A 21-year-old woman volunteers in a research study evaluating the effects of viral infection on immunoglobulin production. The patient is a college student who has no past medical history and does not take any medications. She has not felt ill recently. Her lymphocytes are isolated from whole blood and cultured. The mature B lymphocytes exposed to a specific virus in vitro acquire the ability to proliferate indefinitely while maintaining the capacity to secrete immunoglobulins. Which of the following tests is used to diagnose an in vivo infection with this virus?

Question

A 21-year-old woman volunteers in a research study evaluating the effects of viral infection on immunoglobulin production.  The patient is a college student who has no past medical history and does not take any medications.  She has not felt ill recently.  Her lymphocytes are isolated from whole blood and cultured.  The mature B lymphocytes exposed to a specific virus in vitro acquire the ability to proliferate indefinitely while maintaining the capacity to secrete immunoglobulins.  Which of the following tests is used to diagnose an in vivo infection with this virus?

Quizplus · Accepted Answer

Epstein-Barr virus (EBV) commonly infects B cells, stimulating them to enter the cell cycle and proliferate continuously ("transformation" or "immortalization"). This is accomplished when EBV-encoded oncogenes activate proliferative and anti-apoptotic signaling pathways within the infected B cell. In an immunocompetent host, a vigorous immune response holds EBV-induced B cell proliferation in check. The immortalized B cells maintain the ability to secrete immunoglobulins (Ig) and B-cell activation products (eg, CD23), with very few of them releasing virus particles at any one time. Diagnosing EBV infection relies on detecting a heterogeneous group of heterophile IgM antibodies that react with antigens on horse erythrocytes (or sheep erythrocytes in the classic Paul Bunnell test). Agglutination of these horse erythrocytes by human serum is a sensitive and highly specific (~100%) test for EBV infection in human B cells. The mechanism remains unclear; EBV either induces a humoral response to heterophile antigens or stimulates nonspecific polyclonal activation of B cells. (Choice A) EBV typically causes a latent infection of B cells, with viral genome persistence but no full virion replication, no lytic release, and sparse viral protein expression. Normally, only minimal amounts of EBV-specific antigens circulate in an immunocompetent host; therefore, blood tests for such antigens are insensitive to latent EBV infection. Detection of circulating surface antigen is used to diagnose hepatitis B virus infection. (Choice B) Cryoglobulins, cold-precipitable serum proteins that contain Igs, are most commonly associated with hepatitis C virus infection. (Choice C) Some influenza and parainfluenza viruses are associated with hemadsorption (hemagglutinins or glycoproteins with a high affinity for erythrocytes expressed on the host cell surface). Hemadsorption is not characteristic of EBV. (Choice E) The Papanicolaou test is used to screen cervical cytology specimens for dysplasia caused by oncogenic strains of human papillomavirus. (Choice F) Tzanck smear is used to diagnose herpes simplex or varicella zoster virus infection. The epithelial cells scraped from the ulcer base are prepared with a Wright-Giemsa stain and examined for multinucleated giant cells and intranuclear inclusions. Educational objective: Epstein-Barr virus (EBV) commonly infects B cells, stimulating them to proliferate continuously ("transformation" or "immortalization"). EBV is an oncogenic virus that promotes polyclonal B cell proliferation and heterophile antibody production. The heterophile antibody test is sensitive and highly specific for EBV infection.

A 21-Year-Old Woman Volunteers in a Research Study Evaluating the Effects