Virology Practice Questions

Q: A 9-year-old male presents with a history of fever, nonspecific symptoms, bright red cheeks, and a macular lacy rash over his body. Which of the following viruses is the most likely cause of this disease?

Parvovirus B19. **Explanation:** The clinical presentation described—a 9-year-old with fever followed by **"bright red cheeks" (slapped-cheek appearance)** and a **macular lacy (reticular) rash** on the trunk and extremities—is classic for **Erythema Infectiosum**, also known as **Fifth Disease**. **Why Parvovirus B19 is correct:** Parvovirus B19 is a small, non-enveloped ssDNA virus. It infects and replicates in rapidly dividing erythroid progenitor cells in the bone marrow by binding to the **P-antigen** (globoside). The rash is immune-mediated (Type III hypersensitivity), appearing after the initial viremic phase has resolved, meaning the child is typically no longer contagious once the rash appears. **Why other options are incorrect:** * **HSV-1:** Typically presents with orolabial herpes (cold sores) or gingivostomatitis, not a diffuse lacy rash or slapped-cheek appearance. * **Rubella (German Measles):** Presents with a maculopapular rash that starts on the face and spreads cephalocaudally, often accompanied by characteristic **post-auricular or suboccipital lymphadenopathy**. * **Rubeola (Measles):** Characterized by the "3 Cs" (Cough, Coryza, Conjunctivitis) and **Koplik spots**. The rash is a confluent maculopapular eruption, not lacy. **High-Yield Clinical Pearls for NEET-PG:** * **Aplastic Crisis:** Parvovirus B19 can cause a life-threatening drop in hemoglobin in patients with high red cell turnover (e.g., Sickle Cell Anemia, Hereditary Spherocytosis). * **Hydrops Fetalis:** Infection during pregnancy can lead to severe fetal anemia and congestive heart failure. * **Arthropathy:** In adults, infection often presents as symmetrical small joint arthritis (mimicking Rheumatoid Arthritis). * **Receptor:** It uses the **P-antigen** on RBCs; individuals lacking this antigen are immune.

Q: Which of the following are transfusion-transmitted viruses?

All of the above. **Explanation:** Transfusion-transmitted infections (TTIs) are pathogens that can be inadvertently passed from a donor to a recipient through blood or blood products. For a virus to be efficiently transmitted via transfusion, it must typically have a phase of viremia (presence in the blood) and be capable of surviving storage conditions. * **Hepatitis B (HBV):** This is a classic TTI. Despite rigorous screening for HBsAg and increasingly for anti-HBc or HBV-DNA (NAT), it remains a risk due to the "window period" or occult infections. * **Cytomegalovirus (CMV):** CMV is a leukocyte-associated virus. It is a significant concern for immunocompromised patients and neonates. Risk is mitigated by using "leukoreduced" blood or CMV-seronegative units. * **HTLV-1 and HHV-8:** HTLV-1 (associated with Adult T-cell Leukemia/Lymphoma) is also cell-associated and screened in many countries. HHV-8 (Kaposi Sarcoma-associated Herpesvirus) can be transmitted via blood, particularly in endemic areas, though it is not universally screened. **Why "All of the above" is correct:** All the listed viruses have documented parenteral transmission routes and can persist in various blood components (plasma or cellular elements), making them potential TTIs. **High-Yield Clinical Pearls for NEET-PG:** * **Most common TTI globally:** Hepatitis B. * **Most common TTI in India:** Historically Hepatitis B, but risk is decreasing with NAT (Nucleic Acid Testing). * **Window Period:** The time between infection and detection. NAT significantly reduces this period compared to serology. * **Bacterial Contamination:** Platelets carry the highest risk of bacterial sepsis because they are stored at room temperature (20-24°C). * **Other TTIs:** HIV-1/2, Hepatitis C, Malaria, Syphilis, and emerging threats like Zika or West Nile Virus.

Q: Which of the following genes is associated with the encoding of reverse transcriptase?

Pol. The correct answer is **A. Pol**. ### **Explanation** The Human Immunodeficiency Virus (HIV) and other retroviruses possess three structural genes essential for their life cycle: **gag, pol, and env**. 1. **Pol (Polymerase) Gene:** This gene encodes the essential enzymes required for viral replication and integration. These include: * **Reverse Transcriptase:** Converts viral RNA into proviral DNA. * **Integrase:** Integrates the proviral DNA into the host cell genome. * **Protease:** Cleaves precursor polypeptides into functional proteins during viral maturation. 2. **Gag (Group-specific Antigen) Gene:** Encodes the inner structural proteins, primarily the **p24 capsid protein** (used for early diagnosis) and the p17 matrix protein. 3. **Env (Envelope) Gene:** Encodes the precursor glycoprotein **gp160**, which is cleaved by host proteases into **gp120** (attachment to CD4) and **gp41** (fusion and entry). 4. **LTR (Long Terminal Repeat):** These are non-coding sequences at both ends of the viral genome that act as promoters for gene transcription; they do not encode proteins. ### **High-Yield Clinical Pearls for NEET-PG** * **p24 Antigen:** The earliest serological marker of HIV infection (detected during the window period). * **gp120:** Responsible for tropism; it binds to the CD4 receptor and CCR5/CXCR4 co-receptors. * **Drug Targets:** * **NRTIs/NNRTIs** target Reverse Transcriptase. * **Raltegravir** targets Integrase. * **Maraviroc** targets the CCR5 co-receptor. * **Enfuvirtide** targets gp41 (fusion inhibitor).

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.

Question 1

A 9-year-old male presents with a history of fever, nonspecific symptoms, bright red cheeks, and a macular lacy rash over his body. Which of the following viruses is the most likely cause of this disease?

Accepted Answer

Parvovirus B19

Answer

Herpes simplex virus (HSV) type 1

Answer

Rubella virus

Answer

Rubeola (measles) virus

Question 2

Which of the following are transfusion-transmitted viruses?

Accepted Answer

All of the above

Answer

Hepatitis B

Answer

Cytomegalovirus (CMV)

Answer

Human T-lymphotropic virus 1 (HTLV-1) and Human herpesvirus 8 (HHV-8)

Question 3

Which of the following genes is associated with the encoding of reverse transcriptase?

Accepted Answer

Pol

Answer

Env

Answer

Gag

Answer

LTR

Question 4

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

Accepted Answer

Herpes

Answer

Chlamydia

Answer

Syphilis

Answer

Candida

Question 5

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 6

Which gene codes for the core proteins of HIV?

Accepted Answer

GAG

Answer

ENV

Answer

POL

Answer

TAT

Question 7

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 8

Which RNA virus is inhibited by Actinomycin D?

Accepted Answer

Influenza

Answer

Measles

Answer

Polio

Answer

Rubella

Question 9

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 10

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

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?