Virology Practice Questions

Q: Which of the following is an enveloped virus?

Dengue virus. ***Dengue virus*** - The **Dengue virus** is a member of the **Flaviviridae** family, which are known to be **enveloped viruses**. - Its outer lipid envelope, derived from the host cell, is crucial for its entry into host cells and evading the immune system. *Norwalk virus* - The **Norwalk virus**, also known as **Norovirus**, is a **non-enveloped RNA virus** belonging to the **Caliciviridae** family. - Its lack of an envelope makes it more resistant to disinfectants and environmental stresses, contributing to its high infectivity and ability to cause outbreaks of gastroenteritis. *Hep A virus* - **Hepatitis A virus (HAV)** is a **non-enveloped RNA virus** of the **Picornaviridae** family. - Its non-enveloped nature contributes to its stability in the environment and resistance to gastric acid, facilitating its fecal-oral transmission. *Adenovirus* - **Adenoviruses** are **non-enveloped DNA viruses** known for causing a variety of clinical manifestations, including respiratory infections, conjunctivitis, and gastroenteritis. - Their lack of an outer lipid envelope helps them survive in harsh environmental conditions and makes them highly stable.

Q: Which virus is known for its brick-shaped morphology?

Smallpox. ***Smallpox*** - The **variola virus**, responsible for smallpox, is a type of **poxvirus** which characteristically exhibits a **brick-shaped** or ovoid morphology. - This distinctive shape is due to its **large, complex virion structure** containing a dumbbell-shaped core. *Chickenpox* - Chickenpox is caused by the **varicella-zoster virus (VZV)**, which is a member of the **herpesviridae family**. - Herpesviruses are typically **spherical** with an icosahedral capsid. *CMV* - **Cytomegalovirus (CMV)** is another member of the **herpesviridae family**, sharing the characteristic **spherical shape** with an icosahedral capsid. - Its morphology is not brick-shaped. *EBV* - **Epstein-Barr virus (EBV)** is also a **herpesvirus** and thus possesses a **spherical, icosahedral capsid morphology**. - Its structure is distinct from the brick-shaped poxviruses.

Q: Colorado Tick fever is caused by:

Reoviridae. ***Reoviridae*** - Colorado Tick Fever (CTF) is caused by the **Colorado Tick Fever Virus (CTFV)**, which belongs to the genus **Coltivirus** within the family **Reoviridae**. - Reoviridae viruses are **non-enveloped**, double-stranded RNA viruses. *Filoviridae* - This family includes viruses like **Ebola virus** and **Marburg virus**, which cause severe hemorrhagic fevers. - They are **enveloped**, negative-sense single-stranded RNA viruses, distinct from the CTFV. *Coronaviridae* - This family includes viruses like **SARS-CoV-2 (COVID-19)** and SARS-CoV, which cause respiratory illnesses. - They are **enveloped**, positive-sense single-stranded RNA viruses, structurally different from CTFV. *Caliciviridae* - This family includes viruses like **Norovirus**, a common cause of acute gastroenteritis (viral stomach flu). - They are **non-enveloped**, positive-sense single-stranded RNA viruses and do not cause tick-borne illnesses.

Q: Which virus is primarily responsible for causing Ebola virus disease, a type of hemorrhagic fever?

Ebola virus. ***Ebola virus*** - The disease is named after the **Ebola River** in Congo, where it was first identified. - The **Ebola virus** is a member of the **Filoviridae family**, known for causing severe hemorrhagic fevers. *West Nile virus* - This virus is primarily transmitted by **mosquitoes** and causes **West Nile fever**, which can lead to neurological disease. - It does not cause the hemorrhagic fever associated with Ebola virus disease. *Phlebovirus* - **Phlebovirus** is a genus of viruses that includes several species capable of causing **encephalitis** or **febrile illness** with headache and myalgia. - While some can cause hemorrhagic fevers, it is not the primary agent for the disease specifically known as **Ebola virus disease**. *None of the options* - This option is incorrect because the **Ebola virus** is indeed listed as an option and is the correct pathogen responsible for Ebola virus disease.

Q: Smallpox belongs to which genus of poxviruses?

Orthopoxvirus. ***Orthopoxvirus*** - **Smallpox** (caused by the **variola virus**) is a classic member of the Orthopoxvirus genus. - This genus includes other human pathogens like **monkeypox** and vaccinia virus (used in the smallpox vaccine). *Parapoxvirus* - This genus includes viruses like **Orf virus** (causing contagious pustular dermatitis in sheep and goats) and pseudocowpox virus. - These viruses typically cause milder, localized lesions and are morphologically distinct from orthopoxviruses. *Capripoxvirus* - This genus includes viruses primarily affecting livestock, such as **lumpy skin disease virus**, sheep pox virus, and goat pox virus. - They cause systemic infections and skin lesions in their respective animal hosts and are not associated with human disease like smallpox. *Leporipox virus* - This genus includes viruses that primarily infect rabbits and hares, such as **myxoma virus** and fibroma virus. - These viruses typically cause tumors or severe systemic disease in their rabbit hosts and are not known to infect humans.

Q: Binding of gp120 causes:

Facilitation of co-receptor binding. ***Facilitation of co-receptor*** - **gp120** binding to the **CD4 receptor** on target cells induces a conformational change in gp120, which then exposes or creates a binding site for a **chemokine co-receptor** (CCR5 or CXCR4). - This interaction is crucial for the subsequent steps of viral entry, as it allows the virus to make further contact with the cell surface. *Infection of target cell* - While binding of gp120 is the *first step* in infection, it does not directly cause the infection itself. - Infection occurs after a series of events including co-receptor binding, membrane fusion, and reverse transcription. *Fusing of virus and target cell* - **Fusion** of the viral and cellular membranes is primarily mediated by **gp41**, which is part of the gp160 envelope glycoprotein complex alongside gp120. - This fusion event *follows* the binding of gp120 to CD4 and the co-receptor, as gp120 binding initiates the conformational changes that expose and activate gp41. *None of the options* - One of the provided options accurately describes a direct consequence of gp120 binding, making this option incorrect.

Q: What is the role of p24 in HIV?

Core antigen of HIV. ***Core antigen of HIV*** - **p24** is a **structural protein** that forms the viral capsid, which is the shell enclosing the genetic material of the virus. - Due to its abundance and immunogenicity, **p24** serves as a crucial **biomarker** for initial **HIV infection** and is targeted in diagnostic tests. *Envelop antigen in HIV* - The **envelope antigens** of HIV are typically **glycoproteins** like **gp120** and **gp41**, which are involved in viral attachment and entry into host cells. - These envelope proteins are distinct from **p24**, which is an internal core protein. *Genome of HIV* - The **genome of HIV** consists of **two copies of single-stranded RNA**, not a protein. - This **RNA genome** is contained within the viral capsid, which is primarily composed of **p24 protein**. *Shell antigen* - While **p24** does form a "shell" (the capsid) around the viral genome, the term **shell antigen** is not a standard specific classification in virology for p24. - The more precise term for its location and function is **core antigen**.

Q: Which of the following is a primary cell line?

Chick embryo fibroblasts. ***Chick embryo fibroblasts*** - Primary cell lines are directly derived from **tissues** and have a limited lifespan in culture before undergoing senescence. - **Chick embryo fibroblasts** are isolated directly from chick embryos and propagated for a limited number of passages, making them a true primary cell culture. *Hela cells* - HeLa cells are a well-known example of a **continuous cell line**, meaning they can be cultured indefinitely. - They were originally derived from a cervical cancer patient and are considered **immortalized**. *Vero cells* - Vero cells are an **immortalized cell line** derived from the kidney of an African green monkey. - They are used extensively in virology and vaccine production due to their ability to be propagated for many passages. *WI-38* - WI-38 is a **diploid human cell strain** derived from lung tissue. - While they have a finite lifespan similar to primary cells, they represent a **cell strain** that has been subcultured and characterized, with more homogeneous growth characteristics than fresh primary cultures.

Q: Serological testing of patient shows HBsAg, IgM anti-HBc and HBeAg positive. The patient has -

Acute hepatitis B with high infectivity. ***Acute hepatitis B with high infectivity*** - The presence of **HBsAg** (hepatitis B surface antigen) indicates active infection, while **IgM anti-HBc** (IgM antibody to hepatitis B core antigen) is a marker of recent or acute infection [1]. - **HBeAg** (hepatitis B e-antigen) positivity signifies active viral replication and a high likelihood of infectivity [1]. *Chronic hepatitis B with low infectivity (not acute)* - **Chronic hepatitis B** is characterized by the presence of **HBsAg for more than six months**, but **IgM anti-HBc** would typically be negative; instead, **IgG anti-HBc** would be positive [1]. - **Low infectivity** would be indicated by the absence of **HBeAg**, replaced by **anti-HBe** (antibody to HBeAg) [1]. *Chronic hepatitis with high infectivity* - This diagnosis would show positive **HBsAg and HBeAg**, but the absence of **IgM anti-HBc** (presence of **IgG anti-HBc** instead) would distinguish it from acute infection [1]. - The presence of **IgM anti-HBc** is a crucial marker for an acute phase of hepatitis B rather than chronic. *Acute on chronic hepatitis* - This scenario would involve a patient with pre-existing **chronic hepatitis B** (positive HBsAg, IgG anti-HBc) experiencing a new acute flare-up, which could involve a resurgence of **HBeAg** or a new acute viral insult. - While **HBsAg** and **HBeAg** would be positive, the key differentiator would be the presence of both **IgM anti-HBc** (indicating the acute component) and **IgG anti-HBc** (indicating the chronic component), which is not fully described here to confirm acute on chronic.

Q: Influenza virus culture is done on ?

Allantoic cavity. ***Allantoic cavity*** - The **allantoic cavity** of embryonated chicken eggs is the standard and most effective site for isolating and propagating **influenza viruses** for vaccine production and research. - This cavity provides an optimal environment for viral replication, particularly yielding high titers of **hemagglutinin**, a key influenza antigen. *Chorioallantoic membrane* - While embryonated eggs are used for virus culture, the **chorioallantoic membrane (CAM)** is primarily used for cultivating viruses that produce **pocks** (visible lesions), such as Vaccinia and Herpes Simplex Virus. - Influenza virus growth on the CAM is less efficient and typically doesn't produce distinct pocks, making it unsuitable for high-yield propagation compared to the allantoic cavity. *Yolk sac* - The **yolk sac** of embryonated eggs is ideal for growing viruses or bacteria that require a **lipid-rich environment** and replicate intracellularly, such as Chlamydia or Rickettsia. - It is not the preferred site for influenza virus isolation or proliferation due to suboptimal conditions for viral replication and lower viral yields. *All of the options* - While all these sites are components of an embryonated chicken egg, each serves as a host for different types of microorganisms or for specific purposes in virology. - For **influenza virus culture**, the **allantoic cavity** is the specifically utilized site for optimal growth and high viral yield.

Question 1

Which of the following is an enveloped virus?

Accepted Answer

Dengue virus

Answer

Norwalk virus

Answer

Hep A virus

Answer

Adenovirus

Question 2

Which virus is known for its brick-shaped morphology?

Accepted Answer

Smallpox

Answer

Chickenpox

Answer

CMV

Answer

EBV

Question 3

Colorado Tick fever is caused by:

Accepted Answer

Reoviridae

Answer

Coronaviridae

Answer

Filoviridae

Answer

Caliciviridae

Question 4

Which virus is primarily responsible for causing Ebola virus disease, a type of hemorrhagic fever?

Accepted Answer

Ebola virus

Answer

Phlebovirus

Answer

West Nile virus

Answer

None of the options

Question 5

Smallpox belongs to which genus of poxviruses?

Accepted Answer

Orthopoxvirus

Answer

Leporipoxvirus

Answer

Capripoxvirus

Answer

Parapoxvirus

Question 6

Binding of gp120 causes:

Accepted Answer

Facilitation of co-receptor binding

Answer

Infection of target cell

Answer

Fusing of virus and target cell

Answer

None of the options

Question 7

What is the role of p24 in HIV?

Accepted Answer

Core antigen of HIV

Answer

Envelope antigen in HIV

Answer

Genome of HIV

Answer

Shell antigen

Question 8

Which of the following is a primary cell line?

Accepted Answer

Chick embryo fibroblasts

Answer

Hela cells

Answer

Vero cells

Answer

WI-38

Question 9

Serological testing of patient shows HBsAg, IgM anti-HBc and HBeAg positive. The patient has -

Accepted Answer

Acute hepatitis B with high infectivity

Answer

Chronic hepatitis with high infectivity

Answer

Acute on chronic hepatitis

Answer

Chronic hepatitis B with low infectivity (not acute)

Question 10

Influenza virus culture is done on ?

Accepted Answer

Allantoic cavity

Answer

Chorioallantoic membrane

Answer

Yolk sac

Answer

All of the options

Virology — MCQs

Virology — MCQs

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