Virology Practice Questions

Q: Lysis of a bacterial colony in a culture is caused by which agent?

Bacteriophage. ***Bacteriophage*** - **Bacteriophages** are viruses that infect and **lyse bacteria**, creating clear zones (plaques) on a bacterial lawn. - The lysis of bacterial colonies by bacteriophages is a fundamental observation in **microbiology** used to detect and quantify these viruses. *Pox* - **Poxviruses** infect animal cells, not bacteria, and cause diseases like smallpox or cowpox. - Their replication cycle involves host cell machinery but does not result in the *lysis* of bacterial colonies. *HSV* - **Herpes Simplex Virus (HSV)** is a human virus that causes oral and genital lesions. - HSV infects human cells and does not target or lyse bacterial colonies in culture. *CMV* - **Cytomegalovirus (CMV)** is another human virus, part of the herpesvirus family, causing a wide range of clinical manifestations. - CMV infection is specific to human cells and does not cause lysis of bacterial colonies.

Q: Which of the following statements about arboviruses is correct?

Chikungunya is transmitted by Aedes aegypti.. ***Chikungunya is transmitted by Aedes aegypti.*** - **Chikungunya virus** is primarily transmitted to humans through the bites of infected female **Aedes aegypti** and **Aedes albopictus** mosquitoes. - These mosquitoes are widespread in tropical and subtropical regions and are competent vectors for several arboviruses. *Dengue has only one serotype.* - Dengue virus has **four distinct serotypes** (DEN-1, DEN-2, DEN-3, and DEN-4), meaning infection with one serotype provides immunity to that serotype but not to the others. - Subsequent infection with a different serotype can lead to more severe disease, such as **Dengue Hemorrhagic Fever (DHF)** or **Dengue Shock Syndrome (DSS)**, due to antibody-dependent enhancement. *Kyasanur Forest Disease (KFD) was first identified in Kerala.* - **Kyasanur Forest Disease (KFD)** was first identified in the **Kyasanur Forest** of **Karnataka, India**, not Kerala, in 1957. - It is a **tick-borne hemorrhagic fever** caused by a flavivirus and is endemic to specific regions of India. *Yellow fever is endemic only in Asia.* - **Yellow fever** is endemic in **tropical and subtropical areas of South America and Africa**, not Asia. - The virus is transmitted to humans by infected **mosquitoes, primarily Aedes aegypti**.

Q: Which virus is primarily associated with Kaposi's sarcoma?

Human herpesvirus 8 (HHV-8). ***Human herpesvirus 8 (HHV-8)*** - **HHV-8**, also known as **Kaposi's sarcoma-associated herpesvirus (KSHV)**, is the causal agent for all forms of Kaposi's sarcoma. - It infects endothelial cells, leading to abnormal proliferation and the characteristic vascular lesions of **Kaposi's sarcoma**, particularly in immunocompromised individuals. *Hepatitis C virus (HCV)* - **HCV** is primarily associated with **hepatocellular carcinoma** and certain **lymphomas**, but not Kaposi's sarcoma. - It causes chronic liver inflammation and can lead to **cirrhosis** and liver failure. *Human papillomavirus (HPV)* - **HPV** is primarily known for causing **cervical cancer**, anogenital warts, and certain **oropharyngeal cancers**. - It does not have a direct causal link to Kaposi's sarcoma. *Herpes simplex virus (HSV)* - **HSV** types 1 and 2 cause **cold sores** (oral herpes) and **genital herpes**, respectively. - While it is a herpesvirus, it is not associated with Kaposi's sarcoma; HHV-8 is a distinct type of herpesvirus.

Q: Among the following viruses, which one does NOT cause hemagglutination?

HPV. ***HPV*** - **Human Papillomavirus (HPV)** does not possess **hemagglutinin proteins** on its surface. - Hemagglutination is the process where viruses bind to **red blood cells**, causing them to clump together; HPV does not exhibit this property. *Influenza* - **Influenza viruses** have **hemagglutinin (HA) spikes** on their envelope, which bind to sialic acid residues on red blood cells. - This binding leads to **hemagglutination**, a key property used in diagnostic tests like the hemagglutination inhibition assay. *Rubella* - The **Rubella virus** is known to cause **hemagglutination** of red blood cells, particularly from one-day-old chicks or geese. - This property is utilized in the **hemagglutination inhibition (HI) test** for detecting antibodies against the Rubella virus. *Measles* - **Measles virus**, a paramyxovirus, contains **hemagglutinin proteins** on its surface. - These proteins enable the virus to agglutinate red blood cells, a characteristic contributing to its diagnostic detection.

Q: Which of the following is the envelope glycoprotein of HIV that binds to CD4 receptors for cell entry?

GP120. ***GP120*** - **GP120** is the crucial **envelope glycoprotein** found on the surface of the **Human Immunodeficiency Virus (HIV)**. - It is essential for **viral entry** into host cells by binding to the **CD4 receptor** and a **co-receptor (CCR5 or CXCR4)** on T-helper cells. - This makes it a primary target for **neutralizing antibodies** and **vaccine development**. *Gp73* - **Gp73** is a **Golgi protein** that has been studied as a biomarker for **liver fibrosis** and **hepatocellular carcinoma**. - It is **not associated with HIV** structure or function. *P24* - **P24** is a **capsid protein** of HIV that forms the conical core surrounding the viral RNA. - While it is an important **HIV structural protein** used in diagnostic testing, it is **not an envelope glycoprotein**. - P24 is located **inside the virion**, not on the surface, and does not participate in CD4 receptor binding. *Gp5* - **Gp5** refers to a **glycoprotein** associated with other viruses, such as certain **herpesviruses** like **cytomegalovirus (CMV)**. - It is **not a protein of HIV**.

Q: What is the primary cellular target of Human immunodeficiency virus (HIV)?

CD4+ T cells. ***CD4+ T cells*** - HIV primarily targets and replicates within **CD4+ T lymphocytes**, which are crucial for the body's immune response. - The progressive destruction of these cells leads to **immunodeficiency**, making the body susceptible to opportunistic infections. *Erythrocytes* - **Red blood cells** (erythrocytes) are not directly targeted or infected by HIV. - HIV infection can indirectly lead to **anemia**, but this is not due to direct viral replication within erythrocytes. *Connective tissue cells* - While HIV can have effects on various organs, it does not primarily infect or replicate within **connective tissue cells**. - Its main cellular target is specific immune cells. *Allergy-mediating cells* - **Mast cells** and **basophils** are allergy-mediating cells that are not the primary targets of HIV. - HIV does not directly infect these cells to establish its life cycle.

Q: H1N1 is a subtype of which virus?

Influenza type A virus. ***Influenza type A virus*** - H1N1 refers to the specific **hemagglutinin (H)** and **neuraminidase (N)** proteins on the surface of the virus, which are characteristic of **influenza A viruses**. - Influenza A viruses are known for their ability to undergo **antigenic shift** and cause pandemics, as seen with the 2009 H1N1 pandemic. *SARS virus* - **SARS (Severe Acute Respiratory Syndrome)** is caused by a coronavirus, specifically **SARS-CoV**, which is distinct from influenza viruses. - While both can cause respiratory illness, their genetic structure and mechanisms of infection are entirely different. *Influenza type B virus* - Influenza B viruses primarily infect humans and do not have the same H and N protein classification (e.g., H1N1) that influenza A viruses do. - They tend to cause **seasonal epidemics** but are not typically associated with pandemics. *Influenza type C virus* - Influenza C viruses cause a **mild respiratory illness** and are not classified by H and N subtypes. - They are less common and cause milder symptoms compared to influenza A and B viruses.

Q: Which of the following statements about the influenza virus is NOT true?

All types exhibit antigenic shift.. ***All types exhibit antigenic shift.*** - This statement is **incorrect** (and thus the correct answer to this question asking for what is NOT true). - **Antigenic shift** is a major genetic reassortment event that occurs primarily in **Influenza A virus**, where entire gene segments are exchanged between different strains, potentially leading to pandemic strains. - **Influenza B** can undergo antigenic drift but does NOT typically exhibit antigenic shift due to its limited host range (primarily humans) and lack of reassortment opportunities. - **Influenza C** causes mild respiratory illness and shows minimal antigenic variation. *Only type A shows antigenic drift.* - This statement is **false**. Both **Influenza A and Influenza B** undergo **antigenic drift**. - Antigenic drift involves gradual accumulation of point mutations in hemagglutinin (HA) and neuraminidase (NA) genes, allowing immune evasion. - This is why this is also an incorrect statement, but the question asks for one answer, and "all types exhibit shift" is the more clearly false statement. *Drift is the accumulation of point mutations.* - This statement is **true**. - **Antigenic drift** results from **point mutations** in genes encoding surface proteins (HA and NA). - These minor changes allow the virus to evade existing immunity, causing seasonal epidemics. *None of the above.* - This option is incorrect because there IS a false statement among the options ("All types exhibit antigenic shift").

Q: The most common cause of sporadic viral encephalitis is what?

Herpes simplex encephalitis. ***Herpes simplex encephalitis*** - **Herpes simplex virus (HSV)**, particularly **HSV-1**, is the most frequent cause of **sporadic viral encephalitis** globally. - It often presents with characteristic temporal lobe involvement, leading to **focal neurological deficits** and **seizures** [1]. *Japanese B encephalitis* - This is a prominent cause of **epidemic viral encephalitis** in Asia, primarily affecting children, but not the most common cause of **sporadic cases**. - It is transmitted by **mosquitoes** and typically has a seasonal pattern. *Human immunodeficiency virus encephalitis* - HIV can cause **encephalopathy** and dementia in advanced stages, but it is not typically characterized as **acute viral encephalitis** [1]. - The neurological manifestations of HIV are more chronic and progressive rather than an acute inflammatory process of the brain [1]. *Rubeola encephalitis* - **Rubeola (measles virus)** can cause acute post-infectious encephalomyelitis or the rare, fatal, late-onset condition **subacute sclerosing panencephalitis (SSPE)**. - While serious, these conditions are not the most common cause of **sporadic acute viral encephalitis** in the general population.

Q: Which one of the following hepatitis viruses has significant perinatal transmission?

Hepatitis B virus. ***Hepatitis B virus*** - **Perinatal transmission** is a major mode of HBV spread, occurring from an infected mother to her baby during birth. - Infants born to HBV-positive mothers have a high risk of developing **chronic HBV infection**, leading to serious liver disease later in life if not properly managed with immunization and immunoglobulin. *Hepatitis E virus* - Primarily transmitted via the **fecal-oral route**, often through contaminated water. - While it can be transmitted vertically, significant **perinatal transmission** leading to chronic outcomes in the infant is not a primary concern compared to HBV. *Hepatitis C virus* - While vertical transmission from mother to child can occur, the rate of **perinatal HCV transmission** is much lower (around 5%) compared to HBV. - It is mainly transmitted through exposure to infected blood, such as via **intravenous drug use** or blood transfusions prior to screening. *Hepatitis A virus* - Transmitted almost exclusively via the **fecal-oral route**, usually through contaminated food or water. - Perinatal transmission is **extremely rare** and does not represent a significant mode of global HAV spread or burden of disease.

Question 1

Lysis of a bacterial colony in a culture is caused by which agent?

Accepted Answer

Bacteriophage

Answer

Pox

Answer

HSV

Answer

CMV

Question 2

Which of the following statements about arboviruses is correct?

Accepted Answer

Chikungunya is transmitted by Aedes aegypti.

Answer

Kyasanur Forest Disease (KFD) was first identified in Kerala.

Answer

Dengue has only one serotype.

Answer

Yellow fever is endemic only in Asia.

Question 3

Which virus is primarily associated with Kaposi's sarcoma?

Accepted Answer

Human herpesvirus 8 (HHV-8)

Answer

Hepatitis C virus (HCV)

Answer

Human papillomavirus (HPV)

Answer

Herpes simplex virus (HSV)

Question 4

Among the following viruses, which one does NOT cause hemagglutination?

Accepted Answer

HPV

Answer

Rubella

Answer

Measles

Answer

Influenza

Question 5

Which of the following is the envelope glycoprotein of HIV that binds to CD4 receptors for cell entry?

Accepted Answer

GP120

Answer

Gp73

Answer

P24

Answer

Gp5

Question 6

What is the primary cellular target of Human immunodeficiency virus (HIV)?

Accepted Answer

CD4+ T cells

Answer

Erythrocytes

Answer

Connective tissue cells

Answer

Allergy-mediating cells

Question 7

H1N1 is a subtype of which virus?

Accepted Answer

Influenza type A virus

Answer

SARS virus

Answer

Influenza type B virus

Answer

Influenza type C virus

Question 8

Which of the following statements about the influenza virus is NOT true?

Accepted Answer

All types exhibit antigenic shift.

Answer

Drift is the accumulation of point mutations.

Answer

Only type A shows antigenic drift.

Answer

None of the above.

Question 9

The most common cause of sporadic viral encephalitis is what?

Accepted Answer

Herpes simplex encephalitis

Answer

Japanese B encephalitis

Answer

Human immunodeficiency virus encephalitis

Answer

Rubeola encephalitis

Question 10

Which one of the following hepatitis viruses has significant perinatal transmission?

Accepted Answer

Hepatitis B virus

Answer

Hepatitis E virus

Answer

Hepatitis C virus

Answer

Hepatitis A virus

Virology — MCQs

Virology — MCQs

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