Time-resolved fluoroimmunoassays with monoclonal antibodies for rapid identification of parainfluenza type 4 and mumps viruses

Comparison of monoclonal biotin-avidin enzyme immunoassay and monoclonal time-resolved fluoroimmunoassay in detection of respiratory virus antigens

Background: Detection of respiratory viruses by time-resolved fluoroimmunoassay based on monoclonal antibodies were developed in our laboratories in the late 1980s and they have been successfully used in daily diagnosis for more than seven years. Later, similar Biotin-EIAs were developed but the sensitivities were unsatisfactory.

Objectives: Further optimization of monoclonal Biotin-EIAs and comparison of the optimized assays with TR-FIAs.

Study design: Variations in test format, diluents, incubation times and temperatures, and different monoclonal antibodies were tested, and the final comparisons were made with TR-FIA using stored nasopharyngeal aspirates.

Results: The improvements in Biotin-EIA featured four changes which increased sensitivity in the assay: (a) test diluent contained diethylenetriamino-pentaacetic acid; (b) antigen and biotinylated detector antibody were added simultaneously; (c) reaction time was extended from 1 h at 37°C to overnight at 4°C; (d) from the thirteen monoclonal antibodies used in TR-FIA, ten were optimal also in Biotin-EIA, but in the parainfluenza 1 and 2 assays other monoclonals proved more sensitive. Out of 257 originally positive specimens tested in the comparison studies, 192 (74.7%) were again positive and 54 (21.0%) were negative in both assays; nine were negative in TR-FIA but positive in Biotin-EIA, while two specimens were negative in Biotin-EIA but positive in TR-FIA. The overall agreement between the two assays was 95.7%.

Conclusions: All monoclonal Biotin-EIAs can be optimized to the same sensitivity as TR-FIAs for the detection of respiratory viruses.

Laboratories which have no TR-FIA expertise may use Biotin-EIA in the diagnosis of acute respiratory infections.

Advances in the diagnosis of respiratory virus infections

Background: Advances have been made in selecting sensitive cell lines for isolation, in early detection of respiratory virus growth in cells by rapid culture assays, in production of monoclonal antibodies to improve many tests such as immunofluorescence detection of virus antigens in nasopharyngeal aspirates, in highly sensitive antigen detections by time-resolved fluoroimmunoassays (TR-FIAs) and biotin-enzyme immunoassays (BIOTH-E), and, finally, in the polymerase chain reaction (PCR) detection of respiratory virus DNA or RNA in clinical specimens. All of these advances have contributed to new or improved possibilities for the diagnosis of respiratory virus infections.

Objectives and study design: This review summarizes our experiences during the last 15 years in the development of diagnostic tests for respiratory virus infections, and in use of these tests in daily diagnostic work and in epidemiological studies.

Results: Immunofluorescence tests based on monoclonal antibodies, all-monoclonal TR-FIAs, and biotin-enzyme immunoassays (EIAs) have about the same sensitivities and specificities. They compare well with the sensitivity of virus culture. PCR followed by liquid-phase hybridization is a sensitive method for detecting adenovirus DNA and enterovirus and rhinovirus RNA in clinical specimens. IgG EIA on paired acute and convalescent phase sera is the most sensitive serological test for respiratory virus infections and is a valuable reference method when evaluating the sensitivity of new diagnostic tests. The IgG avidity test can distinguish primary infections from re-infections at least in respiratory syncytial virus (RSV) infections. IgM antibody assays, on the other hand, had low sensitivities in our studies.

Conclusions: The choice of diagnostic methods for respiratory virus infections depends on the type and location of the laboratory, the number of specimens tested, and the previous experience of the laboratory. Virus culture, whenever possible, should be the basic diagnostic method; the results, including identification of the virus, should be available no more than 24 h later than the results of rapid diagnostic tests. In small laboratories, especially in hospitals where specimen transportation is well organized, immunofluorescence may be the best choice for antigen detection with the provision that an experienced microscopist and a good UV microscope are available. If the laboratory receives a large number of specimens and has previous experience with EIAs, then biotin-EIAs or TR-FIAs may be the most practical techniques. Their advantages include the stability of the antigens in clinical samples since intact, exfoliated epithelial cells are not required, treatment of specimens is practical, testing of large numbers of specimens is possible, and reading the printed test result is less subjective than reading fluorescence microscopy. The larger role of PCR in the diagnosis of respiratory virus infections depends on future developments such as practical methods to extract DNA or RNA and to purify the extracts from nonspecific inhibitors, plus further improvements to minimize cross-contamination. Group-specific detection of enteroviruses and rhinoviruses is an example of the potential for PCR technology. In experienced laboratories. EIA IgG antibody tests should be available. Recombinant antigens may be a useful part of such assays.

Detection and identification of human parainfluenza viruses 1, 2, 3, and 4 in clinical samples of pediatric patients by multiplex reverse transcription-PCR

We describe a multiplex reverse transcription-PCR (m-RT-PCR) assay that is able to detect and differentiate all known human parainfluenza viruses (HPIVs). Serial dilution experiments with reference strains that compared cell culture isolation and m-RT-PCR showed sensitivities ranging from 0.0004 50% tissue culture infective dose (TCID(50)) for HPIV type 4B (HPIV-4B) to 32 TCID(50)s for HPIV-3. As few as 10 plasmids containing HPIV PCR products could be detected in all cases. When 201 nasopharyngeal aspirate specimens from pediatric patients hospitalized for lower respiratory illness were tested, m-RT-PCR assay detected 64 HPIVs (24 HPIV-3, 23 HPIV-1, 10 HPIV-4, and 7 HPIV-2), while only 42 of them (21 HPIV-1, 14 HPIV-3, 6 HPIV-2, and 1 HPIV-4 isolates) grew in cell culture. Our m-RT-PCR assay was more sensitive than either cell culture isolation or indirect immunofluorescence with monoclonal antibodies for the detection of HPIV infections. Also, HPIV-4 was more frequently detected than HPIV-2 in this study, suggesting that it may have been underestimated as a lower respiratory tract pathogen because of the insensitivity of cell culture.

Antigen detection in human respiratory Coronavirus infections by monoclonal time-resolved fluoroimmunoassay

BACKGROUND

The diagnosis of respiratory infections by detecting viral antigens has received considerable attention using immunofluorescent assays (IFA) and enzyme immunoassays (EIA). Time-resolved fluoroimmunoassay (TR-FIA) has been developed for several viruses.

OBJECTIVES

To prepare monoclonal antibodies to coronavirus strains, to incorporate them into a TR-FIA, and test the assay on clinical specimens.

STUDY DESIGN

Monoclonal antibodies were prepared to the N nucleoprotein of the two human respiratory coronaviruses, HCV strains 229E and OC43. Monoclonals to both viruses were completely type-specific; they did not cross-react between themselves or with multiple strains of other respiratory viruses. These antibodies were configured into optimized EIA and TR-FIA tests. The all-monoclonal tests were then compared to polyclonal EIA tests in terms of their ability to detect virus in clinical specimens.

RESULTS

The all-monoclonal TR-FIA was uniformly the most sensitive, detecting virus in all 13 229E-positive specimens compared to 69% for the monoclonal EIA and 54% for the polyclonal EIA test. Similar results were obtained for 10 OC43-positive specimens: 100% in TR-FIA, 90% in monoclonal EIA, and 80% in polyclonal EIA. For 229E in TR-FIA, mean positive/negative (P/N) ratios were 143 for 229E-positive human embryonic lung fibroblast (HLF) cell culture fluids and 10 for positive nasopharyngeal aspirate specimens; for OC43 in TR-FIA, mean P/N values were 964 for OC43-positive rhabdomyosarcoma (RD) cell culture fluids and 174 for positive NPA specimens. The sensitivities of the TR-FIA were determined with purified virions to be 0.308 ng virus per well for HCV-229E and 0.098 ng virus per well for HCV-OC43.

CONCLUSIONS

This rapid and sensitive test appears to be much more sensitive than traditional antigen detection assays but will require more extensive field testing on clinical specimens.

Subgrouping of respiratory syncytial virus strains from Australia and Papua New Guinea by biological and antigenic characteristics

Strains of respiratory syncytial virus from 3 major areas of Australia and Papua New Guinea (PNG) were analyzed for variations in their antigenic and biological properties and in the molecular weights of their major structural proteins. Seventy-eight strains from infants and young children with LRI were collected from 1981-1984. The RSV season in the Australian cities lasted from April through September, with major peaks in July of each year, while the RSV season in tropical PNG was year-round, with small peaks in March and October of each year coinciding with excessive rainfall. Fifty-six strains were analyzed in detail; 40 were typed by time-resolved fluoroimmunoassay with monoclonal antibodies as group A strains and 16 were group B; both groups were concurrent. Three children of one family had sequential RSV infections 13 months apart, and the etiologic group A strain was identical both years in terms of growth and antigenic properties with strain-specific ferret antisera; the second infection was milder in all three children. On average, the group A strains replicated considerably better than group B strains in HEp2 cells, producing 53% more syncytia and 99% higher infectious virus titers in 31% less time in culture. Ten group A and B reference strains exhibited the same growth patterns as the A and B regional strains, respectively. Differences in antigenicity as measured with hyperimmune antisera to prototype Long strain were even greater. Group A strains exhibited a mean 68% greater IFA staining than B strains, a 71% greater EIA reaction, and were neutralized to 69% higher serum titers than B strains. Again, the reference A and B strains included as controls gave patterns identical to those of the regional strains. Finally, the P phosphoprotein had consistently higher molecular weight in A strains (mean 35,900) than B strains (mean 33,100). Small variations in the sizes of the F and G glycoproteins were not sufficient to suggest grouping on this basis.