Virus Structure and Classification — MCQs
The paramyxovirus that lacks both hemagglutinin and neuraminidase activities is:
Which of the following statements about Prions is true:
Assertion: VZV vaccine is live attenuated. Reason: It cannot be given to immunocompromised patients.
Which of the following is an enveloped virus?
Which is not a DNA virus?
Based on the type of life cycle, zoonoses are classified into all of the following except -
All of the following are prion associated diseases except?
Which of the following statements about paramyxoviruses is false?
A patient presents with genital grouped vesicles, as shown in the image. What is the most likely causative organism?
Match the following in the Japanese encephalitis virus life cycle 1. Accidental host 2. Amplifier 3. Reservoir 4. Vector a. Ardeid birds b. Culex c. Human d. Pigs
Virus Structure and Classification Indian Medical PG Practice Questions and MCQs
Question 1: 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**.
Question 2: Which of the following statements about Prions is true:
- A. They can be cultured in cell free media
- B. They are infectious proteins (Correct Answer)
- C. They have rich nuclear material
- D. They are made up of bacteria and virus
Explanation: ***They are infectious proteins*** - Prions are uniquely characterized as **infectious proteinaceous particles** that lack nucleic acids. - Their mechanism of pathogenicity involves inducing conformational changes in normal host proteins, leading to disease. *They can be cultured in cell free media* - Prions cannot be cultured in cell-free media because they are **not living organisms** and require host cells to propagate by converting normal proteins. - Their replication depends on the presence of the **normal prion protein (PrPC)** in the host. *They have rich nuclear material* - Prions are fundamentally **devoid of nucleic acids** (DNA or RNA), which is a defining characteristic distinguishing them from viruses, bacteria, and other microorganisms. - Their infectious nature is solely based on their **aberrant protein structure**. *They are made up of bacteria and virus* - Prions are distinct biological entities that are **neither bacteria nor viruses**; they are misfolded proteins. - They are much simpler in structure than even the smallest viruses, lacking the complex genetic material and cellular machinery found in bacteria and viruses.
Question 3: Assertion: VZV vaccine is live attenuated. Reason: It cannot be given to immunocompromised patients.
- A. Both true, reason doesn't explain assertion
- B. Assertion true, reason false
- C. Assertion false, reason true
- D. Both true, reason explains assertion (Correct Answer)
Explanation: ***Both true, reason explains assertion*** - The **VZV (varicella-zoster virus) vaccine** is indeed a **live attenuated vaccine** containing weakened virus - the assertion is **TRUE** - It **cannot be given to immunocompromised patients** due to risk of vaccine-strain disease - the reason is **TRUE** - The reason **directly explains the assertion**: BECAUSE the vaccine is live attenuated, it poses infection risk and therefore cannot be used in immunocompromised individuals - The **causal relationship** is clear: live attenuated nature → contraindication in immunocompromised patients *Both true, reason doesn't explain assertion* - While both statements are factually true, this option would only be correct if the reason was unrelated to the assertion - However, the reason **directly explains WHY** the live attenuated nature is clinically significant - The contraindication is a **direct consequence** of the vaccine being live attenuated, so the reason does explain the assertion *Assertion true, reason false* - The assertion is true (VZV vaccine is live attenuated) - However, the reason is also **TRUE** - live attenuated vaccines are indeed contraindicated in immunocompromised patients due to risk of disseminated vaccine-strain infection - Since both statements are true, this option is incorrect *Assertion false, reason true* - The assertion is **TRUE**, not false - VZV vaccine (Varivax, Zostavax) is a **live attenuated vaccine** containing the Oka strain - This option incorrectly claims the assertion is false - Since the assertion is factually correct, this option cannot be right
Question 4: Which of the following is an enveloped virus?
- A. Dengue virus (Correct Answer)
- B. Norwalk virus
- C. Hep A virus
- D. Adenovirus
Explanation: ***Dengue virus*** - The **Dengue virus** is a member of the **Flaviviridae** family, which are known to be **enveloped viruses**. - Its outer lipid envelope, derived from the host cell, is crucial for its entry into host cells and evading the immune system. *Norwalk virus* - The **Norwalk virus**, also known as **Norovirus**, is a **non-enveloped RNA virus** belonging to the **Caliciviridae** family. - Its lack of an envelope makes it more resistant to disinfectants and environmental stresses, contributing to its high infectivity and ability to cause outbreaks of gastroenteritis. *Hep A virus* - **Hepatitis A virus (HAV)** is a **non-enveloped RNA virus** of the **Picornaviridae** family. - Its non-enveloped nature contributes to its stability in the environment and resistance to gastric acid, facilitating its fecal-oral transmission. *Adenovirus* - **Adenoviruses** are **non-enveloped DNA viruses** known for causing a variety of clinical manifestations, including respiratory infections, conjunctivitis, and gastroenteritis. - Their lack of an outer lipid envelope helps them survive in harsh environmental conditions and makes them highly stable.
Question 5: Which is not a DNA virus?
- A. Rhabdovirus (Correct Answer)
- B. Poxvirus
- C. Papovavirus
- D. Parvovirus
Explanation: ***Rhabdovirus*** - Rhabdoviruses, such as the rabies virus, are characterized by their **single-stranded RNA genome** and distinctive bullet-shaped morphology. - They replicate in the cytoplasm of infected cells, using their **RNA-dependent RNA polymerase** to transcribe their genome. *Papovavirus* - Papovaviruses (now split into Papillomaviridae and Polyomaviridae) are **DNA viruses** known for causing warts and some cancers. - They possess a small, **double-stranded, circular DNA genome**. *Poxvirus* - Poxviruses are large, complex **DNA viruses** that replicate entirely within the cytoplasm of the host cell. - They have a **double-stranded DNA genome** and are notable for causing diseases like smallpox and molluscum contagiosum. *Parvovirus* - Parvoviruses are among the smallest viruses, characterized by their **single-stranded DNA genome**. - They require actively dividing host cells to replicate their **linear DNA**.
Question 6: Based on the type of life cycle, zoonoses are classified into all of the following except -
- A. Cyclo-zoonoses
- B. Anthropozoonoses (Correct Answer)
- C. Sporozoonoses
- D. Meta-zoonoses
Explanation: ***Anthropozoonoses*** - This is **NOT a life cycle-based classification** of zoonoses. - It describes the **direction of transmission** (animals to humans), not the complexity or types of hosts required in the parasite's life cycle. - While a valid classification of zoonoses, it is based on **transmission pattern**, not life cycle characteristics. *Cyclo-zoonoses* - These are zoonoses that require **more than one vertebrate host species** to complete their life cycle, but **no invertebrate host** is involved. - This IS a life cycle-based classification. - Examples include **taeniasis** (tapeworm infections) where the parasite cycles between humans and livestock. *Meta-zoonoses* - These zoonoses require **both vertebrate and invertebrate hosts** to complete their life cycle. - This IS a life cycle-based classification. - The **invertebrate host** acts as an essential part of the life cycle for maturation or multiplication of the pathogen (e.g., **arboviruses** transmitted by mosquitoes, **plague** via fleas). *Sporozoonoses* - While this term is **not part of the standard WHO classification** of zoonoses by life cycle, the prefix "sporo-" refers to **spore-forming stages** in parasitic life cycles. - The standard WHO classification includes: **Orthozoonoses** (direct), **Cyclozoonoses**, **Metazoonoses**, and **Saprozoonoses** (requiring inanimate environment). - However, this term relates to life cycle characteristics (spore stages), not transmission direction.
Question 7: All of the following are prion associated diseases except?
- A. Alzheimer's disease (Correct Answer)
- B. Kuru
- C. Scrapie
- D. Creutzfeldt-Jakob disease
Explanation: ***Alzheimer's disease*** - Alzheimer's disease is primarily characterized by the accumulation of **amyloid-beta plaques** and **neurofibrillary tangles** composed of hyperphosphorylated tau protein, not by prion proteins [4]. - While it shares some features of protein **misfolding and aggregation** seen in prion diseases, its pathogenic mechanism is distinct and does not involve infectious prions [1]. *Kuru* - Kuru is a transmissible spongiform encephalopathy (TSE) caused by infectious **prion proteins**, historically linked to **ritualistic cannibalism** in New Guinea [2]. - It is one of the classic examples of a **human prion disease**, primarily affecting the central nervous system. *Creutzfeldt-Jakob disease (CJD)* - CJD is a progressive, fatal **neurodegenerative disorder** caused by **prion proteins** that can be sporadic, genetic, or acquired [3]. - It is characterized by rapidly progressive dementia and spongiform changes in the brain [3]. *Scrapie* - Scrapie is a **prion disease** that affects **sheep and goats**, causing neurological symptoms and ultimately death. - It is considered the **prototypical prion disease**, and its study provided early insights into the nature of prions. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, p. 1284. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1284-1286. [3] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Manifestations Of Central And Peripheral Nervous System Disease, pp. 712-713. [4] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Central Nervous System, pp. 1292-1294.
Question 8: Which of the following statements about paramyxoviruses is false?
- A. Belong to the family Paramyxoviridae
- B. Are DNA viruses (Correct Answer)
- C. Are RNA viruses
- D. Have linear nucleic acid
Explanation: ***Are DNA viruses*** - Paramyxoviruses are characterized by their **single-stranded, negative-sense RNA genome**, not DNA. - Their replication and transcription processes occur in the cytoplasm, which is typical for RNA viruses. *Belong to the family Paramyxoviridae* - This statement is correct; paramyxoviruses are indeed classified under the **family Paramyxoviridae**. - This family includes important human pathogens like measles, mumps, and respiratory syncytial virus (RSV). *Have linear nucleic acid* - This statement is correct as paramyxoviruses possess a **linear, non-segmented RNA genome**. - The linear nature differentiates them from viruses with segmented genomes, such as influenza viruses. *Are RNA viruses* - This statement is correct; paramyxoviruses are characterized by their **RNA genome**. - Specifically, they are **negative-sense, single-stranded RNA viruses**.
Question 9: A patient presents with genital grouped vesicles, as shown in the image. What is the most likely causative organism?
- A. Herpes simplex virus (Correct Answer)
- B. Haemophilus
- C. Klebsiella
- D. Treponema
Explanation: ***Herpes*** - The image shows **grouped vesicles** on an erythematous base, which is the classic presentation of **genital herpes** caused by the **Herpes simplex virus (HSV)**. - These lesions are typically painful and can recur, indicating a viral etiology. *Haemophilus* - *Haemophilus ducreyi* causes **chancroid**, which presents as **painful genital ulcers** with ragged borders and often associated with inguinal lymphadenopathy. - It does not present as grouped vesicles. *Klebsiella* - *Klebsiella granulomatis* causes **donovanosis (granuloma inguinale)**, characterized by progressive, **painless ulcerative lesions** that are highly vascular and bleed easily. - This organism does not cause vesicular lesions. *Treponema* - *Treponema pallidum* causes **syphilis**, which in its primary stage presents as a **painless chancre** (a solitary ulcer) or in secondary stage as a diffuse rash. - It does not cause grouped vesicles.
Question 10: Match the following in the Japanese encephalitis virus life cycle 1. Accidental host 2. Amplifier 3. Reservoir 4. Vector a. Ardeid birds b. Culex c. Human d. Pigs
- A. 1-d, 2-c, 3-a, 4-b
- B. 1-c, 2-a, 3-d, 4-b
- C. 1-d, 2-c, 3-b, 4-a
- D. 1-c, 2-d, 3-a, 4-b (Correct Answer)
Explanation: ***1-c, 2-d, 3-a, 4-b*** - **Humans** are considered **accidental hosts** because they do not contribute to the transmission cycle, as the viral load in their blood is usually insufficient to infect mosquitoes. - **Pigs** serve as **amplifier hosts** because they develop high viral loads, effectively amplifying the virus for further mosquito transmission. **Ardeid birds** (like herons and egrets) are **reservoir hosts** where the virus naturally persists without causing significant disease, maintaining the virus in the environment. **Culex mosquitoes** are the primary **vectors** responsible for transmitting the virus between hosts. *1-d, 2-c, 3-a, 4-b* - This option incorrectly assigns pigs as accidental hosts and humans as amplifier hosts. Pigs are known **amplifiers** due to their high viral titers. - Humans generally have low viremia and are not effective amplifiers or reservoirs in the transmission cycle. *1-c, 2-a, 3-d, 4-b* - This option incorrectly identifies Ardeid birds as amplifiers and pigs as reservoirs. **Pigs** are the main **amplifiers** of Japanese encephalitis virus. - **Ardeid birds** are generally considered **reservoir hosts**, important for overwintering the virus. *1-d, 2-c, 3-b, 4-a* - This option incorrectly identifies pigs as accidental hosts, humans as amplifiers, and mosquitoes as reservoirs. **Culex mosquitoes** are **vectors**, not reservoirs, and **Ardeid birds** are reservoirs, not vectors. - **Humans** are accidental hosts, and **pigs** are amplifiers.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
Start For Free