Adenovirus demonstrated by immunofluorescence

Replication of respiratory viruses, particularly influenza virus, rhinovirus, and coronavirus in HuH7 hepatocarcinoma cell line

Detection of viral antigens and isolation methods has long been used for the diagnosis of respiratory virus infections. The objective was to determine the ability of HuH7 cells to support the replication of prototype and wild strains of respiratory viruses. The cell culture-adapted strains of influenza viruses A and B, parainfluenza viruses 1-4, respiratory syncytial viruses A and B, both strains of the human metapneumoviruses, numerous rhinoviruses, most of the adenoviruses, coronaviruses 229E and OC43, and a number of enteroviruses (poliovirus type 3, coxsackie virus B1, echovirus type 30) replicate in HuH7. The kinetic study of the replication of influenza A and B viruses showed that there were infected cells in HuH7 and MDCK lines as early as 24 hr post-infection. However, the replication of influenza A and B viruses was more rapid and intense on MDCK cells than on HuH7 cells. During the three winters of 1999-2000, 2000-2001, and 2001-2002, of the 1,226 (23.3%) direct fluorescent assay-positive nasal aspirates from children admitted to hospital, 788 were positive for respiratory syncytial virus, 228 for influenza virus, 133 for parainfluenza virus, and 77 for adenovirus. Of the 4,032 direct fluorescent assay-negative nasal aspirates, 571 virus isolates were identified by using HuH7 cell culture; 272 rhinoviruses, 100 influenza viruses A and B, 85 enteroviruses, 40 adenoviruses, 35 coronaviruses, 31 parainfluenza viruses, and 10 respiratory syncytial viruses. Interestingly, 100/328 (30.5%) influenza viruses A and B, 40/189 (21.1%) adenoviruses, and 31/164 (19%) parainfluenza viruses type 1-3, not detected by direct fluorescent assay, were identified by isolation in HuH7 cell culture.

Comparison of enzyme-linked immunosorbent assay, indirect immunofluorescence assay, and virus isolation for detection of respiratory viruses in nasopharyngeal secretions

Nasopharyngeal secretions obtained from 94 children with acute respiratory illness were examined for the presence of respiratory syncytial virus (RSV), adenovirus, and influenza virus type A by virus culturing (virus isolation technique [VIT]), immunofluorescence assay (IFA), and enzyme-linked immunosorbent assay (ELISA). Similar results were obtained in at least two tests for RSV, influenza virus type A, and adenovirus in 92 (97.9%), 88 (93.6%), and 88 (93.6%) cases, respectively. Both rapid virus detection methods showed good specificity for the diagnosis of these virus infections (greater than or equal to 90.7%) and were more sensitive than was VIT for RSV detection. In a more accurate statistical analysis, the indexes of agreement between VIT and ELISA were substantial for RSV (kappa = 0.69; zeta = 5.5; P less than 0.0001), influenza virus type A (kappa = 0.67; zeta = 5.3; P less than 0.0001), and adenovirus (kappa = 0.71; zeta = 6.0; P less than 0.0001), while it was almost perfect for RSV when ELISA was compared with IFA (kappa = 0.88; zeta = 5.7; P less than 0.0001). Although the observed agreement was good in the comparison of these two tests for these three viruses (89%0, the indexes of agreement were moderate in the comparison of IFA and VIT for RSV (K = 0.55; Z = 2.0; P < 0.05), influenza virus type A (K = 0.42; Z = 9.7; P < 0.0001), and adenovirus (K = 0.41; Z = 6.5; P < 0.0001) and of ELISA and IFA for influenza virus type A (K = 0.55; Z = 7.0; P < 0.0001) and adenovirus (K = 0.59; Z = 6.8; P < 0.0001). All of the statistical evaluations demonstrated better agreement between ELISA and VIT for influenza virus type A and adenovirus.

Rapid diagnosis of viral infections with fluorescent antisera

Viral immunofluorescence tests were performed with commercial antisera on 1046 specimens of respiratory, conjunctival corneal and dermal origin to compare the diagnostic effectiveness of direct examination by immunofluorescence with culture. The fluorescence assays were found to be highly sensitive for respiratory syncytial and measles virus in nasopharyngeal aspirates from children, but less satisfactory for other respiratory viruses. The test detected 38% of the adenovirus positives from conjunctival specimens and 67% of the combined herpes simplex virus positives from the latter 3 groups. Despite the reduced sensitivity of fluorescence for some viruses, a case is presented for more widespread use of fluorescence in routine microbiology laboratories because of its simplicity, speed and cost-effectiveness compared with culture which is labour-intensive and time consuming.

Immunoassay diagnosis of adenovirus infections in children

Direct detection of viral antigen in nasopharyngeal secretions and stool specimens by radioimmunoassay and the determination of serum antibody responses by complement fixation and immunoglobulin class-specific enzyme immunoassay against the hexon antigen were compared for diagnostic efficacy in 52 children with acute adenovirus infections. The highest diagnosis rate (85% of the cases) was obtained by antigen detection in nasopharyngeal secretions. Adenovirus antigen was also detected in stools of 72% of the 18 patients tested. The immunoglobulin G (IgG) antibody enzyme immunoassay detected 77% of the cases, being more sensitive than the complement fixation test with a 67% detection rate. The IgM antibody response was variable with no clear correlation with the age of the patient or severity of the clinical symptoms. IgM antibody response was detected in 48% of the patients and had the normal transient course, with a persistence of the IgM antibodies of approximately 2 months. Determination of IgA antibodies gave a diagnostic increase in titer in 37% of the cases and was found less suitable for serological diagnosis. Because of the clinical importance of rapid laboratory diagnosis, the direct detection of viral antigen in nasopharyngeal secretions or stool or both should be used as the primary diagnostic test in adenovirus infections.