Virology Practice Questions

Q: What characterizes the latent phase of HIV infection?

Viral replication. The concept of "latency" in HIV is often a point of confusion. In HIV infection, **Clinical Latency** does not equate to **Biological Latency**. ### **Explanation of the Correct Answer** **A. Viral Replication:** During the clinical latent phase (also known as the asymptomatic or chronic phase), the virus is **not** dormant. There is persistent, vigorous viral replication occurring primarily within the lymphoid organs. Billions of new virions are produced and destroyed daily. The "latency" refers only to the absence of outward clinical symptoms, while a dynamic equilibrium exists between viral load and the host's immune response (the viral set point). ### **Analysis of Incorrect Options** * **B. Sequestration in lymphoid tissue:** While the virus is highly concentrated in the lymph nodes during this phase, it is not "sequestered" in a static sense. It is actively replicating and circulating in the plasma, albeit at lower levels than during acute infection or AIDS. * **C & D. Infectivity vs. Non-infectivity:** HIV remains **highly infectious** during the latent phase. Even if the patient is asymptomatic, the virus is present in blood, semen, and vaginal secretions. Therefore, "Non-infectivity" is factually incorrect. ### **NEET-PG High-Yield Pearls** * **The Viral Set Point:** The steady-state level of viremia achieved during the latent phase is a strong predictor of the rate of disease progression to AIDS. * **Cellular Reservoir:** True biological latency (where the virus is integrated but not replicating) occurs in **Memory CD4+ T cells**. These reservoirs are the primary obstacle to a functional cure. * **Duration:** Without ART, the clinical latent phase typically lasts 8–10 years. * **Lymph Node Architecture:** During this phase, there is follicular hyperplasia in the lymph nodes; exhaustion of this architecture leads to the terminal stage (AIDS).

Q: What is the commonest hepatotropic virus that causes an increased chronic carrier state?

Hepatitis C Virus (HCV). **Explanation:** The correct answer is **Hepatitis C Virus (HCV)**. The question asks for the virus with the highest propensity to progress to a **chronic carrier state** once an individual is infected. 1. **Why HCV is correct:** While Hepatitis B is more common globally in terms of total numbers, HCV is notorious for its high rate of chronicity. Approximately **75%–85%** of patients infected with HCV fail to clear the virus and develop chronic infection. This is primarily due to the high mutation rate of the virus (lack of proofreading by RNA polymerase), which allows it to evade the host immune response. 2. **Why the other options are incorrect:** * **Hepatitis A (HAV) and Hepatitis E (HEV):** These are transmitted via the feco-oral route and cause **acute hepatitis only**. They do not lead to chronic carrier states or chronic liver disease (Exception: HEV can cause chronicity in severely immunocompromised individuals, but this is rare and not the "commonest"). * **Hepatitis B (HBV):** While HBV causes chronic infection, the rate depends on the age of acquisition. In adults, only about **5%–10%** become chronic carriers. Although the absolute number of HBV carriers is high, the *likelihood* of an individual infection becoming chronic is significantly lower than with HCV. **High-Yield NEET-PG Pearls:** * **Highest Chronicity Rate:** HCV (80%) > HBV (5% in adults, 90% in neonates). * **HCV Screening:** Anti-HCV antibodies (ELISA); **Confirmatory/Gold Standard:** HCV RNA (PCR). * **HCV Genotypes:** Genotype 3 is the most common in India. * **Fulminant Hepatitis in Pregnancy:** Classically associated with **HEV**. * **DNA Virus:** HBV is the only DNA hepatitis virus; all others (A, C, D, E) are RNA viruses.

Q: Which of the following is the pathogen responsible for blindness in advanced HIV infections?

Cytomegalovirus. **Explanation:** **Cytomegalovirus (CMV)** is the most common cause of blindness in patients with advanced HIV/AIDS, typically occurring when the **CD4+ T-cell count falls below 50 cells/mm³**. CMV retinitis is a late-stage opportunistic infection characterized by a full-thickness necrotizing retinitis. It presents classically as the **"Pizza-pie" or "Cheese and Ketchup" appearance** (confluent areas of white retinal necrosis with associated intraretinal hemorrhages). If left untreated, it leads to retinal detachment or optic nerve involvement, resulting in permanent blindness. **Analysis of Incorrect Options:** * **Epstein-Barr virus (EBV):** While EBV is associated with Ocular Adnexal Lymphoma and Burkitt’s lymphoma in HIV patients, it is not a primary cause of retinal blindness. * **Fungus:** Fungal infections like *Cryptococcus neoformans* can cause vision loss secondary to increased intracranial pressure (papilledema) or optic neuropathy, but they are less common causes of direct retinal blindness compared to CMV. *Candida* endophthalmitis usually occurs in IV drug users rather than as a primary manifestation of advanced HIV. * **Toxoplasma:** *Toxoplasma gondii* causes necrotizing retinochoroiditis in HIV patients. While serious, it is less prevalent than CMV and typically presents with more vitreous inflammation ("headlight in the fog" appearance), whereas CMV has minimal vitritis. **High-Yield Clinical Pearls for NEET-PG:** * **Drug of Choice:** Intravenous **Ganciclovir** (or Valganciclovir). Foscarnet and Cidofovir are alternatives. * **Most common ocular finding in HIV:** HIV Microangiopathy (Cotton wool spots), which is benign and non-blinding. * **Immune Recovery Uveitis (IRU):** An inflammatory reaction in the eye that occurs when a patient with CMV retinitis starts HAART and their CD4 count rises.

Q: Which serological marker best diagnoses a recent Hepatitis B infection?

IgM anti-Hepatitis B core antibody. ### Explanation **Correct Option: D. IgM anti-Hepatitis B core antibody (IgM anti-HBc)** **Why it is correct:** IgM anti-HBc is the hallmark of **acute or recent** Hepatitis B infection (typically within the first 6 months). Its clinical significance is paramount during the **"Window Period"**—the interval where HBsAg has disappeared but Anti-HBs has not yet appeared. During this gap, IgM anti-HBc may be the **only** detectable serological marker of a recent infection. **Analysis of Incorrect Options:** * **A. HBsAg:** While it is the first marker to appear and indicates active infection, it does not distinguish between acute and chronic states. It can remain positive for decades in chronic carriers. * **B. IgG anti-HBe:** This antibody indicates reduced viral replication and low infectivity. It appears later in the course of infection and is not a primary tool for diagnosing a *recent* acute event. * **C. Anti-HBs:** This antibody signifies **immunity**, either through recovery from a natural infection or via vaccination. It appears only after the infection has resolved. **NEET-PG High-Yield Pearls:** 1. **Window Period Marker:** IgM anti-HBc is the diagnostic marker of choice when HBsAg and Anti-HBs are both negative. 2. **Vaccination vs. Natural Infection:** * **Vaccinated:** Only Anti-HBs is positive. * **Prior Natural Infection:** Both Anti-HBs and IgG anti-HBc are positive. 3. **Chronic Infection:** Defined by the persistence of HBsAg for >6 months. 4. **HBeAg:** Indicates high viral load and high infectivity ("e" for envelope/excess replication).

Q: The Dane particle is the?

HBV. **Explanation:** The **Dane particle** is the complete, infectious virion of the **Hepatitis B Virus (HBV)**. First identified by DS Dane in 1970 via electron microscopy, it is a spherical structure measuring approximately **42 nm** in diameter. It consists of an inner nucleocapsid core (containing HBcAg, the DNA genome, and DNA polymerase) surrounded by an outer lipoprotein envelope containing the surface antigen (HBsAg). **Analysis of Options:** * **Option A (HBV):** Correct. The 42 nm Dane particle represents the intact, double-shelled virus capable of replication. It is found in the serum along with smaller (22 nm) spherical and tubular forms, which are non-infectious surpluses of HBsAg. * **Option B (IgG anti-HAV):** Incorrect. This is a host antibody indicating past infection or immunity to Hepatitis A; it is not a viral particle. * **Option C (Delta Virus):** Incorrect. This refers to Hepatitis D (HDV), a defective RNA virus that requires the HBsAg coat from HBV to replicate but is not called the Dane particle. * **Option D (HBcAg):** Incorrect. This is the Hepatitis B core antigen, which is a component *inside* the Dane particle, not the particle itself. **High-Yield NEET-PG Pearls:** * **Genome:** HBV is the only DNA virus among the Hepatitis viruses (partially double-stranded circular DNA). * **Morphology:** Under EM, HBV shows three forms: Dane particles (infectious), spherical forms, and filamentous forms (both non-infectious HBsAg). * **Serology:** HBsAg is the first marker to appear in blood; Anti-HBs indicates immunity. * **DNA Polymerase:** HBV possesses reverse transcriptase activity during its replication cycle.

Q: Which staining method is useful for the antemortem diagnosis of rabies?

Direct fluorescent antibody stain. **Explanation:** The **Direct Fluorescent Antibody (DFA) test** is the gold standard for rabies diagnosis. It detects rabies virus antigens in clinical specimens. For **antemortem diagnosis**, the specimen of choice is a **full-thickness skin biopsy from the nape of the neck** (containing hair follicles and cutaneous nerves). DFA is preferred due to its high sensitivity and specificity, allowing for rapid detection before death. **Analysis of Options:** * **Sellers Stain (Option A):** This is used to visualize **Negri bodies** (intracytoplasmic inclusion bodies). While characteristic of rabies, Negri bodies are only present in about 70-80% of cases and are typically identified in **postmortem** brain tissue (Ammon’s horn). * **Macchiavello Stain (Option B):** This stain is historically used to identify **Rickettsiae** and **Chlamydia** (inclusion bodies), not the rabies virus. * **Giemsa Stain (Option C):** This is a versatile hematological stain used for malaria parasites, *Chlamydia*, and *Borrelia*, but it is not specific or diagnostic for rabies. **High-Yield Clinical Pearls for NEET-PG:** * **Gold Standard:** DFA is the most reliable test for both antemortem (skin biopsy) and postmortem (brain tissue) diagnosis. * **Negri Bodies:** These are pathognomonic for rabies but their absence does *not* rule out the disease. * **Specimen for Antemortem Diagnosis:** Skin biopsy from the nape of the neck, saliva (for RT-PCR), and CSF. * **Prophylaxis:** Rabies is 100% fatal once symptoms appear, making post-exposure prophylaxis (PEP) with wound cleaning, vaccine, and RIG (if indicated) critical.

Q: Which of the following types of viruses is MOST likely to undergo an abrupt major antigenic shift, permitting reinfection in a previously exposed individual?

Orthomyxo viruses. **Explanation:** The correct answer is **Orthomyxo viruses** (specifically Influenza A). The underlying medical concept is **Antigenic Shift**, which occurs due to the **segmented genome** of the virus. 1. **Why Orthomyxo viruses are correct:** Influenza A viruses have a genome consisting of 8 distinct RNA segments. When two different strains infect the same host cell (e.g., in a pig or bird), these segments can undergo **reassortment**. This results in a major, abrupt change in the surface glycoproteins (Hemagglutinin and Neuraminidase), creating a novel subtype. Because the population has no pre-existing immunity to this new subtype, it frequently leads to **pandemics**. 2. **Why other options are incorrect:** * **Coxsackie viruses (Picornaviridae):** These are non-enveloped, positive-sense single-stranded RNA viruses. They lack a segmented genome and do not undergo reassortment/antigenic shift. * **Hepadna viruses (Hepatitis B):** These are DNA viruses that replicate via reverse transcription. While they have various genotypes, they do not exhibit abrupt major antigenic shifts. * **Herpes viruses:** These are large, double-stranded DNA viruses. They are known for **latency** rather than antigenic shift. Their surface antigens remain relatively stable over time. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Shift:** Major change (Reassortment) $\rightarrow$ Segmented genome $\rightarrow$ Causes **Pandemics** (Only Influenza A). * **Antigenic Drift:** Minor change (Point mutations) $\rightarrow$ Occurs in both Influenza A and B $\rightarrow$ Causes **Epidemics** and necessitates annual vaccine updates. * **Segmented Viruses Mnemonic (BOAR):** **B**unyaviridae, **O**rthomyxoviridae, **A**renaviridae, **R**eoviridae. These are the viruses capable of reassortment.

Q: Which of the following statements is FALSE regarding Hepatitis C Virus?

Hepatocellular injury is caused by viral replication.. **Explanation:** The correct answer is **C**. In Hepatitis C Virus (HCV) infection, hepatocellular injury is primarily **immune-mediated** rather than a direct cytopathic effect of viral replication. The damage to hepatocytes is caused by the host’s cytotoxic T-lymphocytes (CD8+ T cells) and inflammatory cytokines attempting to clear the infected cells. This chronic inflammatory state leads to fibrosis, cirrhosis, and eventually malignancy. **Analysis of other options:** * **Option A:** HCV is a member of the *Flaviviridae* family. It is an enveloped, **positive-sense, single-stranded RNA** virus. * **Option B:** HCV is a major risk factor for **Hepatocellular Carcinoma (HCC)**. Unlike HBV, HCV does not integrate into the host genome; instead, it promotes carcinogenesis through chronic inflammation and the action of non-structural proteins (like NS5A). * **Option D:** The primary screening tool for HCV is the **anti-HCV antibody test** (ELISA). A positive result is then confirmed by HCV RNA PCR to distinguish between active infection and prior cleared infection. **High-Yield Clinical Pearls for NEET-PG:** * **"The Silent Epidemic":** HCV has the highest rate of chronicity (75–85%) among hepatitis viruses. * **Extrahepatic Manifestations:** Strongly associated with **Mixed Cryoglobulinemia**, Membranoproliferative Glomerulonephritis (MPGN), and Porphyria Cutanea Tarda. * **Treatment:** The goal is "Sustained Virologic Response" (SVR), now highly achievable with Direct-Acting Antivirals (DAAs) like Sofosbuvir. * **Vaccine:** There is **no vaccine** for HCV due to the high antigenic variation of its envelope glycoproteins (E1/E2) and the lack of proofreading by its RNA polymerase.

Q: A 29-year-old male is found to be HBsAg positive with highly increased SGOT levels but HBeAg negative. Which of the following is true about the patient's status?

Precore mutant. ### **Explanation** The clinical presentation of an **HBsAg-positive** patient with **elevated transaminases (SGOT/SGPT)** but **negative HBeAg** is a classic indicator of a **Precore Mutant** of the Hepatitis B Virus (HBV). **1. Why Precore Mutant is Correct:** In the wild-type HBV, the *precore* region of the genome codes for the HBeAg (Hepatitis B e-antigen), which serves as a marker for active viral replication and high infectivity. In a **Precore Mutant**, a point mutation (most commonly a **G-to-A mutation at nucleotide 1896**) creates a premature stop codon. This prevents the synthesis of HBeAg. However, the virus continues to replicate actively, leading to liver damage (elevated SGOT/SGPT) and high HBV DNA levels, despite the absence of HBeAg. **2. Why the Other Options are Incorrect:** * **B. Core-promoter mutant:** While these also result in reduced HBeAg production, the classic NEET-PG scenario for "HBeAg negative but active disease" specifically points toward the precore stop codon mutation. * **C. Wild type:** In a wild-type infection with high viral replication and elevated enzymes, the patient would typically be **HBeAg positive**. * **D. Surface mutant:** These mutations occur in the *S gene* (e.g., the "a" determinant). This results in "diagnostic escape" where HBsAg may be undetectable by standard assays, but it does not primarily explain the absence of HBeAg during active hepatitis. ### **Clinical Pearls for NEET-PG:** * **The Mutation:** The most common precore mutation is **G1896A**. * **Serology:** HBsAg (+), Anti-HBe (+), HBeAg (-), but **HBV DNA is high**. * **Clinical Significance:** Precore mutants are associated with a higher risk of severe liver disease, fulminant hepatitis, and progression to cirrhosis compared to the wild type. * **Treatment:** These patients require treatment even though they are HBeAg negative because the liver enzymes are elevated, indicating active necroinflammation.

Question 1

What characterizes the latent phase of HIV infection?

Accepted Answer

Viral replication

Answer

Sequestration in lymphoid tissue

Answer

Infectivity

Answer

Non-infectivity

Question 2

What is the commonest hepatotropic virus that causes an increased chronic carrier state?

Accepted Answer

Hepatitis C Virus (HCV)

Answer

Hepatitis E Virus (HEV)

Answer

Hepatitis A Virus (HAV)

Answer

Hepatitis B Virus (HBV)

Question 3

Which of the following is the pathogen responsible for blindness in advanced HIV infections?

Accepted Answer

Cytomegalovirus

Answer

Epstein-Barr virus

Answer

Fungus

Answer

Toxoplasma

Question 4

Which serological marker best diagnoses a recent Hepatitis B infection?

Accepted Answer

IgM anti-Hepatitis B core antibody

Answer

Hepatitis B surface antigen (HBsAg)

Answer

IgG anti-Hepatitis B e antibody

Answer

Anti-Hepatitis B surface antibody

Question 5

The Dane particle is the?

Accepted Answer

HBV

Answer

IgG anti HAV

Answer

Delta Virus

Answer

HBC Ag

Question 6

Which staining method is useful for the antemortem diagnosis of rabies?

Accepted Answer

Direct fluorescent antibody stain

Answer

Sellers stain

Answer

Macchiavello stain

Answer

Giemsa stain

Question 7

Which of the following types of viruses is MOST likely to undergo an abrupt major antigenic shift, permitting reinfection in a previously exposed individual?

Accepted Answer

Orthomyxo viruses

Answer

Coxsackie viruses

Answer

Hepadna viruses

Answer

Herpes viruses

Question 8

Infection with herpes simplex virus, a common human pathogen, is best described by which of the following statements?

Accepted Answer

It can be reactivated by emotional disturbances or prolonged exposure to sunlight.

Answer

The central nervous system and visceral organs are usually involved.

Answer

It rarely recurs in a host who has a high antibody titre.

Answer

Initial infection usually occurs by intestinal absorption of the virus.

Question 9

Which of the following statements is FALSE regarding Hepatitis C Virus?

Accepted Answer

Hepatocellular injury is caused by viral replication.

Answer

It has single-stranded RNA.

Answer

It is associated with hepatocellular carcinoma.

Answer

Serologic testing detects antibody to HCV.

Question 10

A 29-year-old male is found to be HBsAg positive with highly increased SGOT levels but HBeAg negative. Which of the following is true about the patient's status?

Accepted Answer

Precore mutant

Answer

Core-promoter mutant

Answer

Wild type

Answer

Surface mutant

Virology — MCQs

Virology — MCQs

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