Virology Practice Questions

Q: Which co-receptor is utilized by the R5 variant of the Human Immunodeficiency Virus?

CCR5. **Explanation:** The entry of HIV into host cells is a multi-step process involving the viral envelope glycoprotein **gp120**. Initially, gp120 binds to the **CD4 receptor** on T-lymphocytes or macrophages. However, for successful fusion and entry, a secondary binding with a **co-receptor** is mandatory. * **CCR5 (Correct Answer):** The **R5 variant** (Macrophage-tropic or M-tropic) utilizes the **CCR5** chemokine receptor. These variants are typically responsible for the initial infection and are found predominantly on macrophages and memory T-cells. Individuals with a homozygous **CCR5-Δ32 mutation** are naturally resistant to HIV infection. * **CXCR4 (Option C):** This co-receptor is used by the **X4 variant** (T-tropic). These variants usually emerge in the later stages of the disease, lead to rapid CD4+ T-cell decline, and signal progression to AIDS. * **Integrin (Option A):** While some integrins (like α4β7) may facilitate HIV binding in the gut-associated lymphoid tissue (GALT), they are not the primary co-receptors defining the R5 or X4 tropism. * **p53 (Option D):** This is a tumor suppressor protein ("guardian of the genome") involved in cell cycle regulation and apoptosis; it plays no role as a viral entry co-receptor. **High-Yield Clinical Pearls for NEET-PG:** 1. **Maraviroc:** A CCR5 antagonist drug that prevents viral entry by blocking the R5 co-receptor. 2. **Tropism Switch:** The progression from asymptomatic HIV to AIDS is often marked by a "switch" from R5 (M-tropic) to X4 (T-tropic) variants. 3. **gp41:** While gp120 handles attachment, the transmembrane protein **gp41** is responsible for the actual fusion of the viral envelope with the host cell membrane.

Q: Varicella-zoster virus (VZV) is the cause of chickenpox and herpes zoster. Which of the following statements regarding VZV are true? a) Primary infection causes Varicella (Chickenpox) b) It remains latent in the B-cells c) Reactivation causes Herpes Zoster (Shingles) d) Post-herpetic neuralgia is a complication e) Live attenuated vaccine is available

a,c,d,e are true; b is false. **Explanation** Varicella-Zoster Virus (VZV), a member of the *Alphaherpesvirinae* subfamily (HHV-3), exhibits distinct clinical stages: primary infection (Chickenpox) and reactivation (Herpes Zoster). **Analysis of Statements:** * **(a) Primary infection causes Varicella (Chickenpox):** This is the initial generalized infection characterized by a centripetal, pleomorphic rash. * **(b) It remains latent in the B-cells:** **FALSE.** VZV remains latent in the **dorsal root ganglia** or cranial nerve ganglia. (Note: EBV is the herpesvirus that stays latent in B-cells). * **(c) Reactivation causes Herpes Zoster (Shingles):** Upon reactivation (due to age or immunosuppression), the virus travels down the sensory nerve to cause a painful, dermatomal vesicular rash. * **(d) Post-herpetic neuralgia is a complication:** This is the most common chronic complication of Shingles, characterized by persistent pain after the rash has healed. * **(e) Live attenuated vaccine is available:** The Oka strain is used for both the Varicella vaccine and the Zoster vaccine (though the Zoster vaccine uses a higher titer). **Why Option C is Correct:** Statements **a, c, d, and e** are scientifically accurate clinical and microbiological facts regarding VZV. Statement **b** is incorrect because VZV is neurotropic, not lymphotropic. **High-Yield NEET-PG Pearls:** * **Tzanck Smear:** Shows **Multinucleated Giant Cells** with Cowdry Type A intranuclear inclusion bodies (seen in VZV and HSV). * **Rash Progression:** "Dewdrop on a rose petal" appearance; hallmark is **pleomorphism** (all stages of rash—papule, vesicle, crust—seen simultaneously). * **Ramsay Hunt Syndrome:** Reactivation involving the geniculate ganglion (CN VII), leading to facial palsy and vesicles in the external auditory canal. * **Drug of Choice:** Oral Acyclovir (for adults/high-risk); Valacyclovir is preferred for Zoster due to better bioavailability.

Q: Epstein-Barr virus (EBV) enters B-cells through which receptor?

CD-21. **Explanation:** **Correct Option: C (CD-21)** Epstein-Barr Virus (EBV), a member of the *Gammaherpesvirinae* subfamily, exhibits a specific tropism for B-lymphocytes. The virus utilizes its envelope glycoprotein **gp350/220** to bind to the **CD-21** receptor (also known as **CR2** or Complement Receptor type 2) found on the surface of mature B-cells. This interaction is the critical first step for viral entry and subsequent transformation of B-cells into immortalized lymphoblastoid cells. **Analysis of Incorrect Options:** * **A. CD-1:** These are MHC-like molecules involved in the presentation of lipid antigens to T-cells, not viral entry. * **B. CD-2:** This is an adhesion molecule found on T-cells and Natural Killer (NK) cells (also known as LFA-2); it is not the primary receptor for EBV. * **C. CD-19:** While CD-19 is a definitive marker for B-lineage cells and forms a complex with CD-21 to signal B-cell activation, it does not serve as the direct attachment site for EBV. **High-Yield Clinical Pearls for NEET-PG:** * **Infectious Mononucleosis (IM):** EBV is the primary cause. Diagnosis is supported by the presence of **Atypical Lymphocytes (Downey Cells)** on peripheral smear—these are actually activated **CD8+ T-cells** reacting against the infected B-cells. * **Malignancies:** EBV is strongly associated with Burkitt Lymphoma (t[8;14]), Nasopharyngeal Carcinoma, and Hodgkin Lymphoma. * **Diagnosis:** The **Paul-Bunnell Test** (Heterophile antibody test) is the classic screening tool. * **Receptor for Epithelial Cells:** While EBV uses CD-21 for B-cells, it uses **MHC Class II** molecules as a co-receptor and different integrins for entry into epithelial cells.

Q: Which of the following viruses does not have an envelope containing hemagglutinin or neuraminidase?

Respiratory syncytial virus. **Explanation:** The question tests your knowledge of the surface glycoproteins of the **Paramyxoviridae** family. All members of this family possess two types of glycoprotein spikes on their envelope: a **Fusion (F) protein** (responsible for cell-to-cell fusion and syncytia formation) and an **Attachment protein**. **Why C is correct:** **Respiratory Syncytial Virus (RSV)** is unique among the Paramyxoviruses because its attachment protein (the **G protein**) lacks both Hemagglutinin (H) and Neuraminidase (N) activity. While it possesses the F protein (hence the name "Syncytial"), it does not agglutinate red blood cells or cleave sialic acid. **Why the other options are incorrect:** * **Mumps and Parainfluenza (A & B):** These viruses possess a combined **HN protein**, which exhibits both Hemagglutinin and Neuraminidase activities. * **Measles (D):** The Measles virus possesses an **H protein** (Hemagglutinin activity) but lacks Neuraminidase (N) activity. **NEET-PG High-Yield Pearls:** 1. **RSV:** It is the most common cause of **bronchiolitis** and pneumonia in infants. It lacks HN activity but has a G protein for attachment. 2. **Palivizumab:** A monoclonal antibody used for RSV prophylaxis; it targets the **F protein**. 3. **Paramyxoviridae Summary:** * **Mumps/Parainfluenza:** Have both H and N (HN protein). * **Measles:** Has H, but No N. * **RSV:** Has neither H nor N (G protein). * **All:** Possess the F (Fusion) protein. 4. **Inclusion Bodies:** Measles produces both intracytoplasmic and intranuclear inclusion bodies (Warthin-Finkeldey cells).

Q: Herpangina is caused by which virus?

Coxsackie virus A. **Explanation:** **Herpangina** is a common pediatric infection primarily caused by **Coxsackie virus Group A** (specifically serotypes A1–A10, A16, and A22). It is characterized by the sudden onset of high fever, sore throat, and distinctive vesicular or ulcerative lesions on the posterior oropharynx (tonsillar pillars, soft palate, and uvula). **Why Option A is Correct:** Coxsackie virus A is the classic causative agent. The pathogenesis involves viral replication in the lymphoid tissue of the pharynx, leading to the characteristic enanthem. It is closely related to Hand-Foot-and-Mouth Disease (HFMD), which is also caused by Coxsackie A16 and Enterovirus 71. **Analysis of Incorrect Options:** * **Option B (Echovirus 18):** While Echoviruses can cause viral meningitis or nonspecific rashes, Echovirus 18 is specifically associated with outbreaks of **infantile diarrhea** and exanthems. * **Option C (Echovirus 16):** This is the causative agent of **Boston Exanthem Disease**, characterized by fever and a rubelliform (maculopapular) rash on the face and trunk, rather than oropharyngeal ulcers. * **Option D (Poliovirus):** Poliovirus selectively targets the anterior horn cells of the spinal cord, leading to **paralytic poliomyelitis**. It does not cause vesicular pharyngitis. **High-Yield Clinical Pearls for NEET-PG:** * **Site of Lesions:** Herpangina affects the **posterior** oral cavity (soft palate/tonsils), whereas Herpetic Gingivostomatitis (HSV-1) affects the **anterior** oral cavity (gingiva/buccal mucosa). * **Hand-Foot-and-Mouth Disease (HFMD):** Most commonly caused by **Coxsackie A16**. * **Pleurodynia (Bornholm disease):** Caused by **Coxsackie B**. * **Myocarditis/Pericarditis:** Most common viral cause is **Coxsackie B**.

Q: A dentist presents with pain, redness, and swelling of the finger, accompanied by fever. Examination reveals small, grouped vesicles containing clear fluid. A Tzanck smear shows Tzanck cells. What is the causative agent?

Herpes simplex virus. **Explanation:** The clinical presentation described is a classic case of **Herpetic Whitlow**. This is a cutaneous infection of the finger caused by **Herpes Simplex Virus (HSV-1 or HSV-2)**. It is frequently seen in healthcare professionals, particularly dentists and respiratory therapists, who have frequent contact with infected oropharyngeal secretions. **Why Herpes Simplex Virus is correct:** * **Clinical Features:** The presence of painful, grouped vesicles on an erythematous base is characteristic of HSV. * **Tzanck Smear:** This is the gold-standard bedside test for Herpesviridae. The finding of **Tzanck cells** (multinucleated giant cells with Cowdry Type A intranuclear inclusion bodies) confirms the presence of HSV or VZV. **Why other options are incorrect:** * **Adenovirus:** Typically causes respiratory infections, conjunctivitis (pink eye), or hemorrhagic cystitis; it does not present with vesicular finger lesions or Tzanck cells. * **Pox virus:** While Molluscum contagiosum (a poxvirus) causes skin lesions, they are typically umbilicated papules, not painful vesicles, and show Henderson-Patterson bodies rather than Tzanck cells. * **Picornavirus:** Hand-foot-and-mouth disease (Coxsackievirus A16) presents with vesicles, but they are usually widespread and not associated with Tzanck cells. **High-Yield NEET-PG Pearls:** * **Tzanck Smear:** Positive in HSV-1, HSV-2, and Varicella-Zoster Virus (VZV). * **Inclusion Bodies:** HSV shows **Cowdry Type A** (intranuclear) inclusions. * **Transmission:** In children, Herpetic Whitlow is often due to autoinoculation from primary herpetic gingivostomatitis (thumb sucking). * **Management:** Incision and drainage are **contraindicated** as they can lead to secondary bacterial infection or systemic spread. Treatment is primarily with Acyclovir.

Q: "Henderson-Patterson" bodies are seen in which of the following conditions?

Molluscum contagiosum. **Explanation:** **Molluscum contagiosum** is the correct answer. It is a common viral skin infection caused by the **Molluscum Contagiosum Virus (MCV)**, a member of the Poxviridae family. The hallmark histopathological feature of this condition is the presence of **Henderson-Patterson bodies** (also known as Molluscum bodies). These are large, eosinophilic, intracytoplasmic inclusion bodies found within the keratinocytes of the stratum spinosum and stratum granulosum. They contain replicating virus particles that displace the host cell nucleus to the periphery. **Analysis of Incorrect Options:** * **Smallpox (Variola virus):** Characterized by **Guarnieri bodies**, which are eosinophilic cytoplasmic inclusion bodies. * **Fowlpox:** Characterized by **Bollinger bodies**, which are large granular proteinaceous inclusion bodies found in the cytoplasm of infected epithelial cells. * **Rabies:** Characterized by **Negri bodies**, which are eosinophilic, sharply outlined inclusion bodies found specifically in the cytoplasm of certain nerve cells (pyramidal cells of the hippocampus and Purkinje cells of the cerebellum). **Clinical Pearls for NEET-PG:** * **Clinical Presentation:** Presents as firm, dome-shaped, pearly, **umbilicated papules**. * **Transmission:** Spread via direct skin-to-skin contact, fomites, or autoinoculation. In adults, it is often considered a Sexually Transmitted Infection (STI). * **HIV Association:** Giant molluscum or extensive facial lesions are often a marker of advanced HIV/AIDS (low CD4 count). * **Histology:** Shows a "cup-shaped" or "crateriform" epidermal invagination containing the Henderson-Patterson bodies.

Q: Presence of HBeAg in serum of a patient of hepatitis-B indicates which stage?

Chronic, infectious stage. **Explanation:** The presence of **HBeAg (Hepatitis B e-antigen)** is a critical marker of **active viral replication** and **high infectivity**. It is a soluble protein derived from the precore/core region and is secreted into the blood only when the virus is actively multiplying. **1. Why Option D is Correct:** While HBeAg appears in both acute and chronic phases, its presence signifies that the patient is in an **infectious stage**. In the context of this question (often based on standard MCQ patterns where HBeAg is used to differentiate infectivity), HBeAg indicates a high viral load and a high risk of transmission. If HBeAg persists beyond 10 weeks, it suggests progression to a **chronic carrier state with high infectivity**. **2. Why Other Options are Wrong:** * **Options A & C:** HBeAg is never associated with a "non-infectious" stage. Its presence always correlates with high levels of HBV DNA in the serum. The "non-infectious" (or low-infectivity) stage is characterized by the disappearance of HBeAg and the appearance of **Anti-HBe antibodies**. * **Option B:** While HBeAg is present in the acute stage, the term "infectious stage" is the defining clinical characteristic of HBeAg. In many competitive exams, if "Chronic, infectious" is the keyed answer, it refers to the high-replicative phase of chronic HBV. **Clinical Pearls for NEET-PG:** * **HBsAg:** First marker to appear; indicates infection (acute or chronic). * **HBeAg:** Marker of **active replication, high infectivity**, and severity. * **Anti-HBs:** Marker of **immunity** (post-vaccination or recovery). * **Anti-HBc (IgM):** Best marker for the **"Window Period"** (when HBsAg and Anti-HBs are both negative). * **HBV DNA:** The most sensitive quantitative marker for viral load and monitoring treatment response.

Question 1

Regarding prions, which of the following statements is true?

Accepted Answer

It catalyzes the abnormal folding of other proteins.

Answer

It is a protein product coded in viral DNA.

Answer

It protects disulfide bonds from oxidation.

Answer

It cleaves normal proteins.

Question 2

Which of the following best explains why hepatitis C is the most common cause of posttransfusion hepatitis?

Accepted Answer

Screening questions designed to identify and exclude individuals at risk for HCV from the blood donor pool lack sufficient specificity.

Answer

Hepatitis C virus (HCV) carriers are highly prevalent in the general population, increasing the risk of transmission through blood donation.

Answer

Blood infected with hepatitis B virus (HBV) is not effectively eliminated by routine screening methods.

Answer

Current serologic tests for HCV fail to reliably exclude carriers.

Question 3

Which co-receptor is utilized by the R5 variant of the Human Immunodeficiency Virus?

Accepted Answer

CCR5

Answer

Integrin

Answer

CXCR4

Answer

p53

Question 4

Varicella-zoster virus (VZV) is the cause of chickenpox and herpes zoster. Which of the following statements regarding VZV are true?

a) Primary infection causes Varicella (Chickenpox)
b) It remains latent in the B-cells
c) Reactivation causes Herpes Zoster (Shingles)
d) Post-herpetic neuralgia is a complication
e) Live attenuated vaccine is available

Accepted Answer

a,c,d,e are true; b is false

Answer

a,b,c,d,e are true; none are false

Answer

a,c, e are true; b,d are false

Answer

b,c,d,e are true; a is false

Question 5

Epstein-Barr virus (EBV) enters B-cells through which receptor?

Accepted Answer

CD-21

Answer

CD-1

Answer

CD-2

Answer

CD-19

Question 6

Which of the following viruses does not have an envelope containing hemagglutinin or neuraminidase?

Accepted Answer

Respiratory syncytial virus

Answer

Mumps

Answer

Parainfluenza

Answer

Measles virus

Question 7

Herpangina is caused by which virus?

Accepted Answer

Coxsackie virus A

Answer

Echovirus 18

Answer

Echovirus 16

Answer

Poliovirus

Question 8

A dentist presents with pain, redness, and swelling of the finger, accompanied by fever. Examination reveals small, grouped vesicles containing clear fluid. A Tzanck smear shows Tzanck cells. What is the causative agent?

Accepted Answer

Herpes simplex virus

Answer

Adenovirus

Answer

Pox virus

Answer

Picornavirus

Question 9

"Henderson-Patterson" bodies are seen in which of the following conditions?

Accepted Answer

Molluscum contagiosum

Answer

Smallpox

Answer

Fowlpox

Answer

Rabies

Question 10

Presence of HBeAg in serum of a patient of hepatitis-B indicates which stage?

Accepted Answer

Chronic, infectious stage

Answer

Acute, non-infectious stage

Answer

Acute, infectious stage

Answer

Chronic, non-infectious stage

Virology — MCQs

Virology — MCQs

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