Virology Practice Questions

Q: Which of the following serological markers is used for epidemiologic studies of Hepatitis B?

Anti HBc. **Explanation** The correct answer is **Anti-HBc (Antibody to Hepatitis B core antigen)**. **1. Why Anti-HBc is the correct answer:** In epidemiological studies, the goal is to determine the **total number of people who have ever been infected** with Hepatitis B (prevalence). Anti-HBc is the most reliable marker for this because it appears shortly after the onset of infection and **persists for life**, regardless of whether the patient recovers or becomes a chronic carrier. Unlike other markers, it does not appear after vaccination; therefore, its presence specifically indicates a natural infection (past or present). **2. Why the other options are incorrect:** * **HBeAg:** This is a marker of **active viral replication** and high infectivity. It is used to assess the degree of infectiousness, not for broad epidemiological prevalence. * **HBcAg:** This is a particulate antigen found inside the hepatocyte. It is **not detectable in the serum** under normal conditions and therefore cannot be used as a serological marker. * **HBsAg:** This is the first marker to appear and indicates **current infection** (acute or chronic). However, it disappears upon recovery. Using HBsAg alone would miss individuals who have cleared the virus, thus underestimating the total disease burden in a population. **3. NEET-PG High-Yield Pearls:** * **Window Period:** The period where HBsAg has disappeared but Anti-HBs has not yet appeared. During this time, **Anti-HBc IgM** is the only diagnostic marker. * **Vaccination vs. Natural Infection:** * **Vaccinated:** Only Anti-HBs is positive. * **Natural Infection (Recovered):** Both Anti-HBs and Anti-HBc (IgG) are positive. * **Anti-HBc IgM:** Indicates acute infection. * **Anti-HBc IgG:** Indicates past or chronic infection.

Q: Which of the following is the next most common cause of blood transfusion-related hepatitis after hepatitis B?

Hepatitis C. ### Explanation **Correct Option: C. Hepatitis C** The primary cause of post-transfusion hepatitis (PTH) globally is **Hepatitis B Virus (HBV)**, largely due to the "window period" where HBsAg is undetectable despite infectivity. **Hepatitis C Virus (HCV)** is the **second most common cause**. Before the introduction of mandatory blood screening for HCV in the 1990s, it was actually the leading cause of "Non-A, Non-B" post-transfusion hepatitis. While modern nucleic acid testing (NAT) has significantly reduced the risk, HCV remains a significant concern due to its high rate of chronicity (75–85%) following acute infection. **Analysis of Incorrect Options:** * **A. Hepatitis A:** This virus is transmitted via the **fecal-oral route**. It has a very brief viremic phase and does not lead to a chronic carrier state, making transfusion-related transmission extremely rare. * **B. Epstein-Barr Virus (EBV):** While EBV can cause hepatitis as part of infectious mononucleosis and can be transmitted via blood, it is a rare cause of clinically significant post-transfusion hepatitis compared to hepatotropic viruses. * **D. Hepatitis D:** HDV is a defective virus that requires the presence of **HBsAg** (HBV co-infection or superinfection) to replicate. While it is blood-borne, it is categorized as a complication of HBV rather than a standalone second-most common cause. **High-Yield Clinical Pearls for NEET-PG:** * **Most common cause of PTH:** Hepatitis B (due to the window period). * **Most common cause of PTH in the 1980s:** Hepatitis C (formerly Non-A, Non-B). * **Screening:** Mandatory screening for blood donors in India includes HIV, HBV (HBsAg), HCV, Syphilis, and Malaria. * **Risk Reduction:** The use of **Nucleic Acid Testing (NAT)** has drastically reduced the "window period" for HCV from ~70 days to only 3–5 days.

Q: Which of the following viruses has NOT been associated with oncogenesis?

Varicella Zoster virus. **Explanation:** The association between viruses and cancer is termed **viral oncogenesis**. This occurs when a virus introduces oncogenes into a host cell or disrupts host tumor-suppressor genes (like p53 or Rb), leading to uncontrolled cell proliferation [2]. **Why Varicella Zoster Virus (VZV) is the correct answer:** VZV (Human Herpesvirus 3) is the causative agent of **Chickenpox** and **Herpes Zoster (Shingles)** [1]. Unlike other members of the Herpesviridae family (like EBV or HHV-8), VZV is not associated with malignancy [3]. It establishes latency in the dorsal root ganglia but does not possess the molecular machinery to transform host cells into a cancerous state [1]. **Analysis of Incorrect Options:** * **Human Papilloma Virus (HPV):** High-risk types (16, 18) produce E6 and E7 oncoproteins which inhibit p53 and Rb proteins, respectively, leading to **Cervical and Oropharyngeal carcinoma** [2], [4]. * **Epstein-Barr Virus (EBV):** Known as the first human virus associated with cancer. It is linked to **Burkitt lymphoma**, Nasopharyngeal carcinoma, and Hodgkin lymphoma. * **Human T-cell Leukemia Virus (HTLV-1):** A retrovirus that causes **Adult T-cell Leukemia/Lymphoma (ATLL)** by producing the *Tax* protein, which stimulates cell proliferation [4]. **High-Yield Clinical Pearls for NEET-PG:** * **DNA Oncogenic Viruses:** HPV, EBV, HBV, HHV-8 (Kaposi Sarcoma), and Merkel Cell Polyomavirus [3]. * **RNA Oncogenic Viruses:** HTLV-1 and Hepatitis C Virus (HCV) [4]. * **Key Mechanism:** Most DNA oncoviruses integrate into the host genome or exist as episomes [4], whereas HCV (an RNA virus) causes cancer primarily through chronic inflammation and hepatocyte regeneration.

Q: Renal involvement is seen in which of the following infections?

Polyoma virus. **Explanation:** The **Polyomaviridae** family, specifically the **BK and JC viruses**, are classic "nephrotropic" viruses. After a primary respiratory infection in childhood, these viruses remain latent in the **renal tubular epithelium**. In immunocompromised states (e.g., renal transplant recipients), the BK virus reactivates, leading to **BK virus-associated nephropathy (BKVAN)** and hemorrhagic cystitis. The JC virus, while primarily known for Progressive Multifocal Leukoencephalopathy (PML), also persists in the kidneys and is excreted in the urine. **Analysis of Options:** * **Polyoma virus (Correct):** It is the most direct answer because the kidney is its primary site of latency and clinical manifestation (BKVAN). * **Cytomegalovirus (CMV):** While CMV can be detected in urine and may cause systemic disease in transplant patients, it primarily targets the lungs (pneumonitis), retina (retinitis), and GI tract rather than being primarily defined by renal involvement. * **Human Papilloma virus (HPV):** HPV is strictly epitheliotropic, targeting the skin and mucosal surfaces (warts, cervical cancer). It does not involve the renal parenchyma. * **HIV:** While HIV can cause "HIV-Associated Nephropathy" (HIVAN), the virus itself infects CD4+ T cells and macrophages. The renal damage is a secondary complication of the systemic infection rather than the virus being primarily nephrotropic. **High-Yield Clinical Pearls for NEET-PG:** * **Decoy Cells:** Look for these in urine cytology; they are renal tubular cells with enlarged, basophilic intranuclear inclusions characteristic of Polyoma virus (BK virus). * **BK Virus:** "B" is for **B**ad **K**idney (Nephropathy/Ureteric stenosis). * **JC Virus:** "J" is for **J**unk **C**erebrum (PML). * **SV40:** A simian polyomavirus known for its potential oncogenic properties in laboratory settings.

Q: All the following viruses are known to cause Lymphomas except:

Japanese Encephalitis virus. **Explanation:** The correct answer is **Japanese Encephalitis Virus (JEV)** because it is a neurotropic virus belonging to the *Flaviviridae* family. It primarily causes acute encephalitis (inflammation of the brain parenchyma) and is not associated with oncogenesis or the development of malignancies like lymphoma. **Analysis of Options:** * **HTLV-I (Human T-cell Leukemia Virus-1):** This retrovirus is the definitive causative agent of **Adult T-cell Leukemia/Lymphoma (ATLL)**. It integrates into the host genome and utilizes the *Tax* protein to drive uncontrolled T-cell proliferation. * **EBV (Epstein-Barr Virus/HHV-4):** A highly oncogenic herpesvirus associated with several B-cell lymphomas, including **Burkitt Lymphoma** (starry-sky appearance), Hodgkin Lymphoma, and Diffuse Large B-cell Lymphoma (DLBCL), especially in immunocompromised patients. * **KSHV/HHV-8 (Kaposi Sarcoma-associated Herpesvirus):** Beyond causing Kaposi Sarcoma, this virus is the primary driver of **Primary Effusion Lymphoma (PEL)** and Multicentric Castleman Disease. **High-Yield NEET-PG Pearls:** * **Oncogenic DNA Viruses:** EBV, HHV-8, HBV, HPV (16, 18), and Merkel Cell Polyomavirus. * **Oncogenic RNA Viruses:** HTLV-1 and HCV (HCV is associated with B-cell Non-Hodgkin Lymphoma). * **JEV Key Fact:** It is transmitted by the *Culex tritaeniorhynchus* mosquito; the "amplifier host" is the pig. It is the most common cause of epidemic viral encephalitis in India. * **Burkitt Lymphoma Marker:** Associated with the **t(8;14)** translocation involving the *c-myc* gene.

Q: Condyloma acuminatum is caused by which types of HPV?

6, 11. **Explanation:** **Condyloma acuminatum**, commonly known as anogenital warts, is a sexually transmitted infection caused by the **Human Papillomavirus (HPV)**. **1. Why Option C is Correct:** HPV types **6 and 11** are classified as **"low-risk"** genotypes. They are responsible for approximately 90% of all cases of Condyloma acuminatum. These types cause benign epithelial proliferation (warts) but have a very low potential for malignant transformation into squamous cell carcinoma. **2. Analysis of Incorrect Options:** * **Option D (16, 18):** These are **"high-risk"** oncogenic types. While they can cause flat lesions, they are primarily associated with cervical intraepithelial neoplasia (CIN), cervical cancer, and other anogenital malignancies (vulvar, anal, and penile cancers). * **Option A (18, 31):** Both are high-risk types associated with malignancy rather than benign condylomas. * **Option B (17, 12):** These types are associated with **Epidermodysplasia verruciformis**, a rare genetic disorder characterized by an increased susceptibility to specific HPV strains and subsequent skin cancer. **3. NEET-PG High-Yield Pearls:** * **Clinical Appearance:** Flesh-colored, cauliflower-like growths in the perianal or genital region. * **Histopathology:** Characterized by **Koilocytes** (keratinocytes with perinuclear halo and wrinkled "raisinoid" nuclei). * **Treatment of Choice:** Podophyllotoxin, Imiquimod (immunomodulator), or destructive methods like cryotherapy and CO2 laser. * **Vaccination:** The quadrivalent vaccine (Gardasil) covers types 6, 11, 16, and 18, protecting against both warts and cervical cancer.

Q: What is the commonest hepatotropic virus that progresses to chronicity?

HCV. **Explanation:** The correct answer is **HCV (Hepatitis C Virus)**. The primary factor determining "chronicity" is the virus's ability to evade the host immune response and persist in the liver for more than six months. **Why HCV is the correct answer:** HCV has the highest rate of progression to chronic infection among all hepatotropic viruses. Approximately **75%–85%** of individuals infected with HCV fail to clear the virus acutely and develop chronic hepatitis [1]. This high rate of chronicity is largely due to the virus's high mutation rate (quasispecies), which allows it to stay ahead of the host’s immune system [1]. **Analysis of Incorrect Options:** * **HAV (Hepatitis A) & HEV (Hepatitis E):** These are transmitted via the fecal-oral route and typically cause acute, self-limiting illness. They **do not** progress to chronicity in immunocompetent individuals [2]. (Note: HEV can cause chronic infection specifically in organ transplant recipients or immunocompromised patients). * **HBV (Hepatitis B):** While HBV can become chronic, the rate depends heavily on the age of acquisition. In adults, only about **5%** of infections become chronic [1]. Although the absolute number of chronic HBV carriers is high globally, the *probability* of an individual infection progressing to chronicity is significantly lower than that of HCV [1]. **High-Yield Clinical Pearls for NEET-PG:** * **Highest risk of chronicity:** HCV (up to 85%) [1]. * **Highest risk of Fulminant Hepatic Failure in pregnancy:** HEV. * **HBV Chronicity Risk:** 90% in neonates (vertical transmission), 20-30% in children, and <5% in adults [1]. * **HCV Screening:** Anti-HCV antibody is the screening test; HCV-RNA (PCR) is the gold standard for confirming active infection [1]. * **DNA vs. RNA:** HBV is the only DNA hepatotropic virus; all others (A, C, D, E) are RNA viruses.

Q: A patient, two months post-renal transplantation, presents with difficulty in breathing. X-ray shows bilateral diffuse interstitial pneumonia. What is the most probable etiologic agent?

Cytomegalovirus (CMV). ### **Explanation** **Correct Option: A. Cytomegalovirus (CMV)** Cytomegalovirus is the most common viral opportunistic infection in solid organ transplant (SOT) recipients, typically manifesting **1 to 6 months post-transplantation** (the period of maximal immunosuppression). In renal transplant patients, CMV classically presents as **interstitial pneumonia**, fever, and leukopenia. The radiological finding of bilateral diffuse interstitial infiltrates is a hallmark of CMV pneumonitis in this clinical context. **Analysis of Incorrect Options:** * **B. Histoplasma capsulatum:** While it can cause fungal pneumonia in immunocompromised hosts, it is geographically restricted (endemic areas) and usually presents with granulomatous lesions or mediastinal lymphadenopathy rather than diffuse interstitial pneumonia 2 months post-op. * **C. Candida species:** Candida is a common cause of oral thrush or candidemia in transplant patients, but it is a very rare cause of primary interstitial pneumonia. * **D. Pneumocystis jirovecii (PJP):** PJP presents similarly with diffuse interstitial infiltrates. However, due to the routine use of **Trimethoprim-Sulfamethoxazole (TMP-SMX) prophylaxis** in the first 6–12 months post-transplant, its incidence has significantly decreased, making CMV the more statistically probable answer in modern clinical scenarios. **High-Yield Clinical Pearls for NEET-PG:** * **Timeline:** CMV is the "King of the Middle Period" (1–6 months post-transplant). * **Diagnosis:** The gold standard for tissue diagnosis is the presence of **"Owl’s eye" inclusion bodies** (intranuclear inclusions with a clear halo). * **Treatment:** Intravenous **Ganciclovir** is the drug of choice for CMV pneumonitis; Valganciclovir is used for prophylaxis. * **Monitoring:** CMV viremia is monitored using quantitative PCR or the pp65 antigenemia assay.

Q: Regarding HIV, which of the following statements is not true?

It is a DNA retrovirus.. ### Explanation **1. Why Option A is the correct (False) statement:** HIV (Human Immunodeficiency Virus) is an **RNA virus**, not a DNA virus. Specifically, it belongs to the family *Retroviridae* and the genus *Lentivirus*. It contains two identical copies of single-stranded, positive-sense RNA (+ssRNA). While it produces a DNA intermediate during its life cycle, the virion itself carries RNA as its genetic material. **2. Analysis of other options:** * **Option B (True):** HIV contains the enzyme **Reverse Transcriptase** (RNA-dependent DNA polymerase). This enzyme is crucial for transcribing the viral RNA into complementary DNA (cDNA), which then integrates into the host genome. * **Option C (True):** While CD4+ T helper cells are the primary targets, HIV also infects other cells expressing the CD4 receptor and coreceptors (CCR5/CXCR4). These include **monocytes, macrophages, dendritic cells, and microglial cells** in the brain. * **Option D (True):** A hallmark of HIV progression to AIDS is the progressive depletion of CD4+ T cells. This occurs through direct viral lysis, syncytia formation, and apoptosis, leading to profound immunodeficiency at the late stage of the disease. ### NEET-PG High-Yield Pearls * **Structure:** HIV is an enveloped, icosahedral virus. The envelope contains spikes of **gp120** (for attachment) and **gp41** (for fusion). * **Key Genes:** * *gag*: Codes for structural proteins (p24 - the major capsid antigen used in early diagnosis). * *pol*: Codes for enzymes (Reverse Transcriptase, Integrase, Protease). * *env*: Codes for envelope glycoproteins (gp160, cleaved into gp120 and gp41). * **Screening vs. Confirmation:** ELISA is the standard screening test (high sensitivity), while **Western Blot** was traditionally the confirmatory test (high specificity), though current protocols often use 4th generation p24/antibody combination assays followed by nucleic acid testing (NAT).

Q: A 30-year-old patient presented with a 10-day history of jaundice. Liver function tests showed a bilirubin of 10 mg/dL, SGOT/SGPT of 1100/1450 IU/L, and serum alkaline phosphatase of 240 IU/L. The patient tested positive for HbsAg. What is the confirmatory test to establish acute hepatitis B infection?

IgM Anti-HBc antibody. ### **Explanation** The clinical presentation of jaundice with significantly elevated transaminases (SGOT/SGPT >1000 IU/L) and positive HBsAg indicates a diagnosis of Hepatitis B. However, HBsAg alone cannot distinguish between a **new acute infection** and a **chronic carrier state** experiencing a flare. **1. Why IgM Anti-HBc is the Correct Answer:** The **IgM antibody to Hepatitis B core antigen (IgM anti-HBc)** is the specific marker for **acute infection**. It appears shortly after HBsAg and remains positive for approximately 6 months. Crucially, it is the only marker present during the **"Window Period"** (the gap between the disappearance of HBsAg and the appearance of Anti-HBs). Its presence confirms that the infection was acquired recently. **2. Analysis of Incorrect Options:** * **HBeAg (Option B):** This is a marker of **active viral replication and high infectivity**. While often present in acute phases, it can also be positive in chronic hepatitis; it does not specifically define the "acute" stage. * **HBV DNA by PCR (Option C):** This measures viral load. While highly sensitive for diagnosing infection and monitoring treatment, it does not differentiate between acute and chronic phases. * **Anti-HBc antibody (Option D):** This refers to "Total" Anti-HBc (IgM + IgG). Since IgG persists for life, a total antibody test cannot distinguish between a current acute infection and a past/chronic infection. **3. NEET-PG High-Yield Pearls:** * **HBsAg:** First marker to appear in blood (1–12 weeks after exposure). * **Window Period Marker:** IgM Anti-HBc is the diagnostic marker of choice when HBsAg has cleared but Anti-HBs hasn't appeared yet. * **Chronic Infection:** Defined by the persistence of HBsAg for **>6 months**. * **Recovery/Immunity:** Marked by the appearance of **Anti-HBs** (also the only marker positive after vaccination).

Question 1

Which of the following serological markers is used for epidemiologic studies of Hepatitis B?

Accepted Answer

Anti HBc

Answer

HBe Ag

Answer

HBc Ag

Answer

HBs Ag

Question 2

Which of the following is the next most common cause of blood transfusion-related hepatitis after hepatitis B?

Accepted Answer

Hepatitis C

Answer

Hepatitis A

Answer

Epstein-Barr hepatitis

Answer

Hepatitis D

Question 3

Which of the following viruses has NOT been associated with oncogenesis?

Accepted Answer

Varicella Zoster virus

Answer

Human Papilloma Viruses

Answer

Epstein Barr virus

Answer

Human T cell leukemia virus

Question 4

Renal involvement is seen in which of the following infections?

Accepted Answer

Polyoma virus

Answer

Cytomegalovirus

Answer

Human Papilloma virus

Answer

HIV

Question 5

All the following viruses are known to cause Lymphomas except:

Accepted Answer

Japanese Encephalitis virus

Answer

Human T cell leukemia Virus (HTLV-I)

Answer

Epstein Barr Virus (EBV)

Answer

KSHV/ HHV-8

Question 6

Condyloma acuminatum is caused by which types of HPV?

Accepted Answer

6, 11

Answer

18, 31

Answer

17, 12

Answer

16, 18

Question 7

What is the commonest hepatotropic virus that progresses to chronicity?

Accepted Answer

HCV

Answer

HEV

Answer

HAV

Answer

HBV

Question 8

A patient, two months post-renal transplantation, presents with difficulty in breathing. X-ray shows bilateral diffuse interstitial pneumonia. What is the most probable etiologic agent?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Histoplasma capsulatum

Answer

Candida species

Answer

Pneumocystis jirovecii

Question 9

Regarding HIV, which of the following statements is not true?

Accepted Answer

It is a DNA retrovirus.

Answer

It contains Reverse Transcriptase.

Answer

It may infect host CD4 cells other than T lymphocytes.

Answer

It causes a reduction in host CD4 cells at a late stage of disease.

Question 10

A 30-year-old patient presented with a 10-day history of jaundice. Liver function tests showed a bilirubin of 10 mg/dL, SGOT/SGPT of 1100/1450 IU/L, and serum alkaline phosphatase of 240 IU/L. The patient tested positive for HbsAg. What is the confirmatory test to establish acute hepatitis B infection?

Accepted Answer

IgM Anti-HBc antibody

Answer

HbeAg

Answer

HBV DNA by PCR

Answer

Anti-HBc antibody

Virology — MCQs

Virology — MCQs

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