Phase 1 evaluation of the respiratory syncytial virus-specific monoclonal antibody palivizumab in recipients of hematopoietic stem cell transplants

Antimicrobial therapy in childhood asthma and wheezing

There is an increasing number of viral and bacterial pathogens suspected of contributing to asthma pathogenesis in childhood, making it more difficult for the practitioner to make specific therapy decisions. This review discusses the role of viruses, e.g. respiratory syncytial virus, human metapneumovirus, influenza viruses and rhinoviruses, as well as the role of the atypical bacteria Chlamydophila pneumoniae and Mycoplasma pneumoniae, as contributors to childhood asthma. Diagnosis, prevention, and therapy are discussed, including a summary of drugs, i.e. macrolide antibacterials, antivirals, and vaccine regimens already available, or at least in clinical trials. For the practitioner dealing with patients every day, drug regimens are assigned to the individual pathogens and an algorithm for the management of atypical infections in patients with asthma or recurrent wheezing is presented.

In vivo selection of respiratory syncytial viruses resistant to palivizumab

Palivizumab (PZ) is the only monoclonal antibody currently available for use in humans against an infectious disease. PZ is administered prophylactically for respiratory syncytial virus (RSV) infections. RSV selected in cell culture for growth in the presence of PZ develops F gene mutations and can be resistant to PZ prophylaxis in cotton rats. Here, we evaluated the potential for PZ-resistant RSV mutants to arise in vivo. Cotton rats were immunosuppressed with cyclophosphamide, administered PZ, and inoculated intranasally with RSV. Lungs were harvested 12 weeks after RSV infection, reverse transcription-PCR-amplified F gene fragments were cloned into plasmids, and the nucleotide sequences of the cloned cDNAs were determined. Three of the five animals had mixed populations of lung virus, and over 50% of the clones from the three animals revealed F gene mutations associated with resistance to PZ. A virus completely resistant to PZ neutralization was recovered from the lung homogenate of a rat that had received PZ. Thus, prolonged pulmonary replication of RSV in the presence of PZ was followed by the appearance of viruses resistant to PZ. The potential for the development of resistance is a consideration as the antibody is used prophylactically against RSV and as passively administered antibodies are under development for other infections, including emerging viruses and agents of biodefense.

Frequent detection of respiratory viruses in adult recipients of stem cell transplants with the use of real-time polymerase chain reaction, compared with viral culture

Background. Respiratory virus infections have been recognized as important causes of severe pneumonia in patients who have undergone stem cell transplantation (SCT). Reported incidences of respiratory virus infection in adult SCT recipients vary in the literature from 3.5% to 36% when determined by viral culture. However, a more sensitive method to assess the presence of respiratory viruses in the lower airways may be important for delineation of the true incidence of respiratory virus—associated pneumonia and may be essential for guidance on implementation of antiviral therapy and prevention or limitation of nosocomial spread of infection with respiratory viruses.

Methods. To determine the incidence and severity of respiratory tract illness (RTI) and to assess the diagnostic value of real-time reverse-transcriptase polymerase chain reaction (RT-PCR) versus viral culture, 72 SCT recipients were monitored during a 6-month period.

Results. A respiratory virus was detected in 21% of episodes of RTI by viral culture and in 63% of RTI episodes by real-time RT-PCR (P < .0001). In lower respiratory tract illness, real-time RT-PCR was much more sensitive than viral culture for detection of respiratory virus (73% vs. 9%; P = .008). The mortality rate for patients with respiratory virus—associated lower respiratory tract illness (25%) was similar to rates reported elsewhere. Respiratory viruses (predominantly rhinovirus) were detected by real-time RT-PCR in 9% of samples obtained from symptom-free SCT recipients at predetermined times by real-time RT-PCR and by viral culture in 1% (P < .0001), indicating that asymptomatic shedding of respiratory viruses also occurs.

Conclusion. We conclude that, although asymptomatic shedding of respiratory virus occurs, respiratory viruses are frequent causes of RTI in SCT recipients.

Advances in the treatment and prevention of severe viral bronchiolitis

Viral bronchiolitis continues to be a major public health problem. Prevention of severe RSV-associated bronchiolitis has been achieved in high-risk infants by passive administration of the humanized monoclonal anti-RSV-F antibody, palivizumab. Development of more potent anti-RSV neutralizing antibodies is underway, and vaccine development continues to progress. Supportive therapy is the mainstay for the treatment of established infection while new antiviral and anti-inflammatory strategies are being explored in preclinical trials.

Treatment of respiratory syncytial virus pneumonia in a lung transplant recipient: case report and review of the literature

A 61-year-old woman who underwent lung transplantation developed severe respiratory syncytial virus (RSV) pneumonia and experienced respiratory failure requiring mechanical ventilation. She was treated initially with aerosolized ribavirin monotherapy; RSV hyperimmune globulin was later added to her regimen. Lung transplant recipients are acutely susceptible to respiratory infections, including community-acquired respiratory viruses. Respiratory syncytial virus is particularly difficult to treat in immunocompromised patients because of the lack of proved pharmaceutical agents and solid scientific evidence by which to guide therapy. The most important factor appears to be the early start of therapy; immunocompromised patients who develop RSV pneumonia and subsequent respiratory failure requiring mechanical ventilation have a mortality rate approaching 100%. This case report demonstrates the successful treatment of RSV pneumonia with the combination of aerosolized ribavirin and RSV hyperimmune globulin in a severely ill lung transplant recipient who required mechanical ventilation.

Combating infections in hematopoietic stem cell transplant recipients

Infections with a diverse group of microorganisms remain the leading causes of morbidity and mortality after hematopoietic stem cell transplantation. Importantly, the epidemiology of infectious complications has shifted substantially with changes in antimicrobial prophylaxis, conditioning regimens and graft manipulation, such that invasive mould infections and late viral infections are now the over-riding concerns. New antivirals and antifungals have entered clinical practice and hold considerable promise for improved outcomes.

Pretransplantation respiratory syncytial virus infection: impact of a strategy to delay transplantation

BACKGROUND

Delay of hematopoietic stem cell transplantation (HSCT) has been suggested if upper respiratory tract infection (URTI) due to respiratory syncytial virus (RSV) occurs in transplantation candidates, but the efficacy of this strategy in preventing posttransplantation RSV infection is unknown.

METHODS

In a retrospective study, we reviewed charts of patients who underwent transplantation at Fred Hutchinson Cancer Research Center (Seattle, WA) during the period of June 1987 through December 2000 and evaluated the strategy of delaying HSCT in candidates with laboratory-confirmed RSV URTI.

RESULTS

Thirty-one of 37 patients had RSV URTI before conditioning, 2 (6.5%) of whom developed RSV infection after HSCT. In 6 of 37 patients, symptoms of URTI were present during the start of conditioning, but RSV virologic confirmation occurred a median of 4.5 days (range, 2-5 days) into the conditioning regimen. Conditioning was aborted for 3 of 6 patients; none had progression to RSV pneumonia. Of the 3 patients in whom HSCT proceeded as scheduled, 2 developed RSV pneumonia. Overall, RSV pneumonia occurred in 1 of 34 patients for whom HSCT was delayed, compared with 2 of 3 patients for whom there was no delay (P=.01).

CONCLUSIONS

In patients with pretransplantation RSV URTI, delay of HSCT was associated with a lower risk of pneumonia than was no delay. Because URTIs can progress to severe complications in patients receiving HSCTs, these results support Centers for Disease Control and Prevention/American Society of Blood and Marrow Transplantation recommendations that HSCT be delayed on the basis of symptoms of URTI rather than waiting for virologic confirmation.

Quantitative Effects of Palivizumab and Donor-Derived T Cells on Chronic Respiratory Syncytial Virus Infection, Lung Disease, and Fusion Glycoprotein Amino Acid Sequences in a Patient Before and After Bone Marrow Transplantation

A patient with respiratory syncytial virus (RSV) infection and severe combined immunodeficiency was studied during a 3-month period of bone marrow transplantation and palivizumab infusion. No RSV isolates with palivizumab escape mutations were identified. Donor lymphocytes, including CD8 cells, appeared to markedly reduce the RSV load but increased the pulmonary symptoms. Immunosuppressive therapy ameliorated lung disease but allowed the RSV load to rebound.

Respiratory syncytial virus-related pneumonia after stem cell transplantation successfully treated with palivizumab and steroid therapy

A case is reported of a 56-y-old woman with a second relapse of Hodgkin's disease who early developed after autologous stem cell transplantation (ASCT) a severe RSV-related interstitial pneumonia successfully treated with 1-d intravenous palivizumab 8 mg/kg plus low-dose systemic steroid therapy. B-cells suppression with CMV antigenaemia were then observed and required treatment with ganciclovir and liposomal amfotericine B.

Management of infectious complications in the hematopoietic stem cell transplant recipient

Despite impressive accomplishments in supportive care over the past decade, infections with a diverse group of microorganisms remain leading causes of morbidity and mortality after hematopoietic stem cell transplantation. The epidemiology of infectious complications has shifted substantially in the past decade with changes in antimicrobial prophylaxis, conditioning regimens, and graft manipulation, such that invasive mould infections and late viral infections are now the overriding concerns. Individual patient risk for infections is predicated on multiple disease-specific, patient-specific, and transplant-related factors but often tracks with the cumulative level of immunosuppression (such as dose of corticosteroids used for the treatment of graft vs host disease [GVHD]). New antivirals and antifungals have entered clinical practice and hold considerable promise for improved outcomes.

The natural history of respiratory syncytial virus infection in cancer and transplant patients: implications for management

Respiratory syncytial virus (RSV) has been reported to cause severe morbidity and mortality among cancer patients receiving chemotherapy with or without autologous peripheral blood stem cell transplantation (APBSCT). However, little is known about the natural history of this infection in these patients, and current standard practice, aerosolized ribavirin plus intravenous immunoglobulin (IVIG), is extremely expensive, difficult to use, and not supported by controlled clinical trials. The purpose of this observational study was to determine the frequency, seasonality, morbidity, and mortality of RSV infection in a group of cancer patients receiving cytotoxic chemotherapy with neither ribavirin nor IVIG treatment. During the period of October 3, 1997, through October 14, 1998, 190 cancer patients (median age, 58 years; 71 women) underwent viral nasopharyngeal washing prior to chemotherapy. Multiple myeloma (MM) accounted for most patients (147, 77%). RSV was recovered from cultures taken from 71 patients (37%) throughout the year, although more frequently during fall and winter seasons (P &lt; .001) than spring and summer. Serious respiratory complications developed in 19 (27%) of 71 RSV-positive patients versus 24 (20%) of 119 patients whose RSV cultures were negative (P = .384). The presence of renal failure or increased lactate dehydrogenase (LDH) prior to chemotherapy and the development of mucositis were the only predictive factors for severe respiratory complications. Recovery of RSV from nasopharyngeal washings among cancer patients is common, occurs throughout the year, and does not appear to increase serious morbidity or mortality. RSV infection may not necessarily be a contraindication for APBSCT or an indication for therapy with aerosolized ribavirin and IVIG.

Supportive care

To optimize treatment outcomes for hematologic malignancies, minimizing the consequences of treatment complications requires as much skill as the choice of the treatment itself. Myelosuppression and immunosuppression are frequent complications and have potentially serious infectious consequences. Invasive fungal infections and infections from respiratory viruses are increasing in frequency and have life-threatening potential. Damage to vital organs, especially the liver, is another important concern. In this chapter, the scope of invasive fungal and respiratory viral infections, recent insights into the pathogenesis of hepatic sinusoidal injury, and recent developments that impact prevention and treatment approaches for these complications are described. In Section I, Dr. John Wingard describes the advantages and disadvantages of various treatment options for invasive infections by the two chief fungal pathogens, Candida and Aspergillus. Adjunctive therapies and practical considerations that clinicians should weigh in choosing one or another of the various agents are discussed. The studies that have evaluated antifungal prophylaxis and empirical treatment strategies are reviewed. Finally, new approaches such as combination therapy, new diagnostics, and efforts to bolster host immunity are considered. In Section II, Dr. W. Garrett Nichols describes the epidemiology of community-acquired respiratory viruses (CRV) in patients with hematologic malignancies. Risk factors, clinical syndromes, and possible indirect effects of CRV infections are discussed. Treatment and prevention options are reviewed. In Section III, Dr. George McDonald describes sinusoidal obstruction syndrome (once known as hepatic veno-occlusive disease). Recent insights into pathogenesis are described. Diagnostic criteria and the advantages and disadvantages of various diagnostic methods are reviewed and prognosis is considered. Prevention and treatment options are discussed.

Respiratory syncytial virus escape mutant derived in vitro resists palivizumab prophylaxis in cotton rats

Palivizumab (PZ) is the only monoclonal antibody in human use against an infectious disease. PZ is a humanized monoclonal antibody that recognizes the fusion protein of respiratory syncytial virus (RSV). PZ prophylaxis reduces the likelihood of hospitalization for young children at risk for severe RSV infections. The quasispecies nature of RNA viruses allows rapid emergence of viruses with a selective advantage. A PZ resistant virus was selected by passage of RSV in the presence of PZ in cell culture. The cell culture-derived virus was completely resistant to PZ prophylaxis in cotton rats. The increasing use of PZ, and in particular, the use of PZ in immunosuppressed patients, provide opportunities for resistant viruses to emerge. Whether such viruses will appear and be of clinical significance for humans is unknown. Preclinical studies in cotton rats predicted the efficacy of PZ in humans; these results suggest that if PZ resistant viruses arise in humans, PZ prophylaxis may be ineffective.

Respiratory virus infections in the immunocompromised host

The number of immunocompromised children in the population is increasing for a variety of reasons. Common respiratory viruses acquired in the community or in the hospital setting include the ortho- and paramyxoviruses and may cause severe lower respiratory tract disease in these children. Measles is again becoming a threat. Particularly in transplant patients, Herpes group viruses and adenoviruses, often part of a reactivation illness, can cause potentially life-threatening disease. The use of rapid molecular diagnostic techniques and an increasing array of antiviral therapies can help ensure a good outcome in many cases, although controlled clinical trial data are often lacking. Immunotherapeutic strategies using specific antibodies or cytotoxic T cells are being developed and are likely to have an increasing role in prophylaxis and pre-emptive therapy in the future. The development and introduction of vaccines against common respiratory diseases will help reduce the risks faced by these susceptible children.

Common community respiratory viruses in patients with cancer: more than just "common colds"

Community respiratory viruses long have been recognized as primary respiratory pathogens among infants and young children. More recently, it has become clear that these viruses cause a considerable disease burden throughout life. The consequences of repeated infections are most evident in elderly and immunocompromised persons. Even in otherwise healthy persons, reinfections often require medical attention but generally are undiagnosed and unrecognized. These reinfections may spread from healthy persons to those at highest risk. Control requires a multifaceted approach combining vaccination, chemoprophylaxis, and aggressive early antiviral treatment of high-risk individuals, as well as education of all populations affected by these viruses.

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.

The quest for an efficacious antiviral for respiratory syncytial virus

Respiratory syncytial virus (RSV) continues as an emerging infectious disease not only among infants and children, but also for the immune-suppressed, hospitalized and the elderly. To date, ribavirin (Virazole) remains the only therapeutic agent approved for the treatment of RSV. The prophylactic administration of palivizumab is problematic and costly. The quest for an efficacious RSV antiviral has produced a greater understanding of the viral fusion process, a new hypothesis for the mechanism of action of ribavirin, and a promising antisense strategy combining the 2'-5' oligoadenylate antisense (2-5A-antisense) approach and RSV genomics.

Viral infections in immunocompromised patients: what's new with respiratory viruses?

PURPOSE OF REVIEW

The leading cause of death in solid organ and hematopoietic stem cell transplant recipients is infection. The respiratory viruses, particularly respiratory syncytial virus, influenza, parainfluenza, adenovirus, and picornaviruses, are increasingly recognized as significant pathogens in these populations.

RECENT FINDINGS

Respiratory syncytial virus has again been found to be the most common of the respiratory viruses causing severe infections in transplant recipients. Advances in prevention, particularly with regard to infection control practices, and to lesser extent treatment have had a substantial impact on the frequency and outcomes of this infection. New studies have clarified the impact of influenza in the hematopoietic stem cell transplant recipients and have provided evidence to support the use of M2 and neuraminidase inhibitors for early treatment. The epidemiology of parainfluenza and adenovirus in transplant recipients has been clarified, although therapeutic modalities are still limited and understudied. New antiviral medications may bring improved outcomes of picornavirus infections in this population. Finally, a new virus, the human metapneumovirus, has recently been described and may be a significant respiratory pathogen in immunocompromised transplant recipients.

SUMMARY

Studies published over the past year have documented a new respiratory pathogen. They have also resulted in improved understanding of the epidemiology of all of the respiratory virus pathogens, and have contributed to improve management of respiratory syncytial virus and influenza infection in hematopoietic stem cell transplant and solid organ transplant recipients.

Preventing opportunistic infections after hematopoietic stem cell transplantation: the Centers for Disease Control and Prevention, Infectious Diseases Society of America, and American Society for Blood and Marrow Transplantation Practice Guidelines and beyond

This review presents evidence-based guidelines for the prevention of infection after blood and marrow transplantation. Recommendations apply to all myeloablative transplants regardless of recipient (adult or child), type (allogeneic or autologous) or source (peripheral blood, marrow or cord blood) of transplant. In Section I, Dr. Dykewicz describes the methods used to rate the strength and quality of published evidence supporting these recommendations and details the two dozen scholarly societies and federal agencies involved in the genesis and review of the guidelines. In Section II, Dr. Longworth presents recommendations for hospital infection control. Hand hygiene, room ventilation, health care worker and visitor policies are detailed along with guidelines for control of specific nosocomial and community-acquired pathogens. In Section III, Dr. Boeckh details effective practices to prevent viral diseases. Leukocyte-depleted blood is recommended for cytomegalovirus (CMV) seronegative allografts, while ganciclovir given as prophylaxis or preemptive therapy based on pp65 antigenemia or DNA assays is advised for individuals at risk for CMV. Guidelines for preventing varicella-zoster virus (VZV), herpes simplex virus (HSV) and community respiratory virus infections are also presented. In Section IV, Drs. Baden and Rubin review means to prevent invasive fungal infections. Hospital design and policy can reduce exposure to air contaminated with fungal spores and fluconazole prophylaxis at 400 mg/day reduces invasive yeast infection. In Section V, Dr. Sepkowitz details effective clinical practices to reduce or prevent bacterial or protozoal disease after transplantation. In Section VI, Dr. Sullivan reviews vaccine-preventable infections and guidelines for active and passive immunizations for stem cell transplant recipients, family members and health care workers.