Virology Practice Questions

Q: Prion structure contains primarily?

Protein. **Explanation:** **1. Why Protein is Correct:** Prions (Proteinaceous Infectious Particles) are unique pathogens because they are composed **entirely of protein** and lack any nucleic acid genome. The underlying medical concept involves the conformational change of a normal host cellular protein, **PrPc** (rich in alpha-helices), into a pathological, misfolded isoform called **PrPsc** (rich in beta-pleated sheets). This misfolded protein is resistant to protease enzymes, heat, and standard disinfection, allowing it to accumulate in the brain and cause neurodegeneration. **2. Why Other Options are Incorrect:** * **B, C, and D (DNA/RNA):** Unlike viruses, bacteria, or fungi, prions do not contain any genetic material. They violate the "Central Dogma" of biology because they replicate by inducing conformational changes in existing host proteins rather than through nucleic acid replication. Any agent containing DNA or RNA would be classified as a virus, viroid, or cellular organism. **3. High-Yield Clinical Pearls for NEET-PG:** * **Resistance:** Prions are notoriously resistant to conventional sterilization (autoclaving at 121°C). The recommended method is **autoclaving at 134°C for 1–1.5 hours** or using **1N NaOH** for 1 hour. * **Histopathology:** Characterized by **spongiform degeneration** (vacuolation of neurons), neuronal loss, and amyloid plaques without any inflammatory response. * **Key Diseases:** * **Humans:** Kuru (associated with cannibalism), Creutzfeldt-Jakob Disease (CJD), and Fatal Familial Insomnia. * **Animals:** Scrapie (sheep) and Bovine Spongiform Encephalopathy (Mad Cow Disease). * **Diagnosis:** Detection of **14-3-3 protein** in CSF is a significant diagnostic marker for CJD.

Q: Which form of hepatitis is considered non-parenteral?

Hepatitis E. ### Explanation **Core Concept: Routes of Transmission** Hepatitis viruses are primarily categorized by their mode of transmission into two groups: **Enteric** (fecal-oral) and **Parenteral** (blood-borne/sexual). **Why Hepatitis E is Correct:** Hepatitis E (HEV) is a **non-enveloped RNA virus** transmitted via the **fecal-oral route**, primarily through contaminated water. Because it does not require blood-to-blood contact or mucosal exposure to infected body fluids for transmission, it is classified as **non-parenteral**. Hepatitis A is the only other major hepatitis virus that shares this non-parenteral, enteric transmission route. **Why the Other Options are Incorrect:** * **Hepatitis B (HBV):** A DNA virus transmitted via parenteral routes (blood transfusion, IV drug use), sexual contact, and vertical transmission (mother-to-child). * **Hepatitis C (HCV):** An RNA virus primarily transmitted through parenteral exposure, most commonly via infected blood (IV drug use or unscreened transfusions). * **Hepatitis D (HDV):** A defective RNA virus that requires the presence of HBV (HBsAg) to replicate; therefore, it follows the same parenteral transmission patterns as Hepatitis B. **NEET-PG High-Yield Pearls:** * **Vowels for the Bowels:** Remember that Hepatitis **A** and **E** are transmitted via the fecal-oral route (enteric). * **Pregnancy Risk:** HEV is notorious for causing high mortality (up to 20%) in **pregnant women**, often leading to Fulminant Hepatic Failure. * **Chronicity:** Unlike HBV, HCV, and HDV, Hepatitis E typically causes acute infection and does not lead to chronic hepatitis (except in severely immunocompromised patients/transplant recipients). * **Zoonosis:** HEV genotype 3 is associated with the consumption of undercooked pork or deer meat.

Q: Which of the following is non-cultivable in vivo?

Hepatitis-C virus. **Explanation:** The term **"non-cultivable"** in this context refers to the inability to grow the pathogen in standard laboratory cell cultures or artificial media. **Hepatitis C Virus (HCV)** is the correct answer because it is notoriously difficult to grow in traditional *in vitro* cell culture systems. For decades, research was hindered because HCV does not replicate efficiently in standard cell lines. While specialized "replicon" systems and specific human hepatoma cell lines (like Huh7) have been developed for research, HCV remains clinically non-cultivable for routine diagnostic or vaccine production purposes. **Analysis of Incorrect Options:** * **Mycobacterium avium (A):** This is a bacterium belonging to the MAC complex. Unlike *M. leprae* (which is truly non-cultivable on artificial media), *M. avium* can be grown on liquid media (Middlebrook 7H12) or solid media (Lowenstein-Jensen), though it grows slowly. * **HIV (B):** Human Immunodeficiency Virus can be readily cultivated in the laboratory using primary human T-lymphocytes or established leukemic T-cell lines. * **Mycoplasma pneumoniae (C):** Although fastidious and requiring specialized media enriched with serum and yeast extract (e.g., PPLO agar), it is cultivable *in vitro*, typically showing characteristic "fried-egg" colonies. **High-Yield Clinical Pearls for NEET-PG:** * **M. leprae** and **T. pallidum** are classic examples of bacteria that are **non-cultivable** on artificial media. * HCV diagnosis relies on **Serology (ELISA)** for screening and **RT-PCR (Viral Load)** for confirmation, as culture is not an option. * HCV belongs to the **Flaviviridae** family and is the most common cause of post-transfusion hepatitis and chronic viral hepatitis leading to HCC.

Q: Which of the following is NOT a cause of viral hemorrhagic fever?

Caliciviridae. **Explanation:** Viral Hemorrhagic Fevers (VHFs) are a group of illnesses caused by four distinct families of RNA viruses: **Arenaviridae, Filoviridae, Bunyaviridae, and Flaviviridae**. These viruses share common features: they are zoonotic, cause multisystem syndrome, and damage the vascular system, leading to hemorrhage. **Why Caliciviridae is the Correct Answer:** **Caliciviridae** (e.g., Norovirus, Sapovirus) primarily causes **acute gastroenteritis**. They are non-enveloped, positive-sense RNA viruses transmitted via the fecal-oral route. They do not cause systemic vascular leakage or hemorrhagic manifestations, which are the hallmarks of VHFs. **Analysis of Other Options:** * **Arenaviridae (Option A):** This family includes viruses like **Lassa fever virus** and South American hemorrhagic fevers (e.g., Junin, Machupo). They are typically transmitted via rodent excreta. * **Marburg virus (Option B):** A member of the **Filoviridae** family, it causes severe hemorrhagic fever with high mortality rates. It was the first filovirus discovered (1967). * **Ebolavirus (Option C):** Also a member of the **Filoviridae** family, it is notorious for causing large-scale outbreaks of fatal hemorrhagic fever, characterized by severe coagulation abnormalities. **High-Yield Clinical Pearls for NEET-PG:** * **Filoviridae:** Characterized by "pleomorphic" or "filamentous" (U-shaped/6-shaped) morphology. * **Flaviviridae:** Includes Yellow Fever and Dengue (DHF/DSS). * **Bunyaviridae:** Includes Crimean-Congo Hemorrhagic Fever (CCHF), Hantavirus, and Rift Valley Fever. * **Vector Tip:** Most VHFs are transmitted by arthropods (ticks/mosquitoes) or rodents, except for Filoviruses (Ebola/Marburg), where **fruit bats** are the natural reservoir.

Q: About parvovirus B19, which of the following statements is false?

Transplacental transfer occurs in only 10% of cases.. **Explanation:** **Parvovirus B19** is a small, non-enveloped, single-stranded DNA virus. Understanding its pathogenesis is crucial for NEET-PG. **1. Why Option D is the Correct (False) Statement:** The statement that transplacental transfer occurs in "only 10%" of cases is incorrect. In reality, if a non-immune pregnant woman is infected with Parvovirus B19, the rate of **transplacental transmission is approximately 30%**. While the transmission rate is high, the risk of actual fetal loss or hydrops fetalis is relatively low (about 5-10%), occurring primarily when infection happens during the second trimester. **2. Analysis of Incorrect Options (True Statements):** * **Option A:** Parvovirus B19 is primarily transmitted via **respiratory droplets**, though it can also be spread through blood products and vertically. * **Option B:** The virus has a specific tropism for **erythroid progenitor cells** (specifically in the bone marrow) because it uses the **P-antigen** (globoside) as its cellular receptor. * **Option C:** Because it destroys red cell precursors, it causes a temporary halt in erythropoiesis. In healthy individuals, this is subclinical; however, in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis), it leads to a life-threatening **Transient Aplastic Crisis**. **Clinical Pearls for NEET-PG:** * **Erythema Infectiosum (Fifth Disease):** Characterized by the classic **"slapped-cheek"** rash followed by a lace-like reticular rash on the trunk. * **Hydrops Fetalis:** Severe fetal anemia leading to high-output heart failure and generalized edema. * **Pure Red Cell Aplasia:** Can occur in immunocompromised patients. * **Receptor:** P-antigen (Globoside) is the key high-yield fact for its entry mechanism.

Q: Which of the following antigens is found within the nuclei of infected hepatocytes and not usually in the peripheral circulation in Hepatitis B infection?

HBcAg. **Explanation:** The correct answer is **HBcAg (Hepatitis B core Antigen)**. **Why HBcAg is the correct answer:** HBcAg is a particulate antigen that forms the inner nucleocapsid of the Hepatitis B virus. During active viral replication, it is synthesized within the **nuclei of hepatocytes**. Unlike HBsAg or HBeAg, HBcAg is sequestered within the viral envelope as it buds from the cell. Consequently, free HBcAg does not circulate in the peripheral blood and cannot be detected by standard serum assays. Its presence can only be demonstrated through immunofluorescence or immunohistochemical staining of liver biopsy tissue. **Analysis of Incorrect Options:** * **HBeAg (Option A):** This is a soluble protein derived from the precore region. It is actively secreted by infected hepatocytes into the blood and serves as a marker of high viral infectivity and active replication. * **Anti-HBc (Option C):** This is an antibody produced by the host against the core antigen. It is easily detectable in the serum and is a crucial marker for the "window period" (IgM) or past exposure (IgG). * **HBsAg (Option D):** This is the surface antigen found on the outer envelope of the virus and as non-infectious spherical/tubular filaments in the blood. It is the primary screening marker for HBV infection. **High-Yield Clinical Pearls for NEET-PG:** * **The "Window Period":** The interval where HBsAg has disappeared and Anti-HBs has not yet appeared. During this time, **IgM Anti-HBc** is the only diagnostic marker of acute infection. * **Dane Particle:** The complete 42nm infectious virion consisting of an inner core (HBcAg) and an outer shell (HBsAg). * **Ground Glass Hepatocytes:** The characteristic histological appearance of hepatocytes in chronic HBV, caused by the accumulation of HBsAg in the endoplasmic reticulum.

Q: Which flavivirus is associated with congenital microcephaly?

Zika virus. **Explanation:** **Zika virus (Option C)** is the correct answer. It is a member of the *Flaviviridae* family, primarily transmitted by the *Aedes aegypti* mosquito. Unlike most other flaviviruses, Zika virus exhibits significant **neurotropism** and can cross the placental barrier (vertical transmission). It infects neural progenitor cells, leading to cell death and disrupted cortical development, which manifests clinically as **Congenital Zika Syndrome**. The hallmark of this syndrome is **microcephaly**, often accompanied by intracranial calcifications, ocular damage, and clubfoot. **Analysis of Incorrect Options:** * **West Nile virus (Option A):** While it can cause neuroinvasive diseases like encephalitis or meningitis in adults, it is not a recognized cause of congenital microcephaly. * **Yellow fever virus (Option B):** Primarily causes a hemorrhagic fever characterized by jaundice (due to liver necrosis/Councilman bodies) and "black vomit." It is not associated with congenital malformations. * **Dengue virus (Option D):** Though transmitted by the same *Aedes* mosquito, Dengue typically presents as "breakbone fever" or Hemorrhagic Fever/Shock Syndrome. It does not cause microcephaly. **High-Yield NEET-PG Pearls:** * **Transmission:** Mosquito-borne (*Aedes*), sexual, blood transfusion, and vertical (transplacental). * **Diagnosis:** RT-PCR (blood/urine) during the acute phase; IgM ELISA later. * **Clinical Sign:** Look for a maculopapular rash, conjunctivitis, and arthralgia in the mother. * **Guillain-Barré Syndrome (GBS):** Zika is also strongly associated with an increased risk of GBS in adults.

Q: All of the following are markers of active replication of chronic hepatitis B, except:

AST & ALT. **Explanation:** The core concept in Hepatitis B (HBV) serology is distinguishing between **viral replication markers** and **biochemical markers of liver injury**. **Why AST & ALT is the correct answer:** AST (Aspartate Aminotransferase) and ALT (Alanine Aminotransferase) are intracellular enzymes released into the bloodstream when hepatocytes are damaged. While elevated levels indicate **active liver inflammation or necrosis** (hepatitis), they do not directly measure the virus's ability to replicate. In chronic HBV, a patient can have high viral replication with normal transaminases (Immune Tolerant phase) or low replication with high transaminases (due to other causes like superinfection or alcohol). **Why the other options are markers of active replication:** * **HBV DNA (Option A):** This is the most sensitive and direct quantitative marker of viral load and active replication. * **HBV DNA Polymerase (Option B):** This enzyme is required for the synthesis of viral DNA; its presence in the serum directly correlates with active viral assembly. * **HBeAg (Option C):** The 'e' antigen is a secretory product of the nucleocapsid gene. Its presence is a classic qualitative marker indicating high infectivity and active viral replication. **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs. The only marker present is **Anti-HBc IgM**. * **Best marker of infectivity:** HBV DNA (Quantitative) > HBeAg (Qualitative). * **First marker to appear:** HBsAg. * **Pre-core Mutants:** These patients are HBeAg negative but still have high HBV DNA levels and active liver disease. * **Ground Glass Hepatocytes:** Histological hallmark of chronic HBV infection.

Q: Which Human Papillomavirus (HPV) type is most commonly implicated in genital (vulval) warts?

HPV 6. **Explanation:** The correct answer is **HPV 6**. Genital warts, also known as **Condyloma acuminata**, are benign epithelial proliferations caused by "low-risk" types of Human Papillomavirus. **HPV 6 and 11** are responsible for approximately 90% of all genital wart cases. These types have a low potential for malignant transformation but are highly contagious and associated with significant morbidity. **Analysis of Options:** * **HPV 6 (Correct):** This is the most common type associated with genital warts. It targets the squamous epithelium of the vulva, vagina, and perianal region. * **HPV 16 & 18 (Incorrect):** These are "high-risk" oncogenic types. HPV 16 is the most common cause of **Cervical Cancer** (squamous cell carcinoma) and Vulvar Intraepithelial Neoplasia (VIN). HPV 18 is strongly associated with cervical **adenocarcinoma**. * **HPV 31 (Incorrect):** This is another high-risk type associated with cervical dysplasia and cancer, but it is less common than types 16 and 18 and rarely causes benign warts. **High-Yield Clinical Pearls for NEET-PG:** * **Low-risk HPV (6, 11):** Associated with Condyloma acuminata and Recurrent Respiratory Papillomatosis (RRP). * **High-risk HPV (16, 18, 31, 33, 45):** Associated with Cervical, Vaginal, Vulvar, Anal, and Oropharyngeal cancers. * **Histology:** The hallmark of HPV infection is **Koilocytosis** (cells with perinuclear halos and wrinkled "raisinoid" nuclei). * **Vaccination:** The Quadrivalent (Gardasil) and Nonavalent vaccines protect against types 6 and 11, thereby preventing genital warts.

Q: Which of the following statements about Hepatitis B virus (HBV) is false?

It has the least chance of chronicity.. **Explanation:** **Why Option D is the correct (false) statement:** Hepatitis B Virus (HBV) does **not** have the least chance of chronicity; in fact, it has a significant risk of becoming chronic, especially when acquired early in life. The risk of chronicity is inversely proportional to age: approximately **90% in neonates** (vertical transmission), 30% in children, and **5–10% in immunocompetent adults**. Among viral hepatitides, Hepatitis C (HCV) has the highest overall rate of chronicity (~75–85%), while Hepatitis A and E do not cause chronic infection at all (except HEV in transplant recipients). **Analysis of incorrect options:** * **Option A (True):** HBV is a member of the *Hepadnaviridae* family. It is a partially double-stranded **DNA virus** that replicates via reverse transcription. * **Option B (True):** HBV is primarily transmitted through parenteral routes (**blood transfusions**, contaminated needles), sexual contact, and vertical transmission (mother-to-child). * **Option C (True):** **HBsAg** (Surface Antigen) is the first serological marker to appear in the blood and is the hallmark of active infection (both acute and chronic). **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The time when HBsAg and Anti-HBs are both negative; **Anti-HBc IgM** is the only marker of acute infection during this phase. * **Infectivity Marker:** **HBeAg** indicates high viral replication and high infectivity. * **Ground Glass Hepatocytes:** Characteristic histopathological finding in chronic HBV infection due to HBsAg accumulation in the endoplasmic reticulum. * **Dane Particle:** The complete, infectious 42nm virion of HBV.

Question 1

Prion structure contains primarily?

Accepted Answer

Protein

Answer

DNA

Answer

RNA

Answer

Both DNA and RNA

Question 2

Which form of hepatitis is considered non-parenteral?

Accepted Answer

Hepatitis E

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis D

Question 3

Which of the following is non-cultivable in vivo?

Accepted Answer

Hepatitis-C virus

Answer

Mycobacterium avium

Answer

HIV

Answer

Mycoplasma pneumoniae

Question 4

Which of the following is NOT a cause of viral hemorrhagic fever?

Accepted Answer

Caliciviridae

Answer

Arenaviridae

Answer

Marburg virus

Answer

Ebolavirus

Question 5

About parvovirus B19, which of the following statements is false?

Accepted Answer

Transplacental transfer occurs in only 10% of cases.

Answer

It is spread by the respiratory route.

Answer

It has an affinity for erythrocyte progenitor cells.

Answer

It causes transient aplastic crisis.

Question 6

Which of the following antigens is found within the nuclei of infected hepatocytes and not usually in the peripheral circulation in Hepatitis B infection?

Accepted Answer

HBcAg

Answer

HBeAg

Answer

Anti-HBc

Answer

HBsAg

Question 7

Which flavivirus is associated with congenital microcephaly?

Accepted Answer

Zika virus

Answer

West Nile virus

Answer

Yellow fever virus

Answer

Dengue virus

Question 8

All of the following are markers of active replication of chronic hepatitis B, except:

Accepted Answer

AST & ALT

Answer

HBV DNA

Answer

HBV DNA Polymerase

Answer

HBeAg

Question 9

Which Human Papillomavirus (HPV) type is most commonly implicated in genital (vulval) warts?

Accepted Answer

HPV 6

Answer

HPV 16

Answer

HPV 18

Answer

HPV 31

Question 10

Which of the following statements about Hepatitis B virus (HBV) is false?

Accepted Answer

It has the least chance of chronicity.

Answer

It is a DNA virus.

Answer

It spreads by blood transfusions.

Answer

HBsAg is a marker of infection.

Virology — MCQs

Virology — MCQs

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