Virology Practice Questions

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: 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: 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.

Q: Which of the following conditions is not caused by the Herpes simplex virus?

Carcinoma of the cervix. ***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.

Q: Among the following retroviruses, which has the strongest established link to direct cancer development?

HTLV - I. ***HTLV-I (Correct Answer)*** - **HTLV-I** is directly linked to **Adult T-cell Leukemia/Lymphoma (ATL)**, a highly aggressive malignancy of CD4+ T lymphocytes - The viral **Tax protein** plays a crucial role in ATL pathogenesis by dysregulating cell cycle progression and inhibiting apoptosis - This represents **direct oncogenesis** through viral protein-mediated cellular transformation - HTLV-I is classified as a Group 1 carcinogen by IARC *HIV (formerly HTLV-III)* - While HIV is associated with increased risk of certain cancers such as **Kaposi's sarcoma** and **Non-Hodgkin lymphoma**, these are primarily due to **immunosuppression** rather than direct viral oncogenesis - HIV itself does not directly transform cells into cancerous ones; instead, it creates an environment conducive to the development of other virally-induced or immune-dysregulation-related cancers - The cancers are **indirect consequences** of immunodeficiency, not direct viral transformation *HTLV-II* - **HTLV-II** has been linked to some neurological disorders, but its association with **cancer development** is much weaker and less established than that of HTLV-I - Unlike HTLV-I, HTLV-II does not have a clear and consistent link to a specific type of human malignancy - No direct oncogenic mechanism has been definitively established *HTLV-IV* - **HTLV-IV** is a relatively newly recognized retrovirus and its association with human disease, especially cancer, is not well-established - Current research suggests it may be a simian virus with limited zoonotic transmission, and its oncogenic potential in humans is largely unknown - No established link to human cancer development

Q: What is another name for HTLV-1?

ATLV. ***ATLV*** - **ATLV (Adult T-cell leukemia virus)** is an older name for **HTLV-1 (Human T-cell lymphotropic virus type 1)**. - This virus is well-known for causing **Adult T-cell Leukemia/Lymphoma (ATL)**, hence the original designation. *HIV* - **HIV (Human Immunodeficiency Virus)** is a completely different retrovirus that causes **Acquired Immunodeficiency Syndrome (AIDS)**. - While both are retroviruses, their genetic makeup, epidemiology, and disease manifestations are distinct. *RSV* - **RSV (Respiratory Syncytial Virus)** is a **paramyxovirus** primarily known for causing respiratory tract infections, especially in infants and young children. - It is an **RNA virus** and is unrelated to HTLV-1. *ALV* - **ALV (Avian Leukosis Virus)** is a retrovirus that infects chickens and other birds, causing various forms of **leukemia and tumors in avian species**. - It is an **animal retrovirus** and not related to human viruses like HTLV-1.

Question 1

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 2

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 3

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 4

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 5

What is a known complication of Parvovirus B19 infection?

Accepted Answer

Aplastic anemia

Answer

Erythema infectiosum

Answer

Arthritis

Answer

All of the options

Question 6

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 7

Which cells does HIV most commonly infect?

Accepted Answer

CD4+ helper cells

Answer

CD8+ cells

Answer

Macrophages

Answer

Neutrophils

Question 8

Which of the following conditions is not caused by the Herpes simplex virus?

Accepted Answer

Carcinoma of the cervix

Answer

Gingivostomatitis

Answer

Mollaret meningitis

Answer

Herpes labialis

Question 9

Among the following retroviruses, which has the strongest established link to direct cancer development?

Accepted Answer

HTLV - I

Answer

HIV (formerly HTLV - III)

Answer

HTLV - II

Answer

HTLV - IV

Question 10

What is another name for HTLV-1?

Accepted Answer

ATLV

Answer

HIV

Answer

RSV

Answer

ALV

Virology — MCQs

Virology — MCQs

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