Differential diagnoses of influenza A virus, influenza B virus, and respiratory syncytial virus infections by direct immunofluorescence using mixtures of monoclonal antibodies of different isotypes.

Differences between isotypes of monoclonal antibodies were employed to detect influenza A and B viruses and respiratory syncytial virus by direct immunofluorescence using fluorescein isothiocyanate or Texas Red conjugates. Examination of 56 specimens for influenza A and B viruses and 112 specimens for influenza A virus and respiratory syncytial virus showed the mixed-isotype test to be comparable to the conventional procedure.

Isolation and characterization of a naturally occurring parainfluenza 3 virus variant.

A parainfluenza 3 virus variant which failed to react with parainfluenza 3 virus-specific monoclonal anti-bodies from two commercial sources was isolated from a 14-month-old boy. Analysis of the coding region of the hemagglutinin-neuraminidase gene identified 36 nucleotide changes and 4 amino acid changes compared with a consensus sequence derived from strains isolated from 1957 through 1983. Two unique amino acid changes occurred at positions 174 and 283, which are close to identified epitopes in the hemagglutinin-neuraminidase protein. Ongoing viral surveillance to detect variants is important, particularly in regard to vaccine development.

Comparison of rapid immunofluorescence procedure with TestPack RSV and Directigen FLU-A for diagnosis of respiratory syncytial virus and influenza A virus.

A rapid immunofluorescence format requiring 20 min for completion was as effective as conventional indirect and direct immunofluorescence procedures for detecting respiratory syncytial virus and influenza A virus antigens in clinical specimens. Rapid immunofluorescence was more sensitive than TestPack RSV and comparable to Directigen FLU-A immunosorbent assays, which require 20 min for completion.

Mixed viral infections: detection and management.

An analysis was done of the incidence and nature of mixed virus infections diagnosed in the same clinical specimen from immunocompetent patients; respiratory viruses were emphasized. Few studies have addressed mixed viral infections in any systematic fashion. The relevant studies reviewed focused on clinical relationships or diagnostic methods. Data relating to multiple infections were usually derived incidentally to the purpose of the investigations. Sixty-three percent of the reports with data on mixed infections identified them in < 5% of the total number of viral infections. Respiratory syncytial virus was the most common coinfecting virus, and respiratory syncytial virus and influenza virus were the most common virus pair identified. In considering rapid diagnostic techniques, in 87% of the reports with available data a virus was diagnosed in > 10% of specimens that were negative for the virus targeted by one method. There was no indication that mixed infections were associated with increased disease in immunocompetent patients or in certain immunocompromised patients. Immunocompromised patients, however, appeared to have a greater incidence of multiple infections. Mixed infections of single cells also occur and may have important clinical implications relative to reactivation of latent viruses and enhanced disease. The requirement for a comprehensive strategy for viral diagnosis involving multiple techniques was indicated by these findings.

Absence of association between cytomegalovirus infection and obliterative transplant arteriopathy in renal allograft rejection.

Cytomegalovirus (CMV) was recently identified, using in situ hybridization, in the coronary arteries of patients with cardiac transplant rejection, suggesting a role of CMV in the development of obliterative transplant arteriopathy in cardiac allografts. We sought to verify this observation by examining arteries in kidney transplants with intimal thickening due to chronic rejection. Eleven renal biopsies and 13 nephrectomies from 24 patients, all showing obliterative transplant arteriopathy, were collected for this study. Of these patients, six were seropositive for CMV before transplantation, three were identified as seropositive following renal transplantation, nine had no evidence of CMV infection, and clinical data were not available for an additional six patients. Paraffin-embedded renal sections were examined for the presence of CMV by immunohistochemistry in situ hybridization and polymerase chain reaction. By these methods, only one case (1/24) was demonstrated to have CMV infected cells in the renal interstitium, tubules, and glomeruli, but none (0/24) showed CMV to be located in any of the renal arteries or arterioles. Thus, our results suggest that obliterative transplant arteriopathy can occur in the absence of demonstrable CMV and is probably unrelated to direct CMV infection of the graft.

A conformational epitope on the dimer of the fusion protein of respiratory syncytial virus detected in natural infections.

A murine monoclonal antibody (MAb), 2D8, was used in immunofluorescence reactions to detect respiratory syncytial virus (RSV) antigen in clinical specimens. Nasopharyngeal epithelial cells from 63 of 66 children with RSV infections reacted with this MAb. The MAb was further characterized and was demonstrated to recognize a conformational epitope on the dimer of the fusion protein of RSV. No reaction was detected with the MAb, 2D8, on Western blots of antigen prepared from RSV-infected HEp-2 cells under reducing conditions. Under non-reducing conditions, 2D8 reacted with a 145-170 K protein; this reactivity was lost when the antigen preparation was heated to 100 degrees C. 2D8 reacted with purified F glycoprotein of RSV Long in an ELISA, neutralized infectivity of RSV by >50% at a dilution of 1:500, and was able to inhibit cell-to-cell fusion of RSV-infected cells. In a competitive ELISA, the epitope detected by 2D8 was localized to antigenic site A. The conformational epitope detected by 2D8 required protein dimerization and glycosylation for full reactivity. This report extends previous characterizations of the F protein in its native state in that the MAb defines a conformational epitope on the fusion protein dimer that is expressed in natural infections and elicits antibody that can neutralize virus infectivity and inhibit cell-to-cell fusion. In addition to its application as a diagnostic reagent, this MAb can be of use in testing preparations of RSV or purified F protein in which the purification or extraction processes could have destroyed conformational epitopes.

Effect of rimantadine on the immune response to influenza A infections.

The effects of rimantadine on lymphocyte responses to mitogens CON-A and PHA, natural killer cell activity, and the development of serum and local antibodies were studied during an epidemic outbreak of influenza A (H3N2). Twenty-three families consisting of 38 adults and 46 children had a member who developed a flu-like illness and were randomly assigned to receive placebo or rimantadine either as treatment or post exposure prophylaxis. Nasal washings for virus isolation and IgG and IgA determination were collected on days 1, 5, and 10 of illness. Blood samples for immunologic studies were obtained on days 1 and 5 of clinical illness and on day 21. No differences in lymphocyte responses to CON-A and PHA or in natural-killer cell activity were noted between placebo and rimantadine groups. The development of neutralizing antibodies to influenza H3N2 was also not affected by rimantadine. However, the presence of IgA in nasal secretions was significantly diminished in the rimantadine group compared to the placebo group (0/9 vs. 6/9, P less than 0.005). The findings indicate that rimantadine had no adverse affect on the systemic immune system. However, local immune response was diminished in individuals taking rimantadine possibly due to the presence of less immunogen resulting from reduction of virus in secretions of individuals taking antivirals.

Comparison of Directigen FLU-A with viral isolation and direct immunofluorescence for the rapid detection and identification of influenza A virus.

Directigen FLU-A, an enzyme immunoassay membrane test, was compared prospectively to isolation in cell culture and direct immunofluorescence (IF) for the detection of influenza A virus. One hundred ninety specimens were evaluated by Directigen FLU-A and cell culture; 184 of these specimens were also tested by direct IF. The sensitivity of Directigen FLU-A compared to isolation in cell culture and direct IF was 100%. The specificities of Directigen FLU-A compared to isolation and direct IF were identical, 91.6%. Fourteen specimens that were positive by Directigen FLU-A did not yield virus in culture; two of the specimens, however, were positive by direct IF, and four other specimens were not specimens of choice for the test. A positive Directigen result had positive predictive values of 62.6 and 75.0% compared to isolation and direct IF, respectively; a positive Directigen result with an intensity reading of 2+ or greater, however, had positive predictive values of 85 and 100% compared to isolation and direct IF, respectively. In all comparisons, the negative predictive value was 100%. There was no evidence that cross-reactivity occurred with non-influenza A antigens. Directigen FLU-A should serve as a convenient screening test for influenza A and as a rapid test supported by isolation in cell culture during an influenza outbreak.

Absence of interferon in sera of patients with Kawasaki syndrome.

We measured serum interferon concentrations in 42 patients with Kawasaki syndrome. The children ranged in age from 7 months to 6 years. All acute sera were obtained within 12 days of the onset of fever. Convalescent sera (illness day 19 to 56) were available from 25 of 42 patients. Sera were also obtained from 40 controls ranging in age from 2 months to 12 years. Control sera included healthy children (n = 14), children with bacterial infection (n = 10) and children with viral infection (n = 16). Sera were coded and interferon concentrations were measured blindly using human diploid fibroblast cell monolayers challenged with 10(4) plaque-forming units of vesicular stomatitis virus. Specimens from 10 of 16 patients with viral infection were positive for interferon. Three of 10 patients with bacterial infection had detectable serum interferon. No interferon was detected in specimens from the 14 healthy control children or the 42 children with Kawasaki syndrome. Despite the use of a sensitive assay we were unable to detect interferon in the sera of patients with Kawasaki syndrome.

Comparison of directigen RSV with viral isolation and direct immunofluorescence for the identification of respiratory syncytial virus.

An enzyme immunoassay membrane test (Directigen RSV) for the detection of respiratory syncytial virus in clinical specimens was compared prospectively with isolation in cell culture and direct immunofluorescence (IF). A total of 315 nasopharyngeal wash specimens from pediatric patients were examined. Directigen RSV was 86.1% sensitive and 91.3% specific for specimens positive by isolation in cell culture and/or IF, with 88.6% agreement. The false-positive rate was 16%; 2 of 20 specimens giving false-positive reactions by Directigen RSV were true-positives by blocking assay. Twenty-seven specimens (8.5%) whose results were initially uninterpretable by Directigen RSV due to filtration difficulties were diluted and upon retesting produced acceptable results. Sixty-three viral isolates and/or IF identifications of virus antigens representing seven virus groups other than respiratory syncytial virus were also found; cross-reactions between Directigen RSV and other viruses were not observed. Directigen RSV will be useful as an immediate procedure and in facilities lacking a comprehensive virology laboratory.

Detection of multiple viral agents in nasopharyngeal specimens yielding respiratory syncytial virus (RSV). An assessment of diagnostic strategy and clinical significance.

A retrospective study of 6 years (1981-1987) experience with clinical specimens of pediatric patients submitted for identification of respiratory viruses was undertaken to determine the prevalence of multiple viral isolates and to assess the impact of dual infections on severity of clinical disease. Respiratory Syncytial Virus (RSV), the most frequently identified agent, was detected in cell culture and/or by immunofluorescence (IF) in 666 of 2,415 specimens examined. A second virus was isolated in cell cultures from 51 of the 666 specimens (7.6%). Cytomegalovirus, rhinoviruses, adenoviruses, influenza and parainfluenza viruses, echoviruses, vaccine strain polio viruses, and herpes simplex virus were identified with RSV. The diagnosis of a dual viral infection would have been missed in 37 of 51 instances (79%) had rapid diagnosis for RSV been employed without inoculation of cell cultures. Demographics and clinical presentations were similar in patients with dual infections or RSV alone. A case-control study comparing patients with dual isolates and patients with RSV alone to determine the effect of multiple viral infections on severity of disease revealed no significant difference. The combined use of rapid methods and isolation in culture provides more complete viral diagnosis and could have an impact on the choice of antiviral agents and the institution of appropriate infection control measures.

Detection of Chlamydia trachomatis in adolescent females using direct immunofluorescence.

Direct immunofluorescent slide tests for the detection of genital Chlamydia trachomatis have attracted considerable attention because of their speed and economy, but most evaluation trials have concentrated on adult, high-risk populations. Using 152 paired specimens, we compared the Syva Micro Trak direct specimen test with culture in a population of adolescent females attending a general adolescent medicine clinic. The direct slide test was 90 percent sensitive and 95 percent specific overall, with positive and negative predictive values of 74 percent and 98 percent, respectively. Prevalence by culture was 13 percent. Six of our 23 positive slide tests could not be confirmed by culture. A positive chlamydia culture was significantly associated with nonwhite race, a positive Gram's stain, and the presence of mucopurulent endocervical discharge, but not with oral contraceptive pill use, obstetrical history, Pap smear results, multiple sexual partners, coexisting vaginitis or gonorrhea, or a history of prior sexually transmitted diseases. The direct test appears to be an acceptable substitute for culture in higher prevalence adolescent settings and a useful screening adjunct in lower prevalence groups.

Comparison of two enzyme-linked immunosorbent assay (EIA) kits with immunofluorescence and isolation in cell culture for detection of respiratory syncytial virus (RSV).

Rapid diagnosis of respiratory syncytial virus (RSV) infections is based upon detection of viral antigen in cells obtained from the respiratory tract and usually employs immunofluorescence (IF) reactions or enzyme-linked immunosorbent assays (EIA). The Pathfinder EIA kit (Kallestad Diagnostics) was compared with the Abbott EIA kit by evaluating each against isolation of RSV in cell culture and detection of antigen by IF. The Pathfinder kit identified 116 of 129 culture-positive and 72 of 90 culture-negative specimens; the sensitivity was 90 percent and the specificity was 80 percent. The sensitivity of the Abbott EIA test compared to isolation of RSV in cell culture was 91% (115 of 127), and the specificity was 83% (74 of 89). Of 165 specimens evaluated by IF, the Pathfinder kit detected 97 of 105 IF-positive and 45 of 60 IF-negative specimens, giving a sensitivity of 92% and a specificity of 75%. The Abbott EIA compared similarly with IF, showing a sensitivity of 91% (98 of 108) and a specificity (42 of 54) of 78%. Visual reading of the Kallestad test resulted in a sensitivity of 92%, a specificity of 91%, positive predictive value of 95%, and negative predictive value of 86%. The Pathfinder EIA kit compared well with IF and the Abbott EIA for detection of RSV antigen but performed faster than the Abbott test and offers the option of a visual reading.

Molecular epidemiology of live, attenuated varicella virus vaccine in children with leukemia and in normal adults.

Restriction endonuclease analysis of varicella-zoster virus (VZV) DNA has been used in unraveling the complex epidemiology of VZV infections in individuals immunized with a live, attenuated varicella virus vaccine. Early rashes appearing within the first six weeks after vaccination are invariably due to vaccine virus. True breakthrough infections with wild-type VZV also occur in vaccinees. Five cases of zoster have been seen in leukemic children vaccinated while in remission. One case appeared 22 months after vaccination in the same general area as the inoculation. The virus isolated was vaccine derived. A second case of zoster appeared in a dermatome unrelated to the sites of vaccination approximately 19 months after apparently natural varicella. This virus was wild type. Vaccine virus can therefore establish latency and can later reactivate as herpes zoster.

Aerosolized ribavirin treatment of respiratory syncytial virus infection in infants hospitalized during an epidemic.

Thirty-three infants with predisposing conditions and/or severely symptomatic with respiratory syncytial virus (RSV) infection were treated with aerosolized ribavirin during a 12-week period at Oklahoma Children's Memorial Hospital. These patients were compared with 97 untreated patients with RSV infection hospitalized during the same epidemic. Despite preconditions which selected for a more seriously ill treatment group, patients who received ribavirin showed prompter resolution of the illness than did untreated controls. Greatest clinical improvement in treated patients occurred between the first and second days of ribavirin therapy; mean ribavirin treatment duration was 4.5 days. Ten of 22 ribavirin-treated patients continued to excrete RSV after conclusion of antiviral therapy. No adverse hematologic, renal or metabolic effects occurred with ribavirin therapy. Our experience with ribavirin therapy during a major epidemic confirms and extends the results of previous controlled evaluations demonstrating this treatment safe and effective in high risk and seriously ill infants with RSV bronchiolitis and bronchopneumonia.

Effect of intravenous immune globulin on natural killer cell activity: possible association with autoimmune neutropenia and idiopathic thrombocytopenia.

Natural killer cell (NK) activity was assessed in patients before and after treatment with intravenously administered immune globulin (IVIG). In eight patients with hypogammaglobulinemia or agammaglobulinemia receiving 300 mg/kg/dose IVIG every 4 weeks, NK activity was significantly lower after therapy than before. In two patients, one with idiopathic thrombocytopenic purpura and one with autoimmune neutropenia, receiving high doses (2 gm/kg) of IVIG, NK activity was unusually high before therapy. After treatment, NK activity decreased in correlation with the clinical response and elevation of peripheral cell counts. These data show that IVIG diminishes NK activity in vivo and that reduction of NK activity may be associated with clinical improvement in idiopathic thrombocytopenic purpura and autoimmune neutropenia. NK activity of lymphocytes obtained from healthy volunteers was reduced by the same concentrations of maltose or sucrose present in Gamimune or Sandoglobulin, respectively; IVIG preparations, however, were more inhibitory. The diminution of NK activity therefore may be related to two components of IVIG preparations, monomeric IgG and maltose or sucrose.

Comparison of polyclonal antiserum versus monoclonal antibodies for the rapid diagnosis of influenza A virus infections by immunofluorescence in clinical specimens.

A pool of monoclonal antibodies was compared with polyclonal antiserum for the rapid detection of influenza A virus in 28 clinical specimens by immunofluorescence. Monoclonal antibodies showed higher sensitivity (69 versus 46%) and accuracy (86 versus 75%) and easier slide interpretation than did polyclonal antiserum. The procedure proved useful for rapid detection of a community outbreak of influenza A virus infection.

Production of monoclonal antibodies against parainfluenza 3 virus and their use in diagnosis by immunofluorescence.

Monoclonal antibodies were produced against parainfluenza virus type 3 (PI-3) and used to identify PI-3 clinical isolates in cell culture and PI-3 antigen in cells obtained from nasopharyngeal (NP) washes of patients. Two (2E9 and 4G5) of the three monoclonal antibodies characterized reacted by immunoblotting with a 67,000-dalton PI-3 protein, and one antibody (4E5) reacted with two viral proteins in the range of 29,000 to 31,000 daltons. The three monoclonal antibodies did not cross-react by indirect immunofluorescence (IFA) with PI-1 or PI-2 and identified by IFA 18 isolates of PI-3 in cell culture. The 2E9 antibody reacted with PI-3 antigen in cells of 8 NP wash specimens that also yielded PI-3 in cell culture. Cells from 12 specimens reactive by IFA for respiratory syncytial virus, 1 specimen yielding adenovirus in cell culture, and 5 specimens yielding influenza virus were not reactive.

Natural killing (NK) of cytomegalovirus (CMV)-infected fibroblasts: a comparison between two strains of CMV, uninfected fibroblasts, and K562 cells.

Spontaneous cytolysis of uninfected human fibroblasts (HF), K562 cells, and HF cells infected with cytomegalovirus (CMV) was associated with nonadherent peripheral blood leukocytes (PBL) that passed through a nylon wool column, and rosetted with sheep erythrocytes at low affinity; cytolysis was further associated with enriched preparations of large granular lymphocytes (LGL). The Leu-7 marker did not correlate as a cell phenotype with functional activity in normal donors. The HF cells infected with the AD169 strain of CMV were as sensitive to cytolysis as K562 cells, although the kinetics of cytolysis differed; HF cells infected with the Davis strain of CMV were generally less sensitive to cytolysis than uninfected fibroblasts. Equivalent amounts of interferon were detected in NK assays containing Davis targets, AD169 targets, or K562 cells; interferon was not detected in NK assays of HF cells. Neither uninfected nor infected HF cells competed effectively against 51Cr-labeled K562 cells in cold competition experiments; K562 cells, however, competed effectively against 51Cr-labeled AD169-CMV targets. Uninfected HF cells were efficient competitors of AD169-CMV targets. Davis-CMV-infected cells were less effective, however, than uninfected HF cells in competition experiments, suggesting that fewer receptors for NK cells were present on these targets.