Virology Practice Questions

Q: Which of the following viruses specifically targets CD4+ T lymphocytes leading to progressive immunodeficiency?

HIV. ***HIV*** - **HIV** primarily targets **CD4+ T lymphocytes**, which are crucial components of the immune system found in lymphoid tissue. - The virus binds to CD4 receptors (along with co-receptors CCR5 or CXCR4) and progressively destroys these cells. - This progressive destruction leads to **immunodeficiency** and the development of AIDS. - HIV's specific tropism for CD4+ T cells distinguishes it from other viruses. *Adenovirus* - **Adenovirus** can infect various cell types, including respiratory epithelium, conjunctival cells, and gastrointestinal tract cells. - It does not have specific tropism for CD4+ T lymphocytes. - While it can cause opportunistic infections in immunocompromised individuals, it does not target T cells specifically. *Herpes virus* - **Herpes viruses** (e.g., HSV, VZV) primarily establish **latency in sensory neurons**. - EBV (a herpes virus) does target B lymphocytes, but not CD4+ T cells. - They do not cause progressive immunodeficiency through CD4+ T cell destruction. *CMV* - **CMV** (Cytomegalovirus) infects a wide range of cell types including fibroblasts, epithelial cells, endothelial cells, and monocytes. - While it can affect immunocompromised individuals, it does not specifically target CD4+ T lymphocytes. - CMV does not cause progressive immunodeficiency through selective CD4+ T cell destruction.

Q: Which of the following is NOT a poxvirus?

Chickenpox. ***Chicken pox*** - **Chickenpox** is caused by the **varicella-zoster virus (VZV)**, which is a member of the **Herpesviridae** family, not the Poxviridae family. - VZV is characterized by its ability to establish **latency** in sensory ganglia, leading to potential reactivation as **shingles** later in life. *Cow pox* - **Cowpox** is a **poxvirus** that causes skin lesions in cattle and can be transmitted to humans, historically being crucial for the development of the **smallpox vaccine**. - It belongs to the **Orthopoxvirus** genus within the Poxviridae family. *Molluscum contagiosum* - **Molluscum contagiosum** is caused by the **molluscum contagiosum virus (MCV)**, which is a specific type of **poxvirus** affecting humans. - It typically causes characteristic **pearly, umbilicated papules** on the skin and is transmitted by direct contact. *Small pox* - **Smallpox** was a severe infectious disease caused by the **variola virus**, a highly virulent member of the **Orthopoxvirus** genus classified within the Poxviridae family. - It was eradicated globally through vaccination efforts, making it one of the greatest achievements in public health.

Q: Which is the most common causative organism involved in infections after kidney transplantation?

Cytomegalovirus. ***Cytomegalovirus*** - **Cytomegalovirus (CMV)** is the most common opportunistic infection after kidney transplantation, occurring in **50-80%** of transplant recipients. - CMV infection or reactivation typically occurs **1-6 months post-transplant** due to intense **immunosuppression** required to prevent graft rejection. - Highest risk is in **donor-positive/recipient-negative (D+/R-)** serostatus, but reactivation can occur in seropositive recipients. - CMV can cause **fever, leukopenia, graft dysfunction**, and invasive disease affecting multiple organ systems. *Klebsiella* - While *Klebsiella* can cause serious bacterial infections, particularly **urinary tract infections** and **pneumonia** in transplant patients, it is not the most common overall causative organism for post-transplant infections. - Bacterial infections like *Klebsiella* are often related to indwelling catheters or surgical sites but are less ubiquitous than viral reactivations in immunosuppressed patients. *Epstein Barr virus* - **Epstein-Barr Virus (EBV)** is another significant viral pathogen in transplant recipients, primarily associated with **post-transplant lymphoproliferative disorder (PTLD)**. - While important, EBV infection or reactivation is not as universally prevalent or as frequently symptomatic as CMV in the post-transplant period. *Herpes simplex virus* - **Herpes simplex virus (HSV)** can cause infections in transplant patients, leading to **mucocutaneous lesions** and occasionally disseminated disease. - HSV infections are generally less severe and less common than CMV, which can affect multiple organ systems and has a higher morbidity burden in this population.

Q: Most common organism causing laryngotracheobronchitis is:

Parainfluenzavirus. ***Parainfluenzavirus*** - **Parainfluenza viruses** (PIVs), particularly PIV-1 and PIV-2, are the **most common causes of croup** (laryngotracheobronchitis) in children. - They primarily cause inflammation and swelling of the **larynx, trachea, and bronchi**, leading to the characteristic **barking cough** and stridor. *RSV* - **Respiratory Syncytial Virus (RSV)** is the **most common cause of bronchiolitis** and pneumonia in infants and young children. - While it can cause upper respiratory symptoms, it is less frequently the primary cause of croup compared to parainfluenza viruses. *Influenza virus* - **Influenza virus** typically causes **influenza** (the flu), which presents with more systemic symptoms like high fever, body aches, and fatigue. - Although influenza can lead to severe respiratory complications, it is a less common cause of isolated laryngotracheobronchitis. *H. influenzae* - **_Haemophilus influenzae_** type b (Hib) was historically a major cause of **epiglottitis**, a severe and life-threatening infection of the epiglottis. - With widespread vaccination, Hib infections are rare, and it is not a common cause of laryngotracheobronchitis.

Q: HIV was discovered in what year?

1983. ***1983*** - HIV (Human Immunodeficiency Virus) was definitively identified and recognized as the cause of AIDS by **Luc Montagnier** at the Institut Pasteur in Paris. - This discovery was crucial for understanding the pathogenesis of AIDS and developing diagnostic tests. *1975* - While documented cases of AIDS occurred in the 1970s, the **virus itself had not yet been identified** in 1975. - Research into rare opportunistic infections and cancers linked to immune deficiency was just beginning to gather momentum. *1995* - By 1995, significant progress had been made in understanding HIV, including the development of **highly active antiretroviral therapy (HAART)**, which revolutionized AIDS treatment. - The initial discovery of the virus happened much earlier. *1985* - In 1985, the first **HIV antibody test** was approved, allowing for widespread screening of blood products and diagnosis of infection. - This was a significant advancement, but it followed the initial discovery of the virus a few years prior.

Q: Japanese encephalitis is caused by which virus?

Arboviruses. ***Arboviruses*** - Japanese encephalitis virus is a **flavivirus**, which belongs to the larger group of **arboviruses**. - **Arboviruses** are viruses transmitted by arthropod vectors, such as mosquitoes, which is how Japanese encephalitis spreads. *Human retrovirus* - **Retroviruses** include viruses like HIV, which are characterized by their ability to reverse-transcribe RNA into DNA. - They are not associated with encephalitis transmitted by insect vectors. *Enteroviruses* - **Enteroviruses** primarily replicate in the gastrointestinal tract and can cause a range of illnesses, including meningitis and hand-foot-and-mouth disease. - They are typically spread via the fecal-oral route, not through mosquito bites. *Cytomegalovirus* - **Cytomegalovirus (CMV)** is a herpesvirus that can cause infections in people of all ages, often asymptomatic but particularly severe in immunocompromised individuals and neonates. - CMV is transmitted through close contact, not via arthropod vectors.

Q: The virus that causes aplastic anemia in chronic hemolytic diseases is

Parvovirus. ***Parvovirus*** - **Parvovirus B19** specifically targets and destroys **erythroid progenitor cells** in the bone marrow. - In patients with chronic hemolytic diseases (e.g., **sickle cell anemia**, **spherocytosis**), where red blood cell turnover is already high, this destruction leads to a severe, acute exacerbation of anemia known as an **aplastic crisis**. *Adenovirus* - Adenoviruses typically cause a range of illnesses, including **respiratory tract infections**, gastroenteritis, and conjunctivitis. - While they can cause severe illness in immunocompromised individuals, they are **not directly implicated** in causing aplastic anemia or aplastic crisis in chronic hemolytic diseases. *Hepatitis virus* - Hepatitis viruses (A, B, C, D, E) primarily cause **inflammation of the liver**. - Although severe viral infections can rarely trigger aplastic anemia, **hepatitis viruses are not the primary or common cause** of aplastic crisis in the context of chronic hemolytic disorders. *EB virus* - **Epstein-Barr virus (EBV)** is known for causing **infectious mononucleosis** and is associated with various lymphoproliferative disorders and malignancies. - While EBV can affect the bone marrow and, in rare instances, be linked to marrow suppression, it is **not the typical or direct cause** of aplastic crisis in chronic hemolytic conditions.

Q: Which one of the following is a function of the enzyme reverse transcriptase, which is unique to retroviruses?

RNA-dependent DNA polymerase activity. ***RNA-dependent DNA polymerase activity*** - **Reverse transcriptase** is a unique enzyme found in retroviruses that synthesizes **DNA from an RNA template**, hence its name "reverse" transcriptase. - This activity is crucial for the retroviral life cycle, as it allows the viral **RNA genome** to be reverse-transcribed into **DNA**, which can then integrate into the host cell's genome. *DNase activity* - **DNase** (deoxyribonuclease) enzymes degrade DNA. This activity is not a primary function of reverse transcriptase. - While integration of the viral DNA into the host genome involves DNA manipulation, the core reverse transcriptase enzyme does not exhibit DNase activity for its primary function. *RNA-dependent RNA polymerase activity* - This activity involves synthesizing **RNA from an RNA template**. It is characteristic of some **RNA viruses** (e.g., influenza virus), but not retroviruses. - Retroviruses use the host cell's machinery to transcribe their integrated DNA provirus into mRNA and new viral RNA genomes, rather than having their own RNA-dependent RNA polymerase. *RNA isomerase activity* - **RNA isomerase activity** is not a standard enzymatic function in the context of nucleic acid synthesis or modification performed by viral enzymes. - Isomerases typically rearrange atoms within a molecule. Reverse transcriptase's primary functions are polymerization and degradation of RNA/DNA hybrids, not isomerization.

Q: Which of the following is a lentivirus?

HIV. ***Correct Answer: HIV*** - **HIV** (Human Immunodeficiency Virus) is the most well-known example of a **lentivirus**, a genus within the **Retroviridae** family. - Lentiviruses are characterized by a long incubation period before disease onset and the ability to cause chronic, slowly progressive diseases. - Key features of lentiviruses include: ability to infect non-dividing cells, integration into host genome, and causing persistent infections. *Incorrect: HBV* - **HBV** (Hepatitis B Virus) belongs to the **Hepadnaviridae** family, not the lentivirus family. - It is a **DNA virus** (not a retrovirus) that primarily infects the liver and can cause acute or chronic hepatitis. *Incorrect: HCV* - **HCV** (Hepatitis C Virus) is a member of the **Flaviviridae** family and is an **RNA virus**. - It is known for causing hepatitis and can lead to chronic infection, cirrhosis, and hepatocellular carcinoma. - Unlike lentiviruses, HCV does not use reverse transcriptase or integrate into the host genome. *Incorrect: Rabies virus* - The **rabies virus** is a member of the **Rhabdoviridae** family, specifically the genus *Lyssavirus*. - It is an **RNA virus** that causes acute encephalitis in mammals, including humans. - Unlike lentiviruses which cause chronic slow infections, rabies causes acute rapidly progressive disease.

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.

Question 1

Which of the following viruses specifically targets CD4+ T lymphocytes leading to progressive immunodeficiency?

Accepted Answer

HIV

Answer

Adenovirus

Answer

Herpes virus

Answer

CMV

Question 2

Which of the following is NOT a poxvirus?

Accepted Answer

Chickenpox

Answer

Molluscum contagiosum

Answer

Smallpox

Answer

Cowpox

Question 3

Which is the most common causative organism involved in infections after kidney transplantation?

Accepted Answer

Cytomegalovirus

Answer

Klebsiella

Answer

Epstein Barr virus

Answer

Herpes simplex virus

Question 4

Most common organism causing laryngotracheobronchitis is:

Accepted Answer

Parainfluenzavirus

Answer

RSV

Answer

Influenza virus

Answer

H. influenzae

Question 5

HIV was discovered in what year?

Accepted Answer

1983

Answer

1975

Answer

1995

Answer

1985

Question 6

Japanese encephalitis is caused by which virus?

Accepted Answer

Arboviruses

Answer

Human retrovirus

Answer

Enteroviruses

Answer

Cytomegalovirus

Question 7

The virus that causes aplastic anemia in chronic hemolytic diseases is

Accepted Answer

Parvovirus

Answer

Adenovirus

Answer

Hepatitis virus

Answer

EB virus

Question 8

Which one of the following is a function of the enzyme reverse transcriptase, which is unique to retroviruses?

Accepted Answer

RNA-dependent DNA polymerase activity

Answer

DNase activity

Answer

RNA-dependent RNA polymerase activity

Answer

RNA isomerase activity

Question 9

Which of the following is a lentivirus?

Accepted Answer

HIV

Answer

HBV

Answer

HCV

Answer

Rabies virus

Question 10

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

Accepted Answer

Bacteriophage

Answer

Pox

Answer

HSV

Answer

CMV

Virology — MCQs

Virology — MCQs

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