Virology Practice Questions

Q: An emerging viral pathogen causing pyelonephritis in kidney allografts is:

Polyomavirus. **Explanation:** **Polyomavirus (specifically BK virus)** is the correct answer because it is a major cause of opportunistic infection in kidney transplant recipients. In the setting of potent immunosuppression, the latent BK virus (a member of the Polyomavirus family) reactivates, leading to **BK virus-associated nephropathy (BKVAN)**. This condition is characterized by viral replication within the tubular epithelial cells, causing inflammation and necrosis that clinically mimics acute cellular rejection. Histologically, it presents with characteristic **intranuclear viral inclusions** (ground-glass appearance) in tubular cells [1]. **Analysis of Incorrect Options:** * **Rotavirus:** Primarily causes viral gastroenteritis in children; it does not have a tropism for renal tissue or cause pyelonephritis. * **Herpes Simplex Virus (HSV):** While HSV can cause systemic infections in immunocompromised hosts, it typically manifests as mucocutaneous lesions, esophagitis, or hepatitis, rather than graft pyelonephritis. * **Influenza Virus:** This is a respiratory pathogen causing pneumonia or systemic flu-like symptoms; it does not target the renal allograft. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Look for **"Decoy cells"** (cells with enlarged nuclei and inclusions) in urine cytology. Definitive diagnosis is made via renal biopsy. * **SV40 Staining:** Immunohistochemistry for the SV40 large T antigen is the gold standard for identifying Polyomavirus in tissue sections. * **Management:** The primary treatment strategy is the **reduction of immunosuppressive therapy** to allow the host immune system to control the viral replication. * **JC Virus:** Another Polyomavirus, but it primarily causes Progressive Multifocal Leukoencephalopathy (PML) rather than nephropathy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 934-935.

Q: All of the following are components of Dane particles except?

Delta antigen. **Explanation:** The **Dane particle** represents the complete, infectious virion of the **Hepatitis B Virus (HBV)**. It is a 42 nm spherical structure consisting of an inner core and an outer envelope. **Why Delta Antigen is the correct answer:** The **Delta antigen (HDAg)** is a component of the **Hepatitis D Virus (HDV)**, not HBV. While HDV is a "defective" virus that requires the presence of HBV (specifically HBsAg) to provide its outer envelope for assembly and transmission, the Delta antigen itself is part of the HDV ribonucleoprotein complex, not a structural component of the Dane particle. **Analysis of incorrect options:** * **Surface Antigen (HBsAg):** This is the outer lipoprotein envelope of the Dane particle. It is produced in excess, appearing as spherical and tubular forms in the serum. * **Core Antigen (HBcAg):** This forms the inner nucleocapsid that encloses the viral genome (partially double-stranded DNA) and the DNA polymerase. * **C-antigen (HBeAg):** This is a soluble protein derived from the precore/core gene. While it is primarily a secretory protein used as a marker of high infectivity, it is structurally associated with the core components of the virus. **Clinical Pearls for NEET-PG:** * **Morphology:** Dane particles are 42 nm; non-infectious spherical/tubular HBsAg particles are 22 nm. * **HBeAg:** Its presence indicates active viral replication and high infectivity. * **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs; **Anti-HBc IgM** is the only diagnostic marker during this phase. * **Ground-glass Hepatocytes:** Characteristic histopathological finding in chronic HBV infection due to HBsAg accumulation.

Q: All of the following are blood-borne infections except?

Hepatitis E. **Explanation:** The core concept tested here is the **mode of transmission** of viral hepatitis. Hepatitis viruses are broadly categorized into two groups based on their transmission routes: **Enteric** (fecal-oral) and **Parenteral** (blood-borne). **Why Hepatitis E is the correct answer:** Hepatitis E Virus (HEV) is primarily transmitted via the **fecal-oral route**, usually through contaminated drinking water. It is not considered a blood-borne infection. While rare instances of transfusion-associated HEV have been reported, its classic and primary epidemiological classification remains enteric. **Why the other options are incorrect:** * **Hepatitis B (HBV):** A classic blood-borne pathogen transmitted through infected blood, needles, sexual contact, and vertically (mother to child). * **Hepatitis C (HCV):** Primarily transmitted through percutaneous exposure to infectious blood (e.g., IV drug use, unscreened blood transfusions). * **Hepatitis G (HGV/GBV-C):** A flavivirus known to be transmitted via blood and blood products, often found as a co-infection with HCV. **High-Yield NEET-PG Pearls:** * **Mnemonic "Vowels are Bowels":** Hepatitis **A** and **E** are transmitted via the fecal-oral route (Enteric). * **Hepatitis E & Pregnancy:** HEV infection in pregnant women (especially in the 3rd trimester) carries a high mortality rate (up to 20%) due to fulminant hepatic failure. * **Hepatitis D:** It is a "defective" virus that requires the HBsAg (Hepatitis B) coat to replicate; thus, it is also blood-borne. * **Chronicity:** Hepatitis A and E generally do not cause chronic infection (except HEV in immunocompromised hosts), whereas B, C, and D frequently lead to chronic carrier states.

Q: What is the primary site of action of the poliovirus in the nervous system?

Anterior horn of the spinal cord. **Explanation:** The correct answer is **C. Anterior horn of the spinal cord.** Poliovirus is a neurotropic enterovirus. After initial replication in the oropharynx and gastrointestinal tract (Peyer's patches), the virus enters the bloodstream (viremia). In a small percentage of cases, it crosses the blood-brain barrier or spreads via retrograde axonal transport to the Central Nervous System (CNS). The virus has a specific predilection for **lower motor neurons (LMNs)** located in the **anterior horn cells** of the spinal cord and the motor nuclei of the brainstem. Destruction of these cells leads to the classic presentation of **asymmetrical flaccid paralysis** with loss of reflexes, while sensory functions remain intact. **Why other options are incorrect:** * **A. Medullary cone (Conus Medullaris):** This is the terminal end of the spinal cord. While polio can affect this region, it is a topographical location, not the specific cellular site of action. * **B & D. Posterior nerve roots/Posterior horn:** These structures are responsible for **sensory** conduction. Poliovirus characteristically spares the sensory pathways; therefore, there is no sensory loss in poliomyelitis. **High-Yield Clinical Pearls for NEET-PG:** * **Transmission:** Fecal-oral route (most common). * **Specimen of choice:** Stool is the most reliable sample for viral isolation (excreted for weeks). * **Most common presentation:** Asymptomatic/Inapparent infection (>90%). * **Post-Polio Syndrome:** Occurs decades after recovery due to the failure of compensated motor neurons. * **Vaccines:** **Salk (IPV)** uses killed virus (IgG response); **Sabin (OPV)** uses live-attenuated virus (IgA and IgG response) and can cause Vaccine-Associated Paralytic Polio (VAPP).

Q: Which of the following is an enveloped DNA virus?

Hepatitis B virus. **Explanation:** To answer this question, one must recall the structural classification of DNA and RNA viruses. Most DNA viruses are double-stranded and non-enveloped, with a few critical exceptions. **1. Why Hepatitis B Virus (HBV) is correct:** Hepatitis B belongs to the **Hepadnaviridae** family. It is a unique DNA virus characterized by a **circular, partially double-stranded DNA** genome and an **envelope** derived from the host cell membrane. The envelope contains the clinically significant Hepatitis B surface antigen (HBsAg). **2. Analysis of Incorrect Options:** * **Rhabdovirus (Option A):** While it is enveloped (bullet-shaped), it is an **RNA virus** (negative-sense, single-stranded), not a DNA virus. It causes Rabies. * **Adenovirus (Option C):** This is a DNA virus, but it is **non-enveloped** (naked). It typically causes respiratory infections, conjunctivitis, and gastroenteritis. * **Parvovirus (Option D):** This is a DNA virus, but it is **non-enveloped**. Notably, it is the only medically important **single-stranded** DNA virus (B19 causes Erythema Infectiosum). **NEET-PG High-Yield Pearls:** * **Mnemonic for Enveloped DNA Viruses:** Remember "**HHP**" — **H**epadna (HBV), **H**erpesvirus, and **P**oxvirus. (Note: Poxvirus is the only DNA virus that replicates in the cytoplasm). * **Mnemonic for Non-Enveloped DNA Viruses:** "**PAP**" — **P**apilloma, **A**deno, and **P**arvo. * **HBV Key Fact:** It uses **reverse transcriptase** during its replication cycle, despite being a DNA virus. * **Smallest DNA Virus:** Parvovirus. * **Largest DNA Virus:** Poxvirus.

Q: Which influenza strain, not of human origin, can cause a pandemic?

H5N1. ### Explanation **Correct Answer: C. H5N1** **Concept: Antigenic Shift and Pandemic Potential** A pandemic occurs when a new influenza virus emerges to which the general population has little to no immunity, and it demonstrates the ability for sustained human-to-human transmission. While **H5N1 (Avian Influenza)** is primarily a pathogen of birds (not of human origin), it is considered a significant pandemic threat. This is due to its high virulence, its ability to cross the species barrier to infect humans directly, and the potential for **Antigenic Shift**—a process where the virus acquires new gene segments (reassortment), potentially gaining the ability for efficient human-to-human spread. **Analysis of Options:** * **A. H1N1:** This strain is already established in the human population. It caused the 1918 Spanish Flu and the 2009 Swine Flu pandemic. Since it currently circulates as a seasonal flu strain, it is considered of human/swine origin in the clinical context. * **B. H2N2:** This strain caused the 1957 "Asian Flu" pandemic. Like H1N1, it is a known human pathogen that has previously circulated in the population. * **D. H9N1:** While H9 subtypes (like H9N2) are found in birds and can occasionally infect humans, they have not shown the same high-pathogenicity or pandemic potential historically associated with the H5 or H7 clusters. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Major genetic changes (reassortment) leading to **Pandemics**. Occurs only in Influenza A. * **Antigenic Drift:** Minor point mutations leading to **Epidemics** and the need for annual vaccine updates. Occurs in both Influenza A and B. * **Drug of Choice:** Oseltamivir (Neuraminidase inhibitor) is the preferred treatment for both seasonal and avian influenza. * **Gold Standard Diagnosis:** RT-PCR is the most sensitive and specific test for identifying influenza strains.

Q: What is the most common cause of viral meningoencephalitis?

Herpes simplex virus. **Explanation:** The correct answer is **Herpes simplex virus (HSV)**. In the context of **meningoencephalitis** (inflammation involving both the meninges and the brain parenchyma), **HSV-1** is the most common cause of sporadic, non-epidemic cases worldwide. It typically affects the temporal lobes, leading to characteristic clinical features like personality changes, seizures, and focal neurological deficits. **Analysis of Options:** * **Herpes simplex virus (Correct):** HSV-1 is the leading cause of fatal sporadic viral encephalitis. It is crucial to distinguish this from HSV-2, which is a more common cause of viral *meningitis* (especially in neonates or as Mollaret’s meningitis). * **Enteroviruses:** These are the most common cause of **viral (aseptic) meningitis**, but they are less frequent causes of true encephalitis compared to HSV. * **Arboviruses:** These (e.g., Japanese Encephalitis, West Nile) are significant causes of **epidemic** encephalitis in specific geographic regions, but they are not the most common cause globally or sporadically. * **Cytomegalovirus (CMV):** CMV typically causes encephalitis only in **immunocompromised** individuals (e.g., advanced HIV/AIDS) and is not the leading cause in the general population. **High-Yield Clinical Pearls for NEET-PG:** * **Site Predilection:** HSV encephalitis has a high affinity for the **temporal lobes** (look for "hemorrhagic necrosis" on pathology). * **Diagnosis:** **CSF PCR** is the gold standard investigation. * **EEG Finding:** Periodic lateralized epileptiform discharges (**PLEDs**) are characteristic. * **Treatment:** Intravenous **Acyclovir** should be started empirically if HSV encephalitis is suspected, as it significantly reduces mortality.

Q: What is the extra gene of HTLV?

Px. **Explanation:** Human T-cell Lymphotropic Virus (HTLV-1) is a retrovirus belonging to the Deltaretrovirus genus. While all retroviruses share a basic genetic structure, HTLV is categorized as a **complex retrovirus** because it contains regulatory genes in addition to the standard structural genes. **Why Px is correct:** The **Px region** is the unique "extra" genetic component located at the 3' end of the HTLV genome. It encodes several non-structural regulatory proteins, most notably **Tax** and **Rex**. * **Tax protein:** Crucial for oncogenesis; it transactivates viral and cellular gene expression (like IL-2 and IL-2 receptor), leading to uncontrolled T-cell proliferation and eventually **Adult T-cell Leukemia/Lymphoma (ATLL)**. * **Rex protein:** Regulates viral mRNA splicing and transport. **Why other options are incorrect:** * **Gag (Group-specific Antigen):** A standard retroviral gene that encodes internal structural proteins (capsid p24, nucleocapsid, and matrix). * **Pol (Polymerase):** A standard gene encoding essential enzymes: Reverse Transcriptase, Integrase, and Protease. * **Env (Envelope):** A standard gene encoding surface glycoproteins (gp46) and transmembrane proteins (gp21) required for viral entry. **High-Yield Clinical Pearls for NEET-PG:** * **Disease Associations:** HTLV-1 is primarily associated with **ATLL** (flower cells on peripheral smear) and **HAM/TSP** (HTLV-1 Associated Myelopathy/Tropical Spastic Paraparesis). * **Transmission:** Similar to HIV (Blood, Sexual, Vertical), but **breastfeeding** is a major route for HTLV-1. * **Target Cells:** Unlike HIV which destroys CD4+ cells, HTLV-1 causes **malignant transformation** of CD4+ T-cells.

Question 1

Which of the following statements is true about Herpes viruses?

Accepted Answer

Herpes Simplex Virus (HSV) encephalitis is treated with acyclovir.

Answer

Oropharyngeal involvement is common in HSV-1.

Answer

Recurrent genital involvement is seen in HSV-2.

Answer

Recurrence is rare in HSV-1.

Question 2

An emerging viral pathogen causing pyelonephritis in kidney allografts is:

Accepted Answer

Polyomavirus

Answer

Rotavirus

Answer

Herpes simplex

Answer

Influenza virus

Question 3

All of the following are components of Dane particles except?

Accepted Answer

Delta antigen

Answer

Surface antigen

Answer

Core antigen

Answer

C-antigen

Question 4

All of the following are blood-borne infections except?

Accepted Answer

Hepatitis E

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis G

Question 5

What is the primary site of action of the poliovirus in the nervous system?

Accepted Answer

Anterior horn of the spinal cord

Answer

Medullary cone

Answer

Posterior nerve roots

Answer

Posterior horn of the spinal cord

Question 6

Which of the following is an enveloped DNA virus?

Accepted Answer

Hepatitis B virus

Answer

Rhabdovirus

Answer

Adenovirus

Answer

Parvovirus

Question 7

Which of the following sequential dengue serotypes infection are associated with the maximum risk of dengue hemorrhagic fever?

Accepted Answer

DENV-1/DENV-2

Answer

DENV-3/DENV-2

Answer

DENV-4/DENV-2

Answer

Similar risk with all

Question 8

Which influenza strain, not of human origin, can cause a pandemic?

Accepted Answer

H5N1

Answer

H1N1

Answer

H2N2

Answer

H9N1

Question 9

What is the most common cause of viral meningoencephalitis?

Accepted Answer

Herpes simplex virus

Answer

Enterovirus

Answer

Arbovirus

Answer

Cytomegalovirus

Question 10

What is the extra gene of HTLV?

Accepted Answer

Px

Answer

Gag

Answer

Pol

Answer

Env

Virology — MCQs

Virology — MCQs

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