Usefulness of two new methods for diagnosing metapneumovirus infections in children

Human metapneumovirus (hMPV) is associated with acute respiratory tract infections, mainly in paediatric patients. The aim of this study was to evaluate the usefulness of two new commercial techniques available for the detection of hMPV in clinical samples from children: an enzyme immunoassay, hMPV EIA (Biotrin International Ltd), and a molecular assay, real-time RT-PCR (Pro hMPV Real Time Assay Kit; Prodesse). A total of 184 nasopharyngeal aspirate specimens from 173 children aged less than 5 years who were hospitalized with acute wheezing were analysed. Respiratory syncytial virus was detected in 27% of the samples, followed by influenza A virus (6%), parainfluenza virus (PIV)3 (2.2%), adenovirus (2%), PIV1 (1.1%), PIV2 (1.1%), and influenza B virus (0.5%). The presence of hMPV was tested in all samples, using the real-time RT-PCR and EIA. Real-time RT-PCR detected 13 hMPV-positive samples (8%), and EIA detected 17 (9.3%). When the EIA results were compared with those of real-time RT-PCR for the detection of hMPV, a good correlation was found (94%). A relatively low co-infection rate (15%) was observed in our patients. RT-PCR and EIA provide robust methods for the diagnosis of hMPV infection in children.     

Rapid diagnosis of influenza: a comparative evaluation of different methods

The results of influenza diagnosis during the outbreak of 1985 are presented. Nasopharyngeal secretions from 94 patients were examined by virus isolation in chick embryos, fluorescent antibody technique (FAT). enzyme-immunoassay (EIA), and dot-blot hybridization method (DBHM). The virus was isolated in 28%, FAT was positive in 22%, EIA in 47% of the cases. Among 94 secretion specimens 40 were tested by DBHM. In this instance, virus was isolated in 37%, EIA was positive in 65%, and DBHM in 85% of the cases. It seems advisable to use EIA based on the detection of the type-specific antigen (matrix protein) and DBHM which identifies the serovariant of influenza virus.     

Comparison of four immunoserologic assays for detection of antibodies to Borrelia burgdorferi in patients with culture-positive erythema migrans.

In view of the significant sequelae associated with Lyme borreliosis, there is a need for timely and accurate diagnosis of erythema migrans (EM). Although Borrelia burgdorferi can be cultured from biopsies of EM lesions, immunodiagnostic testing is more widely available. Four immunoserologic methods were studied by using the sera of 51 patients with EM lesions that were culture positive for B. burgdorferi. Nineteen patients had single primary lesions, and thirty-two had multiple secondary lesions. At the time of biopsy, 40 patients, 8 with primary lesions and all patients with secondary lesions, were seropositive by an immunoglobulin M (IgM) indirect fluorescent-antibody (IgM IFA) test (Bion Enterprises). Twenty-three patients were seropositive by a whole-cell fluorescence enzyme immunoassay (EIA) (BioWhittaker, Inc.), twenty-two were positive by immunoblotting (ViroStat, Inc.), and one was positive by a P39 recombinant EIA (P39 EIA) (General Biometrics, Inc.). Sera from various patient control groups were tested: rheumatoid arthritis (n = 19), infectious mononucleosis (n = 20), systemic lupus (n = 22), syphilis (n = 13), streptococcal sequelae (n = 20), and healthy subjects (n = 16). None of these sera reacted with the IgM IFA test or P39 EIA. Fifteen reacted with the fluorescence EIA. We conclude that the IgM IFA test is an effective and reliable assay for the diagnosis of EM, particularly for patients with secondary lesions. Immunoblot, fluorescence EIA, and P39 EIA lack the sensitivity to reliably diagnose EM.     

Astrovirus as a cause of gastroenteritis in Japan.

We used an enzyme immunoassay (EIA) to screen for astrovirus in stool specimens from outbreaks and sporadic cases of gastroenteritis collected between 1982 and 1992 in six prefectural public health institutes in Japan. Three outbreaks of gastroenteritis involving schoolchildren and adults were confirmed to be attributable to astrovirus. Astrovirus was detected in 6 to 10% of the specimens from patients with sporadic gastroenteritis from whom no other bacterial or viral agent had been identified. Among the sporadic cases, astrovirus was most frequently detected in infants less than 1 year of age, and the incidence peaked in March and April. Using specimens from recent outbreaks, we found that the EIA was more sensitive than electron microscopy (EM) for the detection of astrovirus, and many EM-negative specimens were positive by EIA. However, some stool specimens previously found to have astrovirus-like particles by EM were negative by EIA, perhaps because of inadequate storage conditions, such as long-term storage and repeated freezings and thawings. Our results indicate that astrovirus is more commonly associated with childhood gastroenteritis than has been previously appreciated and suggest that further studies to examine the epidemiology and disease burden of this virus are needed.     

Detection of Norwalk Virus and Other Genogroup 1 Human Caliciviruses by a Monoclonal Antibody, RecombinantAntigen-Based Immunoglobulin M Capture Enzyme Immunoassay

Sera obtained from two groups of adult volunteers infected with Norwalk virus (NV) and two groups of patients involved in two natural outbreaks were tested for NV-reactive immunoglobulin M (IgM) by use of a monoclonal antibody, recombinant-antigen-based IgM capture enzyme immunoassay (EIA). No NV-reactive IgM was detected in the preinoculation sera of 15 volunteers, and 14 of 15 showed NV-reactive antibodies postinfection with NV. All of the volunteers showed IgG seroconversion to NV. In the outbreak studies, all 9 persons in one outbreak and 19 of 24 in another outbreak had NV-reactive IgM. In the first outbreak, only three of nine seroconverted to NV, which was likely due to late collection of acute-phase sera. In the second outbreak, 21 of 24 showed IgG seroconversion to NV. Sequencing of viruses isolated from five stool samples selected from those in the second outbreak showed that they were human calicivirus (HuCV) genogroup 1 viruses related, but not identical, to NV. In the volunteer studies, NV-reactive IgM was first detected 8 days postinoculation. The time of development of NV-reactive IgM antibodies in natural outbreaks was estimated to be similar to that found in the volunteer studies. Sera from three Hawaii virus-infected volunteers, four Snow Mountain virus patients, and 80 healthy individuals were negative for NV-reactive IgM, indicating test specificity for HuCV genogroup I infections. This capture IgM EIA is suitable for diagnosis of NV and other HuCV genogroup I infections and is especially useful when sera and fecal samples have not been collected early in the course of an outbreak.     

Rotavirus etiology of hospital cases of acute gastroenteritis

The etiology of enteric illnesses occurring during hospitalization in children admitted in January-May, 1985, for respiratory tract illnesses was studied by several methods including electron microscopy (EM), enzyme immunoassay (EIA), and PAG electrophoresis. Rotaviruses were detected in 22 (44.9%) t of 49 children with symptoms of intestinal infection, in February in 11 (84.6%) out of 13 patients. The analysis of virus genome RNA of 7 isolates positive in EM and EIA revealed in all the isolates an identical pattern of RNA segment distribution typical of "long" variants of group A rotaviruses. The appurtenance of the isolates to the same electrophoretic type together with epidemiological data allows the examined cases of rotavirus gastroenteritis to be considered as nosocomial ones. A sporadic case of gastroenteritis is described induced by a rotavirus antigenically different from Group A rotaviruses and having the electrophoretic type similar to that described for group C rotaviruses.     

Evaluation of a commercial measles virus immunoglobulin M enzyme immunoassay.

Paired serum samples from 93 patients suspected of having measles were assayed for measles virus-specific immunoglobulin M (IgM) antibodies by an enzyme immunoassay (EIA), and the results were compared with results from a complement fixation assay and an EIA for measles virus IgG. By using significant serologic rises as the standard for comparison, the IgM EIA assay had a sensitivity of 85.7%, a specificity of 81.3%, a positive predictive value of 95.7%, and a negative predictive value of 54.2%. This assay can be expected to perform well in outbreak situations.