Enhanced pulmonary pathology in cotton rats upon challenge after immunization with inactivated parainfluenza virus 3 vaccines.

Vaccine-induced potentiation was studied in cotton rats immunized with formalin-inactivated human parainfluenza type 3, ultraviolet light-inactivated virus, or infection with live virus. Immunized animals and unimmunized controls were later challenged by intranasal inoculation of live virus and evaluated for pulmonary pathology 4 days later. Animals immunized with either of the inactivated vaccines developed marked peribronchiolitis, perivasculitis, and an alveolar cellular infiltration much more severe than seen in animals infected previously, or in unmanipulated but challenged animals. Disease enhancement after immunization with killed virus is thus a characteristic of a member of each of three genera of the family, Paramyxoviridae, and is not restricted to immunization with formalin-inactivated virus.

Physicians' perceptions of the status of adolescent health care within the military health system.

OBJECTIVE: To describe the nature of the health care delivered to dependent adolescents throughout the military and compare services provided in adolescent medicine clinics with those provided in other medical departments and clinics. METHOD: Questionnaires were sent to physicians in pediatrics, internal medicine, family practice, primary care, emergency care, and adolescent medicine at 101 randomly selected military treatment facilities. A subsample of experts was selected to provide facility-specific, informed, representative information on the care provided to adolescents. RESULTS: Sixty-six percent (N = 345) of physicians returned completed questionnaires, providing information on 100% of the facilities sampled. More than half of responders felt that adolescents avoided care in their department. Two-thirds of all physicians, and three-fourths of the expert subsample, believed that adolescents are best served within adolescent medicine clinics. The expert subsample reported that adolescents served in facilities with adolescent medicine clinics received broader services. Only 28% of the facilities sampled provided any specialized adolescent medicine services. CONCLUSION: The military health care system has made progress in providing care to adolescent dependents, but reaching larger numbers of adolescents requires additional efforts.

Effectiveness of RSVIG prophylaxis and therapy of respiratory syncytial virus in an immunosuppressed animal model.

Respiratory syncytial virus (RSV) has emerged as a leading cause of pneumonia, with high mortality, in bone marrow transplant (BMT) recipients, as well as in other profoundly immunocompromised patients, such as myelosuppressed adults with leukemia. We tested the efficacy of immunoglobulin with high anti-RSV neutralizing antibody levels (RSVIG) for prophylaxis and therapy of RSV infection in cotton rats undergoing prolonged immunosuppression with cyclophosphamide. These animals experience persistent infection, a model which is similar to the disease seen in post-BMT humans. Both prophylaxis and therapy reduced pulmonary viral replication over 500-fold to nearly undetectable levels. In animals receiving continual immunosuppression, the use of multiple therapeutic doses of RSVIG was able to prevent rebound viral replication, though virus was not completely eliminated.

Human respiratory syncytial virus produces prolonged alterations of neural control in airways of developing ferrets.

A dysfunction of pathways that normally cause contraction or relaxation of airways has been proposed to explain heightened levels of responsiveness produced by various insults to the airway. For example, we previously reported (4) that infection of cotton rats with the human respiratory syncytial virus (HRSV) leads to a significant decrease in an airway's nonadrenergic noncholinergic inhibitory (NANCi) response shortly after the infection. In the present study we addressed the more chronic effects of HRSV infection on airway function in young ferrets during a period of rapid somatic growth. Animals 1 wk old received HRSV or uninfected cell culture medium intranasally. In vitro studies of airway function were performed on tracheal smooth muscle (TSM) segments at 4, 8, and 24 wk of age. To evaluate neurally mediated contractile responses, frequency-response curves to electrical field stimulation (EFS) were performed with results expressed in terms of the frequency causing 50% of the maximal contractile response (ES50). In addition, contractile responses of TSM to methacholine (MCh) were also assessed with results expressed as the concentration needed to produce 50% of the maximal contractile response (EC50). To gauge NANCi responses, TSM was contracted with neurokinin A in the presence of atropine, propranolol, and indomethacin. Relaxant responses to EFS were assessed at frequencies from 5 to 30 Hz, with results expressed as mean percent relaxation. We found increased contractile responses to EFS in infected animals compared with that in the control group in both 4- and 8-wk old animals (p = 0.001 and p = 0.008, respectively). This difference had resolved by 24 wk of age. There was no difference in TSM responses to MCh between the groups at any age. Although there were no NANCi responses in 4-wk-old ferrets from either group, NANCi responses were significantly decreased in 8-wk-old ferrets previously infected with HRSV in the first week of life (p = 0.0001). A significant difference persisted (p = 0.008), albeit to a lesser degree, at 24 wk of age. These findings demonstrate that HRSV produces prolonged alterations of TSM function in ferret airways in vitro.

Sustaining membership lecture award. Dogma, the shade that blinds.

At the heart of medical science is the responsibility for investigators and practitioners to use the scientific method to seek and apply new knowledge to better understand the mechanisms, diagnosis, treatment, and prevention of disease. At times it is difficult to differentiate hypothesis or speculation from documented fact. This essay describes an episode in human biology and medicine in which authoritative speculation evolved into dogma and impeded investigators' proper interpretation of data about the pathogenesis of respiratory syncytial virus (RSV) bronchiolitis in infants. Speculation-turned-dogma regarding RSV seriously impeded scientific progress regarding RSV disease for nearly a generation. Teachers, biomedical scientists, and medical practitioners must remain vigilant for unsubstantiated dogma that can seriously impede progress in the medical sciences.

Development of a humanized monoclonal antibody (MEDI-493) with potent in vitro and in vivo activity against respiratory syncytial virus.

Neutralizing polyclonal antibody to respiratory syncytial virus (RSV) has been shown to be an effective prophylactic agent when administered intravenously in high-risk infants. This study describes the generation of a humanized monoclonal antibody, MEDI-493, that recognizes a conserved neutralizing epitope on the F glycoprotein of RSV. The affinity of MEDI-493 was found to be equal to or slightly better than an isotype-matched chimeric derivative of the parent antibody. In plaque reduction, microneutralization, and fusion-inhibition assays, MEDI-493 was significantly more potent than the polyclonal preparation. Broad neutralization of a panel of 57 clinical isolates of the RSV A and B subtypes was demonstrated. Pretreatment of cotton rats with MEDI-493 resulted in 99% reduction of lung RSV titers at a dose of 2.5 mg/kg, corresponding to a serum concentration of 25-30 microg/mL. Further, MEDI-493 did not induce increased RSV infection or pathology in either a primary or a secondary challenge.

Immunoprophylaxis of group B respiratory syncytial virus infection in cotton rats.

Two antigenic groups of respiratory syncytial virus (RSV) have been identified: A (RSV/A) and B (RSV/B). Topical administration of human IgG screened for high titers of antibody to RSV/A (RSVIg) is protective against RSV/A infection in the cotton rat model. The study attempted to determine if topical RSVIg would also be protective against RSV/B. Cotton rats were pretreated intranasally with RSVIg or with monospecific antiserum obtained from animals previously infected with RSV/A or RSV/B (day 0), challenged intranasally with RSV/A or RSV/B (day 1), and sacrificed for virus titration (day 5). Cotton rat antiserum to RSV/B protected against RSV/A and RSV/B, while antiserum to RSV/A protected only against RSV/A. RSVIg, although prepared on the basis of activity against RSV/A, was also protective against RSV/B.

Respiratory syncytial virus (RSV) immune globulin intravenous therapy for RSV lower respiratory tract infection in infants and young children at high risk for severe RSV infections: Respiratory Syncytial Virus Immune Globulin Study Group.

OBJECTIVES: To evaluate the efficacy of high-titer intravenous respiratory syncytial virus immune globulin (RSVIG) in the treatment of children at high risk for severe RSV infection who were hospitalized with proven RSV. METHODS: Infants and young children younger than 2 years with bronchopulmonary dysplasia, chronic lung disease, congenital heart disease, or prematurity (<32 weeks' gestational age), hospitalized with a history of lower respiratory tract infection (LRI) of less than 4 days, were enrolled in this study. Patients were randomized in a blinded fashion to receive either 1500 mg/kg RSVIG or placebo in equal volumes. They were evaluated daily for safety and respiratory scores and for RSV nasal shedding. RESULTS: One hundred seven high-risk children were randomized--54 in the RSVIG group and 53 in the placebo group. Of these children, 51 in each group were considered evaluable. Children with pulmonary disease, congenital heart disease, or prematurity were equally distributed between the two treatment groups. However, two important differences were found in baseline variables between the two groups: there were more patients in the placebo group who had histories of previous LRI and there was a trend toward more severe disease at study entry in the RSVIG group. This was manifested by a higher entry respiratory score in the RSVIG group than in the placebo group (3.4 +/- 0.2 vs 3.1 +/- .01). A higher proportion of children in the RSVIG group (47%) than in the placebo group (28%) required intensive care at entry and mechanical ventilation at study entry (31% RSVIG-treated vs 18% placebo-treated patients). No significant difference was found between groups in the mean unadjusted duration of hospitalization (RSVIG group, 9.10 +/- 1.18 days; control group, 8.17 +/- 1.08 days). When the mean was adjusted for entry respiratory score, likewise, no difference was observed between each group (8.41 +/- 0.97 vs 8.89 +/- .99 days). The lack of efficacy observed in the study primary endpoint was observed in all diagnostic groups. No differences between the RSVIG and placebo groups were observed in the following secondary endpoints: duration of intensive care unit stay, duration of intensive care unit stay for RSV, mechanical ventilation, or supplemental oxygen. No significant differences in adverse events were reported in the RSVIG group (16 children) when compared with the control group (10 children). CONCLUSION: RSVIG treatment was safe but not efficacious in the treatment of children with bronchopulmonary dysplasia, congenital heart disease, or premature gestation who were hospitalized with RSV LRI.

Prevention and treatment recommendations for respiratory syncytial virus infection. Background and clinical experience 40 years after discovery.

Though 40 years have passed since its discovery, respiratory syncytial virus (RSV), one of the most ubiquitous viruses known, continues to evade most of our efforts to prevent or treat the clinical disease it causes. Long recognised as the most common cause of lower respiratory tract infections in virtually all children in the first 2 years of life, it has been increasingly recognised as a cause of more serious disease in several 'high risk' populations. These populations include infants with cardiac or pulmonary disease and infants and adults with immunodeficiencies, particularly those undergoing bone marrow transplantation. Early attempts to immunise children with a simple formalin-inactivated vaccine led to severe disease in vaccinated children who subsequently were infected with RSV from the community. Other vaccine constructs have failed for a variety of reasons, although surface glycoprotein subunit vaccines may hold promise. For years, ribavirin, a synthetic nucleoside analogue administered by constant aerosol, has been felt by many to lead to more rapid improvement in clinical disease caused by RSV, but it is still unclear whether its benefits are truly significant. An intravenous immunoglobulin product prepared from donors screened for the presence of high titres of RSV neutralising antibody (known as RSVIG) appears to be well tolerated and relatively effective in protecting high-risk infants against serious RSV disease, although therapeutic use has proven less dramatic. At least one monoclonal antibody undergoing current testing may prove easier to use in similar immunoprophylactic use. Results on the use of corticosteroids as supportive therapy have not been conclusive. In short, RSV will continue to be a challenge for clinicians and researchers well into the next century.

Semi-permissive replication and functional aspects of the immune response in a cotton rat model of human parainfluenza virus type 3 infection.

A cotton rat (Sigmodon fulviventer) model of human parainfluenza virus type 3 (HPIV-3) infection was used to study patterns of HPIV-3 replication in naive and immune hosts. Growth curves revealed that nasal and pulmonary tissues of naive animals were semi-permissive for virus replication, with amounts of progeny virus proportional to inoculating doses. In naive animals there was a total eclipse in nasal tissues beginning 4 h after inoculation. By contrast, there was only partial eclipse of virus in pulmonary tissues, most pronounced at 1 h after inoculation. Immune animals demonstrated a delayed eclipse in pulmonary tissues upon rechallenge. Infection with very low doses of HPIV-3 induced complete protection against high-dose challenge in the absence of systemic neutralizing antibody, suggesting a significant role for other systemic or local immune effectors.

Topical immunoglobulin is an effective therapy for parainfluenza type 3 in a cotton rat model.

A cotton rat model was used to test the efficacy of topical immunotherapy against parainfluenza type 3 (PIV3) infection. On day 3 after experimental infection with 10(5.5) pfu of PIV3, animals were treated with 2-fold dilutions of convalescent cotton rat serum or with one of two purified human immunoglobulin preparations; all three had moderate titers of anti-PIV3 neutralizing antibody (range, 1:200-1:1000). Therapy with high concentrations of all three preparations resulted in significant reductions of > or = 2 logs (> or = 100-fold) of pulmonary virus titers compared with titers for control animals. Little or no reduction in virus titers were seen in nasal tissues.

Human respiratory syncytial virus affects nonadrenergic noncholinergic inhibition in cotton rat airways.

A dysfunction of the nonadrenergic noncholinergic inhibitory (NANCi) system has been invoked as a possible mechanism underlying or contributing to altered airway function. In the present study we assessed whether human respiratory syncytial virus (HRSV) infection affects the airways' neurally mediated contractile and relaxant (NANCi) responses in vitro. NANCi responses were studied on tracheal smooth muscle (TSM) segments obtained from young adult cotton rats, a well-established model for HRSV infection. To assess NANCi responses, TSM segments were removed and placed in tissue baths containing modified Krebs-Henseleit, atropine (1 x 10(-6) M) and propranolol (5 x 10(-6) M). After contraction with neurokinin A (1 x 10(-5) M), electrical field stimulation (EFS) was applied at stimulation frequencies ranging from 5 to 30 Hz. The NANCi responses were measured and expressed as the mean (+/- SE) percent relaxation. To evaluate neurally mediated contractile responses, full frequency response curves (0.5-30 Hz) to EFS were also performed. We found significantly decreased NANCi responses in TSM segments obtained from infected cotton rats (n = 12) compared with control animals (n = 9) (P < 0.002). Furthermore, the contractile responses to EFS were increased in infected animals compared with the control group (P = 0.0001). These findings demonstrate that HRSV infection leads to an enhanced contractile response to EFS and a significant decrease in NANCi response in cotton rat airways in vitro. This disruption of the neural control of airways may lead to the development of altered airway function.

Respiratory syncytial virus (RSV) infection in preterm infants and the protective effects of RSV immune globulin (RSVIG). Respiratory Syncytial Virus Immune Globulin Study Group.

OBJECTIVE: To evaluate the safety and efficacy of respiratory syncytial virus immune globulin (RSVIG) in the prevention of severe respiratory syncytial virus (RSV) lower respiratory tract infection (LRTI) in infants born prematurely with or without bronchopulmonary dysplasia (BPD). METHODS: Data from a prospective, blinded, randomized, multicenter trial during three consecutive RSV seasons involving 249 children. This analysis comprises 162 preterm children, of whom 102 had BPD. The 87 children with congenital heart disease (CHD) were excluded from this analysis. Children were randomized to receive monthly infusions of RSVIG 750 mg/kg (high dose), RSVIG 150 mg/kg (low dose), or no RSVIG: Results from the preterm infants with and without BPD who received RSVIG 750 mg/kg are contrasted with control infants who did not receive RSVIG: RESULTS: As compared with controls, high-dose RSVIG administration significantly reduced the incidences of RSV LRTI (P = .01) and moderate-to-severe LRTI (P = .006). RSV-associated hospitalization also was decreased (P = .06) as well as were total RSV-associated days in the intensive care unit (P = .05). Significantly fewer preterm infants developed severe RSV LRTI in the RSVIG group compared with controls (4/58 [7%] vs 14/58 [24%], respectively; P = .01). Adverse reactions occurred in 5% of RSVIG infusions. These were generally mild and included reversible fluid overload, transient fever, and decreases in oxygen saturation. There was one death unrelated to either RSV or RSVIG administration. CONCLUSIONS: Prophylaxis with RSVIG is safe and is currently the only effective means to prevent severe RSV LRTI in high-risk preterm infants.

Safety and bioequivalency of three formulations of respiratory syncytial virus-enriched immunoglobulin.

Respiratory syncytial virus (RSV) causes serious illness (lower respiratory illness) in preterm infants. RSV antibody-enriched immunoglobulin (RSVIG) that was lyophilized (LYO) protected against RSV lower respiratory illness. The Food and Drug Administration now requires an additional viral inactivation step (VI). We compared LYO, LYO-VI, and a more convenient liquid RSVIG (LIQ-VI) in 30 preterm infants (median age, 7 months; median weight, 5.4 kg). Infants were randomized to receive LYO (n = 10), LYO-VI (n = 10), or LIQ-VI (n = 10) in monthly infusions of 750 mg/kg of body weight per dose (December to March). Children were monitored closely for adverse reactions to RSVIG and for RSV illness.

Systemic immunoprophylaxis of nasal respiratory syncytial virus infection in cotton rats.

The cotton rat model was used to test whether systemically administered immunoglobulin could protect nasal tissues against low challenge doses of respiratory syncytial virus (RSV). Animals were pretreated by intraperitoneal injection of human immunoglobulin with moderate (1:2226) or high (1:15,000) neutralizing antibody titers to RSV (day 0), challenged intranasally with RSV Long at doses ranging from 10(1) to 10(5) pfu (day 1), and sacrificed for virus titration (day 5). Pretreatment with moderate-titer immunoglobulin effected complete or near complete nasal protection against low to moderate (10(1)-10(3) pfu) RSV challenge doses and a significant reduction in nasal RSV titers at high (10(4)-10(5) pfu) challenge doses. Pretreatment with high-titer immunoglobulin effected near complete nasal protection at an RSV challenge dose of 10(3) pfu and highly significant and significant reductions in nasal RSV titers at challenge doses of 10(4) and 10(5) pfu, respectively. Immunoprophylaxis effected complete or near complete pulmonary protection at all RSV challenge doses.

Hyperimmune globulins in prevention and treatment of respiratory syncytial virus infections.

Respiratory syncytial virus (RSV) is an important community and nosocomial respiratory pathogen for infants and young children. RSV causes especially severe disease in the prematurely born or those with chronic cardiopulmonary diseases. Elderly persons and those with T-cell deficiencies, such as bone marrow transplant recipients, are also at high risk for serious lower respiratory tract infections. To date, prevention of RSV infections by vaccination has proven elusive and no preventive drugs exist. Studies in animals and humans have shown that the lower respiratory tract can be protected from RSV infection by sufficient circulating RSV neutralizing antibody levels. Recently, an RSV hyperimmune immune globulin (RSVIG) was developed and tested for the prevention of RSV infections or reduction of disease severity. Passive immunization of high-risk children with RSVIG during the respiratory disease season effected significant reductions in RSV infections, hospitalizations, days of hospitalization, intensive care unit admissions, days in the intensive care unit, and ribavirin use. Studies in cotton rats and owl monkeys show that RSV infections can also be treated with inhalation of immune globulin at doses substantially smaller than required for parenteral treatment. Therapeutic trials of parenteral RSVIG have been completed and are pending analysis. The use of polyclonal, hyperimmune globulins and perhaps human monoclonal antibodies provides an additional approach to the prevention and perhaps the treatment of certain viral lower respiratory tract infections such as those caused by RSV.

Intravenous immune globulin prophylaxis of late-onset sepsis in premature neonates.

To determine whether a single dose of intravenously administered immune globulin (IVIG) decreases late-onset sepsis in premature infants, we prospectively entered 753 neonates with birth weight 500 to 2000 gm, gestation < or = 34 weeks, and age < or = 12 hours into a multicenter, double-blind, controlled trial. Infants were randomly selected to receive a single intravenous infusion, 10 ml/kg, of either IVIG (500 mg/kg) or albumin (5 mg/kg) and were observed for 8 weeks for infection. Maternal and neonatal risk factors for infection did not differ between groups. Although serum IgG values before infusion were related to gestation (R = 0.62), the change in serum IgG or half-life of IgG after IVIG infusion was not (R < or = 0.09). The serum IgG concentration was increased (p < 0.05) in IVIG-treated patients for 8 weeks. There were 88 episodes of late-onset sepsis in 79 neonates (10.5%). Causative organisms included the following: Staphylococcus epidermidis (37 episodes), Enterococcus (9), Staphylococcus aureus (7), Candida (6), Escherichia coli (6), and multiple organisms (11). Sepsis, death, and death as a result of infection were unaffected by treatment. We conclude that a single infusion of IVIG, 500 mg/kg, shortly after birth was not effective prophylaxis for late-onset infection in premature neonates. Future studies of late-onset sepsis prophylaxis should consider IVIG with known pathogen-specific antibody concentrations against organisms causing these infections, in particular S. epidermidis.

Comparison of antibody concentrations and protective activity of respiratory syncytial virus immune globulin and conventional immune globulin.

Relative to conventional immune globulins (IG, 13 lots), IGs prepared from donors with high activity by microneutralization assay to respiratory syncytial virus (RSVIG, 8 lots) had significantly higher neutralizing antibodies to 6 RSV strains (mean enrichment, 5.2-fold; range, 2.6- to 10.0-fold). In contrast, IgG antibody concentrations to whole RSV, fusion protein, or glycoproteins of A and B strains were similar in RSVIG and IG. Treatment of cotton rats with RSVIG at 0.5 g/kg 24 h before RSV challenge reduced RSV by 99% in the lungs (P < .001). RSVIG at 5.0 g/kg reduced RSV by 99% in the nose. IG at 5.0 g/kg had efficacy similar to that of RSVIG at 0.5 g/kg. Serum plaque-reduction neutralization titers of 1/390 resulted in 99% reduction of lung RSV and titers of 1/3500 resulted in 99% reduction in nose RSV. Relative to IG, RSVIG is enriched selectively in RSV neutralizing antibodies and has approximately 10 times greater protective activity in cotton rats.

Viral respiratory diseases in children: classification, etiology, epidemiology, and risk factors.

The epidemiology, molecular structure, cell tropism, and pathophysiology of many human disease-causing viruses have been painstakingly and elegantly characterized during the past 50 years. Vaccines and antiviral drugs of varying efficacy were developed and tested. Despite the relegation of smallpox to a freezer chest and the progress in the control of measles and hepatitis B, the viruses that cause respiratory tract infections remain significant causes of illness and death in pediatric populations worldwide. This discussion surveys the virus groups that contain nearly 200 distinct viruses that cause sporadic and epidemic respiratory infections in children. The epidemiology of infection with the influenza A and B, parainfluenza, and respiratory syncytial viruses and adenoviruses and their impact on infants and children and the groups at highest risk for morbid outcomes are discussed.