Virology Practice Questions

Q: What is the most common genital lesion observed in patients with HIV?

Herpes. **Explanation:** The correct answer is **Herpes Simplex Virus (HSV)**. In the context of HIV, Herpes Simplex Virus type 2 (HSV-2) is the most common cause of genital ulcer disease (GUD) worldwide. There is a synergistic relationship between HIV and HSV: HIV-induced immunosuppression leads to more frequent, severe, and prolonged herpetic outbreaks, while the presence of active herpetic ulcers increases the risk of HIV transmission and acquisition by providing a portal of entry and recruiting CD4+ cells to the site. **Analysis of Options:** * **A. Chlamydia:** While *Chlamydia trachomatis* is a common STI, it typically presents as urethritis or cervicitis rather than a primary genital lesion (ulcer), except in the case of Lymphogranuloma Venereum (LGV), which is less common than HSV. * **C. Syphilis:** Caused by *Treponema pallidum*, it presents as a painless chancre. While prevalent in HIV patients, studies consistently show that HSV accounts for a significantly higher percentage of genital ulcers in this population. * **D. Candida:** *Candida albicans* causes balanitis or vulvovaginitis (itching and discharge) rather than true ulcerative lesions. While common in HIV due to low CD4 counts, it is not classified as the primary "genital lesion" in the context of GUD. **Clinical Pearls for NEET-PG:** * **Most common cause of GUD in HIV:** Herpes Simplex Virus. * **Atypical presentation:** In advanced AIDS, HSV ulcers can become "chronic, giant, or necrotic" and may be resistant to standard Acyclovir therapy. * **Diagnostic Gold Standard:** PCR is the most sensitive test for HSV; however, the **Tzanck smear** (showing multinucleated giant cells) is a classic high-yield bedside test. * **Treatment:** Valacyclovir or Famciclovir are preferred for management and suppression.

Q: All of the following infections may be transmitted by dental instruments except?

Hepatitis E. **Explanation:** The core concept tested here is the **mode of transmission** of various viral pathogens. Dental instruments pose a risk of transmission for infections spread via **blood and body fluids** (parenteral route) due to the potential for mucosal trauma and blood contamination during procedures. * **Why Hepatitis E is the correct answer:** Hepatitis E Virus (HEV) is primarily transmitted via the **fecal-oral route**, usually through contaminated water. It is an enteric virus and is not typically transmitted through blood-borne routes or contaminated medical/dental instruments. * **Why the other options are incorrect:** * **Hepatitis B (HBV):** This is the most significant occupational hazard in dentistry. It is highly infectious and transmitted through blood, saliva, and contaminated needles/instruments. * **Hepatitis C (HCV):** Primarily blood-borne. While the risk is lower than HBV, it can be transmitted via inadequately sterilized dental equipment. * **HIV:** Although the virus is fragile, it is present in blood and can theoretically be transmitted through percutaneous injury with contaminated dental instruments. **High-Yield Clinical Pearls for NEET-PG:** * **Mnemonic for Hepatitis Transmission:** **Vowels (A, E)** are **Enteric** (Fecal-oral); **Consonants (B, C, D)** are **Blood-borne**. * **Hepatitis B** is the most resilient of these viruses on environmental surfaces; hence, strict adherence to **autoclaving** (Universal Precautions) is mandatory in dental practice. * **Hepatitis E** is particularly dangerous in **pregnant women**, where it can cause fulminant hepatic failure with a high mortality rate (~20%).

Q: Which gene codes for the core proteins of HIV?

GAG. The HIV genome consists of three structural genes (**gag, pol, and env**) and several regulatory/accessory genes. Understanding these is high-yield for NEET-PG. ### **Correct Answer: A. GAG** The **gag (group-specific antigen)** gene encodes a polyprotein that is cleaved by viral proteases into the structural **core proteins** of the virus. These include: * **p24:** The major capsid protein (detected early in infection via ELISA). * **p17:** The matrix protein. * **p7/p9:** Nucleocapsid proteins. ### **Why the other options are incorrect:** * **B. ENV (Envelope):** This gene codes for the viral envelope glycoproteins. It produces **gp160**, which is cleaved into **gp120** (for attachment to CD4 receptors) and **gp41** (for fusion and entry). * **C. POL (Polymerase):** This gene codes for essential viral enzymes: **Reverse Transcriptase** (RNA to DNA), **Integrase** (integration into host genome), and **Protease** (cleavage of polyproteins). * **D. TAT (Trans-activator of transcription):** This is a regulatory gene that enhances the efficiency of viral transcription. ### **High-Yield Clinical Pearls for NEET-PG:** 1. **p24 Antigen:** This is the earliest serological marker of HIV infection, appearing before antibodies (the "window period"). 2. **Nef Gene:** It downregulates CD4 and MHC-I expression; it is the most important factor for viral virulence. 3. **LTR (Long Terminal Repeats):** Located at both ends of the genome, these are responsible for the integration of the provirus into the host DNA. 4. **Screening vs. Confirmation:** ELISA (p24 + antibodies) is used for screening, while Western Blot (detecting gp120/160, gp41, and p24) was traditionally used for confirmation.

Q: All of the following statements are true for rabies virus except:

Rabies vaccine is a live attenuated vaccine.. **Explanation:** The correct answer is **D** because the modern rabies vaccines used in humans (such as PCECV and HDCV) are **inactivated (killed) vaccines**, not live attenuated. Live attenuated vaccines are generally avoided in human rabies prophylaxis due to the risk of reversion to virulence in a disease that is virtually 100% fatal. **Analysis of Options:** * **Option A (Incorrect):** This is a true statement. Post-exposure prophylaxis (PEP) involves a combination of **active immunization** (vaccine) to induce long-term immunity and **passive immunization** (Rabies Immunoglobulin/RIG) to provide immediate neutralizing antibodies at the wound site. * **Option B (Incorrect):** This is true. While dogs are the primary reservoir in India and developing nations, wild animals like foxes, raccoons, and skunks are the main reservoirs in developed countries (e.g., USA). * **Option C (Incorrect):** This is true. The **Direct Fluorescent Antibody (DFA)** test on brain tissue (in animals) or skin biopsy from the nape of the neck (in humans) is the "gold standard" for rapid diagnosis, detecting viral antigens. **Clinical Pearls for NEET-PG:** * **Morphology:** Rabies virus is a **bullet-shaped**, negative-sense, single-stranded RNA virus (Rhabdoviridae). * **Pathognomonic Sign:** **Negri bodies** (intracytoplasmic eosinophilic inclusions) found typically in the Hippocampus and Cerebellum (Purkinje cells). * **Neural Spread:** The virus travels via **retrograde axonal transport** to the CNS. * **Vaccine Strains:** Fixed virus (e.g., Pitman-Moore strain) is used for vaccine production, whereas the naturally occurring virus is called the "Street virus." * **Classification:** It belongs to the genus *Lyssavirus*.

Q: Which RNA virus is inhibited by Actinomycin D?

Influenza. **Explanation:** The correct answer is **Influenza**. **1. Why Influenza is the correct answer:** Actinomycin D is an antibiotic that inhibits **DNA-dependent RNA polymerase**, thereby blocking transcription. Most RNA viruses replicate entirely in the cytoplasm and do not require host cell nuclear transcription, making them resistant to Actinomycin D. However, **Orthomyxoviruses (Influenza)** are unique among RNA viruses because they replicate their genome in the **nucleus**. They require host cell DNA transcription to produce "primers" (a process called cap-snatching) to initiate their own viral mRNA synthesis. Because Influenza depends on the host's nuclear DNA-directed RNA synthesis, Actinomycin D inhibits its replication. **2. Why the other options are incorrect:** * **Measles (Paramyxovirus):** Replicates entirely in the cytoplasm using its own RNA-dependent RNA polymerase. It does not depend on host DNA transcription. * **Polio (Picornavirus):** A positive-sense single-stranded RNA virus that replicates in the cytoplasm. It is independent of nuclear functions and thus resistant to Actinomycin D. * **Rubella (Togavirus):** Similar to Polio, it replicates in the cytoplasm and does not utilize the host cell nucleus for its primary replication cycle. **3. High-Yield Clinical Pearls for NEET-PG:** * **Exceptions to the Rule:** Most RNA viruses replicate in the cytoplasm *except* **Influenza** and **Retroviruses** (HIV). * **Exceptions to the Rule:** Most DNA viruses replicate in the nucleus *except* **Poxvirus** (replicates in the cytoplasm). * **Mechanism:** Influenza uses "Cap-snatching," where it steals the 5' methylated cap from host pre-mRNA in the nucleus to use as a primer for viral mRNA. * **Drug Target:** Actinomycin D is primarily used as a chemotherapy agent (Dactinomycin) for Wilms tumor and Rhabdomyosarcoma.

Q: Which of the following is a single-stranded DNA virus with no envelope?

Parvovirus B19. **Explanation:** The correct answer is **Parvovirus B19**. In virology, there is a fundamental rule for DNA viruses: almost all are double-stranded (dsDNA) and show icosahedral symmetry, except for the **Parvoviridae** family, which is **single-stranded (ssDNA)**. Additionally, Parvovirus is a **non-enveloped (naked)** virus, making it highly resistant to environmental degradation. **Analysis of Options:** * **Hepatitis A (Option B):** While it is non-enveloped, it belongs to the Picornaviridae family and is a single-stranded **RNA** virus, not DNA. * **Herpes simplex (Option C):** This is a double-stranded DNA virus. Crucially, it is an **enveloped** virus (derived from the host nuclear membrane), which contradicts the question. * **Human reovirus (Option D):** Reoviruses are unique because they are **double-stranded RNA** viruses. Like Parvovirus, they are non-enveloped, but their genome type is different. **High-Yield Clinical Pearls for NEET-PG:** * **Smallest DNA Virus:** Parvovirus B19 is the smallest DNA virus (25 nm). * **Clinical Presentation:** It causes **Erythema Infectiosum (Fifth Disease)**, characterized by the classic "slapped-cheek" rash in children. * **Receptor:** It binds to the **P-antigen** (globoside) on erythroid progenitor cells. * **Complications:** It can lead to **Aplastic Crisis** in patients with chronic hemolytic anemias (e.g., Sickle Cell) and **Hydrops Fetalis** if a pregnant woman is infected. * **Mnemonic:** Remember "**HHAPPPPy**" for DNA viruses (Hepadna, Herpes, Adeno, Papova, Parvo, Pox). All are dsDNA except **Parvo** (ssDNA). All are icosahedral except **Pox** (complex).

Q: A 19-year-old intravenous drug user has regularly sought human immunodeficiency virus (HIV) testing, always with negative results. He admits to carelessly sharing needles on multiple occasions with individuals later found to be HIV-positive. He has heard that there is an inherited genetic basis for some people to be relatively "immune" to HIV infection. The genetic change that he is referring to is a mutation in a gene coding for which of the following proteins?

CCR5. ### Explanation **Correct Answer: A. CCR5** The entry of HIV-1 into host cells is a multi-step process requiring the binding of the viral envelope to specific host cell receptors. [1] The primary receptor is the **CD4 molecule**, but a **co-receptor** is essential for successful viral entry. In the early stages of infection (and in most transmissions), the virus is **M-tropic** (Macrophage-tropic) and utilizes the **CCR5** chemokine receptor as its co-receptor. [1] A specific genetic mutation known as the **CCR5-Δ32 (delta 32) mutation** results in a truncated, non-functional protein that does not reach the cell surface. Individuals who are **homozygous** for this mutation are highly resistant to HIV infection despite repeated exposure, as the virus cannot fuse with the host cell membrane. Heterozygotes typically show a slower progression to AIDS. --- ### Why the other options are incorrect: * **B. CD4:** This is the primary receptor for HIV. [1] While it is necessary for infection, there are no common genetic mutations in the CD4 gene that confer immunity to HIV in humans. * **C. gp120:** This is a **viral** glycoprotein (encoded by the HIV *env* gene) that mediates initial attachment to the CD4 receptor. It is not a human protein. * **D. gp41:** This is also a **viral** glycoprotein (transmembrane unit) responsible for the fusion of the viral envelope with the host cell membrane. It is the target of the drug **Enfuvirtide**. --- ### NEET-PG High-Yield Pearls: * **CCR5 vs. CXCR4:** Early-stage/transmitted HIV uses **CCR5** (M-tropic). Late-stage HIV often switches to **CXCR4** (T-tropic), which is associated with rapid CD4+ T-cell decline. * **Maraviroc:** A CCR5 antagonist (entry inhibitor) used in HIV treatment; it is only effective against CCR5-tropic strains. * **Berlin Patient:** The first person "cured" of HIV (Timothy Ray Brown) received a bone marrow transplant from a donor homozygous for the **CCR5-Δ32** mutation.

Q: An emerging viral pathogen causing pyelonephritis in kidney allografts is:

Polyomavirus. **Explanation:** **Polyomavirus (specifically BK virus)** is the correct answer because it is a major cause of opportunistic infection in kidney transplant recipients. In the setting of potent immunosuppression, the latent BK virus (a member of the Polyomavirus family) reactivates, leading to **BK virus-associated nephropathy (BKVAN)**. This condition is characterized by viral replication within the tubular epithelial cells, causing inflammation and necrosis that clinically mimics acute cellular rejection. Histologically, it presents with characteristic **intranuclear viral inclusions** (ground-glass appearance) in tubular cells [1]. **Analysis of Incorrect Options:** * **Rotavirus:** Primarily causes viral gastroenteritis in children; it does not have a tropism for renal tissue or cause pyelonephritis. * **Herpes Simplex Virus (HSV):** While HSV can cause systemic infections in immunocompromised hosts, it typically manifests as mucocutaneous lesions, esophagitis, or hepatitis, rather than graft pyelonephritis. * **Influenza Virus:** This is a respiratory pathogen causing pneumonia or systemic flu-like symptoms; it does not target the renal allograft. **High-Yield Clinical Pearls for NEET-PG:** * **Diagnosis:** Look for **"Decoy cells"** (cells with enlarged nuclei and inclusions) in urine cytology. Definitive diagnosis is made via renal biopsy. * **SV40 Staining:** Immunohistochemistry for the SV40 large T antigen is the gold standard for identifying Polyomavirus in tissue sections. * **Management:** The primary treatment strategy is the **reduction of immunosuppressive therapy** to allow the host immune system to control the viral replication. * **JC Virus:** Another Polyomavirus, but it primarily causes Progressive Multifocal Leukoencephalopathy (PML) rather than nephropathy. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Kidney, pp. 934-935.

Q: All of the following are components of Dane particles except?

Delta antigen. **Explanation:** The **Dane particle** represents the complete, infectious virion of the **Hepatitis B Virus (HBV)**. It is a 42 nm spherical structure consisting of an inner core and an outer envelope. **Why Delta Antigen is the correct answer:** The **Delta antigen (HDAg)** is a component of the **Hepatitis D Virus (HDV)**, not HBV. While HDV is a "defective" virus that requires the presence of HBV (specifically HBsAg) to provide its outer envelope for assembly and transmission, the Delta antigen itself is part of the HDV ribonucleoprotein complex, not a structural component of the Dane particle. **Analysis of incorrect options:** * **Surface Antigen (HBsAg):** This is the outer lipoprotein envelope of the Dane particle. It is produced in excess, appearing as spherical and tubular forms in the serum. * **Core Antigen (HBcAg):** This forms the inner nucleocapsid that encloses the viral genome (partially double-stranded DNA) and the DNA polymerase. * **C-antigen (HBeAg):** This is a soluble protein derived from the precore/core gene. While it is primarily a secretory protein used as a marker of high infectivity, it is structurally associated with the core components of the virus. **Clinical Pearls for NEET-PG:** * **Morphology:** Dane particles are 42 nm; non-infectious spherical/tubular HBsAg particles are 22 nm. * **HBeAg:** Its presence indicates active viral replication and high infectivity. * **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs; **Anti-HBc IgM** is the only diagnostic marker during this phase. * **Ground-glass Hepatocytes:** Characteristic histopathological finding in chronic HBV infection due to HBsAg accumulation.

Question 1

What is the most common genital lesion observed in patients with HIV?

Accepted Answer

Herpes

Answer

Chlamydia

Answer

Syphilis

Answer

Candida

Question 2

All of the following infections may be transmitted by dental instruments except?

Accepted Answer

Hepatitis E

Answer

HIV

Answer

Hepatitis C

Answer

Hepatitis B

Question 3

Which gene codes for the core proteins of HIV?

Accepted Answer

GAG

Answer

ENV

Answer

POL

Answer

TAT

Question 4

All of the following statements are true for rabies virus except:

Accepted Answer

Rabies vaccine is a live attenuated vaccine.

Answer

Infection may be prevented by active and passive immunization.

Answer

The animal reservoir differs from country to country.

Answer

It can be diagnosed by direct fluorescent antibody (DFA) testing.

Question 5

Which RNA virus is inhibited by Actinomycin D?

Accepted Answer

Influenza

Answer

Measles

Answer

Polio

Answer

Rubella

Question 6

Which of the following is a single-stranded DNA virus with no envelope?

Accepted Answer

Parvovirus B19

Answer

Hepatitis A

Answer

Herpes simplex

Answer

Human reovirus

Question 7

A 19-year-old intravenous drug user has regularly sought human immunodeficiency virus (HIV) testing, always with negative results. He admits to carelessly sharing needles on multiple occasions with individuals later found to be HIV-positive. He has heard that there is an inherited genetic basis for some people to be relatively "immune" to HIV infection. The genetic change that he is referring to is a mutation in a gene coding for which of the following proteins?

Accepted Answer

CCR5

Answer

CD4

Answer

gp120

Answer

gp41

Question 8

Which of the following statements is true about Herpes viruses?

Accepted Answer

Herpes Simplex Virus (HSV) encephalitis is treated with acyclovir.

Answer

Oropharyngeal involvement is common in HSV-1.

Answer

Recurrent genital involvement is seen in HSV-2.

Answer

Recurrence is rare in HSV-1.

Question 9

An emerging viral pathogen causing pyelonephritis in kidney allografts is:

Accepted Answer

Polyomavirus

Answer

Rotavirus

Answer

Herpes simplex

Answer

Influenza virus

Question 10

All of the following are components of Dane particles except?

Accepted Answer

Delta antigen

Answer

Surface antigen

Answer

Core antigen

Answer

C-antigen

Virology — MCQs

Virology — MCQs

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