Opsonic antibodies to outer membrane protein P2 of nonencapsulated Haemophilus influenza are strain specific

Abstract

The ability of monoclonal antibodies (MAbs) specific for variable and conserved epitopes of outer membrane protein (OMP) P2 (b,c) of nonencapsulated Haemophilus influenzae to promote opsonophagocytosis of this bacterium by human polymorphonuclear leucocytes (PMNs) was determined by flow cytometry. MAbs rendering PMNs fluorescent because of association with fluorescein isothiocyanate-labelled bacteria were defined as stimulating opsonophagocytosis. Opsonophagocytosis was dependent on the presence of both antibodies and complement. Of the 14 MAbs directed to the variable parts of OMP P2 (L.

Fine mapping of outer membrane protein P2 antigenic sites which vary during persistent infection by Haemophilus influenzae

“…Also, the observations that MAbs specific for loop 6 promoted strain-specific complement-dependent killing of H. influenzae in the absence of other antibodies and that a variant with an amino acid alteration in loop 6 survived during selection in the presence of this MAb and complement support the immune selection by antibodies specific only for loop 6 (4, 30). During infection by H. influenzae strain-specific opsonizing antibodies also develop (19,26). Opsonophagocytosis of nonencapsulated H. influenzae is strain specific (26) and has been described to be poor (33).…”

“…MAbs. Strain-specific murine MAbs directed against MOMP P2 of nonencapsulated H. influenzae have been described previously by van Alphen et al (30) and Troelstra et al (26). These MAbs react with whole bacteria in ELISA and with purified MOMP P2 on immunoblot and include six MOMP P2 variantspecific MAbs, two cross-reacting MAbs, and three broadly cross-reacting MAbs (30).…”

“…Recognition of GST-MOMP P2 loop fusion proteins by MOMP P2-specific MAbs. The reactivities of MOMP P2-specific MAbs elicited against bacteria of H. influenzae d1 and variant d3 (26,30) were determined by immunoblotting ( Fig. 1B) and ELISA (Table 2), using purified GST-MOMP P2 loops as antigens.…”

“…b ϩϩϩ, Ͼ2.0; ϩϩ, 1.0 to 2.0; ϩ, 0.5 to 1.0; Ϫ, Ͻ0.5. c Bactericidal in the presence of complement for the homologous variant d3 (30 (26,30). Since MAb 19DA11 recognized a surface-exposed epitope as observed by immunogold electron microscopy (30), the lack of reactivity with the fusion proteins suggests that the epitope for MAb 19DA11 is incomplete or conformational.…”

“…The most important immune mechanisms of the host against bacteria are complement-dependent bactericidal activity and phagocytosis. For H. influenzae, both of these mechanisms are dependent on complement activation (19,26,30). The complement-dependent bactericidal activities of the antibodies elicited during persistence of H. influenzae in the rabbit model were determined.…”