A 23-year-old woman participates in a research study evaluating the effect of monoclonal antibodies on viral infection. The patient has no past medical history and takes no medications. She has not been ill recently. During the study, a peripheral blood specimen is obtained. CD19 positive cells are isolated, purified, and exposed to monoclonal antibodies against cell surface complement receptor CD21. The cells are subsequently incubated along with several viruses being studied. Initial exposure to monoclonal antibodies against CD21 is most likely to prevent cell infection with which of the following viruses?

Question

A 23-year-old woman participates in a research study evaluating the effect of monoclonal antibodies on viral infection.  The patient has no past medical history and takes no medications.  She has not been ill recently.  During the study, a peripheral blood specimen is obtained.  CD19 positive cells are isolated, purified, and exposed to monoclonal antibodies against cell surface complement receptor CD21.  The cells are subsequently incubated along with several viruses being studied.  Initial exposure to monoclonal antibodies against CD21 is most likely to prevent cell infection with which of the following viruses?

Quizplus · Accepted Answer

The initial attachment of the virion envelope or capsid surface proteins to the complementary host cell surface receptors is essential to viral tropism for specific tissues and invasion of cells. Many viruses bind to normal host cell plasma membrane receptors to enter host cells. Epstein-Barr virus (EBV) is a herpesvirus responsible for acute infectious mononucleosis, nasopharyngeal carcinoma, and certain lymphomas (eg, Burkitt lymphoma). More than 90% of the normal adult population is seropositive for EBV, which is primarily transmitted through contact with oropharyngeal secretions. The EBV envelope glycoprotein gp350 binds to CD21 (also known as CR2), the cellular receptor for the C3d complement component. CD21 is normally present on the surface of B cells (CD19-positive cells) and nasopharyngeal epithelial cells. Therefore, exposure to a monoclonal anti-CD21 antibody could interfere with EBV attachment to B cells. (Choice A) Adenovirus has hexon and penton capsomeres on its surface. Rodlike structures ("fibers") that project from the penton base capsomeres are responsible for mediating adsorption to host cells. The cell receptor for most adenovirus fibers is a transmembrane protein member of the immunoglobulin superfamily. (Choice B) Like other herpesviruses, cytomegalovirus requires initial contact with glycosaminoglycan chains on host cell surface proteoglycans for entry into the host cell. It does not require contact with CD21. (Choice D) HIV viruses attach to their major target host cells (CD4⁺ T cells) primarily via the binding of viral envelope glycoprotein gp120 to the cellular CD4 transmembrane glycoprotein and the coreceptor (CCR5 or CXCR4). The HIV envelope then undergoes a conformational change that activates gp41 and initiates membrane fusion. (Choice E) Parvovirus B19 is thought to attach to human erythroid cells via the blood group P antigen (globoside), which is expressed by mature erythrocytes, erythroid progenitors, megakaryocytes, placenta, and the fetal liver and heart. Immature cells of the erythroid family (eg, adult bone marrow, fetal liver) are most vulnerable to parvovirus B19 infection. Educational objective: The initial attachment of the virion envelope or capsid surface proteins to the complementary host cell surface receptors is essential to viral tropism for specific tissues and invasion of cells. Many viruses bind to normal host cell plasma membrane receptors to enter host cells. Known host cell receptor and virion/virion protein binding specificities include: CD4 with HIV gp120, CD21 with Epstein-Barr virus gp350, and erythrocyte P antigen with parvovirus B19.

A 23-Year-Old Woman Participates in a Research Study Evaluating the Effect