Epstein-Barr Virus EBNA-2 gene expression enhances lymphotoxin production by B lymphocytes.

Epstein-Barr Virus (EBV) effectively transforms B lymphocytes into long-term cell lines or tumors through the interaction of viral gene products and cellular proteins induced secondary to the virus infection. The latent membrane protein (LMP) gene, the EBV nuclear antigens (EBNAs) 1 and 2, and the origin of replication genes of the virus are the principal viral effectors of transformation. One of the cellular proteins that enhances the growth and proliferation of B cells is lymphotoxin (LT). We have found that Burkitt's lymphoma cells containing a strain of EBV with a deletion in EBNA-2 had lower constitutive and inducible levels of LT compared to LT production in Burkitt's cells with competent EBV or lymphoblastoid cell lines actively producing EBV. Also, the LT production in the latter cell lines was greater than in cells in which the infecting EBV had a deletion in the LMP gene. The relative decrease in LT production associated with deletions in the LMP was less than that found with EBNA-2 deletions. Overall our results indicate that the EBNA-2 gene enhances the capacity of EBV-infected cells to produce LT.

Respiratory contamination of polymerase chain reactions by human herpesvirus 6.

Human herpesvirus type 6 DNA derived from human breath was discovered to contaminate PCR reactions during routine reaction preparation. Parallel PCR experiments were conducted in which expiratory secretions were blocked by a surgical mask, while others were performed without any attempt to circumvent respiratory contamination. The experimenter was previously determined to harbor HHV-6 DNA in the saliva. All reactions in which expiration was obstructed were negative for HHV-6 DNA via PCR. Reactions in which there was no attempt to obstruct respiratory secretions were positive for HHV-6 DNA. These data suggest that PCR assays investigating the presence of HHV-6 may be highly susceptible to contamination from the experimenter leading to false positive results.

Childhood idiopathic thrombocytopenic purpura: association with human parvovirus B19 infection.

PURPOSE: Infection with human parvovirus B19 is the most common cause of transient aplastic crisis in patients with chronic hemolytic anemia. Multiple reports of children with simultaneous B19 infection and thrombocytopenia as well as the known association between experimental B19 infection and thrombocytopenia prompted us to hypothesize that B19 may be associated with childhood idiopathic, or immune, thrombocytopenic purpura (ITP). Because there is a paucity of evidence regarding a viral etiology for ITP, we performed a comprehensive study to explore its possible relationship to B19 infection. PATIENTS AND METHODS: Thirty-five previously healthy children with ITP were studied prospectively. Bone marrow and peripheral blood were analyzed for B19 DNA using the polymerase chain reaction (PCR). Serum was analyzed for anti-B19 immunoglobulin (Ig) M and IgG antibodies using a B19 VP1 antigen-based enzyme-linked immunosorbent assay. Fourteen healthy children served as controls for peripheral blood PCR and serologic analyses. RESULTS: The presenting clinical and laboratory features of the study population were typical of classic ITP. Seventeen of the 35 patients (49%) had evidence of B19 DNA in the peripheral blood, bone marrow, or both. Six of 35 (17%) had anti-B19 IgM antibodies. Eight of 35 (23%) were anti-B19 IgG seropositive. The control group had no positive PCR or anti-B19 IgM specimens. CONCLUSIONS: Our results suggest that infection with human parvovirus B19 may be associated with childhood ITP. More investigation is warranted regarding the role of PCR methodology and serologic detection methods in defining B19 pathobiology as it relates to ITP.