Neisserial porins induce B lymphocytes to express costimulatory B7-2 molecules and to proliferate.

Abstract

SummaryThe neisserial porins are the major protein components of the outer membrane of the pathogenic Neisseria (N. meningitidis and N. gonorrhoeae). They have been shown to be able to enhance the immune response to poorly immunogenic substances (e.g., polysaccharides, peptides, glycolipids, etc.). To explore the basis of their potent adjuvant activity, the effect of the neisserial porins on T-B cell interactions and T cell costimulation was examined. Neisserial porins increased the surface expression of the costimulatory ligand B7-2 (CD86) but did not affect the expression of B7-1 (CD80). In addition, incubation with the neisserial porins increased the T lymphocyte costimulatory ability ofB lymphocytes, which was inhibited by anti-B7-2 but not anti-B7-1 monoclonal antibodies. Upregulation of B7-2 on the surface ofB lymphocytes may be the mechanism behind the immunopotentiating activity of neisserial porins. p rotein IA (PIA) and protein IB (PIB) of Neisseria gonorrhoeae and class 1, 2, or 3 proteins of N. meningitidis (C1, C2, and C3 respectively) are the most abundant neisserial outer membrane proteins (1). These proteins function as porins (2--4), share significant homology (5-9), and are members of the gram-negative porin superfamily (10). Neisserial outer membrane vesicle vaccines and purified neisserial porin vaccine candidates induce immune responses in humans and animals without the addition of exogenous adjuvants (11)(12)(13)(14). Neisserial porin preparations augment the humoral immune response to poorly immunogenic substances, for example, peptides, and induce a T cell-dependent immune response for normally T cell-independent antigens, for example, polysaccharides (15-18). Meningococcal OMV, mainly consisting of the class 2 protein, are used as carriers to boost the immune response towards the Haemophilus influenzae polysaccharide capsule in the recently licensed H. influenzae type b vaccine (15). The inclusion of purified PIA, PIB, C1, or C3 proteins in noncovalent complexes containing group C meningococcal capsular polysaccharides (CPS) greatly improves the antibody response in immunized mice to the polysaccharide compared with the 1Abbreviations used in this paper: CPS, group C meningococcal capsular polysaccharide; ICAM-1, intraceUular adhesion molecule-I; PIA, PIB, protein IA, IB, respectively; Th, T-helper.Part of this work was presented at the Interscience Conference on Antimicrobial Agents and Chemotherapy, Sept. 17-20, 1995, San Francisco, CA. anti-CPS response in mice immunized with CPS alone (17). Neisserial porins are used as adjuvants in anti-melanoma cancer vaccines to augment the immune response to GM2 and GD3, two gangliosides present at much higher levels on malignant melanoma cells compared with normal human melanocytes (18).We postulated that the porins' adjuvant ability could be related to their effect on interactions between T and B lymphocytes, thereby increasing T cell involvement in the immune response. In the current model ofT lymphocyte stimulation, two sets of signals bet...

The PorB porin from commensal Neisseria lactamica induces Th1 and Th2 immune responses to ovalbumin in mice and is a potential immune adjuvant

“…Purified mouse B lymphocytes (5 × 10 6 /ml) [26] were stimulated in R10 for 24h with Nlac PorB or Nme PorB (10 µg/ml), the TLR2/TLR1 synthetic ligand Pam3CSK4, the TLR2/TLR6 synthetic ligand Pam2CSK4 (100 and 10 ng/ml) and the TLR4 ligand N. meningitidis LOS (100 ng/ml). The culture supernatants were collected and analyzed for cytokine production as described above.…”

“…MTT solvent (100 µl) was added and the absorbance was measured in an ELISA reader at 570 nm with a 690 nm reference. Alternatively, splenic B cells from naive C57Bl/6 mice and TLR2 knockout mice [26] were incubated with Nlac PorB and Nme PorB at 10 µg/ml, LOS (100 ng/ml) and ConA (5 µg/ml) for 44h and cell proliferation was determined as described above. Cell proliferation was expressed in arbitrary units as Stimulation Index, calculated by dividing the average cell proliferation in the wells incubated with each stimulus by the average cell proliferation in the wells incubated with medium alone.…”

“…Although dendritic cells are mostly responsible for initiation of a primary immune response, activation of both DCs and B cells has been extensively characterized in response to Nme PorB [26,31,32] and is a crucial comparison for the effect of Nlac PorB. Purified mouse splenic B cells were incubated with different concentrations of Nlac PorB (20, 10, 1, 0.1 µg/ ml) for 24h and a dose-dependent increase of surface expression of the co-stimulatory molecule CD86, of CD40 and of MHC II was determined by flow cytometry (data not shown).…”

“…Examples of adjuvants are oil emulsions [4][5][6], squalene (MF59) [7], immune stimulating complexes (ISCOMs [8,9]) with Quil-A and both gram-negative bacteria and bacterial products [4,[10][11][12]. These include DNA with immunostimulatory CpG motifs (one of the most powerful adjuvants [13]), Bordetella pertussis toxin [2,14], Corynebacterium granulosum derived P40 component [15], MPL [16], Mycobacterium and its components (Freund adjuvant) [4,17], Cholera toxin [18] and porins from various organisms such as Fusobacterium nucleatum [19], Shigella [20][21][22], Salmonella [22,23] and Neisseria meningitidis and gonorrhoeae [24][25][26][27][28][29].…”

“…Increased expression of CD86/CD80, MHC II and CD40 on the APC surface has been shown in response to porins from pathogenic Neisserial species (and other bacteria) [23,26,[30][31][32], as well as B cell proliferation and increased antibody production [33]. Activated APCs release specific cytokines (i.e.…”