Introduction to the guidelines

Overview of Infections in the Immunocompromised Host

Understanding the components of the immune system that contribute to host defense against infection is key to recognizing infections that are more likely to occur in an immunocompromised patient. In this review, we discuss the integrated system of physical barriers and of innate and adaptive immunity that contributes to host defense. Specific defects in the components of this system that predispose to particular infections are presented. This is followed by a review of primary immunodeficiency diseases and secondary immunodeficiencies, the latter of which develop because of a specific illness or condition or are treatment-related. The effects of treatment for neoplasia, autoimmune diseases, solid organ and stem cell transplants on host defenses are reviewed and associated with susceptibility to particular infections. In conclusion, an approach to laboratory screening for a suspected immunodeficiency is presented. Knowledge of which host defects predispose to specific infections allows clinicians to prevent, diagnose, and manage infections in their immunocompromised patients most effectively.

Palivizumab: where to from here?

Respiratory syncytial virus (RSV) is a common cause of respiratory tract infections. In severely immunosuppressed patients RSV can cause significant morbidity and mortality. The only FDA-approved drug for RSV is aerosolized ribavirin. Given the high morbidity and mortality in high-risk populations and inconsistent results with aerosolized ribavirin, new strategies for prevention and treatment of RSV are being sought. Palivizumab is an RSV-specific monoclonal antibody. A randomized, double-blind, placebo-controlled multicenter study showed significant reduction in hospitalization rates among children at high risk of RSV infection who had been given prophylactic palivizumab; these findings led to palivizumab's approval by the FDA in June 1998. Palivizumab also has a role in prevention of severe respiratory tract infections in high-risk infants. In immunocompromised patients, palivizumab has an excellent safety profile and may be beneficial in the prevention and treatment of RSV infections; however, clinical trials are needed to determine its effectiveness. In this article, we review the role of palivizumab in prevention and treatment of RSV infections in immunocompetent and immunocompromised patients.

Solid organ transplantation and response to vaccination

Although early vaccination is recommended in candidates for solid organ transplantation (SOT), consensual protocols do not yet exist. We applied an SOT vaccination protocol in the Hospital Clinic of Barcelona (Spain). Serology was performed before and after vaccination and compliance with the vaccination schedule was analysed during the period 2003-2004. Two hundred and thirty seven patients (72.9% male; mean age 56.31 years, range 19-72) were included. A total of 74.5% of subjects susceptible to hepatitis B virus infection responded to hepatitis B vaccination. Most patients were protected against hepatitis A, varicella, measles, rubella and mumps. The vaccine protocol was implemented satisfactorily and the administration of two courses of hepatitis B vaccine was shown to be effective.

Factors influencing predisposition to sepsis in children with cancers and acquired immunodeficiencies unrelated to human immunodeficiency virus infection

OBJECTIVES

The main objectives of this review are to provide insight into the various factors that affect the risk of sepsis in immunocompromised children and to discuss special issues that should be considered when such patients are enrolled in clinical trials.

STRATEGY

A literature review was conducted, and authoritative references were consulted when appropriate. This was supported by discussion among experts at an international consensus conference on pediatric sepsis.

OUTCOME

The review discusses general issues as they relate to the factors that are associated with a predisposition to sepsis in children with cancers and non-human immunodeficiency virus (HIV)-related acquired immunodeficiencies. The host defects that are associated with specific infections are discussed, and an overview of the indicators of immune dysfunction in the previously well child is presented. Selected examples of patients with non-HIV-related acquired immunodeficiencies, including those with cancer or who have undergone solid-organ or hematopoietic stem-cell transplants are discussed. Special challenges that may affect clinical trials include the altered immune response as this relates to the definition of infection and disease and the assessment of outcomes and the heterogeneity of study populations due to the variable manifestations of immune deficiency states.

SUMMARY

Knowledge of the factors that are associated with sepsis in immunocompromised patients is important when such patients are to be entered into clinical trials on sepsis. These factors do not necessarily operate in isolation and may occur concurrently or sequentially. With these considerations in mind, clinical trials involving immunocompromised children can go forward and will very likely lead to significant advances in the care of this understudied population.