Virology — MCQs
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Which virus is associated with Hodgkin's lymphoma?
Viroids are characterized by which of the following?
E6 and E7 genes of which virus are implicated in oncogenesis?
In which of the following viruses is the virus shed in stool?
Which of the following statements about Parvovirus B19 infection is correct?
Which hepatitis virus was the first to be successfully cultured in vitro?
Which of the following statements about rabies is true?
What does the term 'Australian antigen' refer to in the context of hepatitis B?
Which cells does HIV most commonly infect?
Which of the following conditions is not caused by the Herpes simplex virus?
Virology Indian Medical PG Practice Questions and MCQs
Question 1421: Which virus is associated with Hodgkin's lymphoma?
- A. Epstein-Barr virus (EBV) (Correct Answer)
- B. Cytomegalovirus (CMV)
- C. Human herpesvirus 8 (HHV8)
- D. Human herpesvirus 6 (HHV6)
Explanation: ***EBV*** - **Epstein-Barr Virus (EBV)** is strongly associated with the development of Hodgkin's lymphoma, particularly in patients presenting with mixed cellularity [1]. - EBV is found in the **Reed-Sternberg cells**, a characteristic feature of Hodgkin's lymphoma [1]. *HHV8* - **HHV8** is mainly associated with Kaposi's sarcoma and primary effusion lymphoma, not Hodgkin's lymphoma. - It typically affects immunocompromised individuals, especially those with HIV/AIDS, which differs from Hodgkin's lymphoma associations. *HHV6* - While **HHV6** can cause certain diseases like roseola in children, it is not linked to Hodgkin's lymphoma. - There is minimal evidence connecting it with lymphomagenesis in broader contexts. *CMV* - **Cytomegalovirus (CMV)** is primarily recognized for causing opportunistic infections, especially in immunocompromised patients. - Its association with Hodgkin's lymphoma is not substantiated, making it irrelevant in this context. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Diseases of White Blood Cells, Lymph Nodes, Spleen, and Thymus, pp. 616-618.
Question 1422: Viroids are characterized by which of the following?
- A. Naked pathogenic human viruses
- B. Fragments of viruses
- C. Small, circular single-stranded RNA (Correct Answer)
- D. DNA with protein coat
Explanation: ***Small, circular single-stranded RNA*** - **Viroids** are infectious agents consisting solely of a short strand of **circular, single-stranded RNA** that is self-replicating. - They lack a protein coat, unlike viruses, and are primarily known to cause diseases in plants. *Naked pathogenic human viruses* - While viroids are **naked** (lacking a protein coat), they are not classified as **viruses** and typically do not infect **humans**. - Viroids are distinct from human-pathogenic viruses in their structure and host range. *Fragments of viruses* - Viroids are not **fragments of viruses** but are distinct infectious entities. - They are much smaller than viruses and have a simpler genetic structure, not derived from viral components. *DNA with protein coat* - Viroids do not contain **DNA**; their genetic material is exclusively **RNA**. - They also lack a **protein coat**, which distinguishes them from conventional viruses that possess both nucleic acid and protein components.
Question 1423: E6 and E7 genes of which virus are implicated in oncogenesis?
- A. HPV (Correct Answer)
- B. Cytomegalovirus (CMV)
- C. Epstein-Barr Virus (EBV)
- D. Human T-lymphotropic Virus type 1 (HTLV-1)
Explanation: ***HPV*** - The **E6** and **E7** oncoproteins of **High-Risk Human Papillomavirus (HPV)** are critical for oncogenesis, primarily in cervical cancer. - **E6** degrades the tumor suppressor protein **p53**, and **E7** inactivates the **retinoblastoma (Rb)** protein, leading to uncontrolled cell proliferation. *Cytomegalovirus (CMV)* - While CMV can be associated with certain cancers like glioblastoma, its direct role in oncogenesis does not involve specific E6/E7 genes. - CMV primarily causes opportunistic infections and congenital abnormalities, not through the mechanism of E6/E7. *Epstein-Barr Virus (EBV)* - EBV is associated with various cancers such as **nasopharyngeal carcinoma** and **Burkitt lymphoma**. - Its oncogenic mechanisms involve proteins like **LMP1** and **EBNA2**, which dysregulate cell growth, rather than E6/E7. *Human T-lymphotropic Virus type 1 (HTLV-1)* - HTLV-1 is the causative agent of **Adult T-cell Leukemia/Lymphoma (ATLL)**. - Its oncogenic potential is linked to the **Tax protein**, which alters gene expression and promotes T-cell proliferation, not through E6/E7.
Question 1424: In which of the following viruses is the virus shed in stool?
- A. Enterovirus (Herpangina) (Correct Answer)
- B. Influenza virus
- C. Varicella virus
- D. Smallpox virus
Explanation: ***Enterovirus (Herpangina)*** - **Enteroviruses** replicate in the gastrointestinal tract and are typically shed in **feces**, providing a route for **fecal-oral transmission**. - Herpangina, caused by coxsackievirus (an enterovirus), is characterized by mouth lesions but the virus itself is excreted via the gastrointestinal route. *Influenza virus* - The influenza virus primarily infects the **respiratory tract** and is shed through **respiratory droplets** and secretions. - It does not typically cause significant gastrointestinal infection or shedding in stool. *Varicella virus* - The varicella-zoster virus (VZV) causes **chickenpox** and shingles, and is primarily spread through **respiratory droplets** and **direct contact** with blister fluid. - There is no significant shedding of varicella virus in stool. *Smallpox virus* - Smallpox is transmitted via **respiratory droplets** and through **direct contact** with scabs or fluid from skin lesions, which contain the virus. - Stool is not a primary route of transmission or shedding for the smallpox virus.
Question 1425: Which of the following statements about Parvovirus B19 infection is correct?
- A. Individuals lacking P antigen are susceptible to Parvovirus B19 infection.
- B. Parvovirus B19 primarily affects myeloid precursors.
- C. Parvovirus B19 infections are typically chronic.
- D. Parvovirus B19 primarily affects erythroid progenitor cells. (Correct Answer)
Explanation: ***Parvovirus B19 primarily affects erythroid progenitor cells.*** - Parvovirus B19 has a tropism for **erythroid progenitor cells** due to their expression of the P antigen, which serves as the primary receptor for the virus. - Infection of these cells leads to their **lysis**, causing a temporary cessation of red blood cell production. *Parvovirus B19 primarily affects myeloid precursors.* - Parvovirus B19 primarily targets **erythroid cells**, not myeloid precursors. - Infection of myeloid precursors is not a characteristic feature of Parvovirus B19 pathogenesis. *Individuals lacking P antigen are susceptible to Parvovirus B19 infection.* - The **P antigen** (globoside) is the primary cellular receptor for Parvovirus B19. - Individuals who genetically lack the P antigen are typically **resistant** to Parvovirus B19 infection. *Parvovirus B19 infections are typically chronic.* - Parvovirus B19 infections are usually **acute and self-limiting** in immunocompetent individuals. - Chronic infections are rare and generally only occur in **immunocompromised** patients, leading to **persistent anemia**.
Question 1426: Which hepatitis virus was the first to be successfully cultured in vitro?
- A. Hepatitis A Virus (HAV) (Correct Answer)
- B. Hepatitis B Virus (HBV)
- C. Hepatitis D Virus (HDV)
- D. Hepatitis C Virus (HCV)
Explanation: ***Hepatitis A Virus (HAV)*** - **HAV** was the **first hepatitis virus successfully cultured in vitro** on primary marmoset liver cells and human fetal kidney cells in the late 1970s. - This breakthrough allowed for detailed study of its replication cycle and the development of diagnostic tests and vaccines. *Hepatitis B Virus (HBV)* - While HBV was identified earlier, its **complex replication cycle** and dependence on hepatocytes made its **in vitro culture significantly more challenging** and delayed. - HBV was first identified through the **Australia antigen** in human serum, not initially by in vitro culture. *Hepatitis D Virus (HDV)* - **HDV is a defective virus** that requires co-infection with HBV to replicate, making its independent **in vitro culture impossible**. - Its replication is dependent on the presence of the **hepatitis B surface antigen (HBsAg)**. *Hepatitis C Virus (HCV)* - **HCV was identified much later** in 1989 through molecular cloning techniques, as it was not cultivable in standard cell lines for a long time. - Due to its **genetic diversity and specific host cell requirements**, sustained in vitro culture systems for HCV were only established in the early 2000s.
Question 1427: Which of the following statements about rabies is true?
- A. Rabies is caused by an enveloped, single-stranded RNA virus. (Correct Answer)
- B. The rabies vaccine provides lifelong immunity.
- C. Rabies is caused by a DNA virus.
- D. Rabies virus replicates primarily in muscle tissue before CNS involvement.
Explanation: ***Rabies is caused by an enveloped, single-stranded RNA virus.*** - The **rabies virus** is a **Lyssavirus** (genus) from the **Rhabdoviridae family**, characterized by its **enveloped**, **bullet-shaped** morphology and a **single-stranded, negative-sense RNA** genome. - This viral structure is crucial for its replication cycle and immune evasion within the host. *The rabies vaccine provides lifelong immunity.* - While **rabies vaccines** are highly effective in preventing the disease, immunity is **not lifelong** and requires **booster doses** or **periodic revaccination** depending on risk exposure. - The duration of immunity wanes over time, and individuals at high risk (veterinarians, laboratory workers) require regular serological monitoring. *Rabies is caused by a DNA virus.* - This is **incorrect** - rabies virus is an **RNA virus**, not a DNA virus. - It contains a **single-stranded, negative-sense RNA** genome approximately 12 kb in length. - The RNA genome encodes five structural proteins essential for viral replication and pathogenesis. *Rabies virus replicates primarily in muscle tissue before CNS involvement.* - While there may be **limited local replication** at the inoculation site (often muscle tissue from a bite wound), the rabies virus does **not primarily replicate in muscle tissue**. - The virus rapidly enters **peripheral nerves** at the wound site and travels via **retrograde axonal transport** to the CNS. - Significant viral replication occurs in the **CNS neurons**, particularly in the hippocampus, brainstem, and spinal cord.
Question 1428: What does the term 'Australian antigen' refer to in the context of hepatitis B?
- A. Hepatitis B Antigen
- B. Hepatitis B Surface Antigen (HBsAg) (Correct Answer)
- C. Hepatitis B Virus (HBV)
- D. Hepatitis B Core Antigen (HBcAg)
Explanation: ***Hepatitis B Surface Antigen (HBsAg)*** - The term "Australian antigen" was the original name given to the **Hepatitis B Surface Antigen (HBsAg)** when it was first discovered by Baruch Blumberg in 1965 in the blood of an Indigenous Australian. - Its presence indicates an **active hepatitis B infection**, either acute or chronic. - This discovery led to the development of diagnostic tests and vaccines for hepatitis B. *Hepatitis B Antigen* - This is a **non-specific general term** and does not refer to a particular antigen of the hepatitis B virus. - Hepatitis B has several distinct antigens (HBsAg, HBcAg, HBeAg), each with different diagnostic significance. *Hepatitis B Virus (HBV)* - This refers to the **entire infectious agent** that causes hepatitis B, not specifically to one of its antigenic components. - The "Australian antigen" specifically refers to the surface antigen, not the whole virus. *Hepatitis B Core Antigen (HBcAg)* - HBcAg is a **different antigenic component** found in the nucleocapsid core of the hepatitis B virus. - It is not directly detected in serum; instead, antibodies to HBcAg (anti-HBc) are measured for diagnostic purposes. - The Australian antigen refers specifically to HBsAg, not HBcAg.
Question 1429: Which cells does HIV most commonly infect?
- A. CD4+ helper cells (Correct Answer)
- B. CD8+ cells
- C. Macrophages
- D. Neutrophils
Explanation: ***CD4+ helper cells*** - HIV primarily targets and infects **CD4+ helper T-lymphocytes** because these cells express the **CD4 receptor** and co-receptors (CCR5 or CXCR4) necessary for viral entry. - The progressive destruction of these cells leads to **immunodeficiency**, characteristic of AIDS. *CD8+ cells* - **CD8+ cytotoxic T-lymphocytes** are crucial in fighting viral infections by killing infected cells, but they do not express the primary receptors that HIV uses for entry. - While they can be affected by the overall immune dysfunction in HIV, they are not the primary target for direct viral infection. *Macrophages* - Macrophages can be infected by HIV, particularly those expressing the **CCR5 co-receptor**, and can serve as a **reservoir for the virus**. - However, the infection rate and impact on overall viral load are significantly lower compared to CD4+ T-cells, which are the main engines of viral replication. *Neutrophils* - **Neutrophils** are phagocytic white blood cells that play a key role in innate immunity, primarily targeting bacterial and fungal infections. - They lack the specific CD4 receptor and co-receptors required for HIV entry and are therefore not directly infected by the virus.
Question 1430: Which of the following conditions is not caused by the Herpes simplex virus?
- A. Gingivostomatitis
- B. Mollaret meningitis
- C. Herpes labialis
- D. Carcinoma of the cervix (Correct Answer)
Explanation: ***Carcinoma of the cervix*** - **Cervical cancer** is primarily caused by **Human Papillomavirus (HPV)**, not the Herpes simplex virus (HSV). - While HSV can cause genital lesions, it is **not oncogenic** for the cervix. *Gingivostomatitis* - **Acute herpetic gingivostomatitis** is a common manifestation of **primary Herpes simplex virus type 1 (HSV-1)** infection, particularly in children. - It causes painful blisters and ulcers in the mouth and gums. *Mollaret meningitis* - **Mollaret's meningitis** is a rare form of **recurrent aseptic meningitis** strongly associated with **Herpes simplex virus type 2 (HSV-2)** infection. - HSV-2 *DNA* can often be detected in the cerebrospinal fluid during episodes. *Herpes labialis* - Commonly known as **cold sores** or **fever blisters**, Herpes labialis is caused by **Herpes simplex virus type 1 (HSV-1)**. - It results in recurrent vesicular lesions on the lips and around the mouth.
Practice by Chapter
Virus Structure and Classification
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Viral Replication
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Pathogenesis of Viral Infections
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DNA Viruses: Herpesviruses
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DNA Viruses: Poxviruses and Adenoviruses
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Hepatitis Viruses
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RNA Viruses: Orthomyxoviruses
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RNA Viruses: Paramyxoviruses
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Enteroviruses and Rhinoviruses
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Arboviruses
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HIV and Retroviruses
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Oncogenic Viruses
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