Virology Practice Questions

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: 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.

Q: Coxsackie virus is classified as which type of virus?

Enterovirus. ***Enterovirus*** - **Coxsackie virus** belongs to the genus *Enterovirus* within the family *Picornaviridae*. - Enteroviruses are characterized as **non-enveloped, positive-sense, single-stranded RNA viruses** and typically infect the gastrointestinal tract. *Herpes virus* - Herpes viruses are **enveloped, double-stranded DNA viruses** known for causing latent infections. - Examples include HSV-1 (oral herpes) and VZV (chickenpox), which are distinct from Coxsackie. *Pox virus* - Pox viruses are **large, enveloped, double-stranded DNA viruses** that replicate in the cytoplasm of infected cells. - Smallpox and molluscum contagiosum are caused by pox viruses, which have different genetic and structural characteristics than Coxsackie virus. *Myxovirus* - **Myxovirus** is an older classification that once included viruses now categorized into *Orthomyxoviridae* (e.g., influenza) and *Paramyxoviridae* (e.g., measles, mumps). - These are **enveloped, negative-sense, single-stranded RNA viruses**, a different viral structure and replication strategy compared to Coxsackie virus.

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: HIV window period indicates:

time period between infection and detection of antibodies. ***time period between infection and detection antibodies*** - The **HIV window period** refers specifically to the time frame after initial infection during which **HIV antibodies** have not yet reached detectable levels in routine serological tests. - During this period, an infected individual can still transmit the virus, even if their test results would appear **negative** for antibodies. *time period between infection and onset of first symptoms* - The onset of **first symptoms**, such as acute retroviral syndrome, can occur before or after antibodies are detectable, and is not the defining characteristic of the window period. - Symptoms are a **clinical manifestation**, whereas the window period is a **diagnostic concept** related to test detectability. *time period between infection and minimum viral load* - **Viral load** (the amount of virus in the blood) is typically **high** shortly after infection, then decreases somewhat before rising again, and its minimum point is not directly related to the antibody window period. - The window period focuses on the host's **immune response** to the virus, specifically antibody production. *time period between infection and maximum viral load* - The **maximum viral load** usually occurs during the acute (early) phase of infection, often before the development of detectable antibodies. - This represents a peak in viral replication, not the interval until the **immune system's antibody response** becomes detectable.

Q: Pharyngeal-conjunctival fever is caused by

Adenovirus 3 and 7. ***Adenovirus 3 and 7*** - **Adenovirus serotypes 3 and 7** are the most common causes of **pharyngoconjunctival fever**, which presents with combination of **pharyngitis**, **conjunctivitis**, and **fever**. - This syndrome often occurs in outbreaks, particularly in children, and can be spread through **respiratory droplets** or contaminated water. *Adenovirus 11, 21* - **Adenovirus 11 and 21** are primarily associated with **hemorrhagic cystitis**, an inflammation of the bladder often presenting with **hematuria**. - They are less commonly implicated in typical pharyngoconjunctival fever, though adenoviruses can cause a spectrum of respiratory symptoms. *Adenovirus 40, 41* - **Adenovirus serotypes 40 and 41** are leading causes of **infantile gastroenteritis**, characterized by **diarrhea** and **vomiting**. - They are not typically associated with respiratory or ocular manifestations like pharyngoconjunctival fever. *Adenovirus 8, 19* - **Adenovirus 8 and 19** are well-known causes of **epidemic keratoconjunctivitis**, a severe form of conjunctivitis often involving the **cornea**. - While they cause a significant eye infection, they are not the primary serotypes linked to the broader syndrome of **pharyngoconjunctival fever** which includes pharyngitis and fever.

Q: Which viral infection is primarily associated with hemolysis?

Epstein-Barr virus. **Epstein-Barr virus** - **Epstein-Barr virus (EBV)** is strongly associated with **cold agglutinin disease**, an **autoimmune hemolytic anemia** where cold-reacting antibodies agglutinate and lyse red blood cells. [4] - Hemolysis in EBV infection can also occur due to direct viral effects on red blood cells or immune-mediated mechanisms beyond cold agglutinins. [1] *Hepatitis B virus* - Hepatitis B virus is primarily known for causing **liver inflammation** and **hepatocellular damage**, rather than direct or immune-mediated hemolysis. [2] - While chronic HBV infection can lead to complications such as cirrhosis or liver cancer, it is not a common cause of hemolytic anemia. *Hepatitis-C* - Hepatitis C virus is a common cause of **chronic liver disease**, leading to **fibrosis**, **cirrhosis**, and **hepatocellular carcinoma**. [3] - Although HCV is sometimes associated with mixed cryoglobulinemia, which can cause vasculitis and organ damage, it does not typically cause significant hemolysis. *Hepatitis A virus* - Hepatitis A virus causes **acute, self-limiting liver inflammation** and is primarily transmitted through the **fecal-oral route**. [2] - It does not typically cause sustained or severe hemolysis; any hemolytic events are rare and usually mild.

Q: What indicates HBV replication?

HBV DNA. ***HBV DNA*** - **HBV DNA** is the **gold standard and most direct marker of active HBV replication** in modern clinical practice - **Quantitative HBV DNA (viral load)** precisely measures the level of viral replication and is essential for: - Diagnosing active infection - Monitoring disease progression - Guiding treatment decisions - Assessing treatment response - Detected by **PCR (Polymerase Chain Reaction)** or other nucleic acid amplification tests - Directly indicates the presence of replicating virus *HBeAg* - **HBeAg (Hepatitis B e-antigen)** is a marker of high viral replication in **HBeAg-positive chronic hepatitis B** - However, it has significant limitations: - **HBeAg-negative variants** can have active replication without HBeAg presence - Not present in all cases of active replication - Less direct than measuring actual viral DNA - Useful as a supplementary marker but not the primary indicator of replication *DNA polymerase* - **HBV DNA polymerase** is an enzyme essential for viral replication - While its activity correlates with replication, it is **not routinely measured** as a primary clinical marker - HBV DNA testing has replaced DNA polymerase assays in modern practice *IgM Anti-HBc* - **IgM Anti-HBc (IgM antibody to hepatitis B core antigen)** indicates **acute or recent HBV infection** - Reflects the **immune response** to infection, not viral replication itself - Can be present during acute phase even as viral replication is being controlled - Not a marker of ongoing chronic replication

Q: Which additional gene is present in the Human T-cell Leukemia Virus (HTLV)?

Tax. ***Tax*** - The **Tax gene** is a unique regulatory gene found in **Human T-cell Leukemia Virus (HTLV)** that is crucial for its oncogenic potential. - It plays a vital role in **viral replication** and **cellular transformation** by modulating host gene expression. *Gag* - The **Gag gene** encodes for **structural proteins** (e.g., matrix, capsid, nucleocapsid) that form the **viral core** and are essential for assembly but are not unique to HTLV. - This gene is present in all retroviruses, including HIV, and is not an "additional" gene specific to HTLV. *Pol* - The **Pol gene** encodes for essential viral enzymes such as **reverse transcriptase**, **protease**, and **integrase**, which are necessary for viral replication and integration. - This gene is also conserved across all retroviruses and does not represent an additional gene specific to HTLV. *Env* - The **Env gene** codes for the **envelope glycoproteins** (e.g., surface and transmembrane proteins) that mediate viral entry into host cells and are involved in receptor binding. - This gene is also a common feature of retroviruses and is therefore not an "additional" gene unique to HTLV.

Q: Reverse transcriptase is a RNA-dependent DNA polymerase. Which of the following uses it?

Hepatitis B virus. ***Hepatitis B virus*** - Hepatitis B virus (HBV) is a **DNA virus** that replicates via an **RNA intermediate** using **reverse transcriptase**. - Its genome is a partially double-stranded circular DNA, and the enzyme is crucial for synthesizing the DNA genome from a pregenomic RNA template. *Hepatitis A virus* - Hepatitis A virus (HAV) is a **single-stranded RNA virus** (positive-sense) that replicates without a reverse transcriptase step. - Its replication involves direct translation of its RNA genome into viral proteins and replication via an RNA-dependent RNA polymerase. *Hepatitis E virus* - Hepatitis E virus (HEV) is a **single-stranded RNA virus** (positive-sense) that, like HAV, does not utilize reverse transcriptase for its replication. - It replicates in the cytoplasm of host cells using an **RNA-dependent RNA polymerase**. *Hepatitis C virus* - Hepatitis C virus (HCV) is a **single-stranded RNA virus** (positive-sense) belonging to the Flaviviridae family. - It replicates its RNA genome directly using an **RNA-dependent RNA polymerase** and does not involve a DNA intermediate or reverse transcription.

Question 1

Colorado Tick fever is caused by:

Accepted Answer

Reoviridae

Answer

Coronaviridae

Answer

Filoviridae

Answer

Caliciviridae

Question 2

Influenza virus culture is done on ?

Accepted Answer

Allantoic cavity

Answer

Chorioallantoic membrane

Answer

Yolk sac

Answer

All of the options

Question 3

Coxsackie virus is classified as which type of virus?

Accepted Answer

Enterovirus

Answer

Pox virus

Answer

Myxovirus

Answer

Herpes virus

Question 4

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 5

HIV window period indicates:

Accepted Answer

time period between infection and detection of antibodies

Answer

time period between infection and onset of first symptoms

Answer

time period between infection and minimum viral load

Answer

time period between infection and maximum viral load

Question 6

Pharyngeal-conjunctival fever is caused by

Accepted Answer

Adenovirus 3 and 7

Answer

Adenovirus 11, 21

Answer

Adenovirus 40, 41

Answer

Adenovirus 8, 19

Question 7

Which viral infection is primarily associated with hemolysis?

Accepted Answer

Epstein-Barr virus

Answer

Hepatitis-C

Answer

Hepatitis A virus

Answer

Hepatitis B virus

Question 8

What indicates HBV replication?

Accepted Answer

HBV DNA

Answer

DNA polymerase

Answer

HBeAg

Answer

IgM Anti-HBc

Question 9

Which additional gene is present in the Human T-cell Leukemia Virus (HTLV)?

Accepted Answer

Tax

Answer

Gag

Answer

Pol

Answer

Env

Question 10

Reverse transcriptase is a RNA-dependent DNA polymerase. Which of the following uses it?

Accepted Answer

Hepatitis B virus

Answer

Hepatitis A virus

Answer

Hepatitis E virus

Answer

Hepatitis C virus

Virology — MCQs

Virology — MCQs

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