Virology Practice Questions

Q: Which of the following is a DNA virus?

Adenovirus. **Explanation:** The classification of viruses based on their genetic material is a fundamental concept in virology. Most animal viruses contain either DNA or RNA. **Correct Answer: B. Adenovirus** Adenoviruses are non-enveloped, icosahedral viruses containing **double-stranded DNA (dsDNA)**. They are a classic example of DNA viruses and are clinically significant for causing respiratory tract infections (pharyngoconjunctival fever), epidemic keratoconjunctivitis, and hemorrhagic cystitis. **Analysis of Incorrect Options:** * **A. Poliovirus:** A member of the *Picornaviridae* family, it is a single-stranded, positive-sense RNA (+ssRNA) virus. * **C. Parvovirus:** While Parvovirus B19 is indeed a DNA virus, it is unique because it is **single-stranded DNA (ssDNA)**. In many standardized exams, if a question asks for "the" DNA virus among options containing both dsDNA and ssDNA, the focus is often on the standard dsDNA structure unless "ssDNA" is specified. However, in a strict classification sense, both B and C are DNA viruses. In the context of typical NEET-PG patterns, Adenovirus is the prototypical dsDNA virus. * **D. Hepatitis A virus:** Like Poliovirus, it belongs to the *Picornaviridae* family and contains +ssRNA. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for DNA Viruses:** "**HHAPPPPy**" – **H**erpes, **H**epadna, **A**deno, **P**apilloma, **P**olyoma, **P**arvo, and **P**ox. * **Exceptions to remember:** All DNA viruses are double-stranded except **Parvovirus** (ssDNA). All DNA viruses are icosahedral except **Poxvirus** (complex/brick-shaped). * **Replication:** All DNA viruses replicate in the **nucleus**, except **Poxvirus**, which replicates in the cytoplasm (carrying its own DNA-dependent RNA polymerase).

Q: What is the significance of mutation of CCR5 protein?

High resistance to HIV infection. ### Explanation **Core Concept:** HIV-1 primarily enters host CD4+ T-cells by binding to the CD4 receptor and a specific co-receptor. The **CCR5 protein** is a chemokine receptor that serves as the essential co-receptor for **M-tropic (Macrophage-tropic)** strains of HIV, which are responsible for the initial infection and transmission. A specific mutation known as the **CCR5-Δ32 (delta 32) mutation** results in a truncated, non-functional protein that is not expressed on the cell surface. Individuals who are **homozygous** for this mutation lack the "doorway" for the virus to enter, conferring **high resistance to HIV infection**. Heterozygotes typically show a slower progression to AIDS. **Analysis of Options:** * **Option A (Correct):** Without a functional CCR5 co-receptor, the virus cannot fuse with the host cell membrane, preventing infection. * **Option B:** A mutation (specifically Δ32) leads to resistance, not susceptibility, because the virus loses its binding site. * **Option C:** Resistance to ART is usually due to mutations in the viral genome (e.g., Pol gene mutations affecting Reverse Transcriptase or Protease), not host receptor mutations. * **Option D:** Virulence is a viral property; host receptor mutations affect the host's "permissiveness" to infection rather than the inherent pathogenicity of the virus. **High-Yield Clinical Pearls for NEET-PG:** * **CXCR4:** This is the co-receptor for **T-tropic** strains, which usually appear later in the course of the disease (associated with rapid CD4 decline). * **Maraviroc:** A drug that acts as a **CCR5 antagonist**, mimicking the effect of the mutation to prevent viral entry. * **Berlin Patient:** The first person cured of HIV received a bone marrow transplant from a donor homozygous for the CCR5-Δ32 mutation. * **GP120:** The viral envelope protein that initially binds to CD4 and then undergoes a conformational change to bind to CCR5/CXCR4.

Q: Which of the following statements regarding rabies is true?

Incubation period depends on the site of the bite.. ### Explanation **Correct Answer: A. Incubation period depends on the site of the bite.** Rabies virus is a neurotropic virus that travels from the site of inoculation to the Central Nervous System (CNS) via **retrograde axonal transport**. Because the virus moves at a relatively constant speed (approx. 50–100 mm/day), the distance between the bite site and the brain determines the incubation period. Bites on the face or neck have a significantly shorter incubation period compared to bites on the leg. **Analysis of Incorrect Options:** * **B. Diagnosis is by eosinophilic intranuclear inclusions:** This is incorrect. Rabies is characterized by **Negri bodies**, which are **intracytoplasmic** (not intranuclear) eosinophilic inclusions found typically in the pyramidal cells of the hippocampus and Purkinje cells of the cerebellum. * **C. It is a DNA virus:** Rabies is caused by the Rabies virus, which belongs to the genus *Lyssavirus* and family *Rhabdoviridae*. It is a **negative-sense, single-stranded RNA virus**. * **D. It is caused only by dogs:** While domestic dogs are the most common source of transmission in India, rabies can be transmitted by any warm-blooded mammal, including cats, monkeys, bats, foxes, and wolves. **High-Yield Clinical Pearls for NEET-PG:** * **Shape:** Bullet-shaped virus with a lipoprotein envelope containing G-spikes. * **Incubation Period:** Usually 1–3 months (range: 1 year). * **Hydrophobia:** Pathognomonic sign caused by spasms of the muscles of deglutition when attempting to swallow water. * **Post-Exposure Prophylaxis (PEP):** Includes wound toilet, Rabies Vaccine (IDRV/IM), and Rabies Immunoglobulin (RIG) for Category III bites. * **Street Virus vs. Fixed Virus:** "Street virus" is the wild strain; "Fixed virus" is the attenuated strain used for vaccine production (e.g., Semple vaccine).

Q: What is the causative agent of hairy leukoplakia, a condition characterized by severe discomfort on the lateral part of the tongue?

Epstein-Barr Virus (EBV). **Explanation:** **Oral Hairy Leukoplakia (OHL)** is a clinical marker of significant immunodeficiency, most commonly associated with HIV/AIDS. The correct answer is **Epstein-Barr Virus (EBV)**. The underlying pathophysiology involves the opportunistic replication of EBV within the squamous epithelium of the tongue. It presents as white, corrugated (hairy), non-scrapable patches, typically localized to the **lateral borders of the tongue**. **Analysis of Options:** * **Epstein-Barr Virus (EBV):** This is the definitive causative agent. While OHL is a sign of HIV progression, the virus actually replicating in the lesion is EBV. * **Human Immunodeficiency Virus (HIV):** While OHL is highly predictive of HIV infection, the virus itself does not cause the epithelial changes; it merely creates the immunosuppressed state that allows EBV to flourish. * **Herpes Simplex Virus (HSV):** HSV typically causes painful, grouped vesicles or punched-out erosions (herpetic stomatitis), not fixed white plaques. * **Human Papillomavirus (HPV):** HPV is associated with oral warts (verruca vulgaris) or condylomas, which present as pedunculated or sessile papules with a "cauliflower" surface, rather than lateral "hairy" plaques. **High-Yield Clinical Pearls for NEET-PG:** * **Differential Diagnosis:** Unlike Oral Candidiasis (Thrush), the lesions of OHL **cannot be scraped off** with a tongue depressor. * **Prognostic Significance:** In an undiagnosed patient, OHL is a "red flag" for HIV and often indicates a CD4 count below 200–300 cells/mm³. * **Treatment:** Usually unnecessary as it is asymptomatic; however, if required, systemic antivirals like Acyclovir or topical Podophyllin can be used. * **Histology:** Look for "balloon cells" (koicyte-like cells) in the upper stratum spinosum and nuclear inclusions.

Q: Which of the following statements is true about Herpes viruses?

Herpes Simplex Virus type 1 (HSV-1) can cause encephalitis.. **Explanation:** **1. Why Option A is Correct:** Herpes Simplex Virus type 1 (HSV-1) is the most common cause of **sporadic fatal viral encephalitis** worldwide. It typically involves the **temporal lobes**, leading to hemorrhagic necrosis. Clinically, patients present with fever, altered consciousness, and focal neurological deficits. In NEET-PG, remember that HSV-1 causes encephalitis in adults/older children, while HSV-2 is more commonly associated with neonatal meningitis. **2. Analysis of Other Options:** * **Option B:** While EBV does infect B lymphocytes (via the CD21 receptor), this statement is technically "true" in a general sense. however, in the context of this specific question format, Option A is the most definitive clinical hallmark often tested. *Note: In many competitive exams, if multiple statements are factually correct, the most clinically significant or "classic" textbook fact is prioritized.* * **Option C:** CMV infection is indeed often asymptomatic in immunocompetent individuals, but it is a major pathogen in immunocompromised hosts (causing retinitis or pneumonia). * **Option D:** Herpes zoster (shingles) is the reactivation of the latent Varicella-Zoster Virus (VZV) from the dorsal root ganglia. **3. NEET-PG High-Yield Clinical Pearls:** * **Tzanck Smear:** Used for HSV and VZV; look for **multinucleated giant cells** and Cowdry Type A inclusion bodies. * **EBV:** Associated with Burkitt’s Lymphoma, Nasopharyngeal Carcinoma, and Infectious Mononucleosis (Heterophile positive). * **CMV:** Characterized by **"Owl’s eye"** intranuclear inclusion bodies. * **HHV-8:** Causative agent of Kaposi Sarcoma in HIV patients. * **Site of Latency:** HSV-1 (Trigeminal ganglia), HSV-2 (Sacral ganglia), VZV (Dorsal root ganglia), EBV (B-cells).

Q: HIV is transmitted by all of the following routes except?

Saliva. ### Explanation **Correct Option: A (Saliva)** While HIV-1 and HIV-2 can be detected in various body fluids, **saliva** is not a significant route of transmission. The concentration of the virus in saliva is extremely low (low viral load). Furthermore, saliva contains endogenous antiviral factors, such as **Secretory Leukocyte Protease Inhibitor (SLPI)** and enzymes like lysozyme, which inhibit HIV infectivity. Therefore, casual contact like kissing, sharing utensils, or exposure to saliva does not pose a clinical risk for transmission. **Analysis of Incorrect Options:** * **B. Needle Prick Injury:** This is a classic example of **parenteral transmission**. The risk of HIV transmission after a percutaneous needle-stick injury involving HIV-infected blood is approximately **0.3%**. * **C. Blood Transmission:** Transfusion of infected whole blood or blood products (e.g., clotting factors) is the most efficient route of transmission, with a risk exceeding **90%** per exposure. * **D. Sexual Intercourse:** This is the most common mode of transmission globally. The risk is higher for receptive anal intercourse compared to vaginal intercourse. **High-Yield Clinical Pearls for NEET-PG:** * **Body fluids with high viral load:** Blood, Semen, Vaginal secretions, and Breast milk. * **Body fluids with negligible risk:** Saliva, Tears, Sweat, and Urine (unless visibly bloody). * **Vertical Transmission:** HIV can be transmitted from mother to child in utero, during delivery (most common), or via breastfeeding. * **Post-Exposure Prophylaxis (PEP):** Should be started as soon as possible, ideally within **2 hours** and no later than **72 hours**, continuing for 28 days.

Q: Which virus is cultivated using human fibroblast cell lines?

Poliovirus. **Explanation:** The cultivation of viruses requires living systems, and cell cultures are the most common method used in diagnostic virology. Cell lines are categorized based on their origin and "lifespan" in vitro. **Why Poliovirus is correct:** Poliovirus is traditionally cultivated using **Human Diploid Cell Strains**, such as **WI-38** or **MRC-5**, which are derived from human embryonic lung **fibroblasts**. These cells are "diploid" because they maintain the normal human chromosome complement and typically undergo about 50 passages before senescence. They are the preferred substrate for isolating fastidious viruses and are extensively used in the production of human viral vaccines (e.g., IPV and OPV). **Analysis of Incorrect Options:** * **Adenovirus:** Typically cultivated in **Continuous (Malignant) Cell Lines** like **HeLa**, HEp-2, or KB cells. These are immortalized cells derived from human cancers. * **HIV:** Primarily cultivated in **primary cultures of human T-lymphocytes** or specific lymphoid cell lines, as the virus requires CD4+ receptors for entry. * **Measles virus:** Often isolated using the **Monkey Kidney cell line (Vero cells)** or primary human embryonic kidney cells. **NEET-PG High-Yield Pearls:** 1. **Primary Cell Lines:** Normal cells taken directly from an animal/human (e.g., Monkey Kidney). They are best for primary isolation but cannot be subcultured indefinitely. 2. **Continuous Cell Lines:** Derived from cancer cells (e.g., **HeLa** from cervical cancer, **Vero** from Vervet monkey kidney). They can be subcultured indefinitely. 3. **Cytopathic Effect (CPE):** Poliovirus produces characteristic "rounding" of cells and rapid cell death in culture. 4. **Eagle’s Medium:** The most common nutrient medium used for maintaining these cell cultures.

Question 1

A latent, measles-like viral infection and, presumably, a defect in cellular immunity is associated with which of the following diseases?

Accepted Answer

Subacute sclerosing panencephalitis (SSPE)

Answer

Progressive multifocal leukoencephalopathy (PML)

Answer

Multiple sclerosis (MS)

Answer

Creutzfeldt-Jakob disease

Question 2

Which of the following is a DNA virus?

Accepted Answer

Adenovirus

Answer

Poliovirus

Answer

Parvovirus

Answer

Hepatitis A virus

Question 3

What is the significance of mutation of CCR5 protein?

Accepted Answer

High resistance to HIV infection

Answer

High susceptibility to HIV infection

Answer

Causes resistance to anti-retroviral therapy

Answer

Causes increased virulence of the virus

Question 4

Which of the following statements regarding rabies is true?

Accepted Answer

Incubation period depends on the site of the bite.

Answer

Diagnosis is by eosinophilic intranuclear inclusions.

Answer

It is a DNA virus.

Answer

It is caused only by dogs.

Question 5

What is the causative agent of hairy leukoplakia, a condition characterized by severe discomfort on the lateral part of the tongue?

Accepted Answer

Epstein-Barr Virus (EBV)

Answer

Human Immunodeficiency Virus (HIV)

Answer

Herpes Simplex Virus

Answer

Human Papillomavirus (HPV)

Question 6

Which of the following statements is true about Herpes viruses?

Accepted Answer

Herpes Simplex Virus type 1 (HSV-1) can cause encephalitis.

Answer

Epstein-Barr Virus (EBV) affects B lymphocytes.

Answer

Cytomegalovirus (CMV) infection is not always symptomatic.

Answer

Herpes zoster is a reactivation of the Varicella-Zoster Virus.

Question 7

HIV is transmitted by all of the following routes except?

Accepted Answer

Saliva

Answer

Needle prick injury

Answer

Blood transmission

Answer

Sexual intercourse

Question 8

Which virus is cultivated using human fibroblast cell lines?

Accepted Answer

Poliovirus

Answer

Adenovirus

Answer

HIV

Answer

Measles virus

Question 9

All of the following statements regarding influenza viruses are true except:

Accepted Answer

Single stranded, segmented RNA

Answer

Helical symmetry

Answer

Haemagglutinin and neuraminidase spikes are present

Answer

Possess RNA-dependent RNA polymerase

Question 10

A 35-year-old man developed headache, nausea, vomiting, and sore throat 8 weeks after returning from a trip abroad. He eventually refused to drink water and had episodes of profuse salivation, difficulty in breathing, and hallucinations. Two days after the patient died of cardiac arrest, it was learned that he had been bitten by a dog while on his trip. Which of the following treatments, if given immediately after the dog bite, could have helped prevent this disease?

Accepted Answer

Rabies immune globulin plus rabies vaccine

Answer

Broad-spectrum antibiotics

Answer

High-dose acyclovir

Answer

IV ribavirin

Virology — MCQs

Virology — MCQs

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