Virology Practice Questions

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: 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: 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: 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: Which of the following sexually transmitted infections is caused by a retrovirus?

Human Immunodeficiency Virus (HIV). ***Human Immunodeficiency Virus (HIV)*** - HIV is a **retrovirus** characterized by its use of the enzyme **reverse transcriptase** to convert its RNA genome into DNA. - This viral DNA then integrates into the host cell's genome, leading to a persistent infection and eventual immune system compromise. *Human Papillomavirus (HPV)* - HPV is a **DNA virus** responsible for causing warts and is associated with various cancers, particularly cervical cancer. - It replicates within the nucleus of host cells without utilizing reverse transcriptase. *Hepatitis B Virus (HBV)* - While HBV has a complex replication cycle involving reverse transcription, it is classified as a **hepadnavirus**, not a retrovirus. - Its genome is partially double-stranded DNA, and reverse transcription is used to produce DNA from an RNA intermediate during replication. *Herpes Simplex Virus (HSV)* - HSV is a **DNA virus** belonging to the Herpesviridae family, known for causing oral and genital lesions. - It replicates its DNA genome directly within the host cell nucleus and does not involve reverse transcriptase.

Q: Which paramyxovirus does not have hemagglutinin and neuraminidase but has a membrane fusion protein?

RSV. ***RSV*** - **Respiratory Syncytial Virus (RSV)** is unique among paramyxoviruses because it lacks both **hemagglutinin (H)** and **neuraminidase (N)** glycoproteins. - Its pathogenicity relies on its **fusion (F) protein**, which causes respiratory epithelial cells to fuse, forming **syncytia**. *Measles* - The **measles virus** (Morbillivirus) possesses both **hemagglutinin (H)** and **fusion (F)** proteins, but it lacks neuraminidase. - The **H protein** is responsible for viral attachment, while the **F protein** mediates membrane fusion and syncytia formation. *Parainfluenza* - **Parainfluenza viruses** all possess both **hemagglutinin-neuraminidase (HN)** protein and **fusion (F)** protein. - The **HN protein** is responsible for both receptor binding and cleaving sialic acid residues, aiding in viral release. *Mumps* - The **mumps virus** also belongs to the paramyxovirus family and possesses both a **hemagglutinin-neuraminidase (HN)** protein and a **fusion (F)** protein. - These proteins are crucial for its ability to attach to host cells and mediate viral entry.

Q: What virus is primarily responsible for causing Exanthema subitum?

HHV-6. ***HHV-6*** - **Human Herpesvirus 6 (HHV-6)** is the primary causative agent of **Exanthema subitum**, also known as **Roseola infantum**. - This virus typically infects infants and young children, leading to a high fever followed by a characteristic rash. *HHV-8* - **Human Herpesvirus 8 (HHV-8)** is primarily associated with **Kaposi's sarcoma**, a cancer that affects individuals with weakened immune systems. - It is not implicated in Exanthema subitum. *Parvovirus* - **Parvovirus B19** causes **Fifth disease** (Erythema infectiosum), characterized by a "slapped cheek" rash. - Its clinical presentation, including the rash distribution and timing relative to fever, differs from Exanthema subitum. *Coxsackievirus* - **Coxsackievirus** is responsible for **Hand-foot-and-mouth disease** and herpangina, which involve rashes and lesions primarily on the hands, feet, and mouth or throat. - Exanthema subitum does not typically present with these specific dermatological features.

Q: What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?

HBsAg, HBeAg, and HBV DNA. **HBsAg, HBeAg, and HBV DNA** - The presence of **HBsAg** indicates ongoing HBV infection [1], while **HBeAg** signifies active viral replication and high infectivity [1]. - **HBV DNA levels** directly quantify the amount of viral genetic material, providing a direct measure of viral load and disease activity [1]. *HBsAg only* - While **HBsAg** indicates the presence of HBV infection, it doesn't provide a complete picture of viral replication or load [1]. - It doesn't differentiate between active replication and chronic carriage with low viral activity [1]. *HBsAg and HBV DNA* - This combination is better than HBsAg alone, as **HBV DNA** directly measures viral load [1]. - However, it misses **HBeAg**, which is a crucial marker for active viral replication and high infectivity, especially in the early phases of chronic infection [2]. *Anti-HBsAg and HBV DNA* - **Anti-HBsAg** (HBsAb) indicates immunity to HBV, either from vaccination or resolved infection, and its presence suggests the absence of active infection [1]. - Therefore, the co-existence of **Anti-HBsAg** with significant **HBV DNA** levels is contradictory and unlikely to represent a high level of active HBV infection.

Q: What is the cause of Herpes Zoster?

Reactivation of latent infection of VZV. ***Reactivation of latent infection of VZV*** - Herpes Zoster, commonly known as **shingles**, occurs when the **varicella-zoster virus (VZV)**, which lies dormant in sensory ganglia after a primary chickenpox infection, reactivates. - This **reactivation** typically happens due to a decline in cellular immunity, often associated with age, stress, or immunosuppression. *Primary infection with VZV* - A primary infection with VZV causes **chickenpox** (varicella), not herpes zoster. - After chickenpox resolves, the virus establishes a **latent infection** in the dorsal root ganglia. *Recurrent infection with VZV* - While VZV can cause recurrent episodes, the term "recurrent infection" usually implies a new exposure or reinfection, which is not the typical mechanism for shingles. - Shingles is specifically due to the **awakening of the existing latent virus**, not a new external infection. *Multiple infection with VZV* - "Multiple infection" implies several separate instances of exposure and infection, which is not the underlying cause of Herpes Zoster. - Herpes Zoster arises from the **viral genome already present** within the host's nerve cells.

Q: Which virus is known to cause latent infections?

HBV. ***HBV*** - Among the options listed, **Hepatitis B virus (HBV)** is the best answer, though it's important to note that HBV causes **chronic infection** rather than true **latent infection**. - In chronic HBV infection, the virus persists in hepatocytes with ongoing low-level replication for years to decades, and viral DNA can integrate into the host genome. - **True latent infections** are classically caused by **herpesviruses** (HSV, VZV, EBV, CMV), where viral genomes remain dormant in neurons or lymphocytes with NO active replication until reactivation. - HBV's persistence and potential for reactivation (especially with immunosuppression) makes it the most appropriate choice among these options. *Rubella* - Rubella virus causes a **self-limiting acute infection** that resolves completely within weeks. - After clearance, individuals develop **lifelong immunity** through antibodies, but the virus does not persist in the body. - No latent or chronic infection occurs. *Influenza virus* - Influenza viruses cause **acute respiratory infections** that resolve within 1-2 weeks. - The virus is completely **cleared from the body** after the immune response. - No latency or chronicity is established. *Rotavirus* - Rotavirus causes **acute gastroenteritis** lasting 3-8 days. - The virus is eliminated from the body after the acute illness resolves. - Does not establish persistent, chronic, or latent infections.

Question 1

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 2

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 3

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 4

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

Accepted Answer

Sacral ganglia

Answer

Trigeminal ganglia

Answer

Otic ganglia

Answer

Ciliary ganglia

Question 5

Which of the following sexually transmitted infections is caused by a retrovirus?

Accepted Answer

Human Immunodeficiency Virus (HIV)

Answer

Hepatitis B Virus (HBV)

Answer

Human Papillomavirus (HPV)

Answer

Herpes Simplex Virus (HSV)

Question 6

Which paramyxovirus does not have hemagglutinin and neuraminidase but has a membrane fusion protein?

Accepted Answer

RSV

Answer

Measles

Answer

Parainfluenza

Answer

Mumps

Question 7

What virus is primarily responsible for causing Exanthema subitum?

Accepted Answer

HHV-6

Answer

HHV-8

Answer

Parvovirus

Answer

Coxsackievirus

Question 8

What serum markers are indicative of a high level of Hepatitis B virus (HBV) infection?

Accepted Answer

HBsAg, HBeAg, and HBV DNA

Answer

HBsAg only

Answer

HBsAg and HBV DNA

Answer

Anti-HBsAg and HBV DNA

Question 9

What is the cause of Herpes Zoster?

Accepted Answer

Reactivation of latent infection of VZV

Answer

Primary infection with VZV

Answer

Recurrent infection with VZV

Answer

Multiple infection with VZV

Question 10

Which virus is known to cause latent infections?

Accepted Answer

HBV

Answer

Rubella

Answer

Influenza virus

Answer

Rotavirus

Virology — MCQs

Virology — MCQs

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