Virology Practice Questions

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: Molluscum contagiosum virus belongs to?

Poxviruses. ***Poxviruses*** - Molluscum contagiosum virus (MCV) is a **DNA virus** belonging to the **Poxviridae family**, genus Molluscipoxvirus. - Poxviruses are among the **largest and most complex viruses**, with a characteristic **brick-shaped or ovoid morphology**. - MCV causes **cutaneous lesions** characterized by smooth, pearly, dome-shaped papules with central umbilication. - Unlike other poxviruses, MCV replicates exclusively in the **cytoplasm** and causes a benign, self-limiting skin infection. *Herpesviruses* - Herpesviruses are also **DNA viruses** (e.g., HSV, VZV, EBV) but belong to the Herpesviridae family. - They are characterized by their ability to establish **lifelong latency** in neurons or lymphocytes. - They have an **icosahedral capsid** with an envelope, distinct from the brick-shaped morphology of poxviruses. - They typically cause vesicular lesions, not the umbilicated papules seen with MCV. *Picornaviruses* - Picornaviruses are **small, non-enveloped RNA viruses** (e.g., poliovirus, coxsackievirus, enteroviruses). - Their name reflects their small size ("pico" = small) and RNA genome. - Their genetic material is **positive-sense single-stranded RNA**, fundamentally different from the DNA genome of MCV. - They cause diverse infections including poliomyelitis, hand-foot-and-mouth disease, and the common cold. *Adenovirus* - Adenoviruses are **non-enveloped, double-stranded DNA viruses** with an **icosahedral capsid**. - They commonly cause respiratory infections, conjunctivitis, and gastroenteritis. - While they are DNA viruses, their morphology, replication strategy, and disease manifestations are distinct from the cutaneous lesions caused by MCV.

Q: Among the following, which is the smallest virus?

Parvovirus. ***Parvovirus*** - **Parvoviruses** are among the smallest viruses, typically measuring around **18-26 nanometers** in diameter. - They are unique in having a **single-stranded DNA genome**. *Herpes virus* - **Herpesviruses** are relatively large, **double-stranded DNA viruses** with diameters ranging from **150-200 nanometers**. - They are known for establishing **latent infections** in the host. *Adenovirus* - **Adenoviruses** are medium-sized, **non-enveloped, icosahedral viruses** with **double-stranded DNA genomes**, typically 70-90 nanometers in diameter. - They are a common cause of respiratory, gastrointestinal, and ocular infections. *Poxvirus* - **Poxviruses** are exceptionally large and complex viruses, measuring approximately **200-400 nanometers** in length, and are visible under a light microscope. - They have a unique **brick-shaped morphology** and a **double-stranded DNA genome**.

Q: What is the window period in HIV infection?

2-4 weeks. ***2-4 weeks*** - The **window period** in HIV infection is the time between initial infection and when a **detectable immune response** can be measured by standard testing. - Modern **4th generation Ag/Ab combination tests** (now standard in most settings) detect both **HIV p24 antigen** and **HIV antibodies**, reducing the window period to **18-45 days (approximately 2-4 weeks)**. - During this phase, individuals are highly infectious, and early testing with 4th generation tests provides the earliest reliable detection. - **HIV RNA/PCR tests** can detect even earlier (10-14 days) but are not routinely used for initial screening. *4-8 weeks* - This represents the window period for **older 3rd generation antibody-only tests**, which are no longer the standard screening method in most clinical settings. - While historically accurate, this timeframe is outdated with current **4th generation testing protocols**. *8-12 weeks* - This extended period may apply to some **point-of-care rapid tests** or in cases with delayed seroconversion, but exceeds the typical window for standard laboratory-based 4th generation tests. - Most individuals will have detectable antibodies well before this timeframe with modern testing. *> 12 weeks* - By this point, nearly all infected individuals would have developed detectable antibodies with any test generation. - A negative test after 12 weeks essentially **rules out HIV infection** (assuming no recent high-risk exposures). - This is well beyond the **window period** for all standard HIV testing methods.

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.

Q: DNA polymerase of HBV is encoded by which of the following ?

P gene. ***P gene*** - The **P gene** (polymerase gene) of the **Hepatitis B virus (HBV)** encodes for the viral DNA polymerase. - This enzyme is crucial for HBV replication, as it functions as both a **reverse transcriptase** and a **DNA-dependent DNA polymerase**. *S gene* - The **S gene** encodes for the **surface antigens (HBsAg)** of HBV, which are involved in viral entry and are the primary targets of the host immune response. - It does not encode for the viral polymerase. *C gene* - The **C gene** encodes for the **HBV core antigen (HBcAg)**, which forms the viral nucleocapsid. - It also produces the **e antigen (HBeAg)**, which is a secreted protein indicating active viral replication. *X gene* - The **X gene** encodes for the **HBV X protein (HBxAg)**, which is a regulatory protein involved in viral transcription and replication. - It plays a role in **hepatocarcinogenesis** but does not encode the polymerase enzyme.

Q: Which of the following is an oncogenic DNA virus primarily associated with lymphoproliferative disorders?

Epstein-Barr Virus (EBV). ***Epstein-Barr Virus (EBV)*** - **EBV** is a DNA virus strongly associated with several **lymphoproliferative disorders**, including **Burkitt lymphoma**, **Hodgkin lymphoma**, and **post-transplant lymphoproliferative disorder (PTLD)**. - It infects **B lymphocytes** and promotes their proliferation, leading to the risk of malignant transformation. *Human Immunodeficiency Virus (HIV)* - **HIV** is an **RNA retrovirus** that causes acquired immunodeficiency syndrome (AIDS), which can lead to an increased risk of various cancers, including lymphomas, but it is not a DNA virus and its primary mechanism of oncogenesis is indirect via immunosuppression. - While HIV is often associated with lymphomas, it does not directly cause lymphoproliferation in the same way **EBV** does; instead, it weakens the immune system, allowing other oncogenic viruses like EBV to cause malignancies. *HTLV* - **Human T-lymphotropic virus (HTLV)** is an **RNA retrovirus** specifically associated with **adult T-cell leukemia/lymphoma**, not primarily B-cell lymphoproliferative disorders. - It is an **RNA virus**, not a DNA virus, and its oncogenic mechanism involves persistent T-cell activation and proliferation. *HBV* - **Hepatitis B virus (HBV)** is a **DNA virus** primarily associated with **hepatocellular carcinoma (HCC)**, a liver cancer. - It is not directly linked to **lymphoproliferative disorders** but rather to chronic liver inflammation and fibrosis, which contributes to liver cancer.

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: Which virus has a double-stranded RNA with a segmented genome?

Rotavirus. ***Rotavirus*** - Rotavirus possesses a **double-stranded RNA (dsRNA) genome** that is **segmented** into **11 segments**. - This unique genomic structure is characteristic of the *Reoviridae* family, to which Rotavirus belongs. *Influenza* - Influenza virus has a **segmented single-stranded RNA (ssRNA) genome** of negative sense, not double-stranded RNA. - It belongs to the *Orthomyxoviridae* family. *Arenavirus* - Arenaviruses have a **segmented single-stranded RNA (ssRNA) genome** with an **ambisense** polarity, not double-stranded. - Their genome typically consists of two segments. *Bunyavirus* - Bunyaviruses contain a **segmented single-stranded RNA (ssRNA) genome** of negative or ambisense polarity, not double-stranded. - Their genome is typically divided into three segments.

Question 1

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 2

Molluscum contagiosum virus belongs to?

Accepted Answer

Poxviruses

Answer

Herpesviruses

Answer

Picornaviruses

Answer

Adenovirus

Question 3

Among the following, which is the smallest virus?

Accepted Answer

Parvovirus

Answer

Herpes virus

Answer

Adenovirus

Answer

Poxvirus

Question 4

What is the window period in HIV infection?

Accepted Answer

2-4 weeks

Answer

> 12 weeks

Answer

8-12 weeks

Answer

4-8 weeks

Question 5

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 6

Which virus is known to cause latent infections?

Accepted Answer

HBV

Answer

Rubella

Answer

Influenza virus

Answer

Rotavirus

Question 7

DNA polymerase of HBV is encoded by which of the following ?

Accepted Answer

P gene

Answer

S gene

Answer

C gene

Answer

X gene

Question 8

Which of the following is an oncogenic DNA virus primarily associated with lymphoproliferative disorders?

Accepted Answer

Epstein-Barr Virus (EBV)

Answer

HTLV

Answer

Human Immunodeficiency Virus (HIV)

Answer

HBV

Question 9

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

Accepted Answer

RSV

Answer

Measles

Answer

Parainfluenza

Answer

Mumps

Question 10

Which virus has a double-stranded RNA with a segmented genome?

Accepted Answer

Rotavirus

Answer

Influenza

Answer

Arenavirus

Answer

Bunyavirus

Virology — MCQs

Virology — MCQs

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