Virology Practice Questions

Q: What is the primary mechanism by which the influenza virus changes antigenically over time?

Antigenic drift. ***Antigenic drift*** - This involves **gradual accumulation of point mutations** in the genes encoding for **hemagglutinin (HA)** and **neuraminidase (NA)** glycoproteins - These **minor changes** allow the virus to **evade immune recognition** partially, necessitating **frequent updates to influenza vaccines** - Occurs **continuously** in both influenza A and B viruses - Responsible for **seasonal epidemics** of influenza *Antigenic shift* - This involves **major changes** due to **reassortment of gene segments** between different influenza virus strains - Results in a **novel subtype** with different HA and/or NA proteins - Can lead to **pandemics** when human population has no immunity - This is a **sudden, major change** rather than the gradual change described in the question *Reassortment* - This is the **mechanism underlying antigenic shift**, where gene segments from different strains exchange during co-infection - While related to influenza variation, the question asks for the **primary ongoing mechanism**, which is antigenic drift - Reassortment is less frequent but creates more dramatic changes *Recombination* - This involves **exchange of genetic material** between viral genomes - **Uncommon in influenza viruses** due to their segmented genome structure - Reassortment, not recombination, is the dominant mechanism for genetic exchange in influenza

Q: A patient presents with painful blisters around the angle of the mouth. What is the most likely pathogen responsible for this condition?

Herpes Simplex Virus. ***Herpes Simplex Virus*** - The image shows a cluster of **small, painful vesicles** on an erythematous base around the mouth, characteristic of **herpes labialis** or cold sores. - HSV-1 is the primary cause of oral herpes, which typically presents with these recurrent painful blister outbreaks. *Coxsackievirus* - Coxsackievirus typically causes **Hand, Foot, and Mouth Disease**, characterized by oral lesions (herpangina) and a rash on the hands and feet. - The painful blisters are usually in the **posterior oral cavity** (soft palate, tonsillar pillars) and are not typically perioral in the depicted clustered vesicular pattern. *Varicella-Zoster Virus* - VZV causes **chickenpox** (widespread vesicular rash) and **shingles** (painful, dermatomal vesicular rash). - While it causes vesicles, they would present as either widespread and generalized or in a unilateral, **dermatomal distribution**, which is not consistent with the perioral presentation shown. *Epstein-Barr Virus* - EBV is primarily known for causing **infectious mononucleosis**, which can lead to fatigue, fever, and lymphadenopathy, and sometimes oral manifestations like palatal petechiae or oral hairy leukoplakia. - It does not typically cause the **painful vesicular lesions** around the mouth as depicted.

Q: Which disease is caused by Coxsackievirus A16?

Hand-foot-mouth disease. ***Hand-foot-mouth disease*** - **Coxsackievirus A16** is one of the most common causes of **hand-foot-mouth disease (HFMD)**, along with Enterovirus 71. - HFMD typically presents with **fever**, **painful vesicles and ulcers in the mouth** (on the tongue, gums, and inside of cheeks), and a **vesicular rash on the palms, soles, and sometimes buttocks**. - It primarily affects young children and is highly contagious. *Yellow fever* - Yellow fever is caused by the **yellow fever virus**, a **flavivirus**, which is transmitted by mosquitoes. - It leads to symptoms like fever, jaundice, and hemorrhage, distinctly different from Coxsackievirus A16 infections. *Rocky Mountain spotted fever* - This disease is caused by the bacterium **Rickettsia rickettsii** and is transmitted by ticks. - It presents with fever, headache, and a characteristic rash that often starts on the ankles and wrists. *Encephalomyocarditis* - While Coxsackieviruses (particularly Coxsackievirus B serotypes) can cause myocarditis and encephalitis, **encephalomyocarditis virus (EMCV)** is a distinct cardiovirus within the Picornaviridae family. - Coxsackievirus A16 is not typically associated with encephalomyocarditis as its primary manifestation.

Q: Which of the following statements about Cytomegalovirus (CMV) is incorrect?

A non-enveloped DNA virus. ***A non-enveloped DNA virus*** - CMV is a **herpesvirus**, which are characterized by being **enveloped DNA viruses**. This statement is incorrect as it claims CMV is non-enveloped. - The viral envelope is crucial for **entry into host cells** and evasion of the immune system. *Most common cause of transplacental infection* - CMV is indeed the **most common viral cause** of congenital infections, transmitted vertically from mother to fetus. - Congenital CMV can lead to various complications, including **hearing loss** and **neurological deficits**. *Produces intranuclear inclusions* - CMV infection is characterized by the presence of **"owl's eye" intranuclear inclusions** in infected cells. - These inclusions are a **histopathological hallmark** used in the diagnosis of CMV infection. *Most common cause of post-transplantation infection* - CMV is a significant opportunistic pathogen in **immunocompromised individuals**, especially after organ transplantation. - It can cause a range of symptoms, from **fever and malaise** to severe organ damage, such as pneumonitis and gastroenteritis, in transplant recipients.

Q: Which of the following statements about Rhabdoviridae is false?

Rabies virus is negative sense double stranded RNA virus. ***Rabies virus is negative sense double stranded RNA virus*** - This statement is **false** because **Rhabdoviridae**, including the rabies virus, are **negative-sense single-stranded RNA viruses**, not double-stranded. - The genome is a single molecule of **linear, non-segmented RNA**. *Contains enveloped viruses with helical nucleocapsid* - This statement is **true** as Rhabdoviridae are characterized by their **bacilliform (bullet-shaped)** morphology, possessing an **envelope** and a **helical nucleocapsid**. - The envelope is derived from the host cell membrane, and the nucleocapsid houses the viral RNA genome. *Rabies virus is inactivated by formalin* - This statement is **true** because **formalin (formaldehyde)** is a strong chemical agent commonly used to inactivate viruses for vaccine production, including the rabies virus. - Formalin denatures viral proteins and nucleic acids, rendering the virus non-infectious while preserving its antigenicity. *Includes vesiculostomatitis virus* - This statement is **true** because **vesicular stomatitis virus (VSV)** is a well-known member of the **Rhabdoviridae** family. - VSV is often used as a model system for studying rhabdoviruses due to its relatively simple genome and ease of manipulation in the lab.

Q: Capsid of viral structure is:

Protein coat around nucleic acid. ***Protein coat around nucleic acid*** - The **capsid** is a protective protein shell that encloses the viral **genetic material** (either **DNA or RNA**). - It plays a crucial role in protecting the viral genome from nucleases and aids in attaching the **virion** to host cells. *Extracellular infectious particle* - An **extracellular infectious particle** refers to the entire **virion**, which includes the capsid and its enclosed nucleic acid, and sometimes an envelope. - The **capsid** is only one component of the **virion**, not the entire particle itself. *Envelope around a virus* - The **envelope** is an outer **lipid bilayer** derived from the host cell membrane that surrounds some, but not all, viruses. - The **capsid** is located *inside* the envelope in enveloped viruses, or forms the outermost layer in non-enveloped viruses. *None of the above* - This option is incorrect because **"Protein coat around nucleic acid"** accurately defines the **capsid**.

Q: Which gene encodes the core antigen (HBcAg) in the Hepatitis B virus (HBV)?

C gene. ***C gene (Correct)*** - The **C gene** (Core gene) of the Hepatitis B virus is responsible for encoding the **HBcAg (Hepatitis B core antigen)**. - This antigen forms the **nucleocapsid** of the virus, encapsulating the viral DNA and polymerase. - HBcAg is found in the hepatocyte nucleus and is a marker of active viral replication. *S gene* - The S gene encodes the **HBsAg (Hepatitis B surface antigen)**, which is the major component of the viral envelope. - HBsAg is critical for viral attachment and entry into host cells and is the primary antigen used in HBV vaccination. - This is a marker of HBV infection and is used for screening. *P gene* - The P gene encodes the **HBV polymerase**, an enzyme with both reverse transcriptase and DNA polymerase activities. - This polymerase is essential for viral replication, converting the pregenomic RNA into DNA. - It is the largest gene in the HBV genome. *X gene* - The X gene encodes the **HBx protein**, a small promiscuous protein known to be a transcriptional transactivator. - HBx plays a role in viral replication, gene expression, and is implicated in the development of **hepatocellular carcinoma**. - This is the smallest gene in the HBV genome.

Q: Ebola virus belongs to?

Filoviridae. ***Filoviridae*** - The **Ebola virus** is a member of the family **Filoviridae**, which includes highly pathogenic viruses known for causing severe hemorrhagic fevers. - Viruses in this family typically have a **filamentous** or thread-like morphology, which is how they get their name ("filo" means thread-like). ***Picornaviridae*** - This family includes viruses like *poliovirus* and *rhinoviruses*, which are generally known for causing respiratory or gastrointestinal illnesses, not hemorrhagic fever. - Picornaviruses are characterized by being very small, non-enveloped RNA viruses. ***Togaviridae*** - This family includes viruses such as *rubella virus* and *alphaviruses* (e.g., Eastern equine encephalitis virus), which are often transmitted by arthropods and cause conditions like rash, arthritis, or encephalitis. - Togaviruses are enveloped RNA viruses with a single-stranded, positive-sense RNA genome. ***Flaviviridae*** - This family includes viruses like *dengue virus*, *Zika virus*, and *yellow fever virus*, which are typically transmitted by mosquitoes or ticks and can cause hemorrhagic manifestations or neurological symptoms. - Flaviviruses are enveloped RNA viruses with a single-stranded, positive-sense RNA genome, but they do not cause Ebola-like hemorrhagic fever.

Q: HSV-2 causes latent infection in which nerve plexus/ ganglia ?

Sacral ganglia. ***Sacral ganglia*** * **HSV-2** primarily causes **genital herpes**, and the virus establishes **latency** in the sensory neurons of the sacral ganglia, which innervate the genital area [1]. * During reactivation, the virus travels down these nerves to cause recurrent lesions in the anogenital region. *Trigeminal ganglia* * The **trigeminal ganglia** are the primary site of latency for **HSV-1**, which is associated with **oral herpes** (cold sores) [1]. * Reactivation from the trigeminal ganglia leads to lesions typically around the mouth. *Otic ganglia* * The **otic ganglia** are **parasympathetic ganglia** associated with the glossopharyngeal nerve and are involved in salivary gland function, not HSV latency. * They are not known to be a site of latency for herpes simplex viruses. *Ciliary ganglia* * The **ciliary ganglia** are also **parasympathetic ganglia** associated with the oculomotor nerve, involved in controlling intrinsic eye muscles (e.g., pupillary constriction). * They do not serve as a site for HSV latency.

Q: Hand foot mouth disease is caused by ?

Coxsackievirus A. ***Coxsackievirus A*** - Hand-foot-and-mouth disease (HFMD) is most commonly caused by **Coxsackievirus A16** and occasionally other **Coxsackievirus A serotypes** (especially **Enterovirus A71** in Asia). - This virus belongs to the **Enterovirus genus** and is responsible for the characteristic vesicular rash on hands, feet, and mouth. *Enterovirus 70* - **Enterovirus 70** is primarily associated with **acute hemorrhagic conjunctivitis** and, less commonly, **acute flaccid paralysis**. - It is not the causative agent for Hand-Foot-and-Mouth Disease. *Coxsackievirus B* - **Coxsackievirus B** serotypes are known for causing illnesses like **pleurodynia**, **myocarditis**, and **pericarditis**. - While also an enterovirus, it is not the primary cause of Hand-Foot-and-Mouth Disease. *Enterovirus* - **Enterovirus** is a broad genus of viruses, encompassing **Coxsackieviruses**, **echoviruses**, and **polioviruses**. - While Coxsackievirus A is an enterovirus, simply stating "Enterovirus" is too general and less specific than the correct answer.

Question 1

What is the primary mechanism by which the influenza virus changes antigenically over time?

Accepted Answer

Antigenic drift

Answer

Recombination

Answer

Reassortment

Answer

Antigenic shift

Question 2

A patient presents with painful blisters around the angle of the mouth. What is the most likely pathogen responsible for this condition?

Accepted Answer

Herpes Simplex Virus

Answer

Coxsackievirus

Answer

Varicella-Zoster Virus

Answer

Epstein-Barr Virus

Question 3

Which disease is caused by Coxsackievirus A16?

Accepted Answer

Hand-foot-mouth disease

Answer

Yellow fever

Answer

Rocky Mountain spotted fever

Answer

Encephalomyocarditis

Question 4

Which of the following statements about Cytomegalovirus (CMV) is incorrect?

Accepted Answer

A non-enveloped DNA virus

Answer

Most common cause of transplacental infection

Answer

Produces intranuclear inclusions

Answer

Most common cause of post-transplantation infection

Question 5

Which of the following statements about Rhabdoviridae is false?

Accepted Answer

Rabies virus is negative sense double stranded RNA virus

Answer

Contains enveloped viruses with helical nucleocapsid

Answer

Rabies virus is inactivated by formalin

Answer

Includes vesiculostomatitis virus

Question 6

Capsid of viral structure is:

Accepted Answer

Protein coat around nucleic acid

Answer

Extracellular infectious particle

Answer

Envelope around a virus

Answer

None of the above

Question 7

Which gene encodes the core antigen (HBcAg) in the Hepatitis B virus (HBV)?

Accepted Answer

C gene

Answer

S gene

Answer

P gene

Answer

X gene

Question 8

Ebola virus belongs to?

Accepted Answer

Filoviridae

Answer

Picornaviridae

Answer

Togaviridae

Answer

Flaviviridae

Question 9

HSV-2 causes latent infection in which nerve plexus/ ganglia ?

Accepted Answer

Sacral ganglia

Answer

Trigeminal ganglia

Answer

Otic ganglia

Answer

Ciliary ganglia

Question 10

Hand foot mouth disease is caused by ?

Accepted Answer

Coxsackievirus A

Answer

Enterovirus 70

Answer

Coxsackievirus B

Answer

Enterovirus

Virology — MCQs

Virology — MCQs

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