Virology Practice Questions

Q: A sexually active woman presents for a routine gynecologic exam with a Pap smear report indicating cervical intraepithelial neoplasia. In situ hybridization reveals the presence of human papillomavirus (HPV) type 16 genomes within the neoplastic cells. Which of the following processes is required for HPV to cause cancer development?

Integration of the viral genome. **Explanation:** The progression of Human Papillomavirus (HPV) infection to cervical carcinoma is fundamentally dependent on the **integration of the viral genome** into the host cell DNA. 1. **Why Option A is correct:** In benign lesions (warts), the HPV genome exists as an episome (circular, extrachromosomal). However, in malignant lesions, the viral DNA integrates into the host genome. This integration typically occurs at the **E1/E2 open reading frame**, leading to the **disruption of the E2 gene**. Since the E2 gene normally functions as a negative regulator (repressor) of the **E6 and E7 oncogenes**, its loss leads to the uncontrolled overexpression of E6 and E7. * **E6** binds to and degrades the **p53** tumor suppressor protein. * **E7** binds to and inactivates the **pRb** (Retinoblastoma) protein. The loss of these "molecular brakes" leads to unrestricted cell cycle progression and genomic instability. 2. **Why the other options are incorrect:** * **Option B:** Loss of E6 and E7 would prevent oncogenesis, as these are the primary drivers of malignancy. * **Option C:** While mutations occur in many cancers, the specific oncogenic transformation by HPV is driven by gene expression changes following integration, not random viral mutations. * **Option D:** Viral replication (the production of new virions) occurs in the superficial layers of the epithelium and usually leads to cell death (lysis), which is contrary to the immortalization required for cancer. **High-Yield Clinical Pearls for NEET-PG:** * **High-risk HPV types:** 16 and 18 (associated with ~70% of cervical cancers). * **Low-risk HPV types:** 6 and 11 (associated with Condyloma acuminatum). * **Koilocytosis:** The hallmark cytological finding on Pap smear (perinuclear halo with wrinkled "raisinoid" nuclei). * **Vaccine:** Gardasil-9 covers types 6, 11, 16, 18, 31, 33, 45, 52, and 58.

Q: Which marker indicates active Hepatitis B Virus (HBV) infection?

HBsAg. ### Explanation **Hepatitis B Surface Antigen (HBsAg)** is the hallmark of active infection. It is the first serological marker to appear in the blood (usually 2–6 weeks after exposure) and its presence indicates that the virus is currently replicating in the host. If HBsAg persists for more than 6 months, the infection is classified as **chronic**. #### Analysis of Options: * **A. HBsAg (Correct):** It is the primary screening tool. Its presence signifies an active (acute or chronic) infection. * **B. HBcAg (Hepatitis B Core Antigen):** This is a particulate antigen found inside the hepatocyte. It is **not secreted into the blood** and therefore cannot be detected by routine serum assays. * **C. IgM anti-HBsAg:** This is not a standard clinical marker. Protective antibodies against the surface antigen are typically of the IgG class. * **D. IgG anti-HBsAg:** This indicates **immunity** to HBV. It appears after recovery from a natural infection or following successful vaccination. It is never present during the active phase of the disease. #### NEET-PG High-Yield Pearls: 1. **Window Period:** The time between the disappearance of HBsAg and the appearance of Anti-HBs. During this gap, **IgM anti-HBc** is the only diagnostic marker present. 2. **Infectivity Marker:** **HBeAg** (Envelope antigen) indicates high viral replication and high infectivity. 3. **Vaccination vs. Natural Infection:** * **Vaccinated:** Only Anti-HBs positive. * **Recovered from Natural Infection:** Both Anti-HBs and Anti-HBc (IgG) positive. 4. **HBV DNA:** The most sensitive marker for monitoring viral load and response to antiviral therapy.

Q: Which organism causes hemagglutination?

Influenza virus. **Explanation:** The correct answer is **Influenza virus**. Hemagglutination is the process by which specific viruses bind to receptors on the surface of red blood cells (RBCs), causing them to form a lattice or clump. **1. Why Influenza Virus is Correct:** Influenza viruses possess a surface glycoprotein called **Hemagglutinin (HA)**. This protein binds to **sialic acid receptors** on the surface of host cells and RBCs (typically guinea pig, chicken, or human O-type). This property is utilized in the laboratory for the Hemagglutination Assay (to quantify virus particles) and the Hemagglutination Inhibition (HI) test (to detect antibodies). **2. Analysis of Other Options:** * **Mumps:** While Mumps (a Paramyxovirus) also possesses a Hemagglutinin-Neuraminidase (HN) protein and can cause hemagglutination, **Influenza** is the "classic" and most potent example taught in medical microbiology regarding this specific mechanism. In the context of standard NEET-PG questions, Influenza is the primary association for HA. * **Adenovirus:** Some serotypes can agglutinate rat or monkey RBCs via their fiber proteins, but it is not their defining diagnostic characteristic compared to Orthomyxoviruses. * **Parvovirus:** Parvovirus B19 binds to the **P-antigen** on erythrocyte precursors, but it is primarily known for causing aplastic crisis and Erythema Infectiosum rather than being the standard answer for general hemagglutination. **High-Yield Clinical Pearls for NEET-PG:** * **HA vs. NA:** Hemagglutinin (HA) is for **attachment/entry**, while Neuraminidase (NA) is for **release/budding** of the virus. * **Antigenic Drift vs. Shift:** Minor mutations in HA/NA cause *Drift* (epidemics); reassortment of segments causes *Shift* (pandemics). * **Hot Topic:** The Hemagglutination Inhibition (HI) test is the gold standard for measuring protective antibody titers following influenza vaccination.

Q: Which of the following viruses has a double-stranded RNA genome?

Poxviruses. **Explanation:** The question asks to identify the virus with a **double-stranded RNA (dsRNA)** genome. However, there is a discrepancy in the provided key: **Reoviruses** are the classic example of dsRNA viruses, while **Poxviruses** are actually double-stranded DNA (dsDNA) viruses. 1. **Why Reoviruses (Option D) is the correct biological answer:** Reoviruses (e.g., Rotavirus) are unique among RNA viruses because their genome consists of **segmented double-stranded RNA**. Most other RNA viruses are single-stranded (ssRNA). 2. **Analysis of Options:** * **Poxviruses (Option B):** These are **dsDNA** viruses. They are unique because they are the largest viruses and replicate in the *cytoplasm* despite being DNA viruses. * **Orthomyxoviruses (Option A):** These (e.g., Influenza) are **segmented, negative-sense ssRNA** viruses. * **Parvoviruses (Option C):** These are unique for being **single-stranded DNA (ssDNA)** viruses (the "Parvo-is-Partial" mnemonic). **High-Yield NEET-PG Pearls:** * **DNA Virus Rule:** All DNA viruses are dsDNA except **Parvoviridae** (ssDNA). * **RNA Virus Rule:** All RNA viruses are ssRNA except **Reoviridae** (dsRNA). * **Segmentation:** High-yield for reassortment/antigenic shift. Remember **BOAR**: **B**unyavirus, **O**rthomyxovirus, **A**renavirus, **R**eovirus. * **Replication Site:** All DNA viruses replicate in the nucleus *except* Poxvirus. All RNA viruses replicate in the cytoplasm *except* Influenza and Retroviruses. *Note: If a question bank marks Poxvirus as dsRNA, it is a factual error; Poxvirus is the prototype for complex dsDNA.*

Q: Which of the following is a Category A bioterrorism agent?

Ebola. **Explanation:** The CDC classifies bioterrorism agents into three categories (A, B, and C) based on their potential for mass dissemination, mortality rates, and public health impact. **Category A** agents are the highest priority because they are easily transmitted, result in high mortality, and require special public health preparedness. **Correct Option: A. Ebola** Ebola virus belongs to the **Viral Hemorrhagic Fevers (VHF)** group, which is a hallmark of Category A. These agents (including Marburg, Lassa, and Machupo) are prioritized due to their extreme virulence, high case-fatality rates, and potential to cause widespread panic. **Analysis of Incorrect Options:** * **B. Yersinia:** While *Yersinia pestis* (Plague) is a Category A agent, the option simply states "Yersinia." In the context of NEET-PG, if a specific virus like Ebola is listed, it remains the most definitive answer for viral Category A agents. (Note: Plague, Anthrax, Tularemia, Smallpox, Botulism, and VHFs constitute the "Big Six" of Category A). * **C. Clostridium botulinum:** While *Botulinum toxin* is a Category A agent, the bacterium itself is generally categorized by its toxin's impact. * **D. Rickettsia:** Most Rickettsial species (like *Rickettsia prowazekii*) are classified as **Category B** agents. They have moderate morbidity and lower mortality rates compared to Category A. **High-Yield Clinical Pearls for NEET-PG:** * **Category A "Big Six":** Anthrax (*B. anthracis*), Botulism (*C. botulinum* toxin), Plague (*Y. pestis*), Smallpox (*Variola major*), Tularemia (*F. tularensis*), and Viral Hemorrhagic Fevers (Ebola, Marburg). * **Category B:** Includes food safety threats (*Salmonella*, *Shigella*), *Brucella*, *Glanders*, and *Q fever*. * **Category C:** Emerging pathogens with potential for future mass dissemination, such as **Nipah virus** and **Hantavirus**.

Q: Viruses can be grown using all of the following methods except:

Enriched media. **Explanation:** The fundamental principle of virology is that **viruses are obligate intracellular parasites**. They lack the cellular machinery (ribosomes, enzymes) required for independent metabolism and protein synthesis. Therefore, they cannot grow on non-living, artificial culture media, regardless of how "enriched" the nutrients are. **Why "Enriched Media" is the correct answer:** Enriched media (like Blood Agar or Chocolate Agar) contain nutrients to support the growth of fastidious **bacteria**. Since viruses require a living host cell to replicate by hijacking its molecular machinery, they will never grow on inanimate agar or broth. **Analysis of other options:** * **Tissue Culture:** This is the most common modern method. It uses living cell lines (e.g., HeLa, Vero, WI-38) to provide the necessary intracellular environment for viral replication. * **Embryonated Eggs:** A classic method (typically using 10–12 day old chick embryos). Different viruses are inoculated into specific sites like the chorioallantoic membrane (Poxvirus), allantoic cavity (Influenza), or yolk sac (Chlamydia/Rickettsia). * **Animals:** The oldest method, still used for primary isolation of certain viruses (e.g., Coxsackie virus in suckling mice) and for studying pathogenesis or immune responses. **High-Yield Clinical Pearls for NEET-PG:** * **Detection of viral growth:** In tissue culture, growth is identified by the **Cytopathic Effect (CPE)**, such as cell swelling, fusion (syncytia), or inclusion bodies (e.g., Negri bodies in Rabies). * **Steinhardt’s Method:** The first use of tissue culture to grow Vaccinia virus. * **Influenza Vaccine:** Most commercial influenza vaccines are still produced using the **Embryonated Egg** method (allantoic cavity).

Q: Which gene encodes the HTLV tax protein?

pX. **Explanation:** Human T-cell Lymphotropic Virus (HTLV-1) is a complex retrovirus. Unlike simple retroviruses, it contains a unique **pX region** located at the 3' end of its genome, which is essential for its oncogenic potential. **1. Why pX is correct:** The **pX region** encodes several non-structural regulatory proteins, most notably **Tax** and **Rex**. * **Tax protein** is a potent transcriptional activator. It upregulates the expression of cellular genes involved in T-cell proliferation (like IL-2 and IL-2 receptors) and inactivates tumor suppressor genes (like p53). This leads to the immortalization of T-cells, eventually causing **Adult T-cell Leukemia/Lymphoma (ATL)**. **2. Why other options are incorrect:** * **Gag (Group-specific antigen):** Encodes the internal structural proteins of the virus, such as the capsid (p24), nucleocapsid, and matrix proteins. * **Pol (Polymerase):** Encodes essential viral enzymes, including Reverse Transcriptase, Integrase, and Protease. * **Env (Envelope):** Encodes the surface glycoproteins (gp46) and transmembrane proteins (gp21) responsible for viral attachment and entry. **Clinical Pearls for NEET-PG:** * **HTLV-1 Association:** Strongly linked to **Adult T-cell Leukemia/Lymphoma (ATL)** (characterized by "flower cells" on peripheral smear) and **Tropical Spastic Paraparesis (TSP)** (a demyelinating disease). * **Transmission:** Similar to HIV (Blood, Sexual contact, and Breastfeeding). * **Tax Protein:** It is the primary oncogenic driver; it induces genomic instability and inhibits DNA repair. * **Rex Protein:** Regulates viral mRNA splicing and export from the nucleus.

Question 1

A sexually active woman presents for a routine gynecologic exam with a Pap smear report indicating cervical intraepithelial neoplasia. In situ hybridization reveals the presence of human papillomavirus (HPV) type 16 genomes within the neoplastic cells. Which of the following processes is required for HPV to cause cancer development?

Accepted Answer

Integration of the viral genome

Answer

Loss of HPV E6 and E7 genes

Answer

Mutation of the virus

Answer

Viral replication

Question 2

Which marker indicates active Hepatitis B Virus (HBV) infection?

Accepted Answer

HBsAg

Answer

HBcAg

Answer

IgM anti-HBsAg

Answer

IgG anti-HBsAg

Question 3

The human immunodeficiency virus (HIV) can be isolated from which of the following body fluids or sources, except?

Accepted Answer

Skin scraping

Answer

Semen

Answer

Saliva

Answer

Blood transfusion

Question 4

Which organism causes hemagglutination?

Accepted Answer

Influenza virus

Answer

Mumps

Answer

Adenovirus

Answer

Parvovirus

Question 5

Which of the following viruses has a double-stranded RNA genome?

Accepted Answer

Poxviruses

Answer

Orthomyxoviruses

Answer

Parvoviruses

Answer

Reoviruses

Question 6

Electron microscopy is helpful in the diagnosis of which of the following viruses?

Accepted Answer

RSV

Answer

Rotavirus

Answer

Herpesvirus

Answer

Prion

Question 7

All the following are true regarding Type A influenza virus, EXCEPT:

Accepted Answer

There are 15 subtypes of hemagglutinin and 9 subtypes of neuraminidase.

Answer

Humans are generally infected by virus of subtype H1, H2 or H3 and N1 or N2.

Answer

It shows both antigenic shift and drift.

Question 8

Which of the following is a Category A bioterrorism agent?

Accepted Answer

Ebola

Answer

Yersinia

Answer

Clostridium botulinum

Answer

Rickettsia

Question 9

Viruses can be grown using all of the following methods except:

Accepted Answer

Enriched media

Answer

Tissue culture

Answer

Embryonated eggs

Answer

Animals

Question 10

Which gene encodes the HTLV tax protein?

Accepted Answer

pX

Answer

Gag

Answer

Pol

Answer

Env

Virology — MCQs

Virology — MCQs

On this page

Practice by Chapter

Want unlimited practice?