3 Classification: Group I ds DNA viruses are highly dependent on the host’s cell cycle because the required the host’s polymerases for replication of the viral genome. Some viruses may induce the cell to forcefully undergo cell division, which may lead to transformation of the cell and, ultimately, cancer.
4 Structure Viral proteins produced during productive infection are Early antigen (EA)Viral capsid antigen (VCA)Glycoproteins of the membrane antigen (MA)Structure and regulation similar to HSV infection.Efficiency of the process is slower and time for replication is longer.Virus interferes with induction of apoptosis in B lymphocytesPrimary infection of B lymphocytes often lead to establishment of latent infection.
5 Transmission Saliva Close oral contact Sharing of toothbrush 1. Virus in saliva initiates infection of oral epithelia and spreads to B cells in lymphatic tissue, -> there is no productive infection of epithelial and B cells.2. Virus promotes growth of B cells3. T cells kill and limit B cell outgrowth. T cells are required for controlling infection. Antibody is limited.4. EBV establishes latency in memory B cells ad is reactivated when B cell is activated.5. T cell (lymphocytes) response contributes to symptoms of infectious mono
6 Pathogenesis of EBVEBV is acquired by close contact between persons through saliva and infects the B cells. The resolution of the EBV infection and many of the symptoms of infectious mononucleosis result from the activation of T cells in response to the infection.
7 Clinical Course of Infectious Mononucleosis Clinical course of infectious mononucleosis and laboratory findings of those with the infection. Epstein-Barr virus infection may be asymptomatic or may produce the symptoms of mononucleosis. The incubation period can last as long 2 months. EA, early antigen; EBNA, Epstein-Barr nuclear antigen; VCA, Viral capsid antigen.
8 Epstein-Barr Virus Case Study A 17-year-old high school student has had low-grade fever and malaise for several days, followed by sore throat, swollen cervical lymph nodes, and increasing fatigue. The patient also notes some discomfort in the left upper quadrant of the abdomen. The sore throat, lymphadenopathy, and fever gradually resolve over the next 2 weeks, but the patient’s full energy level does not return for another 6 weeks.
9 1. What lab tests would confirm the diagnosis of EBV-induced mononucleosis and distinguish it from CMV infection?The clinical diagnosis of infectious mononucleosis is suggested on the basis of the symptoms of fever, sore throat, swollen lymph glands, and the age of the patient.Heterophile antibody test (“Monospot” test)Rapid test for mononucleosis due to EBVSensitive for heterophile antibodies produced by the immune system in response to infection.Effective diagnosis can be made on a single acute-phase serum sample by testing for antibodies.
10 1. What lab tests would confirm the diagnosis of EBV-induced mononucleosis and distinguish it from CMV infection?White blood cell count40%-70% of patients have elevated White Blood Cell (WBC) count of 10,000-20,000 cells/mL10% of patients have a WBC count greater than 25,000 cells/mL of blood by the second week of illness.Approximately 80-90% of patients have lymphocytosis with more than 50% lymphocytes. 20%-40% of the lymphocytes in patients are atypical.WBC appear larger, have a lower nuclear-to-cytoplasmic ratio, and have a nucleus that is less dense than that of normal lymphocytes.
11 EBV serology antigens would confirm for EBV 1. What lab tests would confirm the diagnosis of EBV-induced mononucleosis and distinguish it from CMV infection?EBV serology antigens would confirm for EBVViral capsid antigensEarly antigensEBV nuclear antigen (EBNA)Differentiation if the immunoglobulin G and M of the capsidAntibodies to several antigen complexes can be measured. When monospot test is negative, the optimal combination of EBV serologic testing consists of four markers: IgM and IgG to the viral capsid antigen, IgM to the early antigen, and antibody to EBNA. IgM to the viral capsid antigen appears early in infection and disappears within 4-6 weeks. IgG to the viral capsid antigen appears in the acute phase, peaks at 2-4 weeks after onset, declines and then persists for life. EBV antibody tests, suggest reactivated infection is present.
12 2. To what characteristic diagnostic feature of the disease does mononucleosis refer? Results of antigen-independent proliferation of infected B cells that crowd out RBC and cause anemia.Results from the expansion in numbers of T cells upon stimulation by the EBV-infected B cells.Mononuclear cells are large, with ragged edges and have an abundance of cytoplasm.Mononucleosis-like syndromes accompany other infections of lymphocytes including CMV and HIV. The excess of atypical lymphocytes present in the patients’ blood smear is indicative of mononucleosis.
13 3. What causes the swollen glands and fatigue? Swollen glands and fatigue are caused by activation of the immune responseLong term recovery of the body from mono.Swollen glandsIncreased number of antibodies produced from the lymphocytes and the proliferation of T cellsFatigueSpleen inflammationAbsorbs RBC from the blood in large quantities
14 Immunocompromised individuals 4. Who is at greatest risk for a serious outcome of an EBV infection? What is the outcome? Why?ChildrenAsymptomatic disease or mild symptoms due to their less active immune systemAdolescents & adultsAt risk for infectious mononucleosisImmunocompromised individualsAt highest risk for life-threatening neoplastic diseaseNeoplasm-abnormal mass of tissue
15 ReferencesBennett N. “Pediatric mononucleosis and Epstein-Barr Virus Infection” Medscape. (2012) Retrieved NovemberMurray, P.R. et al. (2005). Medical Microbiology 5th edition. Philadelphia, PA: Elsevier-MosbyWagner, E.K. et al. (2006). Basic Virology (3rd ed.). Malden, MA: Blackwell
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