Virology Practice Questions

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.

Q: Varicella-Zoster virus is not associated with which of the following?

Centrifugal rash. **Explanation:** The correct answer is **Centrifugal rash** because Varicella-Zoster Virus (VZV) typically presents with a **centripetal rash**. In medical terminology, a centripetal distribution means the rash is most dense on the trunk (center) and less dense on the extremities (periphery). This is a classic hallmark of Chickenpox. **Analysis of Options:** * **Centrifugal rash (Correct Option):** This is characteristic of **Smallpox**, where the rash is more dense on the face and limbs than on the trunk. Since VZV causes a centripetal rash, this statement is incorrect regarding VZV. * **Latent infection:** VZV follows the pattern of all Herpesviruses by establishing lifelong latency. It remains dormant in the **dorsal root ganglia** or cranial nerve ganglia after the primary infection. * **Chickenpox:** This is the primary clinical manifestation of VZV infection in non-immune individuals (typically children). * **Thrombocytopenia:** While less common, VZV can cause hematological complications, including transient thrombocytopenia and idiopathic thrombocytopenic purpura (ITP), leading to "hemorrhagic chickenpox" in severe cases. **High-Yield Clinical Pearls for NEET-PG:** * **Pleomorphism:** VZV rash is "pleomorphic," meaning lesions at all stages (papules, vesicles, pustules, and crusts) are seen simultaneously in the same area ("starry sky" appearance). * **Dew-drop on a rose petal:** Classic description of the clear VZV vesicle on an erythematous base. * **Reactivation:** Reactivation of latent VZV results in **Herpes Zoster (Shingles)**, characterized by a painful, unilateral vesicular eruption along a specific dermatome. * **Diagnosis:** Tzanck smear shows **multinucleated giant cells** with Cowdry Type A intranuclear inclusion bodies.

Q: Which of the following viruses causes an acute febrile rash and produces disease in immunocompetent children but has been associated with transient aplastic crises in persons with sickle cell disease?

Parvovirus B19. **Explanation:** **Parvovirus B19** is the correct answer because it is the causative agent of **Erythema Infectiosum (Fifth Disease)**. In immunocompetent children, it typically presents as an acute febrile illness followed by a characteristic "slapped-cheek" rash. The underlying medical concept involves the virus's tropism for **erythroid progenitor cells**. Parvovirus B19 binds to the **P-antigen** (globoside) on red blood cell precursors and replicates within them, leading to temporary cessation of erythropoiesis. In healthy individuals, this is clinically insignificant. However, in patients with high red cell turnover (e.g., **Sickle Cell Disease**, Hereditary Spherocytosis, or Thalassemia), this pause results in a life-threatening **Transient Aplastic Crisis (TAC)**, characterized by a sudden drop in hemoglobin and a low reticulocyte count. **Why other options are incorrect:** * **Rubella:** Causes "German Measles" with post-auricular lymphadenopathy and a maculopapular rash, but does not affect erythropoiesis or cause aplastic crises. * **Varicella-zoster virus:** Causes chickenpox (vesicular rash) and shingles. It is not associated with aplastic crises in sickle cell patients. * **Measles:** Presents with high fever, Cough, Coryza, Conjunctivitis (3 C's), and Koplik spots. While severe, it does not target erythroid precursors. **High-Yield NEET-PG Pearls:** * **Receptor:** P-antigen (Globoside). * **Fetal Infection:** Can cause **Hydrops Fetalis** due to severe fetal anemia (most common in the second trimester). * **Adults:** Often presents as symmetric polyarthritis (mimicking Rheumatoid Arthritis). * **Diagnosis:** Low reticulocyte count is the hallmark of Parvovirus-induced aplastic crisis.

Q: A newborn is infected in utero with an enveloped virus containing double-stranded DNA. The child develops petechiae, hepatosplenomegaly, and jaundice. Brain calcifications are detected on computed tomography (CT). With which of the following viruses is the newborn most likely infected?

Cytomegalovirus. **Explanation:** The clinical presentation of petechiae (blueberry muffin rash), hepatosplenomegaly, jaundice, and intracranial calcifications in a neonate is classic for a **Congenital TORCH infection**. **1. Why Cytomegalovirus (CMV) is correct:** CMV is the most common intrauterine infection. It is an **enveloped, double-stranded DNA virus** (a member of the Herpesviridae family). The hallmark finding on CT is **periventricular calcifications** (calcifications lining the ventricles). This distinguishes it from Toxoplasmosis, which typically presents with diffuse cortical calcifications. Other features like microcephaly, sensorineural hearing loss (the most common long-term sequela), and chorioretinitis are also frequently seen. **2. Why the other options are incorrect:** * **Hepatitis B (HBV):** While it is an enveloped DNA virus, neonatal infection usually occurs during delivery (perinatally) rather than in utero. It typically results in a chronic carrier state rather than acute congenital malformations or intracranial calcifications. * **Hepatitis C (HCV) & Hepatitis D (HDV):** These are **RNA viruses** (HCV is Flavivirus; HDV is a defective Deltavirus). They do not cause the classic TORCH constellation of petechiae and brain calcifications. **Clinical Pearls for NEET-PG:** * **CMV:** Periventricular calcifications + Sensorineural hearing loss (SNHL). * **Toxoplasmosis:** Diffuse calcifications + Hydrocephalus + Chorioretinitis. * **Congenital Rubella:** PDA + Cataracts + SNHL (Blueberry muffin rash). * **Diagnosis:** Urine or saliva PCR within the first 3 weeks of life is the gold standard for congenital CMV. * **Treatment:** Intravenous Ganciclovir or oral Valganciclovir is used to reduce the severity of hearing loss and developmental delays.

Q: Epstein-Barr virus (EBV) is responsible for all of the following conditions except?

Hepatoma. **Explanation:** The **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. **Why Hepatoma is the correct answer:** Hepatoma (Hepatocellular Carcinoma) is primarily associated with chronic infections of **Hepatitis B Virus (HBV)** and **Hepatitis C Virus (HCV)**, as well as cirrhosis and aflatoxin exposure. EBV does not play a role in the pathogenesis of primary liver cancer. While EBV can cause transient hepatitis during acute infection (Infectious Mononucleosis), it does not lead to chronic liver malignancy. **Analysis of other options:** * **Nasopharyngeal Carcinoma:** EBV is strongly linked to the undifferentiated type of this tumor, particularly in Southern China and Southeast Asia. It involves the clonal expansion of EBV-infected epithelial cells. * **Burkitt's Lymphoma:** This is a B-cell malignancy highly associated with EBV, especially the "Endemic" (African) form. It characteristically involves the **t(8;14)** translocation of the *c-myc* oncogene. * **Infectious Mononucleosis (Glandular Fever):** This is the primary acute clinical manifestation of EBV, characterized by the triad of fever, pharyngitis, and lymphadenopathy, with the presence of **Atypical Lymphocytes (Downey cells)** in the peripheral smear. **High-Yield Clinical Pearls for NEET-PG:** * **Receptor:** EBV binds to the **CD21** receptor (CR2) on B-cells. * **Diagnosis:** The **Paul-Bunnell Test** (detecting heterophile antibodies) is the classic screening test. * **Other EBV Associations:** Oral Hairy Leukoplakia (in HIV patients), Hodgkin’s Lymphoma (Mixed cellularity type), and Gastric Carcinoma. * **Atypical Lymphocytes:** These are actually activated **CD8+ T-cells** reacting against the infected B-cells.

Q: All of the following statements are true regarding human T cell leukemia virus 1 except?

It has tropism for CD8+ T cells. **Explanation:** Human T-cell Lymphotropic Virus type 1 (HTLV-1) is a complex retrovirus. The correct answer is **Option B** because HTLV-1 primarily exhibits tropism for **CD4+ T cells**, not CD8+ T cells. It uses the GLUT-1 receptor to enter cells, leading to the malignant transformation of helper T cells. **Analysis of Options:** * **Option A (True):** HTLV-1 is the causative agent of **Adult T-cell Leukemia/Lymphoma (ATLL)**. It is also associated with HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). * **Option C (True):** The virus is known for an exceptionally **long latent period**. Most patients are infected during infancy (via breast milk), but clinical leukemia typically manifests 40 to 60 years later. * **Option D (True):** HTLV-1 has low oncogenic penetrance; only **3–5%** of lifelong carriers eventually develop ATLL. The majority of infected individuals remain asymptomatic carriers. **High-Yield Clinical Pearls for NEET-PG:** * **Oncogenesis:** Unlike other retroviruses, HTLV-1 does not carry a host-derived oncogene. Instead, it uses the **Tax gene**, which activates host cell transcription factors (like NF-κB) to promote proliferation and inhibit apoptosis. * **Morphology:** A characteristic finding in the peripheral blood smear of ATLL patients is the presence of **"Flower cells"** (lymphocytes with polylobated nuclei). * **Transmission:** Similar to HIV—via blood transfusion, sexual contact, and vertically (primarily through prolonged breastfeeding). * **Diagnosis:** Screening is done via ELISA; confirmation is via Western Blot or PCR.

Q: Which one of the following viruses is considered a human tumor virus?

Papillomavirus. **Explanation:** The correct answer is **Papillomavirus (HPV)**. Human tumor viruses, or oncogenic viruses, are those capable of inducing neoplastic transformation in host cells. **1. Why Papillomavirus is correct:** High-risk strains of Human Papillomavirus (primarily **HPV 16 and 18**) are strongly associated with cervical, anogenital, and oropharyngeal cancers. The oncogenic potential lies in the viral proteins **E6 and E7**, which inhibit the host’s tumor suppressor proteins **p53 and Rb**, respectively. This leads to uncontrolled cell cycle progression and genomic instability. **2. Why the other options are incorrect:** * **Epstein-Barr virus (EBV):** While EBV is indeed an oncogenic virus (associated with Burkitt lymphoma and Nasopharyngeal carcinoma), in the context of standard multiple-choice questions where only one "best" answer is sought, HPV is often the classic prototype for "human tumor viruses" due to its direct causal link to major epithelial cancers. *Note: If this were a multiple-select question, EBV would also be correct.* * **HIV:** HIV is a lentivirus that causes immunodeficiency. While it increases the risk of cancers (like Kaposi sarcoma) by suppressing the immune system, it is not considered a direct "tumor virus" because it does not transform cells via oncogenes. * **Varicella-zoster virus (VZV):** VZV causes chickenpox and shingles; it has no known oncogenic potential. **High-Yield NEET-PG Pearls:** * **DNA Oncogenic Viruses:** HPV, EBV, Hepatitis B (HBV), Human Herpesvirus 8 (HHV-8), and Merkel Cell Polyomavirus. * **RNA Oncogenic Viruses:** Hepatitis C (HCV) and Human T-cell Lymphotropic Virus-1 (HTLV-1). * **Mechanism Tip:** Remember **"6-53, 7-Rb"** (E6 acts on p53; E7 acts on Rb) to quickly recall HPV pathogenesis.

Q: Inclusion bodies are not seen in which of the following viral infections?

Epstein-Barr virus (EBV). Inclusion bodies are aggregates of viral proteins or nucleic acids within a cell that are visible under a light microscope. While most members of the *Herpesviridae* family produce characteristic inclusions, **Epstein-Barr Virus (EBV)** is a notable exception. ### **Why EBV is the Correct Answer** EBV primarily infects B-lymphocytes and epithelial cells. Unlike other herpesviruses, EBV does not typically produce visible intracellular inclusion bodies during its replicative cycle. Instead, the hallmark of EBV infection (Infectious Mononucleosis) is the presence of **Atypical Lymphocytes (Downey cells)**—which are activated T-cells reacting to the infected B-cells, not viral inclusions themselves. ### **Analysis of Incorrect Options** * **Cytomegalovirus (CMV):** Characterized by large, basophilic intranuclear inclusions surrounded by a clear halo, giving the classic **"Owl’s eye" appearance**. * **Herpes Simplex Virus (HSV):** Produces eosinophilic intranuclear inclusions known as **Cowdry Type A bodies** (also seen in Varicella-Zoster). * **Rabies Virus:** A classic example of intracytoplasmic inclusions called **Negri bodies**, typically found in the Purkinje cells of the cerebellum and pyramidal cells of the hippocampus. ### **High-Yield Clinical Pearls for NEET-PG** * **Intranuclear Inclusions:** DNA viruses (except Poxvirus). Examples: Cowdry A (HSV), Cowdry B (Polio), Owl's eye (CMV). * **Intracytoplasmic Inclusions:** RNA viruses (except Influenza and Measles). Examples: Negri bodies (Rabies), Guarnieri bodies (Smallpox), Henderson-Patterson bodies (Molluscum contagiosum). * **Both Intranuclear & Intracytoplasmic:** Measles (Warthin-Finkeldey cells). * **Mnemonic:** EBV is "Empty" of inclusions but "Extra" (Atypical) lymphocytes.

Question 1

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

Accepted Answer

CCR5

Answer

CD4

Answer

CD8

Answer

CXCR4

Question 2

Which of the following is NOT a viral inclusion body?

Accepted Answer

Psammoma bodies

Answer

Molluscum bodies

Answer

Negri bodies

Answer

Bollinger bodies

Question 3

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

Question 4

Varicella-Zoster virus is not associated with which of the following?

Accepted Answer

Centrifugal rash

Answer

Latent infection

Answer

Chicken pox

Answer

Thrombocytopenia

Question 5

Which of the following viruses causes an acute febrile rash and produces disease in immunocompetent children but has been associated with transient aplastic crises in persons with sickle cell disease?

Accepted Answer

Parvovirus B19

Answer

Rubella

Answer

Varicella-zoster virus

Answer

Measles

Question 6

A newborn is infected in utero with an enveloped virus containing double-stranded DNA. The child develops petechiae, hepatosplenomegaly, and jaundice. Brain calcifications are detected on computed tomography (CT). With which of the following viruses is the newborn most likely infected?

Accepted Answer

Cytomegalovirus

Answer

Hepatitis B

Answer

Hepatitis C

Answer

Hepatitis D

Question 7

Epstein-Barr virus (EBV) is responsible for all of the following conditions except?

Accepted Answer

Hepatoma

Answer

Nasopharyngeal carcinoma

Answer

Burkitt's lymphoma

Answer

Infectious mononucleosis

Question 8

All of the following statements are true regarding human T cell leukemia virus 1 except?

Accepted Answer

It has tropism for CD8+ T cells

Answer

It causes adult T cell lymphoma/leukemia

Answer

It has a long latent period of about 40 to 60 years

Answer

Leukemia develops in only 3 to 5% of infected individuals

Question 9

Which one of the following viruses is considered a human tumor virus?

Accepted Answer

Papillomavirus

Answer

Epstein-Barr virus (EBV)

Answer

Human Immunodeficiency Virus (HIV)

Answer

Varicella-zoster virus (VZV)

Question 10

Inclusion bodies are not seen in which of the following viral infections?

Accepted Answer

Epstein-Barr virus (EBV)

Answer

Cytomegalovirus (CMV)

Answer

Herpes simplex virus (HSV)

Answer

Rabies virus

Virology — MCQs

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