Virology Practice Questions

Q: What is true about prions?

Cause misfolding of protein. **Explanation:** Prions (Proteinaceous Infectious Particles) are unique pathogens because they lack nucleic acids (DNA or RNA). The fundamental mechanism of prion disease is the **conformational change** of a normal host protein into a pathological isoform. 1. **Why the correct answer is right:** The normal cellular prion protein (**PrPc**), which is rich in alpha-helices, undergoes a post-translational conformational change to become the infectious **PrPsc** (scrapie form), which is rich in **beta-pleated sheets**. This PrPsc acts as a template, inducing other normal PrPc molecules to misfold. These misfolded proteins are resistant to proteases, leading to their accumulation in the brain, resulting in neuronal death and the characteristic "spongiform" appearance. 2. **Why the incorrect options are wrong:** * **A. Are virus-coded:** Prions are not viruses. They are encoded by the host's own genome (specifically the *PRNP* gene on chromosome 20). * **C. Cleave protein:** Prions do not possess enzymatic or proteolytic activity; they cause structural rearrangement through protein-protein interaction. * **D. Are defective in protein synthesis:** Prion diseases are disorders of **protein folding**, not protein synthesis (translation). **High-Yield Clinical Pearls for NEET-PG:** * **Resistance:** Prions are highly resistant to standard sterilization methods (autoclaving, UV light, and boiling). They are inactivated by **1N NaOH for 1 hour** or **porous load autoclaving at 134°C**. * **Human Diseases:** Kuru (associated with cannibalism), Creutzfeldt-Jakob Disease (CJD), and Fatal Familial Insomnia. * **Histology:** Characterized by spongiform degeneration, neuronal loss, and astrocytosis **without** an inflammatory response (no pleocytosis in CSF).

Q: Which of the following infections is known to spread via aerosols leading to epidemics?

Influenza. **Explanation:** The correct answer is **C. Influenza**. **Why Influenza is correct:** Influenza is a classic example of a respiratory virus that spreads primarily via **aerosols** (small droplet nuclei) and large droplets. Because aerosols can remain suspended in the air for long periods and travel significant distances, the virus spreads rapidly through populations. This high transmissibility, combined with "Antigenic Shift" (major genetic changes), leads to periodic **epidemics and pandemics**. **Analysis of Incorrect Options:** * **A. Legionella:** While *Legionella pneumophila* is transmitted via inhalation of contaminated aerosols (e.g., from cooling towers or AC systems), it does **not** spread from person to person. Therefore, it causes localized outbreaks rather than true community-wide epidemics. * **B. Hemophilus:** *Haemophilus influenzae* (despite its name) is a bacterium that primarily spreads through **large respiratory droplets** requiring close contact. It typically causes endemic infections (like meningitis or pneumonia) rather than explosive epidemics. * **D. Mycoplasma:** *Mycoplasma pneumoniae* causes "Walking Pneumonia." While it spreads via respiratory droplets, it has a long incubation period and relatively low transmissibility, leading to slow-moving outbreaks in confined settings (like barracks or dorms) rather than large-scale epidemics. **NEET-PG High-Yield Pearls:** * **Antigenic Shift:** Reassortment of segments (only in Influenza A) → Causes **Pandemics**. * **Antigenic Drift:** Point mutations → Causes **Epidemics**. * **Gold Standard Diagnosis:** RT-PCR is the preferred test for Influenza. * **Drug of Choice:** Oseltamivir (Neuraminidase inhibitor) is used for both treatment and prophylaxis.

Q: What is the most common cause of death in Epstein-Barr virus (EBV) infection?

Meningo-encephalitis. **Explanation:** Epstein-Barr Virus (EBV), the primary cause of Infectious Mononucleosis (IM), is generally a self-limiting condition. However, when fatalities occur, they are most frequently attributed to neurological complications. **1. Why Meningo-encephalitis is correct:** Neurological complications occur in approximately 1–5% of patients with IM. Among these, **meningo-encephalitis** and Guillain-Barré syndrome are the most severe. Encephalitis leads to cerebral edema and increased intracranial pressure, making it the leading cause of EBV-related mortality. **2. Analysis of Incorrect Options:** * **Splenic Abscess:** While **Splenic Rupture** is a classic, high-yield complication of EBV (occurring in 0.1% of cases), splenic *abscess* is not a characteristic feature. Rupture is the second most common cause of death, but it is less frequent than neurological fatalities. * **Fulminant Hepatitis:** EBV commonly causes a mild, transient elevation of liver enzymes (transaminitis). While jaundice may occur, progression to fulminant hepatic failure is extremely rare in immunocompetent hosts. * **Auto-immune Hemolytic Anemia (AIHA):** EBV is associated with "Cold Agglutinin Disease" (IgM antibodies against i-antigen on RBCs). While this causes transient hemolysis in about 2% of cases, it is rarely fatal. **Clinical Pearls for NEET-PG:** * **Triad of IM:** Fever, Pharyngitis, and Lymphadenopathy (typically posterior cervical). * **Diagnostic Hallmark:** Atypical lymphocytes (Downey cells) on peripheral smear (CD8+ T-cells). * **The "Ampicillin Rash":** Administration of Ampicillin or Amoxicillin in a patient with EBV leads to a characteristic maculopapular rash. * **Cancers associated with EBV:** Burkitt Lymphoma, Nasopharyngeal Carcinoma, and Hodgkin Lymphoma (Mixed cellularity type).

Q: Progressive multifocal leukoencephalopathy is caused by which virus?

JC polyomavirus. **Explanation:** **Progressive Multifocal Leukoencephalopathy (PML)** is a rare, demyelinating disease of the Central Nervous System (CNS) caused by the **JC virus (JCV)**, a member of the *Polyomaviridae* family. The virus typically causes a latent infection in the kidneys and lymphoid tissues of healthy individuals. However, in states of severe **immunosuppression** (most commonly AIDS, but also in patients on monoclonal antibodies like Natalizumab), the virus reactivates. It crosses the blood-brain barrier and infects **oligodendrocytes**, the cells responsible for producing myelin in the CNS. This leads to widespread demyelination, presenting clinically with rapidly progressive focal neurological deficits, cognitive decline, and visual disturbances. **Analysis of Incorrect Options:** * **A. Epstein-Barr virus (EBV):** Primarily associated with infectious mononucleosis, Burkitt lymphoma, and Primary CNS Lymphoma in HIV patients, but not demyelinating disease. * **B. Varicella-zoster virus (VZV):** Causes chickenpox and shingles. Neurological complications include encephalitis or vasculopathy, but not PML. * **C. Cytomegalovirus (CMV):** In immunocompromised patients, it typically causes retinitis, esophagitis, or CMV encephalitis (characterized by periventricular calcifications), not multifocal demyelination. **High-Yield Clinical Pearls for NEET-PG:** * **MRI Findings:** PML shows multiple, non-enhancing, subcortical white matter lesions without mass effect (classically in the parieto-occipital region). * **Histopathology:** Look for the triad of **demyelination**, **giant atypical astrocytes**, and **oligodendrocyte nuclei with "ground-glass" viral inclusions**. * **Diagnosis:** Gold standard is PCR for JC virus DNA in the Cerebrospinal Fluid (CSF). * **Mnemonic:** **J**unction **C**onnection (JC virus) destroys the "connections" (myelin) in the brain.

Q: Which of the following is NOT true regarding Hantavirus?

It is a DNA virus. ### Explanation **1. Why Option A is the correct answer:** Hantaviruses belong to the family **Bunyaviridae**. A fundamental characteristic of this family is that they are **enveloped, single-stranded RNA viruses** (specifically negative-sense, segmented RNA). Therefore, the statement that it is a DNA virus is incorrect. In the NEET-PG context, remembering the "ROB" mnemonic (Reovirus, Orthomyxovirus, Bunyavirus) for segmented RNA viruses is crucial. **2. Analysis of other options:** * **Option B (Carried by rodents):** This is true. Hantaviruses are **zoonotic**. They are primarily transmitted to humans through contact with the urine, saliva, or feces of infected rodents (like the deer mouse or cotton rat). * **Option C (Respiratory infections):** This is true. Hantavirus is the causative agent of **Hantavirus Pulmonary Syndrome (HPS)**, characterized by sudden onset flu-like symptoms progressing to severe respiratory failure and non-cardiogenic pulmonary edema. * **Option D (Hemorrhagic manifestations):** This is true. In many parts of the world (especially Asia and Europe), Hantavirus causes **Hemorrhagic Fever with Renal Syndrome (HFRS)**, presenting with fever, hemorrhage, and acute kidney injury. **3. High-Yield Clinical Pearls for NEET-PG:** * **Genome:** Segmented RNA (3 segments: Large, Medium, Small). * **Transmission:** Inhalation of aerosolized rodent excreta (No human-to-human transmission, except for the Andes virus). * **Classic Triad (HFRS):** Fever, hemorrhage, and renal failure. * **Key Serotype:** *Sin Nombre virus* is the most common cause of Hantavirus Pulmonary Syndrome in North America. * **Diagnosis:** Primarily via Serology (ELISA for IgM) or RT-PCR.

Q: What is the most common Human Papillomavirus (HPV) type responsible for cervical cancer?

HPV 16. **Explanation:** Cervical cancer is primarily caused by persistent infection with high-risk Human Papillomavirus (HPV) types. Among these, **HPV 16** is the most oncogenic and prevalent, accounting for approximately **50-60%** of all cervical squamous cell carcinomas worldwide. It has a high affinity for the transformation zone of the cervix, where its E6 and E7 oncoproteins inhibit the tumor suppressor proteins p53 and pRb, respectively, leading to malignant transformation. **Analysis of Options:** * **Option A (HPV 16):** Correct. It is the single most common type identified in cervical cancer globally. * **Option B (HPV 18):** Incorrect. While it is the second most common high-risk type (responsible for ~10-15% of cases), it is specifically associated more frequently with **adenocarcinoma** of the cervix rather than squamous cell carcinoma. * **Option C (HPV 31):** Incorrect. This is a high-risk type, but it accounts for a much smaller percentage of cases compared to 16 and 18. * **Option D (HPV 36):** Incorrect. This is generally considered a low-risk type and is not a significant driver of cervical malignancy. **High-Yield Clinical Pearls for NEET-PG:** * **Most common types:** HPV 16 and 18 together cause ~70% of all cervical cancers. * **Genital Warts (Condyloma Acuminata):** Caused by low-risk types **HPV 6 and 11**. * **Vaccination:** The Quadrivalent vaccine (Gardasil) covers 6, 11, 16, and 18; the Nonavalent vaccine covers five additional high-risk types (31, 33, 45, 52, 58). * **Screening:** The primary screening tool remains the Pap smear (cytology) and HPV DNA testing.

Q: Verrucous carcinoma of the penis is caused by which type of Human Papillomavirus (HPV)?

HPV 11. **Explanation:** **Verrucous carcinoma of the penis**, also known as **Buschke-Löwenstein tumor**, is a rare, well-differentiated variant of squamous cell carcinoma. Unlike typical penile cancer, it is locally aggressive and can grow to a massive size but rarely metastasizes. 1. **Why HPV 11 is correct:** Verrucous carcinoma is strongly associated with **low-risk HPV types 6 and 11**. These types are traditionally linked to benign genital warts (Condyloma acuminata). Verrucous carcinoma is often considered a giant, exophytic version of these warts that exhibits local invasion but lacks the cytological malignancy seen in high-risk infections. 2. **Why the other options are incorrect:** * **HPV 16 & 18:** These are **high-risk HPV types**. They are the primary causative agents for typical (non-verrucous) Squamous Cell Carcinoma of the penis, as well as cervical and anal cancers. They produce E6 and E7 oncoproteins which inhibit p53 and Rb tumor suppressor genes. * **HPV 32:** This type is specifically associated with **Heck’s disease** (Focal Epithelial Hyperplasia), which manifests as multiple white-to-pink papules in the oral cavity, not penile malignancies. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Presents as a "cauliflower-like" fungating mass. * **Histology:** Characterized by a "pushing" deep margin rather than an infiltrating one. It lacks koilocytosis (which is seen in condylomas). * **Management:** Wide local excision is the treatment of choice. **Radiotherapy is contraindicated** as it may trigger anaplastic transformation and increase metastatic potential. * **Prognosis:** Excellent if surgically excised, due to the low risk of lymph node involvement.

Q: All of the following are true regarding R5 strain of HIV except?

Predominates in late stages of HIV. ### Explanation The HIV-1 virus enters host cells by binding to the CD4 receptor and a specific co-receptor (chemokine receptor). Based on co-receptor usage, HIV strains are classified into **R5 (M-tropic)** and **X4 (T-tropic)**. **Why Option B is the Correct Answer (The False Statement):** R5 strains utilize the **CCR5** co-receptor and are the **predominant strains during the early stages** of infection (acute phase and asymptomatic period). They are responsible for the initial establishment of infection. In contrast, **X4 strains** (which use the CXCR4 co-receptor) typically emerge in the **late stages** of the disease, correlating with a rapid decline in CD4+ T-cell counts and progression to AIDS. **Analysis of Other Options:** * **Option A:** R5 strains specifically utilize the **CCR5** co-receptor, which is found on macrophages, dendritic cells, and memory T-cells. * **Option C:** R5 strains are the primary strains involved in **mucosal transmission**. They are more efficiently transmitted sexually compared to X4 strains, even if the donor has both types (the "gatekeeper" effect). * **Option D:** Microglial cells in the central nervous system express CD4 and CCR5; therefore, R5 strains are the primary neurotropic variants that infect these cells, potentially leading to HIV-associated neurocognitive disorders. ### High-Yield Pearls for NEET-PG: * **Maraviroc:** A CCR5 antagonist (entry inhibitor) that is only effective against R5-tropic HIV. A "Tropism Assay" must be performed before starting this drug. * **CCR5-Δ32 Mutation:** A 32-base pair deletion in the CCR5 gene. Individuals homozygous for this mutation are virtually resistant to R5-tropic HIV infection. * **Mnemonic:** **R5** = **M**acrophage-tropic (Early); **X4** = **T**-cell-tropic (Late).

Q: Which type of Human Papillomavirus (HPV) is considered low risk?

Type-6. ### Explanation Human Papillomavirus (HPV) is a double-stranded DNA virus that infects epithelial cells. It is categorized into **Low-risk** and **High-risk** types based on its association with malignancy. **Why Type-6 is Correct:** **HPV Type-6** (along with Type-11) is classified as **Low-risk**. These types primarily cause benign proliferative lesions such as **Condyloma acuminatum** (anogenital warts) and **Laryngeal papillomatosis**. They rarely integrate their DNA into the host genome, meaning they do not typically lead to squamous cell carcinoma. **Analysis of Incorrect Options:** * **Type-16 (Option A):** This is the most oncogenic high-risk type globally. It is responsible for approximately 50-60% of cervical cancers and is also strongly associated with oropharyngeal and anal cancers. * **Type-18 (Option C):** The second most common high-risk type, accounting for about 10-15% of cervical cancers. It is particularly associated with cervical **adenocarcinoma**. * **Type-31 (Option D):** A high-risk type that, along with types 33, 45, 52, and 58, is a significant contributor to cervical intraepithelial neoplasia (CIN) and invasive cancer. **High-Yield Clinical Pearls for NEET-PG:** * **Oncogenesis:** High-risk types (16, 18) produce oncoproteins **E6** (inhibits **p53**) and **E7** (inhibits **pRb**), leading to uncontrolled cell cycle progression. * **Cytopathology:** The hallmark of HPV infection on a Pap smear is the **Koilocyte** (a cell with a perinuclear halo and wrinkled "raisinoid" nucleus). * **Vaccination:** The **9-valent vaccine (Gardasil 9)** covers low-risk types 6, 11 and high-risk types 16, 18, 31, 33, 45, 52, and 58.

Question 1

What is true about prions?

Accepted Answer

Cause misfolding of protein

Answer

Are virus-coded

Answer

Cleave protein

Answer

Are defective in protein synthesis

Question 2

Which of the following infections is known to spread via aerosols leading to epidemics?

Accepted Answer

Influenza

Answer

Legionella

Answer

Hemophilus

Answer

Mycoplasma

Question 3

What is the most common cause of death in Epstein-Barr virus (EBV) infection?

Accepted Answer

Meningo-encephalitis

Answer

Splenic abscess

Answer

Fulminant hepatitis

Answer

Auto-immune hemolytic anemia

Question 4

Progressive multifocal leukoencephalopathy is caused by which virus?

Accepted Answer

JC polyomavirus

Answer

Epstein-Barr virus

Answer

Varicella-zoster virus

Answer

Cytomegalovirus

Question 5

Which of the following is true regarding Parvovirus infection?

Accepted Answer

Erythroid progenitors are affected

Answer

Myeloid precursors are affected

Answer

Individuals with P antigen are resistant to infection

Answer

The majority of infections are chronic

Question 6

Which of the following is NOT true regarding Hantavirus?

Accepted Answer

It is a DNA virus

Answer

It is carried by rodents

Answer

It causes recurrent respiratory infections

Answer

Hemorrhagic manifestations may occur

Question 7

What is the most common Human Papillomavirus (HPV) type responsible for cervical cancer?

Accepted Answer

HPV 16

Answer

HPV 18

Answer

HPV 31

Answer

HPV 36

Question 8

Verrucous carcinoma of the penis is caused by which type of Human Papillomavirus (HPV)?

Accepted Answer

HPV 11

Answer

HPV 16

Answer

HPV 18

Answer

HPV 32

Question 9

All of the following are true regarding R5 strain of HIV except?

Accepted Answer

Predominates in late stages of HIV

Answer

Utilizes CCR5 co-receptor

Answer

Transmits HIV efficiently

Answer

Infects microglial cells

Question 10

Which type of Human Papillomavirus (HPV) is considered low risk?

Accepted Answer

Type-6

Answer

Type-16

Answer

Type-18

Answer

Type-31

Virology — MCQs

Virology — MCQs

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