ANTIBODY-RESPONSE TO MENINGOCOCCAL POLYSACCHARIDE-A AND POLYSACCHARIDE-C IN PATIENTS WITH COMPLEMENT DEFECTS

Patients with defects of terminal complement components are particular ly exposed to the risk of developing neisserial infections and seem to respond poorly to meningococcal capsular polysaccharide (PS) C via na tural immunization. The sole meningococcal PSC is, on the other hand, an excellent immunogen in normal people. Considering the great importa nce of vaccine prophylaxis for the prevention of meningococcal infecti ons in patients with complement defects, it is crucial to study the an tibody response to the sole meningococcal PS in these patients. We the refore analysed the levels of anti-PSA and PSC antibodies in the membe rs of four families including patients with homozygous and heterozygou s defects of C7, C8 or factor H, before and after vaccination with the sole PSA + C. Surprisingly, we found the highest levels of antibodies before vaccination in homozygous subjects, followed by heterozygous a nd normal controls, whereas, after vaccination, homozygous subjects sh owed the lowest increase of specific antibodies, indicating their rela tive incapability to respond to sole meningococcal PS. In conclusion, this study demonstrates (1) the capacity to respond to meningococcal P S via natural immunization by patients with total complement defects, and (2) the low responsiveness to meningococcal PS via vaccine immuniz ation by the same patients. We propose that vaccination should be give n to patients lacking specific antibodies and their serological respon se should be assessed. In addition this study confirms previous observ ations on a likely lower immunogenic power of meningococcal serogroup C via natural immunization compared with the better immunogenicity of the sole PSC.