Virology — MCQs
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Which strain was primarily responsible for the major human influenza pandemic in recent decades?
What is another name for HTLV-1?
Among the following retroviruses, which has the strongest established link to direct cancer development?
Which of the following is not considered to be a slow virus disease?
Which is the most recent pandemic strain of influenza?
Kaposi's sarcoma occurs with infection due to which virus?
What is the primary function of the nucleocapsid proteins in the measles virus?
All of the following are RNA viruses except
Which receptors do avian influenza HA viruses primarily bind to?
The paramyxovirus that lacks both hemagglutinin and neuraminidase activities is:
Virology Indian Medical PG Practice Questions and MCQs
Question 1431: Which strain was primarily responsible for the major human influenza pandemic in recent decades?
- A. H1N1 (Correct Answer)
- B. H5N1
- C. H7N9
- D. H7N7
Explanation: ***H1N1*** - The **H1N1 strain** was responsible for the **2009 swine flu pandemic**, which was a significant global health event in recent decades. - This strain emerged through **reassortment** of avian, swine, and human influenza viruses, possessing genes from each. *H5N1* - **H5N1** is known as highly virulent **avian influenza** (bird flu) and has caused severe human infections, but it has not led to a widespread human pandemic due to its limited human-to-human transmission. - While concerning, it primarily remains a threat to poultry. *H7N9* - **H7N9** is another strain of **avian influenza** that has caused severe human infections, primarily in China, but it has not evolved for efficient human-to-human transmission needed for a pandemic. - Infections are usually linked to direct contact with infected poultry. *H7N7* - **H7N7** is an **avian influenza** strain that has caused localized outbreaks in poultry and some human infections, primarily among those working with infected birds. - It has not demonstrated the sustained human-to-human transmission necessary for a global pandemic.
Question 1432: What is another name for HTLV-1?
- A. HIV
- B. ATLV (Correct Answer)
- C. RSV
- D. ALV
Explanation: ***ATLV*** - **ATLV (Adult T-cell leukemia virus)** is an older name for **HTLV-1 (Human T-cell lymphotropic virus type 1)**. - This virus is well-known for causing **Adult T-cell Leukemia/Lymphoma (ATL)**, hence the original designation. *HIV* - **HIV (Human Immunodeficiency Virus)** is a completely different retrovirus that causes **Acquired Immunodeficiency Syndrome (AIDS)**. - While both are retroviruses, their genetic makeup, epidemiology, and disease manifestations are distinct. *RSV* - **RSV (Respiratory Syncytial Virus)** is a **paramyxovirus** primarily known for causing respiratory tract infections, especially in infants and young children. - It is an **RNA virus** and is unrelated to HTLV-1. *ALV* - **ALV (Avian Leukosis Virus)** is a retrovirus that infects chickens and other birds, causing various forms of **leukemia and tumors in avian species**. - It is an **animal retrovirus** and not related to human viruses like HTLV-1.
Question 1433: Among the following retroviruses, which has the strongest established link to direct cancer development?
- A. HIV (formerly HTLV - III)
- B. HTLV - I (Correct Answer)
- C. HTLV - II
- D. HTLV - IV
Explanation: ***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
Question 1434: Which of the following is not considered to be a slow virus disease?
- A. Kuru
- B. Scrapie
- C. Sarcoidosis (Correct Answer)
- D. Creutzfeldt Jakob disease
Explanation: ***Sarcoidosis*** - Sarcoidosis is a multisystem **granulomatous disease** of unknown etiology, characterized by the formation of **non-caseating granulomas** in various organs. - It is an **inflammatory condition**, not a viral infection, and does not fit the criteria of a slow virus disease which typically refers to **prion diseases**. *Kuru* - Kuru is a **prion disease** caused by the consumption of infected brain tissue, primarily affecting the Fore people of Papua New Guinea. - It is characterized by progressive **cerebellar ataxia** and dementia, with a long incubation period typical of a **slow virus disease**. *Scrapie* - Scrapie is a **prion disease** affecting sheep and goats, leading to neurological degeneration. - It serves as a classic example of a **transmissible spongiform encephalopathy (TSE)** with a prolonged incubation period, classifying it as a slow virus disease. *Creutzfeldt Jakob disease* - Creutzfeldt-Jakob disease (CJD) is a **fatal neurodegenerative prion disease** in humans. - It is characterized by rapidly progressive dementia, myoclonus, and other neurological symptoms, with features consistent with a **slow virus disease** due to its long incubation.
Question 1435: Which is the most recent pandemic strain of influenza?
- A. H1N1 (Correct Answer)
- B. H2N2
- C. H5N1
- D. H3N2
Explanation: ***Correct Option: H1N1*** - The **2009 H1N1 influenza pandemic** (swine flu) represented the **most recent global pandemic** of a novel influenza virus - This strain was a **reassortant virus** with genes from **swine, avian, and human influenza viruses** - Declared a pandemic by WHO in June 2009, lasting until August 2010 *Incorrect Option: H2N2* - The **H2N2 influenza A virus** caused the **1957-1958 Asian Flu pandemic** - This strain **is no longer in circulation** among humans, having been replaced by H3N2 in 1968 - Not the most recent pandemic strain *Incorrect Option: H5N1* - While **H5N1 avian influenza** has caused outbreaks in poultry and sporadic human infections with **high mortality (~60%)** - It has **NOT achieved sustained human-to-human transmission**, hence it is not considered a pandemic strain - Monitored as a potential pandemic threat due to its high virulence *Incorrect Option: H3N2* - The **H3N2 influenza A virus** was responsible for the **1968 Hong Kong Flu pandemic** - It has continued to circulate as a **seasonal influenza strain** since then - Not the most recent pandemic - preceded H1N1 2009 by over 40 years
Question 1436: Kaposi's sarcoma occurs with infection due to which virus?
- A. HHV-8 (Correct Answer)
- B. HHV-4
- C. HHV-2
- D. HHV-1
Explanation: ***HHV-8*** - **Kaposi's sarcoma** is a vascular tumor strongly associated with infection by **Human Herpesvirus 8 (HHV-8)**, also known as Kaposi's sarcoma-associated herpesvirus (KSHV). - HHV-8 is frequently found in the lesions of all forms of Kaposi's sarcoma, including classic, endemic, iatrogenic, and AIDS-related types. *HHV-4* - **HHV-4**, also known as **Epstein-Barr virus (EBV)**, is associated with various lymphomas (e.g., Burkitt lymphoma, Hodgkin lymphoma) and infectious mononucleosis, but not Kaposi's sarcoma. - While EBV can cause malignancies, its mechanism and associated conditions are distinct from those linked to HHV-8. *HHV-2* - **HHV-2**, or **Herpes Simplex Virus type 2 (HSV-2)**, primarily causes **genital herpes** and can be associated with neonatal herpes infections. - HSV-2 is not implicated in the development of Kaposi's sarcoma. *HHV-1* - **HHV-1**, or **Herpes Simplex Virus type 1 (HSV-1)**, is the common cause of **oral herpes** (cold sores). - Like HSV-2, HSV-1 is not associated with Kaposi's sarcoma or its pathogenesis.
Question 1437: What is the primary function of the nucleocapsid proteins in the measles virus?
- A. Protect the RNA from degradation during replication. (Correct Answer)
- B. Facilitate the assembly of the virion structure.
- C. Assist in the packaging of the viral genome.
- D. Protect the genome RNA from nuclease digestion and recognize the location in the cell membrane for budding.
Explanation: **Protect the RNA from degradation during replication.** - The **nucleocapsid proteins** (N proteins) in the measles virus encapsidate the **viral RNA genome**, forming a helical ribonucleoprotein (RNP) complex. - This **encapsidation** provides crucial protection to the RNA from cellular **nucleases**, preventing its degradation and maintaining its integrity for successful replication and transcription. *Facilitate the assembly of the virion structure.* - While nucleocapsid proteins are part of the virion structure, their primary function isn't to **facilitate the assembly** but rather to protect the genetic material within that structure. - **Matrix proteins** and other viral components are more directly involved in the overall assembly and budding process. *Assist in the packaging of the viral genome.* - **Packaging** of the viral genome is a separate, although related, process where the protected nucleocapsid is incorporated into the newly forming virion. - The fundamental role of the nucleocapsid protein is the **protection and organization of the RNA**, which then enables efficient packaging. *Protect the genome RNA from nuclease digestion and recognize the location in the cell membrane for budding.* - **Protecting the genome RNA from nuclease digestion** is indeed a key function of nucleocapsid proteins. - However, **recognizing the location in the cell membrane for budding** is primarily mediated by the viral **matrix (M) protein**, which links the nucleocapsid to the envelope glycoproteins.
Question 1438: All of the following are RNA viruses except
- A. Influenza virus
- B. Parainfluenza virus
- C. Mumps virus
- D. Herpes virus (Correct Answer)
Explanation: ***Herpes virus*** - **Herpesviruses** are a large family of **DNA viruses** that cause diseases in animals, including humans. - They are characterized by their ability to establish **latent infections** and periodically reactivate. *Influenza virus* - The **influenza virus** is an **RNA virus** belonging to the family **Orthomyxoviridae**. - It is known for causing the seasonal **flu** and respiratory infections. *Parainfluenza virus* - **Parainfluenza viruses** are a group of **RNA viruses** in the family **Paramyxoviridae**. - They are a common cause of **respiratory tract infections**, especially in children, leading to conditions like **croup**. *Mumps virus* - The **mumps virus** is an **RNA virus** that is part of the **Paramyxoviridae** family. - It is well-known for causing **mumps**, which is characterized by the swelling of the **parotid glands**.
Question 1439: Which receptors do avian influenza HA viruses primarily bind to?
- A. Alpha 2-9 sialic acid receptors
- B. Alpha 2-6 sialic acid receptors
- C. Alpha 2-8 sialic acid receptors
- D. Alpha 2-3 sialic acid receptors (Correct Answer)
Explanation: ***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 1440: The paramyxovirus that lacks both hemagglutinin and neuraminidase activities is:
- A. Mumps virus
- B. Respiratory syncytial virus (Correct Answer)
- C. Measles virus
- D. Parainfluenza virus
Explanation: ***Respiratory syncytial virus*** - **Respiratory syncytial virus (RSV)** is unique among paramyxoviruses because it **lacks both hemagglutinin (HA) and neuraminidase (NA)** surface glycoproteins. - Instead, RSV uses its **fusion (F) protein** to mediate viral entry and induce syncytia formation. *Mumps virus* - Mumps virus possesses both **hemagglutinin and neuraminidase (HN) activity** on a single surface glycoprotein. - This HN protein is crucial for **viral attachment and release** from host cells. *Measles virus* - Measles virus has **hemagglutinin (H)** activity for attachment but **lacks neuraminidase activity**. - Its F protein is essential for **cell fusion** and spread. *Parainfluenza virus* - Parainfluenza viruses, like mumps, possess a **hemagglutinin-neuraminidase (HN) protein** with both activities. - This dual function is important for their **lifecycle and pathogenesis**.
Practice by Chapter
Virus Structure and Classification
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Viral Replication
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Pathogenesis of Viral Infections
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DNA Viruses: Herpesviruses
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DNA Viruses: Poxviruses and Adenoviruses
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Hepatitis Viruses
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RNA Viruses: Orthomyxoviruses
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RNA Viruses: Paramyxoviruses
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Enteroviruses and Rhinoviruses
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Arboviruses
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HIV and Retroviruses
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Oncogenic Viruses
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