Virology Practice Questions

Q: Which antigen of the rabies virus stimulates antibody production?

Glycoprotein. **Explanation:** The rabies virus is a bullet-shaped, negative-sense single-stranded RNA virus belonging to the *Rhabdoviridae* family. Its structure consists of five major proteins: Nucleoprotein (N), Phosphoprotein (P), Matrix protein (M), Glycoprotein (G), and RNA-dependent RNA polymerase (L). **Why Glycoprotein is the correct answer:** The **G protein (Glycoprotein)** forms the spike-like projections on the viral envelope. It is the most critical antigen because it mediates viral attachment to the host cell (acetylcholine receptors) and is the **only protein that induces and reacts with neutralizing antibodies**. This makes it the primary component used in modern cell-culture vaccines to confer protective immunity. **Analysis of Incorrect Options:** * **Lipoprotein:** While the virus has a lipid bilayer envelope derived from the host cell membrane, it is not the specific antigen responsible for stimulating protective neutralizing antibodies. * **Phosphoprotein (P):** This is an internal protein associated with the viral polymerase complex. While it is antigenic, it does not stimulate neutralizing antibodies. * **Intranuclear protein:** This is a distractor. Rabies is an RNA virus that replicates in the **cytoplasm**, not the nucleus. The characteristic Negri bodies are intracytoplasmic inclusions. **High-Yield Clinical Pearls for NEET-PG:** * **Negri Bodies:** Pathognomonic intracytoplasmic eosinophilic inclusions found most commonly in the **Hippocampus (Ammon’s horn)** and Cerebellum (Purkinje cells). * **Receptor:** Rabies virus binds to **Nicotinic Acetylcholine Receptors (nAChR)** at the neuromuscular junction. * **Centripetal Spread:** The virus travels via retrograde axonal transport to the CNS. * **Vaccine:** Modern vaccines (e.g., Purified Chick Embryo Cell Vaccine) are inactivated and standardized based on the G protein content.

Q: Genetic reassortment is seen with which virus?

Rotavirus. **Explanation:** The core concept behind this question is **Genetic Reassortment**, which occurs only in viruses with **segmented genomes**. When two different strains of a segmented virus infect the same host cell, they can exchange entire gene segments during replication, leading to the emergence of new subtypes. **Why Rotavirus is correct:** Rotavirus belongs to the *Reoviridae* family. It possesses a **segmented, double-stranded RNA (dsRNA) genome** consisting of **11 segments**. This segmentation allows for frequent genetic reassortment, contributing to the diversity of strains and the potential for "antigenic shift." **Analysis of Incorrect Options:** * **Astrovirus:** These are small, non-enveloped viruses with a **single-stranded, non-segmented (+) RNA** genome. Without segments, reassortment cannot occur. * **Herpes virus:** These are large, enveloped viruses with a **linear, double-stranded DNA** genome. While they can undergo genetic recombination, they do not have segmented genomes for reassortment. * **Hepadnavirus (e.g., Hepatitis B):** These have a **circular, partially double-stranded DNA** genome. They replicate via reverse transcription but are non-segmented. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Segmented Viruses:** "**BOAR**" * **B**unyaviridae (3 segments) * **O**rthomyxoviridae (Influenza: 8 segments) * **A**renaviridae (2 segments) * **R**eoviridae (Rotavirus: 11 segments; Coltivirus: 12 segments) * **Antigenic Shift vs. Drift:** Reassortment is the mechanism behind **Antigenic Shift** (major changes), whereas point mutations cause **Antigenic Drift** (minor changes). * Rotavirus is the most common cause of severe diarrhea in infants and young children worldwide ("Wheel-like" appearance on EM).

Q: Two siblings, ages 2 and 4, experience fever, rhinitis, and pharyngitis that result in laryngotracheobronchitis. Both have a harsh, bark-like cough and hoarseness. Which of the following viruses is the leading cause of their syndrome?

Parainfluenza virus. ### Explanation **Correct Option: C. Parainfluenza virus** The clinical presentation described—fever, rhinitis, and pharyngitis progressing to **laryngotracheobronchitis** (commonly known as **Croup**) with a characteristic **bark-like cough** and hoarseness—is the classic hallmark of Parainfluenza virus infection. * **Mechanism:** Parainfluenza virus (specifically Type 1 and 2) causes subglottic edema and narrowing of the airway. * **Radiology:** On an X-ray, this narrowing produces the high-yield **"Steeple Sign"** due to subglottic tracheal constriction. It is the most common cause of croup in children aged 6 months to 3 years. **Incorrect Options:** * **A. Adenovirus:** Typically causes pharyngoconjunctival fever (sore throat + conjunctivitis), pneumonia, or hemorrhagic cystitis. While it can cause respiratory distress, it is not the primary cause of croup. * **B. Coxsackievirus B:** Most commonly associated with pleurodynia (Bornholm disease), myocarditis, and pericarditis. Coxsackievirus A is more famous for Herpangina and Hand-Foot-Mouth disease. * **D. Rhinovirus:** The leading cause of the "common cold." It primarily affects the upper respiratory tract (sneezing, nasal congestion) but rarely causes the subglottic inflammation seen in croup. **High-Yield Clinical Pearls for NEET-PG:** 1. **Croup vs. Epiglottitis:** Croup (Parainfluenza) presents with a barky cough and a "Steeple Sign." Epiglottitis (*H. influenzae*) presents with drooling, tripod positioning, and a **"Thumb Sign"** on X-ray. 2. **Virology:** Parainfluenza belongs to the **Paramyxoviridae** family (enveloped, negative-sense ssRNA). 3. **Treatment:** Management of croup usually involves cool mist, humidified oxygen, and **dexamethasone**. Nebulized epinephrine is used in severe cases to reduce airway edema.

Q: Which small nonparticulate protein leads to enhanced replication of HBV as well as HIV?

HBx Ag. **Explanation:** The correct answer is **HBx Ag** (Option D). **Why HBx Ag is Correct:** The Hepatitis B virus (HBV) genome contains four overlapping open reading frames (ORFs): S, C, P, and X. The **X gene** encodes the **HBx protein**, a small, non-particulate protein that functions as a transcriptional transactivator. It does not bind to DNA directly but interacts with various host cellular proteins (like transcription factors and kinases) to upregulate the expression of both viral and host genes. Crucially, HBx Ag can transactivate the **HIV-1 Long Terminal Repeat (LTR)** promoter, thereby enhancing the replication of HIV in co-infected patients. Furthermore, HBx Ag plays a significant role in hepatocarcinogenesis by interfering with the p53 tumor suppressor gene. **Why Other Options are Incorrect:** * **HBc Ag (Hepatitis B core Antigen):** This is a particulate structural protein that forms the nucleocapsid. It is not secreted into the blood and does not possess transactivating properties. * **HBs Ag (Hepatitis B surface Antigen):** This is the envelope protein found on the surface of the virion and as non-infectious spherical or tubular particles. Its primary role is viral attachment and entry, not transcriptional regulation. * **HBe Ag (Hepatitis B e Antigen):** This is a soluble protein derived from the precore/core ORF. It serves as a marker of high viral infectivity and active replication but does not enhance the replication of other viruses like HIV. **High-Yield Clinical Pearls for NEET-PG:** * **HBx Ag** is the only HBV protein linked directly to the development of **Hepatocellular Carcinoma (HCC)** via p53 inhibition. * **HBe Ag** indicates high infectivity; its disappearance and the appearance of Anti-HBe (seroconversion) usually signify a favorable prognosis. * **Window Period:** The interval where HBsAg and Anti-HBs are both negative; **Anti-HBc IgM** is the sole diagnostic marker during this phase.

Q: Which type of Human Papillomavirus (HPV) is most strongly associated with adenocarcinoma of the cervix?

Type 18. **Explanation:** The correct answer is **Type 18**. While HPV 16 is the most common cause of cervical cancer overall (especially squamous cell carcinoma), **HPV 18** has a specific and disproportionately strong association with **adenocarcinoma** of the cervix. 1. **Why Type 18 is correct:** HPV 18 is found in approximately 50–60% of cervical adenocarcinomas, compared to only about 10–15% of squamous cell carcinomas. It is considered more aggressive, often associated with a faster progression from infection to malignancy and a poorer prognosis compared to HPV 16. 2. **Why the others are incorrect:** * **Types 6 and 11:** These are "low-risk" HPV types. They are primarily responsible for benign lesions like **Condyloma Acuminata** (genital warts) and Recurrent Respiratory Papillomatosis. They do not cause cervical cancer. * **Type 42:** This is also a low-risk HPV type and is not associated with the development of cervical malignancy. **High-Yield Clinical Pearls for NEET-PG:** * **HPV 16:** Most common type in **Squamous Cell Carcinoma** (approx. 60%) and the most common type found in cervical cancer globally. * **HPV 18:** Most common type in **Adenocarcinoma** and **Small Cell Carcinoma** of the cervix. * **Oncogenic Proteins:** HPV E6 inhibits the **p53** tumor suppressor protein, while HPV E7 inhibits the **pRb** (Retinoblastoma) protein. * **Screening:** The transformation zone is the most common site for cervical cancer; however, adenocarcinoma arises from the glandular epithelium of the endocervix, making it harder to detect via routine Pap smear compared to squamous lesions.

Q: A pyrexial and neutropenic immunocompromised patient due to transplantation most likely has which of the following infections?

Cytomegalovirus (CMV). **Explanation:** **Why Cytomegalovirus (CMV) is the correct answer:** In the context of post-transplant patients, **Cytomegalovirus (CMV)** is the most common and clinically significant viral pathogen. It typically manifests between 1 to 6 months post-transplant (the "middle period"). CMV is notorious for causing a systemic syndrome characterized by **fever (pyrexia)** and hematological abnormalities, specifically **neutropenia**, leukopenia, and thrombocytopenia. It can also lead to organ-specific invasive diseases like pneumonitis, hepatitis, or colitis. **Analysis of Incorrect Options:** * **Herpes Simplex Virus (HSV):** While common in immunocompromised hosts, HSV usually presents with mucocutaneous lesions (cold sores or genital ulcers) rather than systemic pyrexia and neutropenia. * **Gram-negative/Gram-positive organisms:** While bacterial infections are the leading cause of fever in neutropenic patients *immediately* after chemotherapy or in the very early post-transplant phase (<1 month), the specific combination of pyrexia *and* induced neutropenia in a stable transplant recipient is a classic hallmark of CMV infection. **High-Yield Clinical Pearls for NEET-PG:** * **CMV Timing:** Most common opportunistic infection 1–6 months post-solid organ transplant (SOT) or hematopoietic stem cell transplant (HSCT). * **Diagnosis:** The gold standard for tissue diagnosis is the presence of **"Owl’s eye" intranuclear inclusion bodies**. For monitoring, **CMV PCR** or pp65 antigenemia assay is used. * **Treatment:** **Ganciclovir** is the drug of choice; Foscarnet is used for resistant cases. * **Prophylaxis:** Valganciclovir is frequently used to prevent CMV disease in high-risk transplant recipients.

Q: Which of the following arboviruses is NOT transmitted by a tick?

Japanese encephalitis. **Explanation:** Arboviruses (Arthropod-borne viruses) are classified based on their primary vectors. The question tests the ability to distinguish between **Mosquito-borne** and **Tick-borne** viruses within the Flaviviridae family. **1. Why Japanese Encephalitis (JE) is the correct answer:** Japanese Encephalitis is transmitted primarily by the bite of infected **Culex mosquitoes** (specifically *Culex tritaeniorhynchus*). It is the leading cause of viral encephalitis in Asia. Unlike the other options, it has no association with tick vectors. Its natural cycle involves pigs (amplifier hosts) and water birds (reservoirs). **2. Analysis of Incorrect Options (Tick-borne Viruses):** * **Kyasanur Forest Disease (KFD):** Known as "Monkey Fever" in India (Karnataka), it is transmitted by the **Hard tick (*Haemaphysalis spinigera*)**. * **Russian Spring-Summer Encephalitis (RSSE):** A classic tick-borne encephalitis (TBE) complex virus transmitted by ***Ixodes* ticks**. * **Omsk Hemorrhagic Fever (OHF):** Found in Siberia, this is also a member of the TBE complex transmitted by ***Dermacentor* ticks** and sometimes through contact with infected muskrats. **High-Yield Clinical Pearls for NEET-PG:** * **Vector Mnemonic:** Remember **"KRO"** for Tick-borne Flaviviruses: **K**yasanur, **R**ussian Spring-Summer, and **O**msk. * **JE Vector:** *Culex* mosquitoes are "night-biters" and breed in stagnant water like rice fields. * **JE Diagnosis:** The gold standard is the detection of **IgM antibodies in CSF** or serum using MAC-ELISA. * **KFD:** Important for Indian exams; look for a history of forest exposure and sudden high fever with prostration.

Q: All of the following are true about the Influenza virus EXCEPT:

The incubation period is typically 2-3 weeks.. **Explanation:** The correct answer is **B** because the incubation period of the Influenza virus is very short, typically ranging from **1 to 4 days** (average 2 days), not 2–3 weeks. Influenza is characterized by a rapid onset of symptoms following exposure, which is a key clinical feature distinguishing it from many other respiratory infections. **Analysis of Options:** * **Option A:** Influenza A is indeed the most common cause of seasonal outbreaks and is the only type capable of causing **pandemics** due to its ability to undergo both antigenic drift and shift. * **Option C:** Reye’s syndrome (acute encephalopathy and fatty liver) is a rare but serious complication associated with **Influenza B** and Varicella, especially in children who are given **Aspirin** (salicylates) during the viral prodrome. * **Option D:** The virus possesses two major surface glycoproteins: **Hemagglutinin (HA)**, which facilitates viral entry/attachment, and **Neuraminidase (NA)**, which aids in the release of new virions from host cells. **High-Yield Clinical Pearls for NEET-PG:** * **Antigenic Drift:** Minor point mutations (causes seasonal epidemics; seen in Types A and B). * **Antigenic Shift:** Major genetic reassortment (causes pandemics; seen **only in Type A**). * **Diagnosis:** Reverse Transcription PCR (RT-PCR) is the gold standard. * **Treatment:** Oseltamivir (Neuraminidase inhibitor) is most effective when started within 48 hours of symptom onset. * **Vaccine:** Usually contains two strains of Influenza A and one or two of Influenza B (Trivalent/Quadrivalent).

Q: What type of rubella-specific antibodies are detected after vaccination or natural infection?

IgG. **Explanation:** The detection of **IgG antibodies** is the hallmark of long-term immunity following either natural infection or vaccination with the Rubella (MMR) vaccine. **1. Why IgG is Correct:** In the primary immune response to Rubella, **IgG** appears shortly after IgM (usually within 1–2 weeks of the rash) and persists for life. Its presence indicates **past exposure or successful immunization**, providing protective immunity against reinfection. In the context of pregnancy screening, a positive IgG titer (without IgM) signifies that the mother is immune and the fetus is not at risk of Congenital Rubella Syndrome (CRS). **2. Why Other Options are Incorrect:** * **IgM:** These are the first antibodies to appear during an **acute/primary infection**. They disappear within 6 weeks to 3 months. While they are diagnostic of a current infection, they do not represent long-term post-vaccination status. * **IgA:** While secretory IgA may be found in the nasopharynx after natural infection (providing mucosal immunity), it is not the standard marker used to confirm systemic immunity or vaccination success in clinical practice. * **IgE:** These antibodies are involved in Type I hypersensitivity (allergic) reactions and parasitic infections; they play no role in Rubella immunity. **High-Yield Clinical Pearls for NEET-PG:** * **Vaccine Strain:** The Rubella vaccine uses the **RA 27/3** live attenuated strain (grown in human diploid cells). * **Congenital Rubella Syndrome (CRS):** The classic **Gregg’s Triad** includes Cataracts, Sensorineural deafness, and Cardiac defects (Patent Ductus Arteriosus). * **Diagnosis of CRS:** Detection of **IgM in the neonate** is diagnostic of CRS, as maternal IgM cannot cross the placenta (only IgG crosses). * **Vaccination Rule:** Live vaccines like MMR are **contraindicated in pregnancy**. Women should avoid pregnancy for at least 4 weeks (1 month) after receiving the Rubella vaccine.

Question 1

Which antigen of the rabies virus stimulates antibody production?

Accepted Answer

Glycoprotein

Answer

Lipoprotein

Answer

Phosphoprotein

Answer

Intranuclear protein

Question 2

Genetic reassortment is seen with which virus?

Accepted Answer

Rotavirus

Answer

Astrovirus

Answer

Herpes virus

Answer

Hepadnavirus

Question 3

Two siblings, ages 2 and 4, experience fever, rhinitis, and pharyngitis that result in laryngotracheobronchitis. Both have a harsh, bark-like cough and hoarseness. Which of the following viruses is the leading cause of their syndrome?

Accepted Answer

Parainfluenza virus

Answer

Adenovirus

Answer

Coxsackievirus B

Answer

Rhinovirus

Question 4

Which small nonparticulate protein leads to enhanced replication of HBV as well as HIV?

Accepted Answer

HBx Ag

Answer

HBc Ag

Answer

HBs Ag

Answer

Hbe Ag

Question 5

Which type of Human Papillomavirus (HPV) is most strongly associated with adenocarcinoma of the cervix?

Accepted Answer

Type 18

Answer

Type 6

Answer

Type 11

Answer

Type 42

Question 6

A pyrexial and neutropenic immunocompromised patient due to transplantation most likely has which of the following infections?

Accepted Answer

Cytomegalovirus (CMV)

Answer

Herpes Simplex Virus (HSV)

Answer

Gram-negative organisms

Answer

Gram-positive organisms

Question 7

Which of the following arboviruses is NOT transmitted by a tick?

Accepted Answer

Japanese encephalitis

Answer

Kyasanur forest disease

Answer

Russian spring summer encephalitis

Answer

Omsk hemorrhagic fever

Question 8

All of the following are true about the Influenza virus EXCEPT:

Accepted Answer

The incubation period is typically 2-3 weeks.

Answer

Influenza A is the most common cause of outbreaks.

Answer

Type B influenza is associated with Reye's syndrome.

Answer

Influenza possesses two main glycoprotein antigens.

Question 9

What type of rubella-specific antibodies are detected after vaccination or natural infection?

Accepted Answer

IgG

Answer

IgM

Answer

IgA

Answer

IgE

Question 10

Reduced cerebrospinal fluid (CSF) sugar is a characteristic finding in which type of viral meningitis?

Accepted Answer

Coxsackie virus

Answer

Rubella

Answer

Mumps

Answer

AIDS

Virology — MCQs

Virology — MCQs

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