Immunoprophylaxis and the control of respiratory syncytial virus disease

The therapeutic potential of monoclonal antibodies against respiratory syncytial virus

Attempts to develop a vaccine against respiratory syncytial virus (RSV), the major cause of lower respiratory tract disease in infants and young children, have been unsuccessful. Passive immunisation with antibody to RSV has been found to be an effective alternative method for prophylaxis. The product currently in use for RSV passive immunisation, a preparation of purified human IgG containing virus-neutralising activity, requires monthly iv. infusions. Monoclonal antibodies (mAbs) are currently under development as an alternative means of treatment that would require lower doses. The first such mAb was recently approved for RSV prophylaxis in the USA. The mucosal delivery of antibodies is also effective and a mAb nose drop treatment for immunoprophylaxis is under development. The potential of passive immunisation for the treatment of existing RSV infections is not clear. Antibody treatment following infection clearly suppresses viral replication but it may not reduce disease once inflammatory processes have been initiated.

Current treatment for acute viral bronchiolitis in infants

This paper provides an update and critical review of available data on the treatment of acute viral bronchiolitis in previously healthy infants, with special focus on new or promising therapies. The main potential benefits of medical assistance in these patients reside in the careful monitoring of their clinical status, the maintenance of adequate hydration and oxygenation, the preservation of the airway opened and cleared of secretions and the option to perform parental education. There is no convincing evidence that any other form of therapy will reliably provide beneficial effects in infants with bronchiolitis and currently, any treatment beyond supportive care should be prescribed on a case-by-case basis with watchful appraisal of its effects. Therapies such as ribavirin, IFN, vitamin A, antibiotics, mist therapy or anticholinergics, have not demonstrated any measurable clinical effect. Several studies and meta-analyses with beta(2)-agonists and corticosteroids have failed to show any benefit of significant extent, however, physicians keep favouring their use. Presently, adrenaline has received rather consistent support from clinical trials but it is not yet widely prescribed. There are other therapeutic strategies, for instance, heliox, hypertonic saline, noninvasive ventilation, physical therapy techniques, thickened feeds or palivizumab that have shown promising potential benefits, but evidence supporting its use is still limited and further studies should be warranted. In the meantime, infants with acute viral bronchiolitis should be treated following evidence-based clinical practice guidelines, keeping the patient central in the process and being sensitive to social, cultural and familiar influences on their treatment strategy.

Selected populations at increased risk from respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is the principal cause of bronchiolitis and pneumonia in infants and young children worldwide. Deficits in cellular immunity appear to promote severe RSV disease in children with malignancies, those undergoing chemotherapy and bone marrow transplant recipients. Respiratory syncytial virus infection appears to exacerbate pulmonary symptoms of cystic fibrosis. In such patients RSV disease may result in a prolonged hospital course, which is often complicated by the need for mechanical ventilation. Retrospective analyses of hospital admissions for RSV bronchiolitis among Native American and Alaskan Native children younger than 1 year of age have demonstrated rates of 62 per 1000 or higher, compared with the national average of 34 per 1000. Among these ethnic groups, specific host factors as well as environmental factors appear to contribute to these comparatively high rates of hospitalization for RSV infection. Respiratory syncytial virus has the potential to cause disease in all age groups. A 3-year observational study found that individuals who lived in a community setting, or who cared for young children on a consistent basis, experienced acute respiratory infections more commonly than those living independently or whose interaction with children was limited.

Clinical patterns and seasonal trends in respiratory syncytial virus hospitalizations in São Paulo, Brazil

The respiratory viruses are recognized as the most frequent lower respiratory tract pathogens for infants and young children in developed countries but less is known for developing populations. The authors conducted a prospective study to evaluate the occurrence, clinical patterns, and seasonal trends of viral infections among hospitalized children with lower respiratory tract disease (Group A). The presence of respiratory viruses in children's nasopharyngeal was assessed at admission in a pediatric ward. Cell cultures and immunofluorescence assays were used for viral identification. Complementary tests included blood and pleural cultures conducted for bacterial investigation. Clinical data and radiological exams were recorded at admission and throughout the hospitalization period. To better evaluate the results, a non- respiratory group of patients (Group B) was also constituted for comparison. Starting in February 1995, during a period of 18 months, 414 children were included- 239 in Group A and 175 in Group B. In Group A, 111 children (46.4%) had 114 viruses detected while only 5 children (2.9%) presented viruses in Group B. Respiratory Syncytial Virus was detected in 100 children from Group A (41.8%), Adenovirus in 11 (4.6%), Influenza A virus in 2 (0.8%), and Parainfluenza virus in one child (0.4%). In Group A, aerobic bacteria were found in 14 cases (5.8%). Respiratory Syncytial Virus was associated to other viruses and/or bacteria in six cases. There were two seasonal trends for Respiratory Syncytial Virus cases, which peaked in May and June. All children affected by the virus were younger than 3 years of age, mostly less than one year old. Episodic diffuse bronchial commitment and/or focal alveolar condensation were the clinical patterns more often associated to Respiratory Syncytial Virus cases. All children from Group A survived. In conclusion, it was observed that Respiratory Syncytial Virus was the most frequent pathogen found in hospitalized children admitted for severe respiratory diseases. Affected children were predominantly infants and boys presenting bronchiolitis and focal pneumonias. Similarly to what occurs in other subtropical regions, the virus outbreaks peak in the fall and their occurrence extends to the winter, which parallels an increase in hospital admissions due to respiratory diseases.

Prophylaxis for respiratory syncytial virus with respiratory syncytial virus-immunoglobulin intravenous among preterm infants of thirty-two weeks gestation and less: reduction in incidence, severity of illness and cost

OBJECTIVE

To determine the impact of respiratory syncytial virus (RSV) prophylaxis among preterm infants of < or =32 weeks gestation by comparing the severity of illness and cost of RSV-related care during the two winter seasons before (1994 to 1995, 1995 to 1996) with the two seasons after initiation of prophylaxis (1996 to 1997, 1997 to 1998).

METHODS

Preterm infants of < or =32 weeks gestation at risk for hospitalization with RSV infection were identified retrospectively from the infants hospitalized in our neonatal units. Infants were included if they (1) were born 6 months before or during four winter seasons (1994 to 1998), (2) were discharged from the neonatal unit and (3) had remained in the university outpatient clinic system during at least the first winter of life. Preterm infants of < or =32 weeks gestation hospitalized with RSV were identified from our RSV database (which includes cost of hospitalization, duration of hospital stay, pediatric intensive care unit stay and intubation). Infants receiving prophylaxis were identified prospectively.

RESULTS

The incidence of hospitalization with RSV was significantly lower among the cohort of infants born after initiation of prophylaxis: 8.7% (17 of 195) vs. 22% (35 of 159), P = 0.00049 by two tailed Fisher's exact test. Among the cohort of infants born after initiation of prophylaxis (n = 195), 100 infants received prophylaxis. The gestational and chronologic ages of the prophylaxis-treated infants were significantly lower than those of the non-prophylaxis-treated infants (n = 95). The prophylaxis-treated infants also were more likely to have bronchopulmonary dysplasia. Only 1 (1%) of the prophylaxis-treated infants required hospitalization for RSV. Comparison of the cohort of infants born before initiation of prophylaxis to the cohort born after initiation of prophylaxis (includes prophylaxis-treated and non-prophylaxis-treated infants) revealed a significant reduction in severity of illness and cost. The length of stay in the cohort born before initiation of prophylaxis was reduced 83.8%: 373.6 days per 100 infants at risk vs. 60.5 (P = 0.00055). The length of stay in the pediatric intensive care unit was reduced 92.7%: 218.2 days per 100 infants at risk vs. 15.9 (P = 0.00029). The duration of intubation was reduced 95.6%: 187.4 days per 100 infants at risk vs. 8.2 (P = 0.00024). The dollars spent for RSV-related care (hospitalizations and prophylaxis) per 100 infants at risk for RSV was reduced 65% in the cohort of infants born after prophylaxis: $670,590 per 100 infants at risk vs. $234,596 (P = 0.00056). This reduction remained significant (64.9%) if the cost of ribavirin (drug and administration fees) was excluded from the cost of hospitalization.

CONCLUSIONS

These data reveal that RSV prophylaxis significantly reduced the incidence of RSV hospitalizations and severity of illness as well as the cost of RSV-related care among these infants.

Safety and pharmacokinetics of an intramuscular monoclonal antibody (SB 209763) against respiratory syncytial virus (RSV) in infants and young children at risk for severe RSV disease

We conducted a multicenter, double-blind, placebo-controlled, randomized trial of a humanized monoclonal antibody against a respiratory syncytial virus (RSV) fusion protein (SB 209763) to evaluate its safety, pharmacokinetics, and fusion inhibition and neutralization titers. Forty-three infants who were either delivered prematurely ( Collapse

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MESH Headings

• Antibodies, Monoclonal/administration & dosage
• Antibodies, Monoclonal/adverse effects
• Antibodies, Monoclonal/pharmacokinetics
• Antibodies, Monoclonal, Humanized
• Antibodies, Viral/administration & dosage
• Antibodies, Viral/immunology
• Child, Preschool
• Double-Blind Method
• Female
• Half-Life
• Humans
• Infant
• Injections, Intramuscular
• Male
• Respiratory Syncytial Virus Infections/immunology
• Respiratory Syncytial Virus Infections/prevention & control
• Respiratory Syncytial Viruses/immunology

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Grants Collapse

Affiliation(s)

H C Meissner Department of Pediatrics, New England Medical Center, Tufts University School of Medicine, Boston, Massachusetts 02111, USA.
J R Groothuis
W J Rodriguez
R C Welliver
G Hogg
P H Gray
R Loh
E A Simoes
P Sly
A K Miller
A I Nichols
D K Jorkasky
D E Everitt
K A Thompson

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[The premature infant confronting community-acquired infections. Which prophylaxis?]

Preterm infants are at high risk of severe community acquired infections. In particular viral respiratory infections, mainly respiratory syncitial virus infections (RVS), are responsible for a high incidence of rehospitalizations of preterm infants during their 2 first years of life. Prevention relies upon 1/the application of an immunization program identical to the program applied to normal term infants, a cardiorespiratory monitoring during 48-72 hours following immunization being recommended in those infants who carry a risk of recurrent apnea; 2/general measures with a demonstrated protective effect, i.e., breast feeding, elimination of smoking at home, and when possible limitation of contacts with infant and children communities. Immunoprophylaxis against RVS infections has been shown to be effective in reducing the severity of RVS infections in preterm infants but is presently not available in European countries.

-Prevention of respiratory syncytial virus infection-

Respiratory syncytial virus (RSV) is responsible for annual outbreaks of severe respiratory disease among infants. Its prevention has been considered for many years but the first vaccination trials resulted in diseases of increased severity. New vaccines are in progress with promising results, although their efficacy in the presence of maternal antibodies, and their tolerance in very young babies, remain to be demonstrated. Concerning passive immunization, intravenous anti-RSV immunoglobulins have been successfully tested in children at risk of severe bronchiolitis; however this prophylaxis is not applicable to healthy children. The use of local immunization with intranasal monoclonal antibodies is under study. While waiting for a safe and efficient immunization against RSV, prevention of nosocomial infections by cohorting and handwashing is recommended.

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.