Growth inhibitory and bactericidal efficacy of sera from Lyme borreliosis patients on B-burgdorferi strains

Two B. afzelii strains EB1 and FEM1, classified in normal human sera (NHS) as serum-resistant, and an intermediate serum-sensitive B. burgdorferi s.s. strain 297, were tested in regard of their serum sensitivity in immune ser a (IS) of patients at all stages of Lyme borreliosis by a growth inhibition assay (GIA). Fifty-four per cent (13/24) of the tested IS were GIA positiv e, while the sera of patients in stage III disease inhibited the growth mor e frequently than did the patients with sera of stage II or stage I disease . Growth inhibition was predominantly directed against strain FEM1 (12/24), less against strain EB1 (4/24) and strain 297 (2/24). A growth inhibiting effect on two strains was only detectable for two IS and merely one stage I II serum inhibited all three strains. Positive results in the GIA required fresh serum and resulted in the killing of the borreliae. The detection of the deposited complement components C3 and C9 on the surfaces of the inhibi ted strains by means of immunofluorescence assays confirmed the role of com plement. In Westernblot analyses of strain FEM1, it was striking that GIA-p ositive IS reacted 3- to 5-fold more often with proteins of molecular masse s of 48.9-, 38.6-, 27.5-, 25-, 23.1- (OspC), 21.7-, and 16-kDa, than did GI A-negative IS. Furthermore, two proteins of approximately 20- and 31.2-kDa reacted exclusively with GIA-positive IS. Antibodies reacting with these pr oteins could play a role in the growth inhibition of NHS-resistant borrelia l strains, OspC.