Prevention of infections in patients with T cell defects.

Although no specific infection is limited entirely to hosts with T-lymphocyte defects, certain microbial organisms have an affinity for such individuals. Effective, safe, and feasible methods are available for the prevention of two of the major life-threatening infections in patients with T-lymphocyte defects, although none of these methods is ideal. Trimethoprim-sulfamethoxazole administered orally daily or thrice weekly is highly effective for the prevention of Pneumocystis carinii pneumonia. For patients who cannot tolerate this drug combination, monthly inhalation of aerosolized pentamidine is an alternative prophylactic approach. Additional drugs in clinical or preclinical trials offer promise for use in preventing this pneumonitis. Varicella is one of the most frequent serious viral infections in patients with cancer, especially children. Varicella-zoster immune globulin (VZIG) has proven effective in reducing the frequency of infection in exposed susceptible individuals; however, breakthrough infections are not uncommon. Of 358 children with acute lymphoblastic leukemia, 62 received VZIG following exposure to varicella, and 16 (26%) of these had breakthrough varicella. A live attenuated varicella-zoster virus vaccine offers promise, especially for the universal immunization of individuals before immunocompromise occurs.