Production of antiserum to respiratory syncytial virus polypeptides: application in enzyme-linked immunosorbent assay

A rapid test for detection of respiratory syncytial virus in nasopharyngeal secretion

A new rapid membrane enzyme immunoassay (MEIA; Directigen RSV) for detection of respiratory syncytial virus (RSV) was evaluated using samples of nasopharyngeal secretion from infants and children with acute respiratory disease. The MEIA was compared with an immunofluorescent antibody (IF) technique using a sensitive biotin-avidin (BA) EIA as reference. Of 242 samples tested, 108 were positive by the MEIA and 123 by the BA-EIA. Of 144 samples which were also tested by the IF technique, 57 were positive by the BA-EIA and 43 by the IF technique. These results give a sensitivity of 86% and 72% for the MEIA and IF technique respectively. Of 57 samples found to be positive by the BA-EIA, 41 were positive by the IF technique, but 48 were positive by the MEIA. The MEIA is thus more sensitive than the IF technique but less sensitive than the BA-EIA in detecting RSV in nasopharyngeal secretions.

Sensitive enzyme immunoassay for the rapid diagnosis of influenza A virus infections in clinical specimens

Samples of nasopharyngeal secretion (NPS) from 100 infants and small children admitted for acute respiratory disease during the period from January to March 1989 were examined for the presence of influenza A virus. All samples were tested by enzyme immunoassay (EIA), fluorescent antibody (FA) technique and by isolation in cell culture 3-6 h after they were obtained from the patients. Of 24 influenza strains found by isolation, 21 were detected by EIA and 19 were FA+. In comparison with virus isolation, EIA gave the following values: sensitivity 88%, specificity 100%, positive prognostic value (PPV) 100%, and negative prognostic value (NPV) 96%. A rabbit anti-influenza-A serum (A-13) was used as catching antibody and a monoclonal anti-influenza-A pool against NP protein was used as detector antibody in EIA. A-13 gave bands corresponding to influenza A core proteins (NP and M1) in Western blot (WB) studies when different H3N2 strains were employed as antigens. A-13 gave only a band corresponding to the NP protein when H1N1 strains were examined by WB. The detection level by EIA for both H3N2 and H1N1 strains precipitated by polyethylene glycol from tissue culture maintenance medium was 1-2 ng.

Chest X-ray appearances in pneumonia and bronchiolitis. Correlation to virological diagnosis and secretory bacterial findings

Chest X-ray findings were related to virus diagnosis, age and secretory bacterial findings in 128 infants and children under 7 years of age with clinical pneumonia and bronchiolitis. They belonged to a cohort examined in connection with the introduction of rapid methods for virological diagnosis. Seventy-six children had a virus infection diagnosed by examination of nasopharyngeal secretion and/or by serological methods. Thirty-seven of these children were classified as having pathogenic bacteria of importance in the respiratory tract. Four groups were compared: virus infected children with or without bacteria in the secretion and the corresponding virus negative groups. The X-rays were normal significantly more often in the virus positive/bacteria negative group compared with the other groups. Alveolar pneumonia appearing as lobar or segmental consolidations ("lobar" pneumonia) was observed with equal frequency and without relation to bacterial findings in the virus positive and the virus negative groups. But it was more often observed in the respiratory syncytial virus (RSV) infected children under 6 months of age compared with the older RSV children. In comparison disperse alveolar infiltrations ("bronchopneumonia") mostly appeared in the virus positive group. Interstitial pneumonia and peribronchitis were often present together in children over 6 months of age. There was no significant difference in the X-ray appearances in the groups with and without bacterial findings in the tracheal secretion except for a higher frequency of normal chest radiographs in the bacteria negative group.

Detection of respiratory syncytial virus and rotavirus by enhanced chemiluminescence enzyme-linked immunosorbent assay

The horseradish peroxidase-catalyzed oxidation of luminol was used in a chemiluminescence avidin-biotin enzyme-linked immunosorbent assay (CL-ABE) to detect respiratory syncytial virus (RSV) and rotavirus (ROV). This CL-ABE was carried out in a new apparatus constructed for the photographic registration of the light emission produced. When measured in a spectrophotometer, the light emission produced by the oxidation of luminol showed a peak emission at 425 nm. The chemiluminescence output reached maximum within 1 min after the initiation of luminol oxidation and diminished to one-half of maximum emission within 8 min. When titrations of purified ROV by avidin-biotin enzyme-linked immunosorbent assay (ABE) were monitored by CL-ABE and by conventional orthophenylenediamine (OPD) staining (OPD-ABE), the detection limits were 0.01 and 0.04 ng of ROV protein, respectively. Similar titrations of purified RSV gave detection limits of 0.2 and 0.8 ng of RSV protein by CL-ABE and OPD-ABE, respectively. When 26 RSV-positive samples of nasopharyngeal secretions (NPS) were titrated by CL-ABE and by OPD-ABE, the mean titers obtained were 737 and 254, respectively. When 19 ROV-positive fecal samples were titrated by CL-ABE and by OPD-ABE, the mean titers obtained were 82,000 and 29,000, respectively. When samples of NPS from 123 infants and children with acute lower respiratory disease were tested for the presence of RSV, 31 NPS samples were RSV positive by CL-ABE, and 29 of these 31 NPS samples were RSV positive by OPD-ABE.

Detection of respiratory syncytial virus in nasopharyngeal secretions by a biotin-avidin ELISA more sensitive than the fluorescent antibody technique

The presence of respiratory syncytial virus (RSV) was investigated by immunofluorescent antibody (IF) technique and by a biotin/avidin (BA) ELISA in 156 samples of nasopharyngeal secretions (NPS) obtained from infants and small children with acute respiratory disease. Of 70 RSV-IF-positive NPS, 68 were positive by BA-ELISA. Of 86 RSV-IF-negative NPS, eight were positive by BA-ELISA. BA-ELISA could detect 0.5-1.0 ng RSV-protein.

Detection of RS-virus IgG-subclass-specific antibodies: variation according to age in infants and small children and diagnostic value in RS-virus-infected small infants

The variation according to age of RS-virus IgG-subclass specific antibodies was investigated by ELISA in 140 acute phase sera from 140 infants and children 1-47 mo of age who were hospitalized with acute respiratory disease. Sixty-nine of these serum samples were obtained from patients with RS-virus infections. Mean OD values of IgG-1 antibodies decreased corresponding to the decrease in maternal antibodies. In patients with RS-virus infections, the mean IgG-1 OD values increased in children who were 3 yr old, but in patients without RS-virus infections this increase was observed in children at 1 yr of age. RS-virus IgG-3 antibodies were detected only in children 1-3 yrs of age, and only in 18% of samples from children without RS-virus infections. The concept of the transient nature of RS-virus IgG-3 antibodies as compared with RS-virus IgG-1 antibodies is supported by these results. RS-virus subclass specific antibodies were studied in paired serum samples from 12 infants 1-5 mo of age with acute lower RS-virus disease. IgG-1 antibodies developed in six infants, but only in one of six infants aged 1-3 mo. IgG-3 antibodies developed in nine infants, including four of six infants who were 1-3 mo old. These results suggest that in small infants with RS-virus infections the detection of IgG-3 antibodies is of higher diagnostic value than the detection of IgG-1 antibodies.

Detection by ELISA of IgG-subclass-specific antibodies in primary respiratory syncytial (RS) virus infections

The IgG-subclass specific antibody response was investigated in primary RS-virus infections in infants and small children by using an ELISA with monoclonal antibodies against the four human IgG subclasses. When 78 serum samples obtained from 21 patients during the first 3-4 mo following the onset of illness were studied, only IgG-1 and IgG-3 antibodies could be detected. Both of these subclass specific antibodies appeared during the second week following the beginning of illness. Approximately 4 wk after the onset of illness, IgG-1 antibodies reached maximum levels, which persisted during the following months. Approximately 3 wk after the onset of illness, IgG-3 antibodies reached maximum levels, which decreased during the following months. Both IgG-1 and IgG-3 antibodies showed neutralizing capacity.

Antibiotic treatment of pneumonia and bronchiolitis. A prospective randomised study

Routine administration of antibiotics in the treatment of pneumonia and bronchiolitis in infants and small children was evaluated in an open randomised prospective trial. From 1979-82 136 children between the age of 1 month and 6 years were allocated to one of two treatment groups shortly after their admission to a paediatric ward. Group A patients were to be given antibiotics but those in group B were not. None of the children had received antibiotics before hospital admission. A viral infection was diagnosed in 38 of the 72 patients from group A and in 34 of the 64 patients from group B. Respiratory syncytial virus was detected in 84% of these patients. Samples of tracheal secretions showed no differences between the groups in respect of cytology and bacterial flora. Nor were there any significant differences in the course of acute disease, the frequency of fever relapse and pulmonary complications. Fifteen patients from group B were subsequently treated with antibiotics: two of these developed secondary purulent infections of the middle ear and one showed a slight pleural effusion. These results do not support the routine use of antibiotics in infants and small children admitted to hospital with pneumonia and bronchiolitis.

Detection by ELISA of IgA and IgM antibodies in secretion and IgM antibodies in serum in primary lower respiratory syncytial virus infection

Twenty-six infants and children with primary lower RS virus infection, diagnosed by the detection of RS virus in nasopharyngeal secretion (NPS) by use of immunofluorescent antibody (FA) technique, were studied with respect to the presence of IgA and IgM antibodies. Samples of NPS and serum obtained during the first 3-4 months following the beginning of illness, were investigated. Employing a reverse ELISA technique, we found IgM antibodies in the acute, but not during the convalescent, phase of illness in NPS from 20 of the patients and in serum from 21 of the patients. The majority of the IgM antibody conversions observed occurred in NPS as well as in serum on days 5-8 following the illness. RS virus IgA antibodies, also detected by a reverse ELISA technique, were demonstrated in NPS in 22 of the patients, with antibody conversions being found in 19 of the patients on days 5-8 following the beginning of the illness. Two patients still had IgA antibodies in NPS approximately 3 months FSOI. By comparison, RS virus was detected in acute-phase NPS by double-antibody sandwich ELISA in 25 of the 26 patients investigated.

Enzyme-linked immunosorbent assay for detection of respiratory syncytial virus infection: development and description

An indirect enzyme-linked immunosorbent assay for detection of respiratory syncytial virus (RSV) antigens was developed, using commercially available antisera. Horse anti-RSV and calf antiserum to bovine RSV were used as capture and detector antibodies, respectively. The assay could detect as few as 50 PFU of unpurified RSV per ml in infected cell culture supernatant fluids and as little as 10 ng of affinity-purified RSV antigen per ml. No cross-reactions were observed with heterologous virus types. Freeze-thaw treatment had no effect on RSV enzyme-linked immunosorbent assay titers, but viral transport medium inhibited RSV enzyme-linked immunosorbent assay titers from 10- to 100-fold. The assay can be easily performed in 24 h and is a sensitive and specific method for the detection of RSV antigens.

Detection of respiratory syncytial virus in nasopharyngeal secretions by ELISA: comparison with fluorescent antibody technique

Samples of nasopharyngeal secretions (NPS) obtained from 140 infants and children with acute respiratory disease were examined for the presence of respiratory syncytial (RS) virus by ELISA. An antiserum produced in rabbits against RS-virus polypeptides was used both as the "capture" antibody and as conjugate in a double-antibody sandwich technique. RS virus was detected by ELISA in specimens of NPS obtained from 72 (51%) of the patients. By comparison RS virus was shown to be present in 86 (61%) of the patients when the immunofluorescent antibody (IF) technique was employed. Samples obtained from 78 of the 140 patients were also examined by inoculation into tissue cultures, and RS-virus was isolated from 47 patients. RS virus was detected by ELISA in 37 (79%) and by IF technique in 43 (91%) of these 47 patients. The IF technique was found to be more sensitive than ELISA, especially in patients older than 9 months and for the examination of specimens of NPS containing only a small percentage of RS-virus antigen-positive cells.

Detection of respiratory syncytial virus in nasopharyngeal secretions by inhibition of enzyme-linked immunosorbent assay

An enzyme-linked immunosorbent assay developed for the demonstration of respiratory syncytial (RS) virus immunoglobulin G antibodies was used for the detection of RS virus in specimens of nasopharyngeal secretions (NPS) obtained from children with acute respiratory disease. Samples of NPS were incubated with a fixed amount of standard serum (human serum antibodies to RS virus) before being added to the enzyme-linked immunosorbent assay test plate. A decrease in the optical density value determined for this standard serum was seen with majority of NPS specimens from which RS virus had been isolated in tissue culture. The reliability and the specificity of this inhibiton test were supported by experiments with purified RS virus and by tests with NPS specimens containing other respiratory viruses.