Virology Practice Questions

Q: Viroids are characterized by which of the following?

Small, circular single-stranded RNA. ***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.

Q: Which virus is associated with Hodgkin's lymphoma?

Epstein-Barr virus (EBV). ***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.

Q: E6 and E7 genes of which virus are implicated in oncogenesis?

HPV. ***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.

Q: Which hepatitis virus was the first to be successfully cultured in vitro?

Hepatitis A Virus (HAV). ***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.

Q: In which of the following viruses is the virus shed in stool?

Enterovirus (Herpangina). ***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.

Q: What is a known complication of Parvovirus B19 infection?

Aplastic anemia. Aplastic anemia - Parvovirus B19 has a tropism for erythroid progenitor cells in the bone marrow, specifically targeting and destroying them [1]. - This destruction can lead to a transient aplastic crisis, especially in individuals with pre-existing hemolytic conditions, causing a severe drop in red blood cell production [1]. Erythema infectiosum - This is the most common clinical manifestation of Parvovirus B19 infection, also known as fifth disease, characterized by a "slapped cheek" rash [1]. - While it is a symptom or disease caused by the virus, it is not considered a complication in the sense of a secondary, adverse outcome. Arthritis - Arthralgia and arthritis are common manifestations of Parvovirus B19 infection, particularly in adults, especially women [1]. - Similar to erythema infectiosum, it is a direct clinical manifestation rather than a "complication" representing a secondary, undesirable event. All of the options - While erythema infectiosum and arthritis are common clinical presentations of Parvovirus B19, they are direct disease manifestations. - Aplastic anemia stands out as a true complication, representing a secondary and potentially severe adverse outcome due to the virus's specific cellular tropism [1].

Q: What does the term 'Australian antigen' refer to in the context of hepatitis B?

Hepatitis B Surface Antigen (HBsAg). ***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.

Q: Which cells does HIV most commonly infect?

CD4+ helper cells. ***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 1

Viroids are characterized by which of the following?

Accepted Answer

Small, circular single-stranded RNA

Answer

Naked pathogenic human viruses

Answer

Fragments of viruses

Answer

DNA with protein coat

Question 2

Which virus is associated with Hodgkin's lymphoma?

Accepted Answer

Epstein-Barr virus (EBV)

Answer

Cytomegalovirus (CMV)

Answer

Human herpesvirus 8 (HHV8)

Answer

Human herpesvirus 6 (HHV6)

Question 3

E6 and E7 genes of which virus are implicated in oncogenesis?

Accepted Answer

HPV

Answer

Cytomegalovirus (CMV)

Answer

Epstein-Barr Virus (EBV)

Answer

Human T-lymphotropic Virus type 1 (HTLV-1)

Question 4

Which hepatitis virus was the first to be successfully cultured in vitro?

Accepted Answer

Hepatitis A Virus (HAV)

Answer

Hepatitis B Virus (HBV)

Answer

Hepatitis D Virus (HDV)

Answer

Hepatitis C Virus (HCV)

Question 5

Which of the following statements about Parvovirus B19 infection is correct?

Accepted Answer

Parvovirus B19 primarily affects erythroid progenitor cells.

Answer

Individuals lacking P antigen are susceptible to Parvovirus B19 infection.

Answer

Parvovirus B19 primarily affects myeloid precursors.

Answer

Parvovirus B19 infections are typically chronic.

Question 6

In which of the following viruses is the virus shed in stool?

Accepted Answer

Enterovirus (Herpangina)

Answer

Influenza virus

Answer

Varicella virus

Answer

Smallpox virus

Question 7

Which of the following statements about rabies is true?

Accepted Answer

Rabies is caused by an enveloped, single-stranded RNA virus.

Answer

The rabies vaccine provides lifelong immunity.

Answer

Rabies is caused by a DNA virus.

Answer

Rabies virus replicates primarily in muscle tissue before CNS involvement.

Question 8

What is a known complication of Parvovirus B19 infection?

Accepted Answer

Aplastic anemia

Answer

Erythema infectiosum

Answer

Arthritis

Answer

All of the options

Question 9

What does the term 'Australian antigen' refer to in the context of hepatitis B?

Accepted Answer

Hepatitis B Surface Antigen (HBsAg)

Answer

Hepatitis B Antigen

Answer

Hepatitis B Virus (HBV)

Answer

Hepatitis B Core Antigen (HBcAg)

Question 10

Which cells does HIV most commonly infect?

Accepted Answer

CD4+ helper cells

Answer

CD8+ cells

Answer

Macrophages

Answer

Neutrophils

Virology — MCQs

Virology — MCQs

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