Virology Practice Questions

Q: Which of the following statements about the P24 antigen of HIV is NOT true?

It remains during the asymptomatic phase.. ### Explanation **Why Option D is the Correct Answer (The False Statement):** The **p24 antigen** is the major internal capsid protein of HIV-1. During the natural course of infection, p24 levels rise sharply during the acute phase but **disappear or become undetectable during the asymptomatic (latent) phase**. This happens because the host’s immune system produces anti-p24 antibodies, which bind to the antigen to form immune complexes, effectively "clearing" free p24 from the serum. It only reappears later during the progression to AIDS as the immune system collapses. **Analysis of Other Options:** * **A. It can be detected during the window period:** This is true. The p24 antigen appears in the blood roughly 1–3 weeks after infection, well before the development of detectable antibodies (the "window period"). This makes it a crucial marker for early diagnosis. * **B. Free P24 antigen disappears after the appearance of IgM/IgG response:** This is true. As the humoral immune response kicks in, antibodies (initially IgM, then IgG) neutralize the free antigen, leading to its decline in the serum. * **C. Viral load parallels P24 titre:** This is true. p24 is a direct component of the virus; therefore, its concentration in the blood correlates with the level of active viral replication (viral load). **Clinical Pearls for NEET-PG:** * **4th Generation ELISA:** Also known as the "Combo" or "Duo" test, it detects both **p24 antigen and HIV-1/2 antibodies** simultaneously, significantly shortening the window period. * **Earliest Marker:** While p24 is the earliest *protein* marker, **HIV-RNA (via PCR)** is the overall earliest detectable marker of infection (detectable within 7–10 days). * **Prognostic Value:** A reappearance of p24 antigen in a previously asymptomatic patient indicates clinical deterioration and progression toward AIDS.

Q: Which type of Hepatitis is known to be transmitted vertically?

Hepatitis B. **Explanation:** **Hepatitis B Virus (HBV)** is the most common cause of vertical transmission (mother-to-child) among the hepatitis viruses. This transmission typically occurs **perinatally** during delivery through contact with maternal blood and vaginal secretions, or in utero (less common). The risk of transmission is highest (up to 90%) if the mother is positive for both HBsAg and HBeAg, indicating high viral replication. **Analysis of Options:** * **Hepatitis B (Correct):** It is a blood-borne DNA virus. Vertical transmission is a major route of infection globally, often leading to chronic carrier states in neonates (90% risk of chronicity if infected at birth). * **Hepatitis A & E:** These are transmitted via the **fecal-oral route**. While Hepatitis E is notorious for high mortality in pregnant women (up to 20%), it is not typically characterized by vertical transmission. * **Hepatitis C:** While vertical transmission of HCV is possible, the rate is significantly lower (approx. 3–5%) compared to HBV, making HBV the primary answer for this classic exam question. **High-Yield Clinical Pearls for NEET-PG:** * **Immunoprophylaxis:** To prevent vertical transmission, infants born to HBsAg-positive mothers must receive both the **HBV vaccine** and **Hepatitis B Immunoglobulin (HBIG)** within 12 hours of birth. * **Chronicity Rule:** The younger the age at the time of HBV infection, the higher the risk of developing chronic hepatitis. * **HBeAg Status:** The presence of HBeAg in the mother is the single most important predictor of vertical transmission risk.

Q: Most common involvement of the genitourinary system is seen in which of the following?

Herpes Simplex Virus 2 (HSV-2). **Explanation:** The correct answer is **Herpes Simplex Virus 2 (HSV-2)**. **1. Why HSV-2 is correct:** Historically and clinically, HSV-2 is the primary cause of **Genital Herpes**. It is predominantly transmitted through sexual contact and is the most common cause of recurrent genital ulcer disease worldwide. While HSV-1 can also cause genital lesions (and is increasing in frequency due to changing sexual practices), HSV-2 remains the classic and most frequent pathogen associated with the genitourinary system, characterized by painful vesicles, ulcers, and a high rate of latent reactivation in the **sacral ganglia**. **2. Why other options are incorrect:** * **HSV-1:** This virus is traditionally associated with **"above the waist"** infections, such as gingivostomatitis, herpes labialis (cold sores), and keratoconjunctivitis. It establishes latency in the **trigeminal ganglia**. * **HHV-8 (Human Herpesvirus 8):** Also known as Kaposi Sarcoma-associated Herpesvirus (KSHV), it is the causative agent of **Kaposi Sarcoma**, Primary Effusion Lymphoma, and Multicentric Castleman Disease, typically in immunocompromised patients. * **HSV-12:** This is a **distractor**. Human Herpesviruses are classified from 1 to 8 (HSV-1, HSV-2, VZV, EBV, CMV, HHV-6, HHV-7, and HHV-8). There is no medically recognized "HSV-12." **Clinical Pearls for NEET-PG:** * **Diagnosis:** Tzanck smear showing **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusions (non-specific for HSV-1 vs HSV-2). * **Gold Standard:** PCR is the most sensitive test for diagnosis. * **Neonatal Herpes:** Most commonly transmitted during birth via an infected maternal genital tract (usually HSV-2). * **Treatment:** Acyclovir is the drug of choice, which acts by inhibiting viral DNA polymerase.

Q: The 'bowl of spaghetti' appearance is characteristic of which of the following?

Ebola virions. **Explanation:** The characteristic **'bowl of spaghetti'** appearance refers to the unique morphology of **Ebola virions** when viewed under an electron microscope. Ebola belongs to the **Filoviridae** family (from the Latin *filum*, meaning thread). These viruses are pleomorphic, appearing as long, filamentous, non-segmented forms that can be straight, curved, or coiled into "6-shaped," "U-shaped," or circular configurations. When multiple long, intertwined filaments are present in a sample, they resemble a bowl of spaghetti. **Analysis of Options:** * **Ebola Virions (Correct):** As members of the Filoviridae family, their elongated, thread-like structure (up to 14,000 nm in length) creates the classic "spaghetti" or "shepherd’s crook" appearance. * **Adenovirus:** These are non-enveloped, **icosahedral** viruses with fibers protruding from the vertices (pentons), giving them a "space satellite" or "soccer ball" appearance. * **Marburg Virus:** While also a Filovirus, Marburg typically presents as shorter filaments or distinct "6-shaped" structures. While morphologically similar to Ebola, the specific descriptive term 'bowl of spaghetti' is most classically associated with Ebola in standardized medical literature. * **Poliovirus:** A member of the Picornaviridae family, it is a very small (approx. 30 nm), simple **icosahedral** virus. **High-Yield NEET-PG Pearls:** * **Filoviridae Characteristics:** Negative-sense ssRNA, enveloped, helical nucleocapsid. * **Transmission:** Direct contact with infected blood, secretions, or organs (often via fruit bats as natural reservoirs). * **Diagnosis:** Gold standard for early detection is **RT-PCR**. Electron microscopy is used for structural identification. * **Other "Shapes":** * **Rabies:** Bullet-shaped. * **Poxvirus:** Brick-shaped. * **Rotavirus:** Wheel-like (*Rota* = wheel).

Q: Human papillomavirus (HPV) type 6 is most often implicated in the causation of which of the following conditions?

Condyloma acuminata. **Explanation:** **Condyloma acuminata**, also known as anogenital warts, are primarily caused by **Human Papillomavirus (HPV) types 6 and 11**. These are considered "low-risk" HPV types because they have a low potential for malignant transformation but are highly infectious and responsible for approximately 90% of genital warts. They typically present as cauliflower-like, flesh-colored growths in the perineal and perianal regions. **Analysis of Incorrect Options:** * **A. Cervical cancer:** This is primarily associated with "high-risk" HPV types, most notably **HPV 16 and 18**. These types produce E6 and E7 oncoproteins that inhibit tumor suppressor genes p53 and Rb, respectively. * **C. Flat warts (Verruca plana):** These are smooth, flat-topped papules commonly found on the face and dorsum of hands. They are most frequently associated with **HPV types 3 and 10**. * **D. Common warts (Verruca vulgaris):** These hyperkeratotic, dome-shaped papules are most commonly caused by **HPV types 2 and 4** (and sometimes type 1). **High-Yield Clinical Pearls for NEET-PG:** * **HPV 1:** Most common cause of deep **plantar warts** (myrmecia). * **HPV 5 and 8:** Associated with **Epidermodysplasia verruciformis** and a high risk of Squamous Cell Carcinoma (SCC). * **Butcher’s Warts:** Caused by **HPV 7**. * **Heck’s Disease (Focal Epithelial Hyperplasia):** Associated with **HPV 13 and 32**. * **Histopathology:** Look for **koilocytes** (keratinocytes with perinuclear halos and pyknotic nuclei), which are pathognomonic for HPV infection.

Q: Which of the following is NOT true about the dengue virus?

DEN 4 is the most common serotype in India.. **Explanation:** **1. Why Option B is the correct answer (The False Statement):** While all four serotypes (DEN 1–4) circulate in India, **DEN 2** has historically been the most common and dominant serotype associated with severe outbreaks and Dengue Hemorrhagic Fever (DHF). Recent epidemiological shifts have shown a rise in DEN 1 and DEN 3 in certain regions, but **DEN 4** remains the least common serotype in the Indian subcontinent. **2. Analysis of Incorrect Options (True Statements):** * **Option A:** Dengue virus is a member of the genus *Flavivirus* within the **Flaviviridae** family. * **Option C:** The primary vector is ***Aedes aegypti*** (the "Tiger mosquito," a day-biter that breeds in artificial collections of clean water). ***Aedes albopictus*** is the secondary vector. * **Option D:** The virus possesses a **single-stranded, positive-sense RNA** genome, which is enveloped and icosahedral in symmetry. **3. Clinical Pearls for NEET-PG:** * **Antibody-Dependent Enhancement (ADE):** This occurs when a person is infected with a different serotype for the second time. Non-neutralizing antibodies from the first infection facilitate viral entry into macrophages, leading to a massive cytokine storm and **Dengue Hemorrhagic Fever (DHF)** or **Dengue Shock Syndrome (DSS)**. * **Diagnosis:** * **NS1 Antigen:** Best marker for early diagnosis (Day 1–5). * **IgM ELISA:** Appears after Day 5 (indicates current/recent infection). * **IgG ELISA:** Indicates past infection or secondary infection if titers are very high. * **Tourniquet Test:** A positive test (≥10 petechiae per square inch) is a clinical indicator of capillary fragility in DHF.

Q: Which is the usual marker for the detection of hepatitis B infection?

Hepatitis B surface antigen (HBsAg). **Explanation:** **Hepatitis B surface antigen (HBsAg)** is the correct answer because it is the first serological marker to appear in the blood after infection, typically detectable 2 to 8 weeks before clinical symptoms or biochemical evidence (elevated ALT/AST) emerge. It indicates that the virus is present in the body (acute or chronic) and is the primary screening tool used to identify an active HBV infection. **Analysis of Incorrect Options:** * **Hepatitis B surface antibody (HBsAb/anti-HBs):** This marker indicates immunity. It appears after the disappearance of HBsAg or following successful vaccination. It is not used to detect an active infection but rather to confirm recovery or immune status. * **Hepatitis B core antigen (HBcAg):** This is an internal component of the virion. It is sequestered within the HBsAg coat and is **not** detectable in the serum; it can only be found in infected hepatocytes via biopsy. * **Hepatitis B core antibody (HBcAb/anti-HBc):** While IgM anti-HBc is a marker of acute infection (and the only marker positive during the "window period"), total anti-HBc indicates past or current infection but does not distinguish between the two as reliably as HBsAg for initial screening. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The interval between the disappearance of HBsAg and the appearance of anti-HBs. During this time, **IgM anti-HBc** is the most reliable diagnostic marker. * **Chronic Infection:** Defined by the persistence of HBsAg in the blood for more than 6 months. * **Infectivity Marker:** **HBeAg** (Envelope antigen) indicates high viral replication and high infectivity. * **Vaccine Response:** A person vaccinated against HBV will be positive for **anti-HBs** only (negative for anti-HBc).

Q: Which carcinoma is associated with Epstein-Barr virus?

Carcinoma of the nasopharynx. **Explanation:** **Epstein-Barr Virus (EBV)**, also known as Human Herpesvirus 4 (HHV-4), is a potent oncogenic virus with a strong tropism for B-lymphocytes and epithelial cells. **Why Option C is Correct:** **Nasopharyngeal Carcinoma (NPC)**, specifically the undifferentiated type (WHO Type III), has a definitive causal association with EBV. The virus enters nasopharyngeal epithelial cells via the CD21 receptor (or through fusion mechanisms). Once inside, it establishes a **latency type II pattern**, expressing specific viral oncogenes like **LMP-1** (Latent Membrane Protein-1), which mimics CD40 signaling to promote cell survival and proliferation, leading to malignant transformation. This is particularly prevalent in Southern China and parts of Africa. **Why Other Options are Incorrect:** * **Options A & D (Larynx and Maxilla):** While Head and Neck Squamous Cell Carcinomas (HNSCC) are common, laryngeal and maxillary cancers are primarily linked to tobacco use, alcohol, and occasionally High-Risk HPV (for oropharyngeal sites), but not EBV. * **Option B (Bladder):** Carcinoma of the bladder is strongly associated with smoking, occupational exposure to aromatic amines (aniline dyes), and *Schistosoma haematobium* infection (Squamous cell type), but has no established link to EBV. **High-Yield Clinical Pearls for NEET-PG:** * **EBV-Associated Malignancies:** Burkitt Lymphoma (starry-sky appearance, t(8;14)), Hodgkin Lymphoma (Mixed cellularity), and Gastric Carcinoma (subset). * **Diagnostic Marker:** Elevated titers of **IgA antibodies against Viral Capsid Antigen (VCA)** are used for screening and monitoring recurrence in NPC. * **Non-Malignant EBV Disease:** Infectious Mononucleosis (Glandular fever) and Oral Hairy Leukoplakia (in HIV patients).

Question 1

The protein of envelope is found in which of the following virus families?

Accepted Answer

Myxovirus

Answer

Togavirus

Answer

Parvovirus

Answer

Adenovirus

Question 2

Which of the following statements about the P24 antigen of HIV is NOT true?

Accepted Answer

It remains during the asymptomatic phase.

Answer

It can be detected during the window period.

Answer

Free P24 antigen disappears after the appearance of IgM response to it.

Answer

Viral load parallels P24 titre.

Question 3

Which type of Hepatitis is known to be transmitted vertically?

Accepted Answer

Hepatitis B

Answer

Hepatitis A

Answer

Hepatitis E

Answer

Hepatitis C

Question 4

Most common involvement of the genitourinary system is seen in which of the following?

Accepted Answer

Herpes Simplex Virus 2 (HSV-2)

Answer

Herpes Simplex Virus 1 (HSV-1)

Answer

Herpes Simplex Virus 8 (HSV-8)

Answer

Herpes Simplex Virus 12 (HSV-12)

Question 5

Parvovirus infection is associated with which of the following conditions?

Accepted Answer

None of the above

Answer

Hydrops fetalis

Answer

Aplastic crisis

Answer

Sixth disease

Question 6

The 'bowl of spaghetti' appearance is characteristic of which of the following?

Accepted Answer

Ebola virions

Answer

Adenovirus

Answer

Marburg Viruses

Answer

Poliovirus

Question 7

Human papillomavirus (HPV) type 6 is most often implicated in the causation of which of the following conditions?

Accepted Answer

Condyloma acuminata

Answer

Cervical cancer

Answer

Flat warts

Answer

Common warts

Question 8

Which of the following is NOT true about the dengue virus?

Accepted Answer

DEN 4 is the most common serotype in India.

Answer

It belongs to the Flaviviridae family.

Answer

The main vectors are Aedes aegypti and Aedes albopictus.

Answer

The virus has positive-sense RNA.

Question 9

Which is the usual marker for the detection of hepatitis B infection?

Accepted Answer

Hepatitis B surface antigen (HBsAg)

Answer

Hepatitis B surface antibody (HBsAb)

Answer

Hepatitis B core antigen (HBcAg)

Answer

Hepatitis B core antibody (HBcAb)

Question 10

Which carcinoma is associated with Epstein-Barr virus?

Accepted Answer

Carcinoma of the nasopharynx

Answer

Carcinoma of the larynx

Answer

Carcinoma of the bladder

Answer

Carcinoma of the maxilla

Virology — MCQs

Virology — MCQs

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