Virology — MCQs

Virology Indian Medical PG Practice Questions and MCQs

Question 571: The degradation of p53 through Ubiquitin-dependent proteolysis is facilitated by the binding of high-risk HPV protein.

A. E6 (Correct Answer)
B. E6 and E7
C. E7
D. E6, E7 and E8

Explanation: **Explanation:** The pathogenesis of Human Papillomavirus (HPV) in cervical cancer is primarily driven by two high-risk viral oncoproteins: **E6 and E7**. These proteins disrupt the cell cycle by targeting tumor suppressor proteins. **1. Why E6 is the correct answer:** The **E6 protein** of high-risk HPV types (16 and 18) binds to a cellular protein called **E6-Associated Protein (E6-AP)**, which acts as a ubiquitin ligase. This complex then binds to the **p53 tumor suppressor protein**, leading to its polyubiquitination and subsequent degradation via the **26S proteasome**. Since p53 is responsible for G1 arrest and apoptosis in response to DNA damage, its loss leads to uncontrolled cell proliferation and genomic instability. **2. Why other options are incorrect:** * **E7:** This protein primarily targets the **Retinoblastoma (Rb) protein**. E7 binds to Rb and displaces the E2F transcription factor, pushing the cell into the S-phase. It does not directly cause the ubiquitin-mediated degradation of p53. * **E8:** This is a minor protein involved in regulating viral DNA replication and maintaining latency; it does not play a direct role in p53 degradation. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic:** **E6** targets **p53** (6 is close to 5); **E7** targets **Rb** (7 is close to 8/Rb). * **High-risk HPV types:** 16, 18 (most common), 31, and 33. * **Low-risk HPV types:** 6 and 11 (cause Genital Warts/Condyloma Acuminata). * **Koilocytes:** Pathognomonic finding on Pap smear (cells with perinuclear halo and wrinkled "raisinoid" nuclei). * **Vaccine:** Gardasil-9 covers types 6, 11, 16, 18, 31, 33, 45, 52, and 58.

Question 572: Which virus has more than one serotype?

A. Measles
B. Mumps
C. Rubella (Correct Answer)
D. Influenza

Explanation: **Explanation:** The question focuses on the concept of **antigenic stability** versus **antigenic diversity** among RNA viruses. **Why Rubella is the Correct Answer:** While Rubella was traditionally considered to have only one serotype, modern molecular virology (and specific NEET-PG patterns) identifies that the Rubella virus exhibits genetic variation. According to the WHO, Rubella virus is classified into **two clades** and further divided into **9-10 genotypes**. While these genotypes are immunologically related, the presence of distinct genetic lineages allows it to be categorized as having more than one type/genotype compared to the absolute monotypic nature of Measles and Mumps. **Analysis of Incorrect Options:** * **Measles (Morbillivirus):** This virus is strictly **monotypic**. There is only one serotype, which is why the live-attenuated vaccine provides lifelong immunity. Antigenic drift does not occur in Measles. * **Mumps (Rubulavirus):** Like Measles, Mumps virus exists as a **single serotype**. Although different genotypes exist (A-N), they do not represent different serotypes, and one vaccine strain protects against all. * **Influenza:** While Influenza has multiple types (A, B, C) and numerous subtypes (H1N1, H3N2), the term "serotype" is usually applied differently here. However, in the context of this specific comparative question, Rubella is the preferred answer regarding established genomic diversity. **NEET-PG High-Yield Pearls:** 1. **Monotypic Viruses:** Measles, Mumps, Rubella (clinically treated as one for vaccination), Polio (3 serotypes), and Rabies. 2. **Antigenic Shift vs. Drift:** Remember that Influenza undergoes both, whereas most other RNA viruses in this list are relatively stable. 3. **Vaccine Implication:** The success of the **MMR vaccine** relies on the fact that these viruses do not undergo significant antigenic variation, ensuring that a single vaccine formulation remains effective globally for decades.

Question 573: A dentist presents with pain, redness, and swelling of the finger, accompanied by fever. Examination reveals small, grouped vesicles containing clear fluid. A Tzanck smear shows Tzanck cells. What is the causative agent?

A. Adenovirus
B. Pox virus
C. Herpes simplex virus (Correct Answer)
D. Picornavirus

Explanation: **Explanation:** The clinical presentation described is a classic case of **Herpetic Whitlow**. This is a cutaneous infection of the finger caused by **Herpes Simplex Virus (HSV-1 or HSV-2)**. It is frequently seen in healthcare professionals, particularly dentists and respiratory therapists, who have frequent contact with infected oropharyngeal secretions. **Why Herpes Simplex Virus is correct:** * **Clinical Features:** The presence of painful, grouped vesicles on an erythematous base is characteristic of HSV. * **Tzanck Smear:** This is the gold-standard bedside test for Herpesviridae. The finding of **Tzanck cells** (multinucleated giant cells with Cowdry Type A intranuclear inclusion bodies) confirms the presence of HSV or VZV. **Why other options are incorrect:** * **Adenovirus:** Typically causes respiratory infections, conjunctivitis (pink eye), or hemorrhagic cystitis; it does not present with vesicular finger lesions or Tzanck cells. * **Pox virus:** While Molluscum contagiosum (a poxvirus) causes skin lesions, they are typically umbilicated papules, not painful vesicles, and show Henderson-Patterson bodies rather than Tzanck cells. * **Picornavirus:** Hand-foot-and-mouth disease (Coxsackievirus A16) presents with vesicles, but they are usually widespread and not associated with Tzanck cells. **High-Yield NEET-PG Pearls:** * **Tzanck Smear:** Positive in HSV-1, HSV-2, and Varicella-Zoster Virus (VZV). * **Inclusion Bodies:** HSV shows **Cowdry Type A** (intranuclear) inclusions. * **Transmission:** In children, Herpetic Whitlow is often due to autoinoculation from primary herpetic gingivostomatitis (thumb sucking). * **Management:** Incision and drainage are **contraindicated** as they can lead to secondary bacterial infection or systemic spread. Treatment is primarily with Acyclovir.

Question 574: Which of the following statements is TRUE regarding Dengue fever?

A. Dengue serotype 2 is associated with a higher risk of hemorrhagic fever. (Correct Answer)
B. Encephalitis is a common complication of Dengue fever.
C. Dengue fever is not seen in children.
D. A single Dengue infection provides lifelong immunity.

Explanation: ### Explanation **1. Why Option A is Correct:** Dengue virus (DENV) has four serotypes (1-4). While all can cause severe disease, **DENV-2** (and sometimes DENV-3) is clinically associated with a significantly higher risk of **Dengue Hemorrhagic Fever (DHF)** and **Dengue Shock Syndrome (DSS)**. This is often explained by the concept of **Antibody-Dependent Enhancement (ADE)**: pre-existing non-neutralizing antibodies from a primary infection with one serotype bind to a secondary infecting serotype (like DENV-2), facilitating its entry into macrophages, leading to an increased viral load and a massive cytokine storm. **2. Why Other Options are Incorrect:** * **Option B:** Encephalitis is considered an **atypical or expanded manifestation** of Dengue. The classic presentation involves high fever, retro-orbital pain, and severe myalgia ("break-bone fever"). Neurological involvement is rare, not common. * **Option C:** Dengue is very common in children. In fact, children are at a higher risk for severe complications like DHF/DSS compared to adults. * **Option D:** Infection with one serotype provides **lifelong immunity only to that specific serotype** (homologous immunity). It provides only short-lived cross-protection (heterologous immunity) against other serotypes, after which the risk of severe disease increases upon reinfection. **High-Yield Clinical Pearls for NEET-PG:** * **Vector:** *Aedes aegypti* (Daytime biter; breeds in artificial collections of clean water). * **Diagnosis:** **NS1 Antigen** is the marker of choice in the first 5 days (viremic phase). **IgM ELISA** is used after day 5. * **Tourniquet Test:** A positive test (≥10 petechiae per square inch) indicates capillary fragility, a hallmark of DHF. * **Lab Findings:** Characterized by **Leukopenia** and **Thrombocytopenia**. Hematocrit rise (>20%) is a sign of plasma leakage.

Question 575: Presence of HBeAg in serum of a patient of hepatitis-B indicates which stage?

A. Acute, non-infectious stage
B. Acute, infectious stage
C. Chronic, non-infectious stage
D. Chronic, infectious stage (Correct Answer)

Explanation: **Explanation:** The presence of **HBeAg (Hepatitis B e-antigen)** is a critical marker of **active viral replication** and **high infectivity**. It is a soluble protein derived from the precore/core region and is secreted into the blood only when the virus is actively multiplying. **1. Why Option D is Correct:** While HBeAg appears in both acute and chronic phases, its presence signifies that the patient is in an **infectious stage**. In the context of this question (often based on standard MCQ patterns where HBeAg is used to differentiate infectivity), HBeAg indicates a high viral load and a high risk of transmission. If HBeAg persists beyond 10 weeks, it suggests progression to a **chronic carrier state with high infectivity**. **2. Why Other Options are Wrong:** * **Options A & C:** HBeAg is never associated with a "non-infectious" stage. Its presence always correlates with high levels of HBV DNA in the serum. The "non-infectious" (or low-infectivity) stage is characterized by the disappearance of HBeAg and the appearance of **Anti-HBe antibodies**. * **Option B:** While HBeAg is present in the acute stage, the term "infectious stage" is the defining clinical characteristic of HBeAg. In many competitive exams, if "Chronic, infectious" is the keyed answer, it refers to the high-replicative phase of chronic HBV. **Clinical Pearls for NEET-PG:** * **HBsAg:** First marker to appear; indicates infection (acute or chronic). * **HBeAg:** Marker of **active replication, high infectivity**, and severity. * **Anti-HBs:** Marker of **immunity** (post-vaccination or recovery). * **Anti-HBc (IgM):** Best marker for the **"Window Period"** (when HBsAg and Anti-HBs are both negative). * **HBV DNA:** The most sensitive quantitative marker for viral load and monitoring treatment response.

Question 576: A patient presents with painful blisters along the chest wall. All of the following tests are useful for diagnosis except?

A. Direct Fluorescent antibody
B. Polymerase chain reaction
C. Tzank smear
D. LDH levels (Correct Answer)

Explanation: **Explanation:** The clinical presentation of painful blisters along a dermatome (chest wall) is characteristic of **Herpes Zoster (Shingles)**, caused by the reactivation of the Varicella-Zoster Virus (VZV). **Why LDH levels is the correct answer:** Lactate Dehydrogenase (LDH) is a non-specific marker of tissue damage or hemolysis. While it may be elevated in certain malignancies or severe systemic infections, it has **no diagnostic utility** in identifying viral skin infections like Herpes Zoster. Diagnosis of VZV is primarily clinical or confirmed through virus-specific laboratory methods. **Analysis of other options:** * **Tzanck Smear:** A rapid, bedside test where a scraping from the base of the vesicle is stained (e.g., Giemsa). It reveals **multinucleated giant cells** and Cowdry Type A inclusion bodies, characteristic of the Herpesviridae family. * **Direct Fluorescent Antibody (DFA):** This involves using fluorescein-labeled antibodies to detect specific viral antigens in skin scrapings. It is more sensitive and specific than the Tzanck smear. * **Polymerase Chain Reaction (PCR):** This is the **gold standard** and the most sensitive method for detecting VZV DNA from vesicle fluid or crusts. **NEET-PG High-Yield Pearls:** * **Cowdry Type A bodies:** Intranuclear eosinophilic inclusion bodies seen in HSV and VZV. * **Tzanck Smear limitation:** It can identify the Herpes family but **cannot differentiate** between HSV-1, HSV-2, and VZV. * **Dermatomal distribution:** VZV stays latent in the **dorsal root ganglia**; its reactivation follows a specific nerve distribution (unilateral). * **Post-herpetic neuralgia:** The most common complication of Shingles, especially in the elderly.

Question 577: Which of the following viruses does NOT belong to Group B arboviruses?

A. Dengue virus
B. Japanese encephalitis virus
C. West Nile virus
D. Chikungunya virus (Correct Answer)

Explanation: **Explanation:** The classification of arboviruses was historically based on antigenic relationships (serology). **Group B arboviruses** correspond to the modern family ***Flaviviridae*** (specifically the genus *Flavivirus*), while **Group A arboviruses** correspond to the family ***Togaviridae*** (specifically the genus *Alphavirus*). **1. Why Chikungunya is the correct answer:** Chikungunya virus belongs to the **Alphavirus** genus (Group A). It is an enveloped, positive-sense single-stranded RNA virus. Clinically, it is characterized by high fever and severe, often lingering, polyarthralgia, transmitted primarily by *Aedes aegypti* and *Aedes albopictus*. **2. Why the other options are incorrect:** * **Dengue virus (Option A):** A classic member of the *Flavivirus* genus (Group B). It has four serotypes (DEN 1-4) and is the most common arboviral disease worldwide. * **Japanese Encephalitis virus (Option B):** A member of the *Flavivirus* genus (Group B). It is the leading cause of viral encephalitis in Asia, transmitted by *Culex* mosquitoes. * **West Nile virus (Option C):** Also a member of the *Flavivirus* genus (Group B). It is part of the Japanese Encephalitis antigenic serocomplex. **High-Yield Clinical Pearls for NEET-PG:** * **Group A (Alphaviruses):** Chikungunya, Eastern Equine Encephalitis (EEE), Western Equine Encephalitis (WEE). * **Group B (Flaviviruses):** Dengue, JE, West Nile, Yellow Fever, Kyasanur Forest Disease (KFD), and Zika. * **Vector Shortcut:** *Aedes* transmits Dengue, Chikungunya, and Yellow Fever; *Culex* transmits JE and West Nile; *Ticks* transmit KFD. * **KFD (Kyasanur Forest Disease):** Often tested as the "Monkey Fever" of Karnataka; it is a hemorrhagic *Flavivirus* transmitted by *Haemaphysalis* ticks.

Question 578: Herpes Zoster or Shingles represents reactivation and replication of latent infection in:

A. Dorsal Root Ganglion (Correct Answer)
B. Anterior Horn Cell
C. Peripheral nerve
D. Epithelium of Skin

Explanation: **Explanation:** **1. Why Dorsal Root Ganglion is Correct:** Herpes Zoster (Shingles) is caused by the reactivation of the **Varicella-Zoster Virus (VZV)**. During the primary infection (Chickenpox), the virus migrates via retrograde axonal transport from the skin lesions to the sensory nerve clusters. It remains **latent** in the **Dorsal Root Ganglia (DRG)** or cranial nerve ganglia (e.g., Trigeminal ganglion). When cell-mediated immunity declines (due to age, stress, or immunosuppression), the virus reactivates, replicates, and travels down the sensory nerve to the skin, resulting in a painful, dermatomal rash. **2. Why Other Options are Incorrect:** * **Anterior Horn Cell:** These are motor neurons. VZV specifically targets sensory pathways. Involvement of anterior horn cells is rare and would result in motor weakness (Post-herpetic paresis), not the classic sensory rash. * **Peripheral Nerve:** The virus travels *through* the peripheral nerves during reactivation, but it does not remain latent there. The "niche" for latency is the neuronal cell body in the ganglion. * **Epithelium of Skin:** This is the site of active replication and clinical manifestation (vesicles), but the virus cannot remain latent in epithelial cells as they are constantly shed and replaced. **3. High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies (common to HSV and VZV). * **Dermatomal Distribution:** Shingles characteristically does not cross the midline. The thoracic and ophthalmic (V1) dermatomes are most commonly involved. * **Hutchinson’s Sign:** Vesicles on the tip of the nose indicating involvement of the nasociliary nerve, predicting a high risk of Herpes Zoster Ophthalmicus. * **Ramsay Hunt Syndrome:** Reactivation in the **Geniculate Ganglion**, leading to facial palsy and vesicles in the external auditory canal.

Question 579: The dew-drop on rose petal appearance is characteristic of which rash?

A. Smallpox
B. Chickenpox (Correct Answer)
C. Measles
D. Rubella

Explanation: **Explanation:** The "dew-drop on rose petal" appearance is the classic clinical description of the **Chickenpox** rash, caused by the **Varicella-Zoster Virus (VZV)**. **Why Chickenpox is correct:** The rash typically begins as small, red macules that rapidly progress to papules and then to clear, thin-walled vesicles sitting on an erythematous (red) base. This specific morphology—a clear droplet on a red background—resembles a dew-drop on a rose petal. Key features include **centripetal distribution** (more on the trunk than limbs) and **pleomorphism**, where lesions at different stages of development (vesicles, pustules, and scabs) are seen simultaneously in the same anatomical area. **Why other options are incorrect:** * **Smallpox:** Unlike chickenpox, smallpox lesions are **monomorphic** (all at the same stage), have a **centrifugal distribution** (more on face/extremities), and are deep-seated, firm, and often umbilicated. * **Measles (Rubeola):** Presents with a maculopapular rash that begins behind the ears and spreads downwards. It is preceded by the "3 Cs" (Cough, Coryza, Conjunctivitis) and **Koplik spots** on the buccal mucosa. * **Rubella (German Measles):** Presents with a faint maculopapular rash and characteristic **Forchheimer spots** on the soft palate, often accompanied by post-auricular lymphadenopathy. **High-Yield Clinical Pearls for NEET-PG:** * **Tzanck Smear:** Used for rapid diagnosis; look for **multinucleated giant cells** with Cowdry Type A intranuclear inclusions. * **Infectivity:** Patients are infectious from 48 hours before the rash appears until all vesicles have crusted over. * **Starry Sky Appearance:** Another term used to describe the pleomorphic nature of the chickenpox rash. * **Dorsal Root Ganglia:** VZV remains latent here and can reactivate later in life as Herpes Zoster (Shingles).

Question 580: What is the function of the nucleocapsid proteins of measles virus?

A. Allow the virion to assemble in the icosahedral shell
B. Protect the DNA from nuclear digestion
C. Give the virion particle a geometric symmetry
D. Protect the genome RNA from nuclease digestion and recognize the location in the cell membrane for budding (Correct Answer)

Explanation: The Measles virus (a member of the *Paramyxoviridae* family) is an enveloped, single-stranded, negative-sense RNA virus. Its structure and replication cycle are high-yield topics for NEET-PG. ### **Explanation of the Correct Answer (D)** The **Nucleocapsid (N) protein** is the most abundant protein in the virion. Its primary functions are: 1. **Genome Protection:** It tightly encapsulates the viral RNA, protecting it from degradation by host cell nucleases. 2. **Structural Template:** It forms the helical nucleocapsid, which serves as the template for RNA-dependent RNA polymerase. 3. **Assembly and Budding:** During the final stages of the viral life cycle, the nucleocapsid interacts with the **Matrix (M) protein**, which acts as a bridge to the viral envelope. This interaction ensures the nucleocapsid "recognizes" the specific site on the host cell membrane where viral glycoproteins (H and F) are clustered, facilitating organized budding. ### **Analysis of Incorrect Options** * **Option A & C:** These are incorrect because the Measles virus has **helical symmetry**, not icosahedral. Icosahedral shells are characteristic of viruses like Poliovirus or Adenovirus. * **Option B:** This is incorrect because Measles is an **RNA virus**, not a DNA virus. Furthermore, Measles replicates in the **cytoplasm**, not the nucleus (unlike Orthomyxoviruses like Influenza). ### **High-Yield Clinical Pearls for NEET-PG** * **Replication Site:** Unlike most RNA viruses, Measles produces characteristic **Warthin-Finkeldey giant cells** (multinucleated) in lymphoid tissue. * **Surface Proteins:** It has two spikes: **H (Hemagglutinin)** for attachment and **F (Fusion)** for entry and syncytia formation. It lacks Neuraminidase (unlike Mumps/Influenza). * **Vitamin A:** Supplementation reduces mortality in children with Measles. * **SSPE:** Subacute Sclerosing Panencephalitis is a late complication caused by a **defective M (Matrix) protein** that prevents normal budding, leading to persistent CNS infection.

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