Increased detection of herpes simplex virus in MRC-5 cells treated with dimethyl sulfoxide and dexamethasone

Physical and chemical methods for enhancing rapid detection of viruses and other agents

Viral replication events can be enhanced by physical, chemical, or heat treatment of cells. The centrifugation of cells can stimulate them to proliferate, reduce their generation times, and activate gene expression. Human endothelial cells can be activated to release cyclo-oxygenase metabolites after rocking for 5 min, and mechanical stress can stimulate endothelial cells to proliferate. Centrifugation of virus-infected cultures can increase cytopathic effects (CPE), enhance the number of infected cells, increase viral yields, and reduce viral detection times and may increase viral isolation rates. The rolling of virus-infected cells also has an effect similar to that of centrifugation. The continuous rolling of virus-infected cultures at < or = 2.0 rpm can enhance enterovirus, rhinovirus, reovirus, rotavirus, paramyxovirus, herpesvirus, and vaccinia virus CPE or yields or both. For some viruses, the continuous rolling of infected cell cultures at 96 rpm (1.9 x g) is superior to rolling at 2.0 rpm for viral replication or CPE production. In addition to centrifugation and rolling, the treatment of cells with chemicals or heat can also enhance viral yields or CPE. For example, the treatment of virus-infected cells with dimethyl sulfoxide can enhance viral transformation, increase plaque numbers and plaque size, increase the number of cells producing antigens, and increase viral yields. The infectivity of fowl plague virus is increased by 80-fold when 4% dimethyl sulfoxide is added to culture medium immediately after infection. The heat shocking of virus-infected cells also has been shown to have a stimulatory effect on the replication events of cytomegalovirus, Epstein-Barr virus, and human immunodeficiency virus. The effects of motion, chemicals, or heat treatments on viral replication are not well understood. These treatments apparently activate cells to make them more permissive to viral infection and viral replication. Perhaps heat shock proteins or stress proteins are a common factor for this enhancement phenomenon. The utility of these treatments alone or in combination with other methods for enhancing viral isolation and replication in a diagnostic setting needs further investigation.

HHV-6 inhibition by two polar compounds

Dimethyl sulphoxide and dimethyl formamide, two polar compounds and powerful cell differentiation inducers, inhibit HHV-6 infection when added to HHV-6-infected HSB2 cultures. This was established by a delay in the time-course of infection and in the development of virus-induced cytopathic effects. Furthermore, viral titration of supernatants showed a significant reduction (3 log10) of the number of infectious particles. Electron microscopy confirmed that viable cells and extracellular virions were present in the cultures containing the polar compounds, while in the non-treated cultures all cells were lysed and no extracellular virus was evident. The mode of action of these compounds is still unclear and warrants further investigation.

Pneumonitis associated with coinfection by human herpesvirus 6 and Legionella in an immunocompetent adult

The authors report a case of pneumonitis in a young healthy man caused by coinfection with human herpesvirus 6 (HHV-6) and Legionella pneumophila. The patient's course was complicated by severe respiratory, renal, hepatic, and central nervous system dysfunctions, which were believed to be primarily the results of his Legionella infection. Aggressive antibiotic treatment produced no response, and Legionella remained isolatable from lung tissue throughout several weeks of antimicrobial therapy. Human herpesvirus 6 was isolated from a sample of peripheral blood during the acute stage of the patient's illness, and numerous HHV-6--infected macrophages and lymphocytes were detected by immunohistochemical staining of biopsy-derived lung tissue. Paradoxically treatment of the patient with high-dose corticosteroids resulted in dramatic improvement of his condition, including clearance of the Legionella infection. The demonstration that corticosteroids efficiently inhibit HHV-6 replication in vitro suggests that the virus may have contributed to the patient's pneumonitis by enhancing tissue inflammation, by compromising the function of pulmonary macrophages, and, perhaps, by destroying the patient's CD4+ T lymphocytes. Human herpesvirus 6 may be able to function as a synergistic cofactor in lung infections by Legionella and other pathogens.

Comparison of enzyme immunoassay, shell vial culture, and conventional cell culture for the rapid detection of herpes simplex virus

Specimens submitted for the detection of herpes simplex virus (HSV) were inoculated into conventional cell-culture tubes and fresh MRC-5 shell vials. The shell vial centrifugation cultures (SVCs) were examined at 16 hr postinoculation for HSV by using type-specific monoclonal antibodies (SVC-FA); they were also analyzed for HSV antigen by using an enzyme-linked immunoassay (SVC-ELISA). Mink Lung (ML) and rhabdomyosarcoma (RD) cells were used in the cell-culture tubes. Of 182 specimens, 35 (19%) were positive in cell-culture tubes, 16 (9%) were positive by SVC-ELISA, and 22 (12%) were positive SVC-FA. All specimens that were positive by SVC-ELISA, SVC-FA, and in culture tubes displayed cytopathic effect (CPE) at 16 hr. Those specimens that had a negative ELISA and/or FA result and were positive in culture were evaluated for the time in which it took to detect CPE. At 16 hr, 48% of the positive tubes were detected; at 40 hr (second day), 83% of the positive tubes were detected; and by the third day, 94% were detected. The RD cell line displayed CPE at the same time or earlier than ML cells did in 92% of the positive cases. The sensitivity of the SVC-ELISA at 16 hr was 46% with 100% specificity. The sensitivity of the SVC-FA at 16 hr was 63% with 99% specificity. Given the increased sensitivity, rapid display of CPE, and reduced cost and handling time of cell cultures, our laboratory found that rapid SVC-ELISA and SVC-FA procedures for HSV detection have no clinical or laboratory advantage.