Virology Practice Questions

Q: What is the most common viral antigen used for the diagnosis of HIV?

P24. The diagnosis of HIV relies on detecting specific viral components, primarily the **p24 antigen**. This protein forms the **inner viral capsid** (core) that surrounds the RNA genome. **Why p24 is the correct answer:** The p24 antigen is the most abundant viral protein produced during early infection. It is detectable in the blood approximately **1 to 3 weeks** after exposure, appearing even before the development of host antibodies (the "window period"). Modern **4th Generation ELISA** tests (p24 antigen + HIV-1/2 antibodies) utilize this to significantly reduce the diagnostic window, making it the gold standard for early screening. **Analysis of Incorrect Options:** * **B. p17:** This is the **matrix protein** located between the viral envelope and the capsid. While essential for viral assembly, it is not the primary target for diagnostic assays. * **C. p7:** This is a **nucleocapsid protein** that directly binds to the viral RNA. It is much smaller and less immunogenic than p24. * **D. p14:** This is not a standard structural protein of HIV. (Note: HIV accessory proteins include Tat, Rev, Nef, Vif, Vpu, and Vpr). **High-Yield Clinical Pearls for NEET-PG:** * **Window Period:** The time between infection and the appearance of detectable antibodies [1]. p24 detection narrows this period. * **Gag Gene:** Encodes the structural proteins **p24 (capsid)**, **p17 (matrix)**, and **p7/p9 (nucleocapsid)**. * **Env Gene:** Encodes **gp120** (attachment to CD4) and **gp41** (fusion/transmembrane). * **Pol Gene:** Encodes essential enzymes: Reverse Transcriptase, Integrase, and Protease. * **Western Blot:** Historically used for confirmation, it specifically looks for antibodies against p24, gp41, and gp120/160.

Q: Which of the following viruses is not an enveloped virus but contains double-stranded RNA?

Reovirus. ### Explanation The correct answer is **Reovirus**. This question tests your knowledge of viral structure, specifically the classification of genomes and envelopes. **1. Why Reovirus is correct:** The **Reoviridae** family (which includes Rotavirus and Coltivirus) is unique because it is one of the few virus families that possesses a **double-stranded RNA (dsRNA)** genome. Structurally, Reoviruses are **non-enveloped** (naked) and exhibit a characteristic double-layered icosahedral capsid. A high-yield mnemonic for dsRNA is: *"A **Double**-stranded **R**eovirus **R**aces"* (dsRNA = Reovirus). **2. Why the other options are incorrect:** * **Adenovirus (Option A):** While it is a non-enveloped (naked) virus, its genome consists of **double-stranded DNA (dsDNA)**, not RNA. It is a common cause of conjunctivitis and pharyngitis. * **Cytomegalovirus (Option C):** CMV belongs to the Herpesviridae family. These are **enveloped** viruses with a **dsDNA** genome. * **Hepatitis B Virus (Option D):** HBV is an **enveloped** virus. Its genome is unique—**partially double-stranded circular DNA**—and it uses reverse transcriptase during replication. **3. High-Yield Clinical Pearls for NEET-PG:** * **Rotavirus:** The most common cause of severe diarrhea in infants and children worldwide. It has a **segmented genome** (11 segments), allowing for genetic reassortment. * **Naked Viruses:** Remember the mnemonic **PAPP H**elp **C**alculate **R**eality (**P**apilloma, **A**deno, **P**arvo, **P**olyoma, **H**epna, **C**alici, **R**eo). These are generally more resistant to environmental heat and detergents. * **RNA Genomes:** Almost all RNA viruses are single-stranded (ssRNA) *except* for Reoviridae.

Q: Which is an unenveloped ssRNA virus?

Hepatitis E virus (HEV). ### Explanation The correct answer is **Hepatitis E virus (HEV)**. To master Hepatitis viruses for NEET-PG, it is essential to categorize them based on their genomic structure and the presence of an envelope. **1. Why Hepatitis E is correct:** Hepatitis E is a **non-enveloped (naked)** virus with a **single-stranded, positive-sense RNA (ssRNA)** genome. It belongs to the *Hepeviridae* family. Because it lacks a lipid envelope, it is stable in the environment and resistant to bile, allowing it to be transmitted via the **fecal-oral route**. **2. Analysis of Incorrect Options:** * **Hepatitis B virus (HBV):** This is the only DNA hepatitis virus. It is a **double-stranded DNA (dsDNA)** virus and is **enveloped**. * **Hepatitis C virus (HCV):** While HCV is an **ssRNA** virus (Flaviviridae), it is **enveloped**. The presence of an envelope makes it fragile, necessitating transmission through blood and body fluids (parenteral) rather than the fecal-oral route. **3. High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Envelopes:** Remember **"Vowels are Bowels."** Hepatitis **A** and **E** are transmitted via the fecal-oral route and are **non-enveloped** (naked). All others (B, C, D) are enveloped. * **Mnemonic for Genome:** All Hepatitis viruses are **RNA**, except for Hepatitis **B** (DNA). * **HEV in Pregnancy:** HEV infection is associated with high mortality (up to 20%) in pregnant women due to fulminant hepatic failure. * **Zoonosis:** HEV genotype 3 is commonly associated with the consumption of undercooked pork.

Q: Burkitt's lymphoma is characterized by elevated "early antigen" tests with a restricted pattern of fluorescence. This disease is caused by which of the following agents?

Epstein-Barr virus. **Explanation:** **Epstein-Barr Virus (EBV)**, a member of the Gammaherpesvirinae family (HHV-4), is the causative agent of Burkitt’s lymphoma. The diagnosis often relies on serological markers. In EBV-infected cells, the **Early Antigen (EA)** is produced during the lytic cycle. * **Restricted pattern (EA-R):** Fluorescence is restricted to the cytoplasm. This pattern is highly characteristic of **Burkitt’s lymphoma**. * **Diffuse pattern (EA-D):** Fluorescence is seen in both the nucleus and cytoplasm, typically associated with **Infectious Mononucleosis** and **Nasopharyngeal Carcinoma**. **Analysis of Incorrect Options:** * **A. Cytomegalovirus (CMV):** While a herpesvirus (HHV-5), it is associated with "Owl’s eye" intranuclear inclusions and infectious mononucleosis-like syndrome (heterophile negative), not Burkitt’s lymphoma. * **B. Borrelia burgdorferi:** This is a spirochete causing Lyme disease, characterized by Erythema chronicum migrans, not viral oncogenesis. * **D. Lymphogranuloma venereum (LGV):** Caused by *Chlamydia trachomatis* (serotypes L1-L3), it presents with genital ulcers and painful inguinal lymphadenopathy (Groove sign). **High-Yield Clinical Pearls for NEET-PG:** * **Translocation:** Burkitt’s lymphoma is classically associated with **t(8;14)**, involving the **c-myc** oncogene. * **Histology:** Shows a characteristic **"Starry-sky appearance"** (macrophages containing apoptotic debris amidst a sea of neoplastic B-cells). * **Other EBV Associations:** Oral Hairy Leukoplakia (in HIV), Hodgkin’s Lymphoma (Mixed cellularity type), and Duncan’s syndrome (X-linked lymphoproliferative disorder). * **Receptor:** EBV binds to B-cells via the **CD21** receptor (CR2).

Q: Epstein Barr virus is associated with all EXCEPT?

Laryngeal carcinoma. **Explanation:** The correct answer is **D. Laryngeal carcinoma**. Epstein-Barr Virus (EBV), also known as Human Herpesvirus 4 (HHV-4), is a potent oncogenic virus with a strong tropism for B-lymphocytes and epithelial cells. While EBV is implicated in several head and neck malignancies, **Laryngeal carcinoma** is primarily associated with risk factors like chronic smoking, alcohol consumption, and Human Papillomavirus (HPV) types 16 and 18, rather than EBV. **Analysis of Options:** * **A. Hodgkin’s Disease:** EBV is found in approximately 40-50% of Hodgkin’s cases, particularly the Mixed Cellularity subtype. The virus expresses LMP-1 (Latent Membrane Protein), which mimics CD40 signaling to drive B-cell proliferation. * **B. Burkitt’s Lymphoma:** This is the classic association, especially the **Endemic (African)** form, where EBV is found in nearly 100% of cases. It involves the characteristic t(8;14) translocation of the c-myc oncogene. * **C. Nasopharyngeal Carcinoma:** This is strongly linked to EBV, particularly the undifferentiated type (Type III). It is highly prevalent in Southern China and is characterized by elevated titers of IgA antibodies against EBV viral capsid antigen (VCA). **High-Yield Clinical Pearls for NEET-PG:** * **Other EBV Associations:** Infectious Mononucleosis (Glandular fever), Oral Hairy Leukoplakia (in HIV patients), and Gastric Carcinoma (approx. 10%). * **Diagnostic Marker:** Heterophile antibodies (Monospot Test) are positive in Infectious Mononucleosis but negative in other EBV-related malignancies. * **Receptor:** EBV enters B-cells via the **CD21** receptor (also the receptor for C3d complement component). * **Atypical Lymphocytes:** Known as **Downey cells**, these are actually activated T-cells (CD8+) reacting against the EBV-infected B-cells.

Q: What is the descending order of types of viruses causing paralytic polio?

Type 1, type 3, type 2. **Explanation:** The Poliovirus belongs to the *Enterovirus* genus and exists in three distinct serotypes: 1, 2, and 3. The correct descending order of their ability to cause paralytic disease is **Type 1 > Type 3 > Type 2**. 1. **Type 1 (Brunhilde):** This is the most common serotype and is responsible for the majority of paralytic poliomyelitis cases and large-scale epidemics. It possesses the highest neurovirulence. 2. **Type 3 (Leon):** This is the second most common cause of paralytic polio. 3. **Type 2 (Lansing):** This type is the least frequent cause of paralysis. Notably, Wild Poliovirus Type 2 (WPV2) was the first to be declared eradicated globally by the WHO in 2015. **Analysis of Incorrect Options:** * **Option A & B:** These are incorrect because Type 2 is the least common cause of paralysis, not the second or most common. * **Option D:** This incorrectly places Type 2 as the most common cause. **High-Yield Clinical Pearls for NEET-PG:** * **Eradication Status:** Wild Poliovirus Type 2 (WPV2) was eradicated in 2015; Type 3 (WPV3) was declared eradicated in 2019. Currently, only **Wild Poliovirus Type 1** remains endemic (primarily in Afghanistan and Pakistan). * **VAPP & VDPV:** While Type 2 wild virus is eradicated, it is the most common cause of **Vaccine-Derived Poliovirus (VDPV)** and **Vaccine-Associated Paralytic Polio (VAPP)** associated with the Oral Polio Vaccine (OPV). * **Switch:** Due to the risk of VDPV2, the Global Polio Eradication Initiative transitioned from Trivalent OPV (tOPV) to **Bivalent OPV (bOPV)**, which contains only types 1 and 3.

Q: Which feature is characteristic of the virus causing Infectious Mononucleosis?

Double-stranded, enveloped DNA virus. **Explanation:** Infectious Mononucleosis (Glandular Fever) is primarily caused by the **Epstein-Barr Virus (EBV)**, which belongs to the **Herpesviridae** family (specifically, Human Herpesvirus 4). **1. Why Option A is Correct:** All members of the Herpesvirus family, including EBV, share a specific structural morphology: * **Genome:** They contain **linear, double-stranded DNA (dsDNA)**. * **Capsid:** An icosahedral nucleocapsid. * **Envelope:** They are **enveloped** viruses, acquiring their lipid bilayer from the host cell's nuclear membrane. **2. Why Other Options are Incorrect:** * **Option B:** Non-enveloped dsDNA viruses include Adenovirus and Papillomavirus. EBV requires its envelope for host cell entry via the gp350/220 receptor. * **Option C:** This describes viruses like HIV, Influenza, or Paramyxoviruses. While some RNA viruses cause fever and lymphadenopathy, they do not cause classic Infectious Mononucleosis. * **Option D:** This describes Parvovirus B19, which is the only clinically significant single-stranded DNA virus. **3. High-Yield Clinical Pearls for NEET-PG:** * **Target Cells:** EBV infects **B-lymphocytes** via the **CD21 receptor** (CR2). * **Diagnostic Hallmark:** The presence of **Atypical Lymphocytes (Downey Cells)** on a peripheral smear; these are actually activated **CD8+ T-cells** reacting against the infected B-cells. * **Monospot Test:** Detects **Heterophile antibodies** (IgM) that agglutinate sheep or horse RBCs. * **Associated Malignancies:** Burkitt Lymphoma (t8;14), Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **Classic Triad:** Fever, Pharyngitis, and Posterior Cervical Lymphadenopathy. Avoid Ampicillin/Amoxicillin as it can trigger a characteristic maculopapular rash.

Q: Which of the following is not a prion-associated disease?

SSPE. **Explanation:** The correct answer is **SSPE (Subacute Sclerosing Panencephalitis)**. **Why SSPE is the correct answer:** SSPE is not a prion disease; it is a chronic, progressive neurodegenerative disorder caused by a **persistent infection with a mutant strain of the Measles virus**. It typically occurs years after an initial measles infection due to defective viral replication in the brain. Unlike prions, which are infectious proteins lacking nucleic acids, SSPE is caused by a conventional (though mutated) RNA virus. **Analysis of incorrect options (Prion Diseases):** Prion diseases (Transmissible Spongiform Encephalopathies) are caused by the accumulation of misfolded proteins ($PrP^{Sc}$). * **Scrapie:** This is the prototypical prion disease affecting **sheep and goats**, characterized by intense itching and neurodegeneration. * **Kuru:** Historically found in the Fore tribe of Papua New Guinea, it was transmitted through **ritualistic cannibalism**. * **Creutzfeldt-Jakob Disease (CJD):** The most common human prion disease. It presents as rapidly progressive dementia with myoclonus and characteristic periodic sharp-wave complexes on EEG. **NEET-PG High-Yield Pearls:** * **Prion Characteristics:** Resistant to standard sterilization (autoclaving at 121°C). They require **134°C for 1 hour** or immersion in **1N NaOH**. * **SSPE Diagnosis:** Look for high titers of anti-measles antibodies in the CSF (**intrathecal synthesis**) and "burst-suppression" patterns on EEG. * **Histopathology:** Prion diseases show **spongiform vacuolation** without inflammation. SSPE shows **Cowdry type A** intranuclear inclusion bodies.

Question 1

What is the most common viral antigen used for the diagnosis of HIV?

Accepted Answer

P24

Answer

P17

Answer

P7

Answer

P14

Question 2

Which of the following viruses is not an enveloped virus but contains double-stranded RNA?

Accepted Answer

Reovirus

Answer

Adenovirus

Answer

Cytomegalovirus (CMV)

Answer

Hepatitis B virus

Question 3

An outbreak of diarrhea occurred among elderly patients in an assisted care facility, which had been repeatedly cited by the public health department for poor hygiene practices. The agent that caused the infections had a star-like morphology in electron micrographs. Enzyme immunoassay (EIA) tests for several agents of viral gastroenteritis were negative. Which virus was most likely responsible for this outbreak?

Accepted Answer

Astrovirus

Answer

Adenovirus 40/41

Answer

Hepatitis A virus (HAV)

Answer

Norovirus

Question 4

Which is an unenveloped ssRNA virus?

Accepted Answer

Hepatitis E virus (HEV)

Answer

Hepatitis B virus (HBV)

Answer

Hepatitis C virus (HCV)

Answer

None of the above

Question 5

Burkitt's lymphoma is characterized by elevated "early antigen" tests with a restricted pattern of fluorescence. This disease is caused by which of the following agents?

Accepted Answer

Epstein-Barr virus

Answer

Cytomegalovirus

Answer

Borrelia burgdorferi

Answer

Lymphogranuloma venereum

Question 6

Epstein Barr virus is associated with all EXCEPT?

Accepted Answer

Laryngeal carcinoma

Answer

Hodgkin's disease

Answer

Burkitt's lymphoma

Answer

Nasopharyngeal carcinoma

Question 7

What is the descending order of types of viruses causing paralytic polio?

Accepted Answer

Type 1, type 3, type 2

Answer

Type 1, type 2, type 3

Answer

Type 2, type 1, type 3

Answer

Type 2, type 3, type 1

Question 8

Dengue hemorrhagic fever most commonly occurs when:

Accepted Answer

A person previously infected with one dengue serotype is infected with a different serotype

Answer

Malnourished patients

Answer

Immunocompromised patients

Answer

Persons experiencing high-grade fever

Question 9

Which feature is characteristic of the virus causing Infectious Mononucleosis?

Accepted Answer

Double-stranded, enveloped DNA virus

Answer

Double-stranded, non-enveloped DNA virus

Answer

Single-stranded, enveloped RNA virus

Answer

Single-stranded, non-enveloped DNA virus

Question 10

Which of the following is not a prion-associated disease?

Accepted Answer

SSPE

Answer

Scrapie

Answer

Kuru

Answer

Creutzfeldt-jakob disease

Virology — MCQs

Virology — MCQs

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