Rapid diagnosis of influenza by immunofluorescent techniques

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 influenza A and B by 24-h fluorescent focus assays

Murine monoclonal antibodies directed against type-specific antigens of influenza A and B viruses have been shown to be useful diagnostic reagents for the detection of influenza viruses by immunofluorescence testing of nasopharyngeal cells. We have developed fluorescent focus assays utilizing these antibodies in cell culture chamber slides and shell vials for the rapid diagnosis of influenza A and B. Chamber slide assays were compared with virus isolation in 160 specimens from 135 patients with symptoms of influenza. Virus isolation was compared with immunofluorescence testing in 38 of the 160 specimens. Compared with virus isolation, 24-h cell culture chamber slide assays had a sensitivity of 75% and a specificity of 96%. Immunofluorescence testing of nasopharyngeal cells was only 38% sensitive and 91% specific. Shell vial assays were compared with virus isolation for 89 specimens. At 16 to 18 h postinoculation, the shell vial assay was 84% sensitive and 100% specific. We conclude that both chamber slide and shell vial assays are rapid, sensitive, and specific techniques for the diagnosis of influenza.

Use of monoclonal antibodies for rapid detection of influenza A virus in nasopharyngeal secretions

Two monoclonal antibodies against influenza A virus were assessed for use as diagnostic reagents in an indirect immunofluorescence assay (IFA) of nasopharyngeal secretions. Monoclonal antibody IA-52, directed at an internal antigen, reacted with all influenza A tested. The high stability of this epitope permitted its use in a rapid IFA test, which gave results comparable to those obtained with polyclonal antibodies and viral isolation. The second monoclonal antibody, IA-279 was directed at a surface epitope (hemagglutinin); it reacted with almost all H3 subtype strains. Positive IFA using these monoclonal antibodies permitted rapid preliminary differentiation between the current two major subtypes of influenza A virus (H1N1, H3N2).

Virus infections in children with acute lymphoblastic leukaemia

The pattern of virus isolation and illness was studied in 64 children with acute lymphoblastic leukaemia (ALL) during periods of apparent infection and when the children were well. The virus isolation rate of 2.2 viruses per child a year is similar to that previously found in normal children. In only 32% of children with symptoms were viruses found and 14.5% had viruses isolated when asymptomatic. The children with ALL appear to be more vulnerable to multiple virus infections and to excrete the virus for longer periods. This may be due to failure of production of both local and systemic antibodies. The failure in the past to recognise the true importance of virus infections in ALL may have been due to inadequate diagnostic techniques.

Preparation of sera for subtyping of influenza A viruses by immunofluorescence

The conditions for preparation of type-specific and subtype-specific influenza A virus reagents to be used in the immunofluorescence technique have been evaluated. Type A-specific antibodies were prepared by passing an antivirion hyperimmune serum through an immunoadsorbent column containing antigens from disrupted virions of a different influenza A virus subtype. The type-specific antibodies were recovered from the immunoadsorbent by desorption with 3 M NaI. For subtype determination, antisera against the various hemagglutinins were used. Such sera could be prepared by removal of irrelevant influenza A virus antibodies from sera directed against purified virions and isolated peplomers, respectively. This was performed by passing the antisera through immunoadsorbent columns containing antigens from disrupted virions of appropriate strains. However, attempts to obtain a hemagglutin-specific antiserum from a serum directed against allantoic fluid virus suspension failed with this procedure. Antisera obtained after immunization with purified hemagglutinin were also elaborated. These sera were shown to be superior for subtyping of influenza A virus infections by immunofluorescence, but could not a priori be regarded as subtype-specific. The usefulness of subtype-specific sera has been demonstrated on clinical specimens for rapid virus diagnosis.

The coating of respiratory syncytial (RS) virus-infected cells in the respiratory tract by immunoglobulins

During the course of 26 respiratory syncytial (RS) virus infections, infected cells in the respiratory tract become coated with immunoglobulins (IgA, IgG, and IgM), IgA being predominant. Methods are described for detecting both intracellular virus and coating immunoglobulin using a double staining technique and immunofluorescence. IgA coating antibody appears in small amounts very early in the illness. The relationship of coating antibody to pathogenesis, prevention, and recovery from RS virus infection is discussed.

Trigger factors and HL-A antigens in chronic active hepatitis

Forty-six patients with histologically verified chronic active hepatitis (CAH) were divided into three groups according to whether the CAH was virus-induced, drug-induced, or cryptogenic. The frequency of the HL-A antigens 1 and 8 was increased in the cryptogenic group while the other groups did not differ significantly from healthy controls. Autoantibodies were often found in high titres in the drug-induced and cryptogenic groups but were infrequent in the virus-induced group.

Gastric 'flu influenza B causing abdominal symptons in children

Influenza-B virus was identified in 102 children admitted to hospital during two epidemics in 1973 and 1974, enzbling the symptomatology of infection with this virus to be assessed in detail for the first time. Abdominal pain, often severe enough to require differentiation from acute appendicitis, emerged as a dominant symptom, especially in older children. Respiratory symptoms were often insignificant, although the lower respiratory tract was sometimes involved. Other symptoms in some children included convulsions and acute myalgia. The immunofluorescent method of virus diagnosis was found to be reliable for influenza B, except in a few cases ehere nasopharyngeal secretions were scanty, giving 97-5 percent copositivity with standard isolation techniques. The rapid result provided by immunofluorescence was helpful in clinical diagnosis and management and also in the control of hospital cross-infection.

Comparison of immunofluorescence and isolation techniques in the diagnosis of respiratory viral infections of children

The immunoflourescent antibody technique (IFAT) and cell culture isolation procedures were compared for their efficiency in the etiological diagnosis of viral respiratory illness in children. Before the IFAT was incorporated as a routine procedure, antisera used in the test were carefully calibrated to insure specificity. A study was then conducted in which 375 nasopharyngeal suctions were investigated by both IFAT and isolation for the presence of parainfluenza virus types 1, 2, and 3, respiratory syncytial, influenza A, and influenza B viruses. Methods already established in our hospital for patient management and specimen collection were not altered for the purposes of the study. The IFAT, as conventionally practiced in the detection of respiratory virus antigens, requires adequate numbers of ciliated epithelial cells. There were 68.5% specimens which contained cells suitable for IFAT, whereas 31.5% had either an insufficient number or inappropriate types of cells and could be used only for virus isolation. Cell-associated immunoglobulins were detected in 16% of those specimens with adequate cells. When all specimens were considered regardless of their cell population, IFAT was inferior to isolation in diagnostic efficiency. However, isolation complemented by IFAT resulted in a statistically significant increase in number of positive virus identifications. Under routine working conditions in a large pediatric hospital, it was found that IFAT could not replace isolation techniques but could, if used in conjunction with isolation, provide a significant overall increase in number of positive diagnoses. The time that the specimen was taken in relation to first symptoms was found to be an important variable with respect to the method most likely to succeed in virus identification.

Early detection of influenza virus in cell culture by means of immunofluorescence

An indirect fluorescent antibody technique using human serum for the rapid detection of influenza A virus in monkey kidney cell cultures is described. Influenza A2 virus was isolated from 38 of 88 nose/throat swabs received from patients with suspected influenza during the winter of 1971-72.Thirty-two strains isolated in monkey kidney cell cultures were identified by immunofluorescence on the day haemadsorption was observed, 22 of them within a week of receipt of the specimen. Human antiserum was found to be very satisfactory for this purpose.

The post-mortem diagnosis of influenzal infection by fluorescent IgG, IgA and IgM antibody studies on necropsy blood

Necropsy blood from cases diagnosed as dying from influenza A was examined for specific antibody in the IgG, IgA and IgM fractions and a specific diagnosis of recent infection was made if either IgM or IgA antibody and low titres of IgG antibody were found. By these criteria a diagnostic rate of 77% was found in those cases from whom no virus was isolated. The use of infected cell monolayers grown on polytetrafluoroethylene-coated slides gave a simple method of carrying out these antibody assays, and the use of necropsy blood did not require any special methods of transport of specimens to the virus laboratory.

Observations on clinical and immunofluorescent diagnosis of parainfluenza virus infections

Immunofluorescent techniques have been applied to nasopharyngeal secretions for the rapid diagnosis of parainfluenza virus types 1, 2, and 3 infections. Seventy-five infections were found by isolation techniques; 55 of these had nasopharyngeal secretions taken and 53 were positive by direct examination. A comparison of the results of 60 neutralization tests with immunofluorescence applied to monkey kidney isolations showed complete agreement. Immunofluorescence appeared to be a satisfactory method for differentiating the various haemadsorption viruses. The importance of parainfluenza viruses and respiratory syncytial virus in croup was noted and the association of the parainfluenza viruses with acute respiratory virus infection was confirmed. The clinical relationship between respiratory syncytial virus and parainfluenza virus type 3 is discussed.