Respiratory tract viral infections in inner-city asthmatic adults.

BACKGROUND: Respiratory tract viral infections (RTVIs) have been identified frequently in association with asthma exacerbations in children, but few studies have shown similar rates of viral infections in adults with asthma. Further studies using newer diagnostic techniques to evaluate the frequency of RTVIs in adults with acute exacerbations of asthma need to be performed. METHODS: Twenty-nine asthmatic adults were recruited from the pulmonary clinic of an urban county hospital and were followed up in a longitudinal cohort study for signs and symptoms of asthma and RTVI. One hundred twenty-two asthmatic adults presenting to the emergency department (ED) of the same hospital with acute symptoms of asthma underwent evaluation for RTVI in a cross-sectional prevalence study. In both studies, respiratory secretions and paired serum samples were collected from subjects with acute wheezing episodes and evaluated using virus culture, serologic testing, and reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: In the longitudinal cohort study, 138 respiratory illnesses, of which 87 were asthma exacerbations, were evaluated; 41% of all illnesses and 44% of asthma exacerbations were associated with an RTVI. In the ED study, 148 asthma exacerbations were evaluated; 55% were associated with an RTVI. An RTVI was identified in 21 (50%) of 42 of the subjects hospitalized in the ED study. Picornaviruses (rhinoviruses), coronaviruses, and influenza viruses were the most commonly identified causes of RTVI. Forty-six (60%) of the 77 picornavirus infections and 22 (71%) of the 31 coronavirus infections were identified only using RT-PCR. CONCLUSIONS: Asthmatic exacerbations in adults are frequently associated with an RTVI. Identification of such infections often requires newer diagnostic methods, such as virus-specific RT-PCR. The high frequency of RTVIs identified in association with asthmatic exacerbations in adults from the inner city suggests that strategies for the prevention of RTVI should be targeted toward this population.

Influenza vaccination of children during acute asthma exacerbation and concurrent prednisone therapy.

OBJECTIVES: The influenza vaccination rate is very low among children with moderate to severe asthma. This may be partly because of poor patient motivation and failure to visit clinics for vaccination. Another important factor may be health care providers' deferral of vaccination because of concern about the efficacy and safety of influenza vaccination during asthma exacerbations and concurrent prednisone therapy. We therefore examined the safety and immunogenicity of influenza vaccination during acute asthma exacerbation with concomitant prednisone therapy. SETTING: A pediatric allergy and pulmonology clinic and a pediatric emergency department. DESIGN: Children (n = 109) with a known diagnosis of asthma 6 months to 18 years of age were recruited. All participating patients, 59 without asthma symptoms (no prednisone, control group) and 50 with acute asthma exacerbation requiring prednisone burst therapy (prednisone group) received trivalent subvirion influenza vaccine. Fifteen children in the control group and 12 in the prednisone group received a booster dose according to American Academy of Pediatrics guidelines. Serum antibody titers to influenza A/Beijing/32/92 (H3N2), influenza A/Texas/36/91 (H1N1), and influenza B/Panama/45/90 were measured before and 2 weeks after vaccination. Adverse effects noted within 48 hours after vaccine dose were ascertained during the follow-up visit. RESULTS: The antibody response was analyzed by comparing mean postvaccine titers, the percentage of patients achieving protective antibody levels (> or = 5log2), and the percentage of patients achieving rises in titers of 2log2 or greater. Antibody responses to influenza A/Beijing/32/92 (H3N2) and influenza A/Texas/36/91 (H1N1) in the prednisone-treated and control groups were not different. A significantly better response to the influenza B/Panama/45/90 antigen was seen in the prednisone group for all three parameters. Children who received a booster dose and the subgroup of children with low prevaccination titers (< or = 3log2) showed similar patterns. Adverse effects, including asthma exacerbation, local swelling at the injection site, fever, rash, and headache, were not different in the two groups. CONCLUSIONS: Influenza vaccination can be given safely and effectively to asthmatic children regardless of asthma symptoms or concurrent prednisone therapy when necessary. Vaccination of all moderate to severe asthmatic patients visiting clinics or emergency departments would improve the overall vaccination rate significantly.

Relation of serum antibody to glycoproteins of respiratory syncytial virus with immunity to infection in children.

Immunity in relation to passively transferred maternal and naturally-induced serum antibody to the viral proteins was determined in 34 children who were followed from birth through three years of age for respiratory syncytial virus infection (RSV). Sera were tested by immunoglobulin class-specific enzyme-linked immunosorbent assay using the attachment and fusion proteins of the Long strain. The basis for immunity for maternal antibody in primary infection was assessed by a comparison of the distribution of antibody titers in a) 7 children who had an upper respiratory illness to 12 whose illness was accompanied by lower respiratory disease and of b) 13 children with an RSV-associated illness in the first 6 months of life who were age-matched as to month and approximate day of birth with 11 not infected in the same period. Infection induced immunity was evaluated by a comparison of antibody titers in 19 children who were reinfected with RSV in the year following their primary infection to 15 in whom reinfection was not documented. A statistical analysis of titers revealed that antibody to the fusion protein is an important correlate of immunity. In all three comparisons, the children with less RSV disease had significantly higher IgG anti-F titers prior to infection. No differences were observed between IgA anti-F or IgG and IgA anti-G titers.

Influenza A virus outbreak in a neonatal intensive care unit.

BACKGROUND: Nosocomial infections with influenza virus are rarely recognized in neonatal intensive care units (NICU). An outbreak of influenza A virus infection in the NICU of an urban county hospital during the 1997 to 1998 influenza season is reported. METHODS: Clinical and virologic data were recorded in all symptomatic NICU patients after influenza A infection was diagnosed in one infant in October, 1997. RESULTS: Influenza A/H3N2 was isolated from two of four symptomatic infants. The application of rapid diagnostic techniques for the characterization of influenza virus infection allowed the timely institution of basic infection control measures, limiting this outbreak. Resistance to amantadine was documented for the first time in this patient population by reverse transcription-PCR within 48 h of treatment in one case. CONCLUSIONS: Prevention by immunization is a priority in those caring for high risk NICU patients.

Typing and subtyping clinical isolates of influenza virus using reverse transcription-polymerase chain reaction.

BACKGROUND: Influenza virus infections are a major cause of morbidity and the identification of the type or subtype of a clinical isolate has important clinical and epidemiological implications. OBJECTIVES: To evaluate the ability of a reverse transcription-polymerase chain reaction (RT-PCR) assay to type and subtype clinical human isolates of influenza virus. STUDY DESIGN: Reference strains of influenza A H1N1, A/H3N2, and B viruses and human clinical isolates of influenza virus representing antigenic variants from the last 15 years were evaluated using an RT-PCR assay. RESULTS: Amplicons of 325, 198 and 365 base pairs in length were obtained from RNA extracted from influenza A/H1N1, A/H3N2 and B viruses, respectively. All human-derived A/H1N1, A/H3N2, and B reference strains and antigenic variants tested were correctly identified. CONCLUSIONS: RT-PCR is an effective alternative to traditional methods for typing and subtyping influenza viruses.

Comparison of reverse transcription-PCR with tissue culture and other rapid diagnostic assays for detection of type A influenza virus.

We applied a reverse transcription (RT)-PCR assay for influenza A virus to combined nasal wash-throat swab specimens previously obtained from an outpatient pediatric population with acute respiratory illness during concurrent epidemics of influenza A virus and respiratory syncytial virus. The results of the RT-PCR assay were compared with those previously reported with virus cultivation and commercially available rapid diagnostic kits (E.A. Dominguez, L.H. Taber, and R.B. Couch, J. Clin. Microbiol. 31:2286-2290, 1993). With virus cultivation as the "gold standard", the RT-PCR assay had a sensitivity, specificity, and efficiency of 95, 98, and 97%, respectively, compared with 75, 100, and 93%, respectively, for the best diagnostic kit (Becton Dickinson Directigen). RT-PCR is an effective alternative to virus isolation for the detection of influenza A virus in clinical specimens.

Comparison of different tissue cultures for isolation and quantitation of influenza and parainfluenza viruses.

Rhesus and cynomolgus monkey kidney tissue cultures and two continuous lines, Madin-Darby canine kidney (MDCK) and LLC-MK2, were compared in titrations and isolations of influenza and parainfluenza viruses. Tube cultures were inoculated with laboratory virus strains or stored patient specimens and observed for hemadsorption. Trypsin was added to the medium of the continuous lines to increase sensitivity. All four tissue cultures gave similar titers of influenza A/USSR (H1N1), A/Texas (H3N2), and B/HK, but lower titers of parainfluenza 1, 2, and 3 were observed with MDCK. Cynomolgus kidney was the best single tissue culture for reisolation of the six viruses, but foamy-virus contamination of many lots was a serious problem. Reisolation of influenza viruses was as successful with MDCK as with primary monkey kidney. LLC-MK2 was similar to rhesus kidney but less successful than cynomolgus kidney. For reisolation of parainfluenza viruses, LLC-MK2 was superior to rhesus monkey kidney and similar to cynomolgus kidney. MDCK was less useful for parainfluenza viruses. Thus, LLC-MK2 would be an acceptable single tissue alternative to primary monkey kidney. The combination of MDCK and LLC-MK2 would provide optimal sensitivity for isolation of all six viruses.

Attenuation of rhinovirus type 15: relation of illness to plaque size.

Rhinovirus type 15 passaged three times in WI-38 cells produced illness in only one of 35 volunteers, but infection resulted in formation of significant quantities of antibodies in the serums of 100%, and in nasal secretions of 89%, of infected volunteers. The inoculum contained large- (60%) and small- (40%) plaque variants. "Purified" large- and small-plaque inocula were prepared, and each was administered to 20 volunteers. There was a significant association of illness with the small-plaque inocula (P < 0.01) but the incidence of infection, quantitative virus shedding patterns, and mean serum and nasal secretory antibodies were not significantly different between the two groups. These findings suggest that plaque size may be an in vitro marker of attenuation of illness production by rhinoviruses.

Maintenance of viability and comparison of identification methods for influenza and other respiratory viruses of humans.

A comparison of Hanks balanced salt solution, veal infusion broth (VIB), and charcoal viral transport medium for maintaining viability of type A influenza virus indicated approximately equal survival of virus on all three media at -70 and 4 degrees C, whereas at 25 degrees C virus survived best in VIB. VIB supplemented with bovine serum albumin was used as transport medium in a community-wide surveillance of febrile respiratory disease for influenza viruses. Unfrozen throat swab specimens were placed in VIB and stored at 4 degrees C for up to 5 days without effect on isolation frequencies of either type A or type B influenza virus or type 1 or type 3 parainfluenza virus. Comparison of indirect immunofluorescence with hemadsorption for detection of type A influenza virus in rhesus monkey kidney cultures revealed a requirement for at least five fluorescing cells to eliminate false positive indirect immunofluorescence tests and at least 3 days of incubation to eliminate false negative tests when compared with hemadsorption at later times. Detection frequencies for the two methods after 2 and 3 days of incubation were not significantly different.

Maternal immunization with influenza or tetanus toxoid vaccine for passive antibody protection in young infants.

Women in the last trimester of pregnancy were given trivalent inactivated influenza virus vaccine (TIV; A/Sichuan/H3N2, A/Taiwan/H1N1, B/Victoria) or tetanus toxoid (TT). Maternal blood was drawn before immunization and at delivery (median, 5 weeks later); infant blood was obtained within 5 days of birth and 2 months later. Antibody responses to TIV and TT were determined by microneutralization assay and ELISA. T cell response was determined by lymphocyte proliferation. Maternal seroconversion to vaccine antigens was found to one or more influenza antigen in all TIV recipients and to TT in 9 of 13 TT recipients. Significantly higher IgG antibodies to maternal vaccine antigens were present in cord and infant serum. Significant blastogenic responses were seen to influenza A and B in maternal cells of TIV-immunized women but not in cord or infant lymphocytes. Maternal immunization resulted in higher infant levels of vaccine-specific IgG antibody but not in the transfer of specific T lymphocyte response(s) or production of neonatal IgM antibody.

Determination of immunoglobulin A concentrations in human nasal secretions with a serum immunoglobulin A standard.

By quantitative immunodiffusion tests, nasal secretion immunoglobulin A was underestimated by approximately 5.6-fold when the serum 7S immunoglobulin A standard was employed.

Cold recombinant influenza B/Texas/1/84 vaccine virus (CRB 87): attenuation, immunogenicity, and efficacy against homotypic challenge.

Healthy susceptible young adults were inoculated intranasally with increasing doses of wild-type influenza B/Texas/1/84, or the cold-adapted vaccine possessing the genes specifying the hemagglutinin and neuraminidase of the wild-type parent and the six internal genes of cold adapted B/Ann Arbor/1/66 (CRB 87). Most volunteers inoculated with 10(6.6)-10(7.6) TCID50 of CRB 87 were infected, but a high frequency of serum antibody responses was seen only at the highest dose (17/29; 59%). The dose of CRB 87 necessary to infect 50% of all human volunteers (1 HID50) was approximately 10(5.4) TCID50. All volunteers given 10(3.9)-10(7.1) TCID50 of the wild-type virus were infected (i.e., 1 HID50 was less than 10(3.9) TCID50). The frequency of mild febrile reactions, mean peak titer of virus in respiratory secretions, and duration of virus shedding were significantly greater in volunteers given 10(7.1) TCID50 of wild-type virus than in those given 10(7.6) TCID50 of CRB 87. Thirteen volunteers were rechallenged with a second 10(7.6) TCID50 dose of CRB 87 3-4 months after vaccination. The frequencies of mild upper respiratory symptoms and signs, virus shedding, and infection were significantly reduced in prior vaccinees compared with volunteers inoculated with a similar dose for the first time. These data suggest that CRB 87 is attenuated, immunogenic, and can confer protection against homotypic virus challenge in this susceptible population.

Dual respiratory virus infections.

We retrospectively reviewed eight prospective epidemiological studies conducted between 1991 and 1995 for dual respiratory virus infection (DRVI) to determine the frequency, associated comorbid conditions, clinical presentations, and morbidity related to DRVI among immunocompetent persons. Two viruses were identified as the cause of 67 (5.0%) of 1,341 acute respiratory virus infections. DRVI was detected in patients from < 1 year to 79 years of age, in both sexes, and in many races. Forty-two percent of patients with DRVI were < or = 4 years old. Fifty-eight percent of patients with DRVI had underlying chronic lung disease. DRVI was associated with upper respiratory tract illness; lower respiratory tract illness, including pneumonia; systemic influenza-like illnesses; and exacerbations of asthma or chronic obstructive pulmonary disease. All of the common acute respiratory viruses were identified; picornaviruses and influenzavirus A were the most common. The rate of DRVI (11.6%) was highest in the epidemiological studies in which cell culture, serology, and polymerase chain reaction were used together. Patients with DRVI were hospitalized significantly more often than those with respiratory infection due to a single virus (46.3% vs. 21.7%; P < .01). The percentage of DRVIs increased proportionally with the number of diagnostic methods used.

Development and application of an enzyme immunoassay for coronavirus OC43 antibody in acute respiratory illness.

Study of coronavirus OC43 infections has been limited because of the lack of sensitive cell culture systems and serologic assays. To improve this circumstance, we developed an indirect enzyme immunoassay (EIA) to detect serum antibody to OC43. Antigen (100 ng) prepared by polyethylene glycol precipitation provided optimal results without a postcoat procedure. Evaluation of intraplate variation indicated that a > or = 2.5-fold increase in serum titer was significant. Sixteen of 18 (89%) paired serum samples with previously identified, reproducible increases in the level of hemagglutination inhibition (HAI) antibody to OC43 also showed significant increases as detected by EIA. Specificity for the EIA was established with paired sera obtained from persons given influenza immunizations or experiencing a respiratory infection. No rise in antibody titers occurred among 33 persons with documented coronavirus 229E infection. EIA was then performed on each of 419 paired serum samples from ambulatory chronic obstructive pulmonary disease patients and healthy older adults, from asthmatic adults presenting for emergency room treatment, and from persons hospitalized with acute respiratory symptoms. Twenty-three antibody rises to OC43 were detected; only nine of these were detected by the HAI test, and the HAI test did not detect any increases in antibody titers that were not detected by EIA. Nineteen of 25 coronavirus OC43 infections for which a month of infection could be assigned occurred between November and February. Overall, 4.4% of acute respiratory illnesses in the studied populations were associated with a coronavirus OC43 infection.

Studies on reactogenicity and immunogenicity of attenuated bivalent cold recombinant influenza type A (CRA) and inactivated trivalent influenza virus (TI) vaccines in infants and young children.

Fifty-two infants seronegative to or without prior infection with influenza type A viruses were enrolled in a study to evaluate reactogenicity and immunogenicity of three bivalent cold recombinant type A (CRA) and two trivalent inactivated influenza (TI) vaccines. Controls consisted of infants receiving normal saline by nose drops (Pli.n.) or intramuscularly (Pli.m.). CRA and TI vaccines were monitored for local and systemic reactions after vaccination. Serum specimens obtained prior to and 6 weeks postvaccination were analysed for neutralizing antibody to influenza H1N1 and H3N2 viruses. CRA vaccines and Pli.n. recipients had similar numbers of acute respiratory infections and comparable rates of illnesses during the trial. Significantly fewer CRA vaccinees without an intercurrent viral infection had fever (0/16 versus 4/10, p = 0.04) and cough (4/16 versus 9/10, p = 0.002) than CRA vaccinees with a confirmed intercurrent viral infection. Recipients of TI vaccine and Pli.m. did not develop reactions at the injection site. For each of the CRA vaccines tested, a dominant CRA virus was identified. The dominant CRA viruses were isolated from a greater number of infants or for a longer duration than the non-dominant CRA viruses. All 14 non-dominant CRA viruses were recovered from infants within the first week after vaccination; 24 of 77 dominant CRA viruses were recovered more than 7 days after vaccination. The immunogenicity of CRA vaccines was not affected by a confirmed intercurrent viral infection or low titres of influenza-specific antibody.(ABSTRACT TRUNCATED AT 250 WORDS)

Interlaboratory study evaluating quantitation of antibodies to Haemophilus influenzae type b polysaccharide by enzyme-linked immunosorbent assay.

An interlaboratory study was conducted to determine whether an enzyme-linked immunosorbent assay (ELISA) with an antigen preparation composed of various-sized fragments of Haemophilus influenzae type b polysaccharide conjugated to human serum albumin could be standardized across laboratories and whether the ELISA-derived results from different laboratories are equivalent to those obtained by the standard radioactive antigen binding assay (RABA) for quantitation of anti-H, influenzae type b polysaccharide antibodies. Twenty coded human serum samples were quantitated by ELISA in 11 laboratories and by RABA in 5 laboratories. The mean RABA-derived values served as the basis for all comparisons. While the overall correspondence of antibody values between the two methods was good, significant differences were found among some of the 11 ELISA data sets and among the mean RABA values. Seven laboratories generated higher ELISA antibody values for low-titered sera. Four laboratories generated antibody concentrations that were not statistically different between the two assay methods. The results therefore indicate that the ELISA can tolerate substantial variations in protocol, such as the use of different plates and different antibody reagents, without affecting the quantitation of serum antibodies. However, attention should be focused on low-titered sera, as some assay conditions may yield spurious results. This ELISA is a serologic assay which can serve as an alternative to the RABA for quantitation of antibodies to H. influenzae type h polysaccharide.