Virology Practice Questions

Q: Virus lacking hemagglutinin and neuraminidase but having a prominent membrane fusion (F) protein as its major surface glycoprotein is?

Respiratory Syncytial Virus (RSV). ***Respiratory Syncytial Virus (RSV)*** - RSV is characterized by the presence of a **prominent fusion (F) protein** as its major surface glycoprotein, which mediates membrane fusion and viral entry into host cells. - Unlike influenza viruses, RSV **lacks hemagglutinin and neuraminidase proteins**. - The **F protein is the primary virulence factor** and target for antibody-mediated immunity. *Cytomegalovirus (CMV)* - CMV is a **herpesvirus** that does not possess hemagglutinin or neuraminidase. - Its entry mechanism involves **multiple glycoproteins** (gB, gH, gL) that work together for fusion, rather than a single prominent F protein like RSV. *Herpes Simplex Virus (HSV)* - HSV is another **herpesvirus** that utilizes **various glycoproteins** (gB, gD, gH, gL) working in concert for binding and membrane fusion. - It **lacks hemagglutinin and neuraminidase** but does not have a single prominent fusion protein. *Epstein-Barr Virus (EBV)* - EBV, a member of the **herpesvirus family**, also does not have hemagglutinin or neuraminidase. - Its entry involves **specific glycoproteins** (gH, gL, gp42, gB) that are responsible for receptor binding and membrane fusion in a coordinated manner.

Q: Herpes zoster ophthalmicus is caused by:

VZV. ***Correct Answer: VZV*** - **Varicella-zoster virus (VZV)** is the causative agent of **herpes zoster ophthalmicus**, which is a reactivation of the virus in the ophthalmic division of the trigeminal nerve. - The initial infection with VZV causes **chickenpox (varicella)**, and the virus remains dormant in sensory ganglia to reactivate later as shingles. *Incorrect - HPV* - **Human papillomavirus (HPV)** is primarily known for causing **warts** and is a significant risk factor for certain **cancers**, particularly cervical cancer. - HPV does not cause vesicular rashes associated with herpes zoster or ophthalmic involvement. *Incorrect - HSV* - **Herpes simplex virus (HSV)** causes different forms of herpes infections, such as **oral (cold sores)** and **genital herpes**, and can also cause keratitis but is distinct from zoster ophthalmicus. - While HSV can affect the eye, leading to **herpes simplex keratitis**, it produces a different clinical picture and does not involve the dermatomal rash characteristic of zoster. *Incorrect - CMV* - **Cytomegalovirus (CMV)** is a common virus often causing asymptomatic infections in healthy individuals. - In immunocompromised patients, CMV can cause serious diseases, including **retinitis**, but it does not cause herpes zoster ophthalmicus.

Q: All of the following are true about the papovavirus except:

They are RNA viruses.. ***They are RNA viruses*** - Papovaviruses, including **polyomaviruses** and **papillomaviruses**, are **double-stranded DNA viruses**, not RNA viruses. - Their genome is composed of **DNA**, which is a key characteristic distinguishing them from RNA viruses. *Papovaviruses can produce papillomas in humans* - **Human Papillomaviruses (HPVs)**, a subgroup of papovaviruses, are well-known for causing **papillomas** (warts) in humans. - Certain high-risk HPVs are also associated with **cervical cancer** and other anogenital cancers. *SV - 40 is oncogenic* - **Simian Virus 40 (SV40)**, a type of polyomavirus (which falls under the broader papovavirus group), is indeed **oncogenic** in certain animal models. - It has been studied extensively for its ability to induce tumors and transform cells in vitro through its **tumor antigens**. *They are non-enveloped icosahedral viruses* - Both **polyomaviruses** and **papillomaviruses** share the structural characteristic of being **non-enveloped**. - They also possess an **icosahedral capsid** symmetry, which encases their DNA genome.

Q: Viroids are characterized by which of the following?

Small, circular single-stranded RNA. ***Small, circular single-stranded RNA*** - **Viroids** are infectious agents consisting solely of a short strand of **circular, single-stranded RNA** that is self-replicating. - They lack a protein coat, unlike viruses, and are primarily known to cause diseases in plants. *Naked pathogenic human viruses* - While viroids are **naked** (lacking a protein coat), they are not classified as **viruses** and typically do not infect **humans**. - Viroids are distinct from human-pathogenic viruses in their structure and host range. *Fragments of viruses* - Viroids are not **fragments of viruses** but are distinct infectious entities. - They are much smaller than viruses and have a simpler genetic structure, not derived from viral components. *DNA with protein coat* - Viroids do not contain **DNA**; their genetic material is exclusively **RNA**. - They also lack a **protein coat**, which distinguishes them from conventional viruses that possess both nucleic acid and protein components.

Q: Which hepatitis virus was the first to be successfully cultured in vitro?

Hepatitis A Virus (HAV). ***Hepatitis A Virus (HAV)*** - **HAV** was the **first hepatitis virus successfully cultured in vitro** on primary marmoset liver cells and human fetal kidney cells in the late 1970s. - This breakthrough allowed for detailed study of its replication cycle and the development of diagnostic tests and vaccines. *Hepatitis B Virus (HBV)* - While HBV was identified earlier, its **complex replication cycle** and dependence on hepatocytes made its **in vitro culture significantly more challenging** and delayed. - HBV was first identified through the **Australia antigen** in human serum, not initially by in vitro culture. *Hepatitis D Virus (HDV)* - **HDV is a defective virus** that requires co-infection with HBV to replicate, making its independent **in vitro culture impossible**. - Its replication is dependent on the presence of the **hepatitis B surface antigen (HBsAg)**. *Hepatitis C Virus (HCV)* - **HCV was identified much later** in 1989 through molecular cloning techniques, as it was not cultivable in standard cell lines for a long time. - Due to its **genetic diversity and specific host cell requirements**, sustained in vitro culture systems for HCV were only established in the early 2000s.

Q: What does the term 'Australian antigen' refer to in the context of hepatitis B?

Hepatitis B Surface Antigen (HBsAg). ***Hepatitis B Surface Antigen (HBsAg)*** - The term "Australian antigen" was the original name given to the **Hepatitis B Surface Antigen (HBsAg)** when it was first discovered by Baruch Blumberg in 1965 in the blood of an Indigenous Australian. - Its presence indicates an **active hepatitis B infection**, either acute or chronic. - This discovery led to the development of diagnostic tests and vaccines for hepatitis B. *Hepatitis B Antigen* - This is a **non-specific general term** and does not refer to a particular antigen of the hepatitis B virus. - Hepatitis B has several distinct antigens (HBsAg, HBcAg, HBeAg), each with different diagnostic significance. *Hepatitis B Virus (HBV)* - This refers to the **entire infectious agent** that causes hepatitis B, not specifically to one of its antigenic components. - The "Australian antigen" specifically refers to the surface antigen, not the whole virus. *Hepatitis B Core Antigen (HBcAg)* - HBcAg is a **different antigenic component** found in the nucleocapsid core of the hepatitis B virus. - It is not directly detected in serum; instead, antibodies to HBcAg (anti-HBc) are measured for diagnostic purposes. - The Australian antigen refers specifically to HBsAg, not HBcAg.

Q: Hydrops fetalis in a fetus can be due to:

Parvovirus B19. ***Parvovirus B19*** - **Parvovirus B19** infection in a fetus can lead to severe **anemia** and **hydrops fetalis** because the virus targets **erythroid progenitor cells**, impairing red blood cell production. - The resulting severe anemia causes **high-output cardiac failure**, leading to widespread edema, ascites, pleural effusions, and pericardial effusions, which characterize hydrops fetalis. *Epstein-Barr virus* - While **Epstein-Barr virus (EBV)** can infect the fetus, it is more commonly associated with conditions like **lymphoproliferative disorders** or **hepatosplenomegaly**, not typically hydrops fetalis as a primary manifestation. - EBV infection in pregnancy is often asymptomatic or causes mild illness and is not a common cause of severe fetal anemia or hydrops. *Human papilloma virus* - **Human papilloma virus (HPV)** is known to cause **genital warts** and is associated with **cervical cancer**, but it does not cause hydrops fetalis. - Vertical transmission of HPV can occur, leading to conditions like **recurrent respiratory papillomatosis** in the infant, but it does not affect red blood cell production or fluid balance in the fetus in a way that would cause hydrops. *Influenza Virus* - **Influenza virus** infection during pregnancy can lead to complications such as **preterm delivery** or **low birth weight**, but it is not a direct cause of hydrops fetalis. - The influenza virus primarily affects the respiratory system and does not directly target fetal erythroid cells or cause the severe anemia necessary for hydrops.

Q: Among the following retroviruses, which has the strongest established link to direct cancer development?

HTLV - I. ***HTLV-I (Correct Answer)*** - **HTLV-I** is directly linked to **Adult T-cell Leukemia/Lymphoma (ATL)**, a highly aggressive malignancy of CD4+ T lymphocytes - The viral **Tax protein** plays a crucial role in ATL pathogenesis by dysregulating cell cycle progression and inhibiting apoptosis - This represents **direct oncogenesis** through viral protein-mediated cellular transformation - HTLV-I is classified as a Group 1 carcinogen by IARC *HIV (formerly HTLV-III)* - While HIV is associated with increased risk of certain cancers such as **Kaposi's sarcoma** and **Non-Hodgkin lymphoma**, these are primarily due to **immunosuppression** rather than direct viral oncogenesis - HIV itself does not directly transform cells into cancerous ones; instead, it creates an environment conducive to the development of other virally-induced or immune-dysregulation-related cancers - The cancers are **indirect consequences** of immunodeficiency, not direct viral transformation *HTLV-II* - **HTLV-II** has been linked to some neurological disorders, but its association with **cancer development** is much weaker and less established than that of HTLV-I - Unlike HTLV-I, HTLV-II does not have a clear and consistent link to a specific type of human malignancy - No direct oncogenic mechanism has been definitively established *HTLV-IV* - **HTLV-IV** is a relatively newly recognized retrovirus and its association with human disease, especially cancer, is not well-established - Current research suggests it may be a simian virus with limited zoonotic transmission, and its oncogenic potential in humans is largely unknown - No established link to human cancer development

Q: Which receptors do avian influenza HA viruses primarily bind to?

Alpha 2-3 sialic acid receptors. ***Alpha 2-3 sialic acid receptors*** - Avian influenza viruses preferentially bind to **alpha 2-3 sialic acid receptors**, which are abundant in the **gastrointestinal tract of birds**. - This specificity explains why these viruses primarily infect birds and generally require adaptation to infect humans efficiently. - The α2-3 linkage configuration allows optimal binding of avian HA proteins. *Alpha 2-6 sialic acid receptors* - These receptors are the **primary binding targets for human-adapted influenza A viruses**, found abundantly in the **human upper respiratory tract**. - Avian influenza viruses typically bind less efficiently to α2-6 receptors unless specific mutations occur in the HA protein. - The shift from α2-3 to α2-6 binding preference is a key adaptation for human transmission. *Alpha 2-8 sialic acid receptors* - Alpha 2-8 linkages exist in **polysialic acid chains** and certain gangliosides but are **not recognized binding targets for influenza HA proteins**. - Influenza viruses specifically recognize α2-3 or α2-6 linkages, not α2-8. *Alpha 2-9 sialic acid receptors* - Alpha 2-9 linkages are **not biologically relevant receptors for influenza viruses**. - The key receptor specificity determinant for influenza is the distinction between α2-3 (avian) and α2-6 (human) linkages.

Question 1

Virus lacking hemagglutinin and neuraminidase but having a prominent membrane fusion (F) protein as its major surface glycoprotein is?

Accepted Answer

Respiratory Syncytial Virus (RSV)

Answer

Herpes Simplex Virus (HSV)

Answer

Cytomegalovirus (CMV)

Answer

Epstein-Barr Virus (EBV)

Question 2

Herpes zoster ophthalmicus is caused by:

Accepted Answer

VZV

Answer

HPV

Answer

HSV

Answer

CMV

Question 3

All of the following are true about the papovavirus except:

Accepted Answer

They are RNA viruses.

Answer

Papovaviruses can produce papillomas in humans.

Answer

SV - 40 is oncogenic

Answer

They are non-enveloped icosahedral viruses

Question 4

Viroids are characterized by which of the following?

Accepted Answer

Small, circular single-stranded RNA

Answer

Naked pathogenic human viruses

Answer

Fragments of viruses

Answer

DNA with protein coat

Question 5

Which hepatitis virus was the first to be successfully cultured in vitro?

Accepted Answer

Hepatitis A Virus (HAV)

Answer

Hepatitis B Virus (HBV)

Answer

Hepatitis D Virus (HDV)

Answer

Hepatitis C Virus (HCV)

Question 6

What does the term 'Australian antigen' refer to in the context of hepatitis B?

Accepted Answer

Hepatitis B Surface Antigen (HBsAg)

Answer

Hepatitis B Antigen

Answer

Hepatitis B Virus (HBV)

Answer

Hepatitis B Core Antigen (HBcAg)

Question 7

Hydrops fetalis in a fetus can be due to:

Accepted Answer

Parvovirus B19

Answer

Human papilloma virus

Answer

Influenza Virus

Answer

Epstein-Barr virus

Question 8

Among the following retroviruses, which has the strongest established link to direct cancer development?

Accepted Answer

HTLV - I

Answer

HIV (formerly HTLV - III)

Answer

HTLV - II

Answer

HTLV - IV

Question 9

Which receptors do avian influenza HA viruses primarily bind to?

Accepted Answer

Alpha 2-3 sialic acid receptors

Answer

Alpha 2-9 sialic acid receptors

Answer

Alpha 2-6 sialic acid receptors

Answer

Alpha 2-8 sialic acid receptors

Virology — MCQs

Virology — MCQs

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