Virology Practice Questions

Q: Negri bodies in brain are characteristically seen in which of the following conditions?

Rabies. **Explanation:** **Negri bodies** are the hallmark histopathological finding in **Rabies**, caused by the Rabies virus (a Rhabdovirus). These are pathognomonic **intracytoplasmic, eosinophilic, round-to-oval inclusion bodies** found in the cytoplasm of neurons. They represent sites of viral replication and are most commonly observed in the **Purkinje cells of the cerebellum** and the **pyramidal cells of the hippocampus (Ammon’s horn)**. **Analysis of Options:** * **Botulism (A):** Caused by *Clostridium botulinum* toxin, which inhibits acetylcholine release at the neuromuscular junction. It does not produce inclusion bodies and primarily affects peripheral nerves, not brain parenchyma. * **Chickenpox (B):** Caused by Varicella-Zoster Virus (VZV). While it can cause encephalitis, the characteristic inclusions are **Cowdry Type A** (intranuclear), not Negri bodies. * **Herpes Encephalitis (D):** Caused by HSV-1. It typically presents with hemorrhagic necrosis of the temporal lobes. Histologically, it shows **Cowdry Type A intranuclear inclusions** (Lipschütz bodies), not cytoplasmic inclusions. **High-Yield Clinical Pearls for NEET-PG:** * **Morphology:** Negri bodies contain viral nucleocapsids and appear as eosinophilic structures with internal "basophilic granules." * **Staining:** Best visualized using **Sellers stain** (basic fuchsin and methylene blue) or Mann’s stain. * **Location:** While Negri bodies are diagnostic, they are absent in about 20% of rabies cases; their absence does not rule out the disease. * **Rabies Virus Shape:** Bullet-shaped (Rhabdoviridae family). * **Transmission:** Retrograde axonal transport from the site of the bite to the CNS.

Q: Viral gastroenteritis may be caused by all of the following in infants and young children except?

Enterovirus. **Explanation:** The correct answer is **Enterovirus**. While the name "Enterovirus" suggests an intestinal origin, these viruses (such as Poliovirus, Coxsackievirus, and Echovirus) primarily replicate in the gastrointestinal tract but **do not typically cause gastroenteritis**. Instead, they cause systemic manifestations like meningitis, herpangina, hand-foot-mouth disease, and myocarditis. **Analysis of Options:** * **Enterovirus (Option A):** These are members of the Picornaviridae family. They enter via the fecal-oral route and replicate in the Peyer’s patches, but they are transient inhabitants of the gut and do not cause mucosal damage leading to diarrhea. * **Coronavirus (Option B):** Certain strains of Coronaviruses are recognized causes of pediatric viral diarrhea, though they are less common than Rotavirus. * **Calicivirus (Option C):** This family includes **Norovirus** and Sapovirus. Norovirus is the leading cause of gastroenteritis outbreaks across all age groups worldwide. * **Adenovirus (Option D):** Specifically, **serotypes 40 and 41** (Enteric Adenoviruses) are significant causes of prolonged watery diarrhea in infants and young children. **Clinical Pearls for NEET-PG:** * **Rotavirus:** The most common cause of severe infantile diarrhea worldwide (Reovirus family, double-stranded RNA, wheel-like appearance). * **Norovirus:** The most common cause of epidemic gastroenteritis (cruise ships, schools). * **Mechanism:** Viral gastroenteritis typically causes **osmotic diarrhea** due to the destruction of mature enterocytes at the tips of villi, leading to malabsorption. * **Management:** The cornerstone of treatment is **ORS** and Zinc supplementation; antibiotics are contraindicated.

Q: Both intranuclear and intracytoplasmic inclusions are present in which of the following viruses?

Measles virus. ### Explanation The presence of inclusion bodies is a hallmark of viral infections, representing sites of viral replication or accumulation of viral proteins. **1. Why Measles Virus is Correct:** Measles virus (a member of the *Paramyxoviridae* family) is unique because it produces **both intranuclear and intracytoplasmic inclusion bodies**. These are known as **Warthin-Finkeldey cells**, which are multinucleated giant cells containing these characteristic inclusions. This occurs because the virus replicates in the cytoplasm but its nucleocapsid proteins also accumulate within the nucleus. **2. Analysis of Incorrect Options:** * **Pox Virus:** These are large DNA viruses that replicate entirely in the cytoplasm. Therefore, they produce **only intracytoplasmic** inclusions (e.g., **Guarnieri bodies** in Smallpox or **Molluscum bodies** in Molluscum contagiosum). * **Hepatitis B Virus (HBV):** HBV is associated with "ground-glass hepatocyte" appearance due to HBsAg accumulation in the cytoplasm, but it does not typically present with the classic dual inclusion pattern described in the question. * **HIV:** As a retrovirus, HIV integrates into the host genome. While it causes syncytia formation in cell cultures, it is not characterized by the diagnostic dual inclusion bodies seen in Measles. **3. High-Yield Clinical Pearls for NEET-PG:** * **Dual Inclusions (Both):** Measles virus and Cytomegalovirus (CMV). *Note: CMV is famous for "Owl’s eye" intranuclear inclusions, but also has small cytoplasmic inclusions.* * **Intracytoplasmic Only:** Poxvirus (Guarnieri bodies), Rabies (Negri bodies), Reovirus. * **Intranuclear Only:** Herpes Simplex Virus (Cowdry Type A), Adenovirus (Cowdry Type B), Papovavirus. * **Measles Mnemonic:** Remember the **3 C's** (Cough, Coryza, Conjunctivitis) + **Koplik spots** (pathognomonic).

Q: What is true about HSV encephalitis?

All of the above. **Explanation:** Herpes Simplex Virus (HSV) encephalitis is the most common cause of sporadic fatal encephalitis worldwide. The correct answer is **D (All of the above)** based on the following clinical and pathological features: 1. **Causative Agent (Option A):** In adults and children beyond the neonatal period, HSV encephalitis is almost exclusively caused by **HSV-1** (usually due to reactivation of the virus in the trigeminal ganglion). In contrast, HSV-2 is more commonly associated with neonatal encephalitis and aseptic meningitis. 2. **Pathology (Option B):** A hallmark of HSV encephalitis is its predilection for the **temporal lobes**. It causes necrotizing, **hemorrhagic inflammation**, which can be visualized as hyperintensities on MRI (T2/FLAIR) and often leads to focal neurological deficits or seizures. 3. **Histology (Option C):** Microscopic examination of infected brain tissue reveals characteristic **Cowdry Type A inclusion bodies**. These are intranuclear, **eosinophilic** (acidophilic) droplets surrounded by a clear halo, representing viral replication sites. **High-Yield Clinical Pearls for NEET-PG:** * **Site Predilection:** Temporal lobes and orbital-frontal cortex (look for "temporal lobe involvement" in clinical vignettes). * **Diagnosis:** **CSF PCR** is the gold standard (highly sensitive and specific). * **EEG Findings:** Periodic lateralized epileptiform discharges (PLEDs). * **Treatment:** Immediate IV **Acyclovir** is the drug of choice; do not wait for PCR results if clinical suspicion is high. * **Clinical Sign:** Patients may present with sudden onset fever, headache, and psychiatric symptoms/personality changes (due to temporal lobe necrosis).

Q: What oncogenic risk is associated with HPV types 6 and 11?

Low. **Explanation:** Human Papillomavirus (HPV) is a double-stranded DNA virus with over 100 genotypes, classified based on their association with malignancy. **Why Option B is Correct:** HPV types **6 and 11** are classified as **low-risk types**. While they are highly infectious and cause significant morbidity, they rarely integrate their DNA into the host genome. Instead, they typically exist as episomes (extrachromosomal DNA), leading to benign epithelial proliferations rather than invasive squamous cell carcinoma. They are the primary causative agents of **Condyloma acuminata** (anogenital warts) and **Laryngeal Papillomatosis**. **Why Other Options are Incorrect:** * **Option A (High):** High-risk types include **HPV 16 and 18** (most common), along with 31 and 33. These types produce E6 and E7 oncoproteins that inhibit p53 and Rb tumor suppressor proteins, respectively, leading to cervical, anal, and oropharyngeal cancers. * **Option C (None):** While "low risk," these types are not "no risk." Rare cases of malignant transformation (e.g., Buschke-Löwenstein tumors) can occur, particularly in immunocompromised states. * **Option D (Variable):** HPV risk is consistently categorized by genotype; 6 and 11 are strictly defined in the low-risk category in clinical oncology. **High-Yield NEET-PG Pearls:** * **Laryngeal Papillomatosis:** HPV 6 and 11 are the most common cause of benign tumors of the larynx in children (acquired during birth). * **Vaccination:** The Quadrivalent (Gardasil) and Nonavalent vaccines cover types 6 and 11 to prevent genital warts. * **Koilocytes:** The hallmark cytological finding of HPV infection (shrunken "raisin-like" nucleus with a large perinuclear halo).

Q: Which chemokine co-receptor for HIV is found on macrophages?

CCR5. ### Explanation HIV entry into host cells is a multi-step process requiring both a primary receptor and a co-receptor. The primary receptor for HIV is the **CD4 molecule**, while the co-receptors are members of the chemokine receptor family. **1. Why CCR5 is correct:** HIV-1 strains are classified based on their co-receptor tropism. **M-tropic (Macrophage-tropic)** strains, also known as R5 strains, utilize the **CCR5** co-receptor. These strains are typically responsible for the initial infection and are found on macrophages, dendritic cells, and memory T-cells. **2. Analysis of Incorrect Options:** * **CD4 (Option A):** This is the **primary receptor** for HIV, not a chemokine co-receptor. It is found on T-helper cells, macrophages, and monocytes. * **CD8 (Option B):** This is a marker for cytotoxic T-cells. HIV does not typically infect CD8+ cells as they lack the CD4 receptor. * **CXCR4 (Option D):** This is the co-receptor for **T-tropic (T-cell-tropic)** or X4 strains. These strains emerge later in the course of the disease and are associated with a rapid decline in CD4 counts and progression to AIDS. **3. High-Yield Clinical Pearls for NEET-PG:** * **Maraviroc:** A CCR5 antagonist (entry inhibitor) used in HIV treatment; it is only effective against R5-tropic strains. * **CCR5-Δ32 Mutation:** A 32-base pair deletion in the CCR5 gene. Individuals homozygous for this mutation are resistant to HIV infection, while heterozygotes show delayed progression to AIDS. * **gp120 & gp41:** The viral envelope protein **gp120** binds to CD4 and the co-receptor, while **gp41** mediates the fusion of the viral envelope with the host cell membrane.

Q: Which of the following is NOT a viral inclusion body?

Psammoma bodies. **Explanation:** Inclusion bodies are characteristic aggregates (usually proteins) found in the cytoplasm or nucleus of cells infected by specific viruses. They serve as "viral factories" or sites of viral assembly. **Why Psammoma bodies is the correct answer:** Psammoma bodies are **not** viral inclusions. They are microscopic, concentric lamellated calcifications. They are associated with specific **neoplastic conditions** (e.g., Papillary thyroid carcinoma, Serous papillary ovarian cystadenocarcinoma, and Meningioma) rather than viral infections. **Analysis of incorrect options (Viral Inclusions):** * **Molluscum bodies (Henderson-Patterson bodies):** Large, eosinophilic cytoplasmic inclusions seen in keratinocytes infected by the *Molluscum contagiosum* virus (Poxvirus). * **Negri bodies:** Pathognomonic intracytoplasmic, eosinophilic inclusions found in the pyramidal cells of the hippocampus and Purkinje cells of the cerebellum in **Rabies**. * **Bollinger bodies:** Large granular eosinophilic cytoplasmic inclusions seen in **Fowlpox**. (Note: Borrel bodies are the smaller minute particles found within Bollinger bodies). **High-Yield Clinical Pearls for NEET-PG:** * **Intranuclear Inclusions:** * *Cowdry Type A:* Herpes Simplex Virus (HSV), Varicella-Zoster Virus (VZV). * *Cowdry Type B:* Poliovirus. * *Owl’s Eye appearance:* Cytomegalovirus (CMV) — Note: CMV shows both intranuclear and intracytoplasmic inclusions. * **Intracytoplasmic Inclusions:** * *Guarnieri bodies:* Smallpox (Variola). * *Torres bodies:* Yellow Fever. * **Mnemonic for Psammoma bodies (PSaMM):** **P**apillary (thyroid), **S**erous (ovary), **M**eningioma, **M**esothelioma.

Q: A 31-year-old man with AIDS complains of difficulty swallowing. Examination of his oral cavity demonstrates whitish membranes covering much of his tongue and palate. Endoscopy also reveals several whitish, ulcerated lesions in the esophagus. Which of the following enzymes converts the HIV genome into double-stranded DNA in host cells?

Reverse transcriptase. The clinical presentation of a patient with AIDS presenting with oral thrush (candidiasis) and esophageal ulcers is highly suggestive of advanced immunosuppression. The question focuses on the replication cycle of the **Human Immunodeficiency Virus (HIV)**, a retrovirus. **1. Why Reverse Transcriptase is Correct:** HIV is an RNA virus. Upon entering the host cell (CD4+ T cell), its single-stranded RNA genome must be converted into double-stranded DNA (dsDNA) to be integrated into the host genome [1]. This process is catalyzed by the enzyme **Reverse Transcriptase (RNA-dependent DNA polymerase)**. This enzyme lacks proofreading capabilities, leading to the high mutation rate characteristic of HIV. **2. Why the Other Options are Incorrect:** * **DNA Polymerase (Pol-1 & Pol-2):** These are host cell enzymes involved in eukaryotic DNA replication and repair. They synthesize DNA from a DNA template, not from the viral RNA template. * **Integrase:** This viral enzyme is responsible for inserting (integrating) the newly synthesized viral dsDNA into the host cell's nuclear DNA [1]. It acts *after* reverse transcriptase has completed its job. **Clinical Pearls for NEET-PG:** * **HIV Genes:** * *gag:* Codes for structural proteins (p24 capsid). * *pol:* Codes for enzymes (**Reverse Transcriptase, Integrase, Protease**). * *env:* Codes for envelope glycoproteins (gp120 for attachment, gp41 for fusion). * **Diagnostic Marker:** p24 antigen is the earliest detectable protein in the blood during the window period. * **Opportunistic Infection:** Esophageal candidiasis is an **AIDS-defining illness**, typically occurring when the CD4 count falls below 100 cells/mm³. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of the Immune System, pp. 255-256.

Question 1

Negri bodies in brain are characteristically seen in which of the following conditions?

Accepted Answer

Rabies

Answer

Botulism

Answer

Chickenpox

Answer

Herpes encephalitis

Question 2

Which of the following is an oncogenic retrovirus?

Accepted Answer

HTLV-1

Answer

HPV

Answer

EBV

Answer

HBV

Question 3

Viral gastroenteritis may be caused by all of the following in infants and young children except?

Accepted Answer

Enterovirus

Answer

Coronavirus

Answer

Calicivirus

Answer

Adenovirus

Question 4

Which of the following statements is true about HIV?

Accepted Answer

Male-to-female transmission of HIV is higher than female-to-male transmission.

Answer

HIV is not transmitted through semen.

Answer

There are more chances of HIV transmission during LSCS than normal labor.

Answer

HIV is more infectious than hepatitis B.

Question 5

Both intranuclear and intracytoplasmic inclusions are present in which of the following viruses?

Accepted Answer

Measles virus

Answer

Pox Virus

Answer

Hepatitis B virus

Answer

HIV

Question 6

What is true about HSV encephalitis?

Accepted Answer

All of the above

Answer

Caused by HSV-1

Answer

Hemorrhagic lesion seen

Answer

Eosinophilic inclusion bodies seen

Question 7

What oncogenic risk is associated with HPV types 6 and 11?

Accepted Answer

Low

Answer

High

Answer

None

Answer

Variable

Question 8

Which chemokine co-receptor for HIV is found on macrophages?

Accepted Answer

CCR5

Answer

CD4

Answer

CD8

Answer

CXCR4

Question 9

Which of the following is NOT a viral inclusion body?

Accepted Answer

Psammoma bodies

Answer

Molluscum bodies

Answer

Negri bodies

Answer

Bollinger bodies

Question 10

A 31-year-old man with AIDS complains of difficulty swallowing. Examination of his oral cavity demonstrates whitish membranes covering much of his tongue and palate. Endoscopy also reveals several whitish, ulcerated lesions in the esophagus. Which of the following enzymes converts the HIV genome into double-stranded DNA in host cells?

Accepted Answer

Reverse transcriptase

Answer

DNA polymerase (Pol-1)

Answer

DNA polymerase (Pol-2)

Answer

Integrase

Virology — MCQs

Virology — MCQs

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