiration of a lymph node

Answer

Hepatitis B surface antigen

Answer

HIV test

Virology — MCQs

Virology — MCQs

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