Virology Practice Questions

Q: How does Epstein –Barr virus (EBV) cause Burkitt’s lymphoma?

Chromosomal translocation. ### ***Chromosomal translocation*** - EBV promotes lymphomagenesis in Burkitt's lymphoma by causing the **t(8;14) translocation**, which places the **c-MYC oncogene** on chromosome 8 under the constitutive control of the **immunoglobulin heavy chain promoter** on chromosome 14. - This dysregulation leads to **overexpression of c-MYC**, a transcription factor that drives rapid cell cycle progression and uncontrolled **B-cell proliferation**. ### *Primer insertion* - Primer insertion is a concept related to **polymerase chain reaction (PCR)** laboratory techniques and is not a mechanism of oncogenesis. - There is no documented mechanism where EBV causes cancer through the insertion of primers into the host cell machinery. ### *Receptor insertion* - Receptor insertion is generally related to the expression of **viral entry receptors** on a cell surface, enabling viral tropism. - This is not a mechanism involved in the malignant transformation of B-cells in Burkitt's lymphoma. ### *Viral integration into host genome* - While some viruses (like Retroviruses/HTLV-1) cause transformation via integration, **EBV persists as an episome** (extrachromosomal circular DNA) within the host cell nucleus rather than integrating into the host genome. - The oncogenic potential of EBV in Burkitt's lymphoma is driven by its ability to immortalize B-cells, creating a population susceptible to the specific genetic translocations mentioned above, rather than by direct insertional mutagenesis.

Q: The Paul-Bunnell test is primarily used for the diagnosis of:

Epstein-Barr Virus (Infectious Mononucleosis). ***Epstein-Barr Virus (Infectious Mononucleosis)*** - The **Paul-Bunnell test** functions as a **heterophile antibody test** that detects antibodies produced by the body in response to an EBV infection, which agglutinate sheep or horse red blood cells. - It is historically considered a specific, though less sensitive, diagnostic marker for **infectious mononucleosis** caused by the **Epstein-Barr Virus**. *Cytomegalovirus infection* - **Cytomegalovirus (CMV)** typically causes heterophile-negative mononucleosis, meaning it does not trigger the production of the antibodies detected by the **Paul-Bunnell test**. - Diagnosis of CMV is usually confirmed through **serology (IgM/IgG)** or **PCR testing** for viral DNA, rather than heterophile antibody agglutination. *Herpes Simplex Virus infection* - **Herpes Simplex Virus (HSV)** infections primarily manifest as vesicular lesions or encephalitis; they are not associated with heterophile antibody production. - The **Paul-Bunnell test** has no role in the diagnosis of HSV, which is typically identified via **viral culture** or **PCR**. *Rubella* - **Rubella** is a viral infection characterized by a maculopapular rash and lymphadenopathy, but it does not produce the heterophile antibodies targeted by the **Paul-Bunnell test**. - Diagnosis relies on the detection of specific **rubella-specific IgM** or a rise in **IgG titers**.

Q: A patient presents with fever, sore throat, cervical lymphadenopathy, and laboratory findings show atypical lymphocytes on peripheral blood smear. Which of the following is the most likely causative organism?

Epstein–Barr virus. ***Epstein–Barr virus*** - This virus is the primary cause of **infectious mononucleosis**, characterized by the classic triad of **fever, tonsillar pharyngitis, and posterior cervical lymphadenopathy**. - The peripheral blood smear typically demonstrates **atypical lymphocytosis** (reactive CD8+ T cells), which is a key diagnostic hallmark alongside positive **heterophile antibody tests**. *Cytomegalovirus* - Often presents with a **mononucleosis-like syndrome** but typically lacks the severe **pharyngitis** and **cervical lymphadenopathy** seen in EBV infections. - Patients are usually **heterophile antibody negative** and may present with hepatitis or pneumonitis in immunocompromised hosts. *Human herpesvirus -6* - Primarily causes **exanthem subitum (roseola infantum)**, which typically presents in infants with a high fever followed by a **maculopapular rash**. - While it can occasionally cause lymphadenopathy, it does not typically present with the classic **acute pharyngitis** or widespread **atypical lymphocytosis** associated with EBV. *Adenovirus* - Frequent cause of **pharyngoconjunctival fever**, which includes pharyngitis, fever, and **conjunctivitis**. - Unlike EBV, it does not classically produce **atypical lymphocytes** on a peripheral blood smear.

Q: What is the primary vector responsible for Chikungunya fever transmission?

Aedes aegypti and Aedes albopictus. ***Aedes aegypti and Aedes albopictus*** - These mosquitoes are the primary vectors for **Chikungunya virus**, an **alphavirus** transmitted through the bite of infected females. - Both species are also well-known for transmitting other **arboviruses** such as **Dengue**, **Zika**, and **Yellow fever**. *Anopheles mosquito* - This vector is the primary transmission route for **Plasmodium** species, which cause **Malaria**. - Unlike Aedes, Anopheles species typically bite during the **night** or during **crepuscular** hours. *Culex mosquito* - This mosquito is most notably the vector for **Japanese Encephalitis** and **West Nile virus**. - It is also the primary vector for **lymphatic filariasis** caused by **Wuchereria bancrofti** in many regions. *Mansonia mosquito* - Mansonia species are primarily recognized as the vectors for **Brugian filariasis** (**Brugia malayi**). - They are characterized by their larvae's ability to attach to the roots of **aquatic plants** to obtain oxygen.

Question 1

How does Epstein –Barr virus (EBV) cause Burkitt’s lymphoma?

Accepted Answer

Chromosomal translocation

Answer

Primer insertion

Answer

Receptor insertion

Answer

Viral integration into host genome

Question 2

The Paul-Bunnell test is primarily used for the diagnosis of:

Accepted Answer

Epstein-Barr Virus (Infectious Mononucleosis)

Answer

Cytomegalovirus infection

Answer

Herpes Simplex Virus infection

Answer

Rubella

Question 3

A patient presents with fever, sore throat, cervical lymphadenopathy, and laboratory findings show atypical lymphocytes on peripheral blood smear. Which of the following is the most likely causative organism?

Accepted Answer

Epstein–Barr virus

Answer

Cytomegalovirus

Answer

Human herpesvirus -6

Answer

Adenovirus

Question 4

How does the Ebola virus cause severe hemorrhagic manifestations in infected patients?

Accepted Answer

Inhibition of interferon response and targeting of endothelial cells with coagulation dysfunction

Answer

Direct cytopathic effect on hepatocytes only

Answer

Selective destruction of bone marrow

Answer

Autoimmune destruction of platelets

Question 5

What is the primary vector responsible for Chikungunya fever transmission?

Accepted Answer

Aedes aegypti and Aedes albopictus

Answer

Anopheles mosquito

Answer

Culex mosquito

Answer

Mansonia mosquito

Virology — MCQs

Virology — MCQs

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