Glucose elevates ornithine decarboxylase expression in Vero cells.

The addition of Earle's balanced salt solution (EBSS) of amino acids that are transported by a Na+-dependent cotransport system was not required by Vero cells for ornithine decarboxylase (ODC:EC 4.1.1.17) amplification. Vero cell ODC activity was elevated tenfold above basal levels when confluent cells were incubated for 5 hr in EBSS alone. ODC activity increased as a function of the incubation time in EBSS and was not elevated above basal enzyme levels when cells were incubated in EBSS minus glucose. ODC expression increased as a function of the glucose concentration in EBSS, with 20 mM glucose producing a 90-fold increase in ODC activity. ODC expression is more responsive to glucose in high-density quiescent cultures than in low-density growing cultures. Enhanced ODC expression by glucose depended on Na+ and K+ concentrations. The specific activity of ODC was also elevated above basal levels when mannose or fructose replaced glucose in EBSS. The addition of alanine or asparagine to EBSS enhanced ODC activity above levels obtained with EBSS containing standard (5.5 mM) glucose concentrations. In the absence of glucose, alanine was more effective than asparagine in enhancing ODC expression. These results suggest that the transport of amino acids is not an absolute requirement for Vero cell ODC expression and that ODC expression is linked to changes in cellular energetics and/or ion fluxes.

Diagnostic efficacy of two rapid tests for detection of respiratory syncytial virus antigen.

With the availability of ribavirin therapy for serious respiratory syncytial virus (RSV) infections, rapid diagnostic tests for the detection of RSV antigen are increasingly important. Efficacies of a commercially available enzyme immunoassay (EIA) (Abbott Laboratories, North Chicago, Ill.) and a fluorescent-antibody assay (FA) were evaluated in a study involving 135 specimens from children with respiratory symptoms. A nasal wash specimen was cultured immediately on RSV-sensitive A549 cells; the nasal wash was also used for EIA. FA was performed on a nasopharyngeal swab specimen with bovine anti-RSV and anti-bovine immunoglobulin G antisera (Burroughs Wellcome Co., Research Triangle Park, N.C.). A total of 39 specimens (28%) were tissue culture positive, including 35 EIA-positive and 37 FA-positive samples (sensitivities, 90 and 95%, respectively). All 96 tissue culture-negative specimens were EIA negative (specificity, 100%); 94 of these 96 specimens were FA negative (specificity, 98%). Positive and negative predictive values for the tests were as follows: 100 and 96% for EIA, respectively, and 95 and 98% for FA, respectively. Other viruses, including influenza A virus, adenovirus, enterovirus, and herpes simplex virus, were isolated in nine cases. One adenovirus-positive specimen had a false-positive RSV FA result; all nine specimens were RSV EIA negative. Both tests performed well in our study and provide cost-effective alternatives to tissue culture. The RSV EIA, in particular, uses standard serologic techniques and equipment and does not require expertise in virology. More widespread availability of rapid diagnostic tests for RSV will hopefully result in early and appropriate use of antiviral therapy in patients at risk for serious RSV infections.

Experimental primary cytomegalovirus infection in pregnancy: timing and fetal outcome.

In contrast to intrauterine rubella infection, the relationship between timing of maternal cytomegalovirus (CMV) infection and fetal outcome has not been clearly defined. In order to investigate this relationship, a guinea pig model was utilized to assess the fetal consequences of maternal CMV infection during the first, second, or third trimester of pregnancy. Congenital infection occurred in 24 of 35 newborn guinea pigs (69%) delivered to mothers infected during the third trimester, with localization of virus to salivary gland in 17 of the 24 infected newborn guinea pigs. In contrast, only one of 28 (5%) progeny sacrificed following first-trimester maternal infection was congenitally infected (p less than 0.01). Second-trimester maternal infection was associated with an intermediate risk of intrauterine infection with transmission of virus to 17 of 54 progeny (33%) (p less than 0.01). Eight of the 10 fetuses delivered after second-trimester infection had virus in multiple organs including the brain. These data suggest that timing of maternal CMV infection is an important variable affecting fetal outcome, with increased risk of intrauterine infection when maternal infection occurs late in pregnancy. However, if fetal infection occurs earlier in pregnancy, it appears to present a greater threat to the fetus, with the potential for dissemination of virus in multiple fetal tissues, including the brain.