Rapid detection of herpes simplex virus (HSV) antigen in human ocular infections.

The new HERPCHEK (Dupont, No. Billerica, MA) enzyme immunosorbent assay (EIA) was used in a double-blind clinical study for rapid and specific detection of ocular herpes simplex virus (HSV) infection. This 4-hour assay can be used to demonstrate conclusively the presence of HSV antigen without culture and thereby rapidly differentiate between HSV and other clinically similar ocular infectious diseases. Ocular samples were collected from 180 individuals including 30 patients with acute HSV, 90 with latent HSV (ie, currently asymptomatic but with a positive history), 11 with acute or latent varicella zoster virus, 30 with nonherpetic infections (due to adenovirus, Acanthamoeba or bacteria), and 19 normal controls. A clinical diagnosis was made by one of us (DPL) and duplicate tear-film samples obtained by swabbing the conjunctival cul-de-sac and cornea. Coded samples were tested by routine viral culture on Vero cell monolayers and also were run independently in the HERPCHEK test. During active HSV infection, the HERPCHEK correlated 100% with clinical diagnosis, and virus culture correlated 90% with clinical diagnosis. In all latent HSV ocular infections, other nonherpetic ocular infections and normal samples, both the HERPCHEK and culture assays were negative.

Widespread outbreaks of clam- and oyster-associated gastroenteritis. Role of Norwalk virus.

Consumption of raw shellfish has long been known to be associated with individual cases and sporadic outbreaks of enteric illness. However, during 1982, outbreaks of gastroenteritis associated with eating raw shellfish reached epidemic proportions in New York State. Between May 1 and December 31, there were 103 well-documented outbreaks in which 1017 persons became ill: 813 cases were related to eating clams, and 204 to eating oysters. The most common symptoms were diarrhea, nausea, abdominal cramps, and vomiting. Incubation periods were generally 24 to 48 hours long, and the duration of illness was 24 to 48 hours. Bacteriologic analyses of stool and shellfish specimens did not reveal a causative agent. Norwalk virus was implicated as the predominant etiologic agent by clinical features of the illness and by seroconversion and the formation of IgM antibody to Norwalk virus in paired serum samples from persons in five (71 percent) of seven outbreaks in which testing was done. In addition, Norwalk virus was identified by radioimmunoassay in clam and oyster specimens from two of the outbreaks. Determining the source of the shellfish was not always possible, but northeastern coastal waters were implicated. The magnitude, persistence, and widespread nature of these outbreaks raise further questions about the safety of consuming raw shellfish.

An outbreak of Norwalk-related gastroenteritis at a boys' camp.

An acute gastrointestinal tract illness affected 213 (52%) of 407 campers and 64 (53%) of 121 staff members attending a boys' camp in the Catoctin Mountains of Maryland during the summer of 1981. Nausea was the predominant symptom for ill campers and staff members (73%), but more staff members experienced diarrhea (49%) than did campers (9%). Twenty-three individuals had more than one episode of illness compatible with the case definition. Eight of nine paired blood specimens from ill staff members showed a fourfold increase in antibody titer to Norwalk virus by radioimmunoassay. Environmental inspections and laboratory tests failed to implicate a common source of exposure.

Serological responses among teenagers after natural exposure to Norwalk virus.

Twenty-one teenagers exposed to a contaminated water supply during an outbreak of gastroenteritis were tested for seroconversion to Norwalk virus. Serum specimens were collected within 72 hr of exposure and four weeks later. Each of the 11 individuals who developed symptoms and five of the 10 who remained well had a whole-antibody response in serum. None of the remaining five teenagers became ill or seroconverted. Neither seroconversion nor susceptibility to illness was associated with an absence of detectable antibody from acute-phase serum specimens. These findings support the view that immunity to Norwalk virus is not determined by serum antibody. Furthermore, the results are consistent with the possibility, suggested by previous studies in volunteers, that susceptibility is determined by Norwalk virus-specific intestinal receptor sites. IgM responses to the Norwalk virus were detected in only seven persons who became ill (64%) and nine who seroconverted (56%). The seroassay for the Norwalk IgM component might have proved a more sensitive diagnostic tool in this outbreak if convalescent-phase specimens had been collected sooner than four weeks after the onset of illness.

Detection of rotavirus in human stools by using monoclonal antibody.

A monoclonal antibody, 3F7, that reacts with the common rotavirus antigen on the sixth viral gene product was prepared. It was used in a direct monoclonal antibody radioimmunoassay (RIA) as a diagnostic reagent for detection, in 3.5 h, of rotavirus in human pediatric stool specimens. In the 177 samples tested, a concordance of 96% was seen between the monoclonal RIA and the well-established and commonly used commercially available Rotazyme test. Six discrepant specimens that were positive by monoclonal RIA but negative by Rotazyme were shown to be positive by either electron microscopy or confirmatory blocking immunoassay. A seventh discrepant specimen was positive by Rotazyme and negative by monoclonal RIA as well as by both direct and immune electron microscopy. The monoclonal RIA test appears to be highly sensitive and specific, and merits additional evaluation as a rapid, convenient diagnostic assay that can reduce currently encountered problems associated with diagnosing rotavirus infection by immunoassay.

A community waterborne gastroenteritis outbreak: evidence for rotavirus as the agent.

A community waterborne nonbacterial gastroenteritis outbreak occurred in Eagle-Vail, Colorado in March 1981. Illness (defined as vomiting and/or diarrhea) was statistically associated with water consumption (chi 2 for linear trend = 7.07, p less than .005). Five of seven persons associated with the outbreak were infected with rotavirus as shown by virus detection or serological methods. Bacterial pathogens, Giardia lamblia, and Norwalk virus were excluded as responsible agents. Rotavirus should be looked for as a cause of waterborne outbreaks.

Comparative analysis of serum antibody responses to Pseudomonas aeruginosa exotoxin A by cystic fibrosis and intensive care unit patients.

Pulmonary infection with Pseudomonas aeruginosa is a major cause of morbidity and mortality in cystic fibrosis (CF) patients. P. aeruginosa toxin is one of several proposed virulence factors which may be responsible for chronic P. aeruginosa infections in these patients. With a highly specific, sensitive, and quantitative radioimmunoassay (RIA) and a cell culture assay, the humoral immune responses of CF patients in terms of total antitoxin, antitoxin immunoglobulins A and M, and neutralizing antitoxin were compared with those of P. aeruginosa-infected intensive care unit patients and controls. The P. aeruginosa-infected CF patients were divided into severe and moderate disease groups based on mortality observed over an 8-year period. The intensive care unit patients were divided by the site of infection and the controls were healthy children and uninfected CF patients. Antibodies to toxin were found in the sera of all subjects by radioimmunoassay. Neutralizing antibody was associated with current infection. Elevated titers of antitoxin immunoglobulin A were found only in subjects with pulmonary P. aeruginosa infections. No significant differences in any antibody class were observed between the severe and moderate disease groups. In addition, no differences were observed in the antitoxin immune response of chronically infected CF patients and intensive care unit patients with acute pulmonary infections.

Rotavirus as a cause of severe gastroenteritis in adults.

Rotavirus was identified as the only etiological agent in 5% of adults (28 of 526) with diarrhea who were admitted to Bamrasnaradura Hospital in Nonthaburi, Thailand, during a 1-year period. Infection was determined by detection of rotavirus in diarrheal stools by enzyme-linked immunosorbent assay accompanied by a greater than fourfold rise in serum complement fixation and radioimmunoassay antibody titers to rotavirus. Adults with clinical rotavirus infections were as severely ill as patients with most bacterial enteric infections; only patients with cholera passed more watery stools and were more dehydrated than those with rotavirus infections. Only 2 of the 28 adults with rotavirus infections had known recent contact with young children with diarrhea. Rotavirus infections in these adults occurred most frequently in the cooler, drier months in Thailand than during the rest of the year. In some settings, rotavirus should be considered in the differential diagnosis of severe diarrhea in adults as well as in young children.

Age-specific prevalence of antibody to rotavirus, Escherichia coli heat-labile enterotoxin, Norwalk virus, and hepatitis A virus in a rural community in Thailand.

A serological survey in rural Thailand demonstrated that inhabitants acquired antibody to rotavirus between the ages of 6 months and 6 years, to Norwalk virus between the ages of 4 and 5 years, and to hepatitis A between the ages of 6 and 35 years. Antibody of Escherichia coli heat-labile toxin was most prevalent between 1 and 4 years and 18 and 25 years of age.

Immunoglobulin M responses to the Norwalk virus of gastroenteritis.

Eighty-seven serum specimens from 20 human subjects experimentally inoculated one or more times with Norwalk virus were quantitatively examined for virus-specific immunoglobulin M (IgM). A sensitive and specific radioimmunoassay for anti-Norwalk virus blocking activity was applied to whole serum and to separate IgM and IgG fractions obtained by sucrose density gradient ultracentrifugation. The peak IgM response occurred at about 2 weeks after illness, but IgM was detectable at lower titers for up to 21 weeks after infection. The IgM response was seen in volunteers who became ill, whether or not prechallenge total serum antibody was present. On long-term (27 to 42 months) rechallenge, volunteers who were previously ill and had produced IgM antibody again developed illness, and a secondary IgM response greater than the first was detected. Inoculated volunteers who did not develop illness, as well as previously ill volunteers on short-term rechallenge (4 to 14 weeks), usually failed to generate an IgM response, whether or not an IgG response had occurred. In ill subjects, the rise in IgM and IgG occurred concomitantly. Virus-specific IgM is not necessarily indicative of primary infection with Norwalk agent inasmuch as reinfection produces an enhancement of the IgM response. Furthermore, Norwalk-specific IgM responses do not appear to be associated with subclinical illness.

Affinity chromatography purification of Pseudomonas aeruginosa exotoxin A on specifically linked NAD agarose.

The specific binding of P. aeruginosa exotoxin A to NAD was exploited for the rapid purification of the toxin. Affinity chromatography on a column of agarose-N6-(aminohexyl)carbamoylmethyl-NAD resulted in an enzymatically, biologically, and immunologically active purified toxin preparation. Other NAD-agarose resins were not efficient substrates for toxin purification.

Antibodies to gastroenteritis viruses in cystic fibrosis patients.

Infectivity of certain enteric viruses including rotavirus is profoundly affected by proteolytic enzymes. To test whether cystic fibrosis patients, possessing chronically decreased levels of pancreatic enzymes, show altered susceptibility to gastroenteritis viruses, we examined sera from patients and controls for antibodies to two major pathogens. In cystic fibrosis patients, normal rotavirus antibody levels were found and Norwalk virus antibody prevalence was unchanged.

Susceptibility of mice to rotavirus infection: effects of age and administration of corticosteroids.

We examined susceptibility to the murine rotavirus, epizootic diarrhea of infant mice virus (EDIM), in normal suckling and weaned mice and in suckling mice treated with glucocorticoids. Normal mice 1 to 40 days old were inoculated by gastrin intubation with high doses of EDIM and subsequently evaluated for rotavirus infection by solid-phase radioimmunoassay, by electron microscopy of intestinal tissue sections or by both. Radioimmunoassay and electron microscopy showed a concordance of 89.5% in the detection of rotavirus infection. After a period of low susceptibility to EDIM infection during the first 3 days after birth (23%), susceptibility was high for the next 11 days (95%), but decreased abruptly as mice approached weaning (41% on days 15 through 17). Mice 34 days or older did not develop EDIM infection after inoculation, but rotavirus antigen was detected in 12% of uninoculated mothers nursing inoculated litters. Administration of cortisone acetate to 8-day-old mice induced partial intestinal maturation prematurely. At 3 to 6 days after cortisone acetate treatment, susceptibility to EDIM infection decreased to 60% compared with 94% in age-matched controls. Our data suggest (i) that susceptibility of mice to EDIM infection is age dependent, decreasing in concert with intestinal maturation, and (ii) that glucocorticoids, which induce premature partial intestinal maturation, modulate susceptibility of mice to EDIM.

Travelers' diarrhea among American Peace Corps volunteers in rural Thailand.

Diarrheal disease was studied prospectively in 35 Peace Corps volunteers during their first five weeks in rural Thailand. Twenty (57%) developed the syndrome of travelers' diarrhea. Recognized bacterial enteric pathogens were isolated from stools during 47% of 39 episodes of travelers' diarrhea. Enterotoxigenic Escherichia coli was isolated during 26% and Shigella during 13% of the episodes. Of the 20 volunteers, 50% had bacteriologic and/or serologic evidence of infection with enterotoxigenic E. coli. Sixty-one percent of isolates of enterotoxigenic E. coli and 92% of isolates of Shigella were resistant to doxycycline. Other enteric pathogens, including Campylobacter jejuni/coli, Yersinia enterocolitica, Salmonella, rotavirus, Norwalk agent, and Entamoeba histolytica, were associated with episodes of travelers' diarrhea. Aeromonas hydrophila, isolated from 31% of 39 episodes of travelers' diarrhea, was of unknown pathogenic importance. Thus, episodes of travelers' diarrhea in Thailand were associated with a variety of organisms, among which antibiotic-resistant bacterial enteropathogens were common.