Virology Practice Questions

Q: The Hella cell line belongs to which category of cell culture?

Continuous cell line. **Explanation:** The **HeLa cell line** is the most famous example of a **Continuous cell line** (also known as immortalized or established cell lines). These are derived from cancer cells or by transforming normal cells with oncogenic viruses or chemicals. 1. **Why "Continuous cell line" is correct:** Continuous cell lines are characterized by their ability to undergo **infinite subcultures** (immortality). HeLa cells were originally derived from a cervical carcinoma biopsy of a patient named Henrietta Lacks in 1951. Because they are malignant in nature, they have lost contact inhibition and can be maintained indefinitely in vitro, making them ideal for large-scale virus vaccine production and research. 2. **Why other options are incorrect:** * **Primary cell culture:** These are normal cells taken directly from an animal/human organ (e.g., Monkey kidney cells). They can only be subcultured once or twice before dying. * **Diploid cell strains:** These are cells that maintain a normal chromosome complement and can be subcultured about 50 times before undergoing senescence (e.g., WI-38, MRC-5). * **Tissue culture:** This is a broad, generic term encompassing all types of cell, organ, and protoplast cultures; it is not a specific category of cell line longevity. **High-Yield Facts for NEET-PG:** * **HeLa Cells:** Derived from Human Cervical Adenocarcinoma. * **Other Continuous Lines:** **HEp-2** (Human Epithelioma of Larynx), **Vero** (Vervet Monkey Kidney), **BHK-21** (Baby Hamster Kidney). * **Diploid Strains:** Used for producing human vaccines (e.g., Rabies, Rubella) because they are non-oncogenic. * **Cytopathic Effect (CPE):** The structural changes in host cells caused by viral invasion, often visualized using these cell lines.

Q: Mumps is caused by which type of virus?

Paramyxovirus. **Explanation:** **Mumps** is caused by the Mumps virus, which belongs to the genus *Rubulavirus* within the **Paramyxoviridae** family. These are pleomorphic, enveloped viruses containing a single-stranded, negative-sense RNA genome. The virus is primarily known for its tropism for glandular tissue (especially the parotid glands) and the central nervous system. **Analysis of Options:** * **Paramyxovirus (Correct):** This family includes Mumps, Measles (Morbilivirus), and Parainfluenza viruses. They possess a characteristic helical nucleocapsid and an envelope containing Hemagglutinin-Neuraminidase (HN) and Fusion (F) proteins. * **Orthomyxovirus (Incorrect):** This family includes the Influenza viruses. While similar to paramyxoviruses, they have a **segmented** genome, which allows for antigenic shift. * **Rhinovirus (Incorrect):** A member of the Picornaviridae family, these are small, non-enveloped RNA viruses and are the most common cause of the "common cold." * **Epstein-Barr virus (Incorrect):** A DNA virus belonging to the Herpesviridae family, primarily responsible for Infectious Mononucleosis. **High-Yield Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Characterized by painful, usually bilateral, **parotid swelling**. * **Complications:** The most common complication in post-pubertal males is **orchitis** (usually unilateral, rarely leads to sterility). In females, **oophoritis** can occur. It is also a leading cause of **aseptic meningitis** and **acute pancreatitis**. * **Diagnosis:** Elevated serum **amylase** is a classic biochemical marker (due to parotitis or pancreatitis). * **Prevention:** Live attenuated vaccine (Jeryl Lynn strain) administered as part of the **MMR vaccine**.

Q: An AIDS patient is presenting with watery diarrhea. What could be the causative organism?

Cryptosporidia. **Explanation:** In an immunocompromised patient, particularly those with AIDS (CD4 count <200 cells/mm³), the most common cause of chronic, severe, watery diarrhea is **Cryptosporidium parvum**. **1. Why Cryptosporidia is correct:** Cryptosporidium is an acid-fast protozoan that infects the intestinal epithelium. While it causes self-limiting diarrhea in healthy individuals, it leads to life-threatening, voluminous, non-bloody watery diarrhea in AIDS patients due to the lack of T-cell mediated immunity. Diagnosis is typically made using **Modified Acid-Fast staining** (Kinyoun stain), which reveals bright red oocysts. **2. Why other options are incorrect:** * **Candida:** While common in AIDS (oral thrush, esophagitis), it rarely causes primary watery diarrhea. It is more associated with mucosal infections. * **Vibrio cholerae:** Causes "rice-water" stools through a toxin-mediated mechanism, but it is an acute epidemic infection and not specifically associated with the chronic immunosuppression of AIDS. * **ETEC:** A common cause of Traveler’s diarrhea. Like Cholera, it causes acute watery diarrhea but is not a characteristic opportunistic infection defining the clinical course of an AIDS patient. **Clinical Pearls for NEET-PG:** * **Other AIDS-related Diarrhea:** If CD4 <50, consider **Microsporidia** (very small spores) or **MAC (Mycobacterium avium complex)**. * **Staining:** Cryptosporidium, Isospora, and Cyclospora are all **Acid-Fast**. Cryptosporidium is the smallest (4-6 µm). * **Treatment:** In AIDS patients, the primary treatment is **HAART** (to boost CD4 count); Nitazoxanide has limited efficacy in severe immunosuppression.

Q: Which of the following microorganisms commonly shows antigenic drift in its pathogenicity?

Influenza virus. **Explanation:** The correct answer is **C. Influenza virus**. **1. Why Influenza Virus is Correct:** Antigenic drift refers to the gradual accumulation of **point mutations** in the genes encoding surface glycoproteins, specifically **Hemagglutinin (HA)** and **Neuraminidase (NA)**. Because the viral RNA polymerase lacks proofreading capability, these minor genetic changes occur frequently. This results in altered viral strains that can partially evade the host’s preexisting immune system, necessitating the annual update of the influenza vaccine. This phenomenon occurs in Influenza types A, B, and C. **2. Why Other Options are Incorrect:** * **A, B, and D (Cholera, Diphtheria, and Plague):** These are bacterial pathogens (*Vibrio cholerae, Corynebacterium diphtheriae,* and *Yersinia pestis*). Unlike RNA viruses, bacteria have more stable genomes with DNA repair mechanisms. While they can undergo genetic variation (e.g., horizontal gene transfer or strain variation), they do not exhibit "antigenic drift," which is a specific virological term describing the mechanism of seasonal epidemic variation in viruses. **3. NEET-PG High-Yield Pearls:** * **Antigenic Drift:** Minor change (point mutations); causes **epidemics**; seen in Influenza A and B. * **Antigenic Shift:** Major change (genetic **reassortment** of segments); causes **pandemics**; seen **only in Influenza A** because it has a broad host range (humans, birds, pigs). * **Segmented Genome:** Influenza is an Orthomyxovirus with 8 RNA segments (Type A and B), which is the structural prerequisite for antigenic shift. * **Vaccine Strain Selection:** The WHO Global Influenza Surveillance and Response System monitors "drift" to decide the composition of the next season's quadrivalent vaccine.

Q: Hepatitis E infection spreads by which route?

Feco-oral route. **Explanation:** Hepatitis E Virus (HEV) is a non-enveloped, single-stranded RNA virus belonging to the *Hepeviridae* family. The primary mode of transmission for HEV (specifically genotypes 1 and 2) is the **feco-oral route**, typically through the consumption of contaminated water. This mirrors the transmission pattern of Hepatitis A Virus (HAV). * **Why Option A is correct:** HEV is excreted in the feces of infected individuals. In areas with poor sanitation, the virus enters the water supply, leading to large-scale waterborne outbreaks. * **Why Options B and C are incorrect:** While rare instances of parenteral transmission (blood transfusion) have been documented for HEV, they are not the primary or characteristic route of spread. Parenteral and blood-borne transmission are the hallmark routes for Hepatitis B, C, and D. * **Why Option D is incorrect:** Rectal transmission is not a recognized primary epidemiological route for HEV; it is specifically associated with waterborne ingestion. **High-Yield Clinical Pearls for NEET-PG:** * **Pregnancy Risk:** HEV is notorious for causing high mortality (up to 20%) in pregnant women, particularly during the third trimester, due to Fulminant Hepatic Failure. * **Zoonosis:** HEV genotypes 3 and 4 are zoonotic, often transmitted via undercooked pork or deer meat. * **Chronicity:** HEV is generally acute and self-limiting; however, chronic infection can occur in immunocompromised individuals (e.g., organ transplant recipients). * **Mnemonic:** Remember **"Vowels (A and E) hit the Bowel"** to recall that Hepatitis A and E are transmitted via the feco-oral route.

Q: Which of the following diseases shows centrifugal spread of rash?

Smallpox. **Explanation:** The distribution of a rash is a high-yield clinical marker in virology. **Smallpox (Variola virus)** is characterized by a **centrifugal spread**, meaning the lesions are most dense on the distal extremities (palms and soles) and the face, with fewer lesions on the trunk. This is the opposite of Chickenpox (Varicella), which shows a centripetal distribution (concentrated on the trunk). In Smallpox, the rash also progresses synchronously (all lesions are at the same stage of development). **Analysis of Incorrect Options:** * **Dengue:** Typically presents with a "white islands in a sea of red" appearance—a generalized maculopapular rash that may have petechiae, but it does not follow a specific centrifugal pattern. * **Rocky Mountain Spotted Fever (RMSF):** While the rash begins on the wrists and ankles and spreads inward (centripetal), it is a rickettsial disease, not primarily classified by the same viral distribution terminology as Smallpox. * **Erythema Multiforme:** Characterized by "target" or "bulls-eye" lesions. While it often involves the extremities, it is an immune-mediated reaction rather than a classic infectious centrifugal exanthem. **High-Yield Clinical Pearls for NEET-PG:** * **Smallpox vs. Chickenpox:** Smallpox is **Centrifugal** (Extremities > Trunk) and **Synchronous**. Chickenpox is **Centripetal** (Trunk > Extremities), **Asynchronous** (pleomorphic), and spares the palms and soles. * **Deep-seated lesions:** Smallpox vesicles are firm, umbilicated, and deep-seated, whereas Varicella vesicles are superficial ("dewdrops on a rose petal"). * **Eradication:** Smallpox was officially declared eradicated by the WHO on May 8, 1980.

Q: What is the usual causative agent of infection in renal transplant patients?

Cytomegalovirus (CMV). **Explanation:** **Cytomegalovirus (CMV)** is the most common clinically significant viral pathogen in renal transplant recipients, typically manifesting within the first 1 to 6 months post-transplantation. The primary medical concept involves the **reactivation of latent virus** (sequestered in monocytes and macrophages) or transmission via the donor organ during a period of intense therapeutic immunosuppression. CMV is a major cause of morbidity, leading to "CMV syndrome" (fever, malaise, leucopenia) or tissue-invasive diseases like pneumonitis, hepatitis, and colitis. **Analysis of Incorrect Options:** * **HIV (Option B):** While HIV-positive patients can undergo transplants, HIV is not a "usual" causative agent of post-transplant infection; rather, it is a pre-existing condition or a rare transfusion/transplant-acquired risk. * **Herpes Simplex Virus (Option C):** HSV reactivation is common (causing mucocutaneous lesions), but it occurs less frequently and with less systemic severity than CMV in the modern era of prophylaxis. * **Salmonella species (Option D):** While transplant patients are at risk for intracellular bacterial infections, *Salmonella* is far less common than viral opportunistic infections like CMV. **NEET-PG High-Yield Pearls:** * **Timing:** CMV typically appears in the "middle period" (1–6 months) post-transplant. * **Diagnosis:** The gold standard for monitoring is **Quantitative PCR** for CMV DNA. Histopathology shows characteristic **"Owl’s eye" intranuclear inclusions**. * **Treatment:** **Valganciclovir** (prophylaxis/mild disease) and **Ganciclovir** (treatment of choice for active infection). * **Other Viral Risks:** **BK Virus** is another high-yield pathogen specifically linked to **ureteric stenosis and nephropathy** in renal transplants.

Q: A 33-year-old male with AIDS and a history of shingles develops a severe, multifocal encephalitis. Therapy is instituted with acyclovir, but the man dies on the fourth day of his hospital admission. Which of the following viruses is the most likely cause of his encephalitis?

Herpes zoster-varicella. **Explanation:** The correct answer is **Herpes zoster-varicella (VZV)**. This diagnosis is clinically supported by the patient’s history of shingles (reactivation of VZV) and his immunocompromised state (AIDS). In HIV-positive patients, VZV can cause a severe, multifocal, and often fatal encephalitis or vasculopathy. While **Acyclovir** is the treatment of choice, mortality remains high in advanced immunosuppression if therapy is delayed. **Analysis of Options:** * **Cytomegalovirus (CMV):** While CMV is a common cause of encephalitis in AIDS (typically when CD4 <50), it usually presents as a subacute periventricular encephalitis or ventriculitis rather than a multifocal pattern following a history of shingles. * **Herpes simplex type I (HSV-1):** This is the most common cause of sporadic fatal encephalitis in the general population, typically localized to the **temporal lobes**. It does not specifically correlate with a prior history of shingles. * **Herpes simplex type II (HSV-2):** In adults, HSV-2 is more commonly associated with **aseptic meningitis** rather than severe multifocal encephalitis, though it can cause encephalitis in neonates. **Clinical Pearls for NEET-PG:** * **VZV Encephalitis:** Look for the triad of **HIV/Immunosuppression + History of dermatomal rash (shingles) + Neurological deficit.** * **Imaging:** VZV often shows multifocal small and large infarcts (vasculopathy) at the gray-white matter junction. * **HSV-1 Key Fact:** Characterized by hemorrhagic necrosis of the temporal lobes and "Cowdry Type A" intranuclear inclusion bodies. * **Treatment:** High-dose intravenous Acyclovir is the gold standard for both HSV and VZV encephalitis.

Question 1

The Hella cell line belongs to which category of cell culture?

Accepted Answer

Continuous cell line

Answer

Primary cell culture

Answer

Diploid cell strains

Answer

Tissue culture

Question 2

Mumps is caused by which type of virus?

Accepted Answer

Paramyxovirus

Answer

Orthomyxovirus

Answer

Rhinovirus

Answer

Epstein-Barr virus

Question 3

An AIDS patient is presenting with watery diarrhea. What could be the causative organism?

Accepted Answer

Cryptosporidia

Answer

Candida

Answer

Vibrio cholerae

Answer

ETEC (Enterotoxigenic Escherichia coli)

Question 4

What is the characteristic pathological manifestation in Rabies?

Accepted Answer

Brainstem encephalitis

Answer

Ventriculitis

Answer

Basal ganglia affection

Answer

Meningitis

Question 5

Which of the following microorganisms commonly shows antigenic drift in its pathogenicity?

Accepted Answer

Influenza virus

Answer

Cholera

Answer

Diphtheria

Answer

Plague

Question 6

Hepatitis E infection spreads by which route?

Accepted Answer

Feco-oral route

Answer

Parenteral

Answer

Blood transfusion

Answer

Rectal

Question 7

Which of the following diseases shows centrifugal spread of rash?

Accepted Answer

Smallpox

Answer

Dengue

Answer

Rocky Mountain spotted fever

Answer

Erythema multiforme

Question 8

What is the usual causative agent of infection in renal transplant patients?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Human Immunodeficiency Virus (HIV)

Answer

Herpes Simplex Virus

Answer

Salmonella species

Question 9

A 33-year-old male with AIDS and a history of shingles develops a severe, multifocal encephalitis. Therapy is instituted with acyclovir, but the man dies on the fourth day of his hospital admission. Which of the following viruses is the most likely cause of his encephalitis?

Accepted Answer

Herpes zoster-varicella

Answer

Cytomegalovirus

Answer

Herpes simplex type I

Answer

Herpes simplex type II

Question 10

During pre-operative investigations, a man was found to have positive serological results for HIV. Which of the following is a highly specific test for HIV antibodies in this patient?

Accepted Answer

Western blot

Answer

ELISA

Answer

Southern blot

Answer

Northern blot

Virology — MCQs

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