Immune competence after alemtuzumab treatment of multiple sclerosis.

OBJECTIVE To determine the immunocompetency of patients with multiple sclerosis treated with the lymphodepleting humanized monoclonal antibody alemtuzumab. METHODS In this pilot case-control study, we assessed immunocompetence in 24 patients after alemtuzumab treatment by measuring antibody responses to 3 vaccines (diphtheria, tetanus, and poliomyelitis vaccine, Haemophilus influenzae type b and meningococcal group C conjugate vaccine, and pneumococcal polysaccharide vaccine). In 20 patients, antibodies to common viruses (mumps, rubella, varicella-zoster, and Epstein-Barr virus) were measured before alemtuzumab treatment, then at 1 and 9-11 months after treatment. Results were compared with well-defined historical controls. RESULTS Serum antibodies against common viruses remained detectable after treatment, and vaccine responses were normal to T-cell-dependent recall antigens (tetanus, diphtheria, and polio), a T-cell-dependent novel antigen (meningococcus C), and T-cell-independent antigens (pneumococcal). There was no evidence for a diminished response to vaccinations in 5 patients studied within 6 months of alemtuzumab treatment. CONCLUSION In this small historically controlled pilot study, we demonstrated i) retained humoral immunologic memory (in the form of antibodies against common viruses and response to recall antigens), and ii) the retained ability to mount a humoral immune response against a novel antigen after treatment with alemtuzumab. CLASSIFICATION OF EVIDENCE This pilot study provides Class III evidence that patients with relapsing-remitting multiple sclerosis appear immunocompetent after treatment with alemtuzumab.