Haemophilus influenzae Type b-Outer Membrane Protein Complex Glycoconjugate Vaccine Induces Cytokine Production by Engaging Human Toll-Like Receptor 2 (TLR2) and Requires the Presence of TLR2 for Optimal Immunogenicity

Abstract

Conjugate vaccines consisting of the capsular polysaccharide (PS) of Haemophilus influenzae type b (Hib) covalently linked to carrier proteins, unlike pure PS, are immunogenic in infants and have significantly reduced Hib infections in the United States, but require multiple doses to induce protective anti-PS Ab titers. Hib-meningococcal outer membrane protein complex (OMPC) conjugate vaccine, however, elicits protective anti-PS Ab titers after one dose. We found that OMPC and Hib-OMPC engaged human Toll-like receptor 2 (TLR2) expressed in human embryonic kidney (HEK) cells, inducing IL-8 production, and engaged mouse TLR2 on bone marrow-derived dendritic cells, inducing TNF release. Hib conjugated to the carrier proteins CRM197 and tetanus toxoid did not engage TLR2 on HEK or dendritic cells. Engagement of TLR2 by Hib-OMPC was MyD88 dependent, as Hib-OMPC-induced TNF production was ablated in MyD88 knockout (KO) mice. Hib-OMPC was significantly less immunogenic in TLR2 KO mice, inducing lower Hib PS IgG and IgM titers compared with those in wild-type mice. Splenocytes from OMPC-immunized TLR2 KO mice also produced significantly less IL-6 and TNF-α than those from wild-type mice. Hib-OMPC is unique among glycoconjugate vaccines by engaging TLR2, and the ability of Hib-OMPC to elicit protective levels of Abs after one dose may be related to TLR2-mediated induction and regulation of cytokines produced by T cells and macrophages in addition to the peptide/MHC II-dependent recruitment of T cell help commonly afforded by carrier proteins. TLR2 engagement by an adjuvant or carrier protein may be a useful strategy for augmentation of the anti-PS Ab response induced by glycoconjugate vaccines.

An oligosaccharide-based HIV-1 2G12 mimotope vaccine induces carbohydrate-specific antibodies that fail to neutralize HIV-1 virions

“…The OMPC carrier used for the current study is a component of a licensed pediatric vaccine, and its ability to promote Ig class switching has been demonstrated (21). In addition, OMPC displays potent adjuvant capabilities as a result of its ability to activate toll-like receptor types 2 and 4 (22,23). We used 4 as a candidate for vaccine evaluation because quantities of 5 were limiting, and previous surface plasmon resonance data had shown similar binding profiles of 4 and 5 to 2G12 (20).…”

Pneumococcal Capsular Polysaccharide Is Immunogenic When Present on the Surface of Macrophages and Dendritic Cells: TLR4 Signaling Induced by a Conjugate Vaccine or by Lipopolysaccharide Is Conducive

“…The effectiveness of PS4-p458 conjugates administered in PBS drew our attention to the possibility that the PS4-p458 conjugate might work as adjuvants, and not only as a combination of T cell and B cell epitopes. It was recently reported that an outer membrane protein complex from the meningococcus (outer membrane protein complex) conjugated to the CPS of Haemophilus influenzae acted as an adjuvant-like molecule by inducing cytokine secretion in vitro in mice with intact TLR2; the induction of resistance to challenge was not examined in that study (30). The adjuvant-like property of PS4-p458 was demonstrated in this study by its ability to induce the macrophage cell line RAW to secrete IL-12 in vitro (Fig.…”

Staphylococcus aureus lipoproteins trigger human corneal epithelial innate response through toll-like receptor-2

“…Human embryonic kidney epithelial cells expressing functional TLR2 or TLR9 along with plasmid cell lines [40] were seeded in six-well dishes. After overnight starvation in DMEM, they were treated with 0.5 mg/ml saLP.…”