Immune-Complex Mimics as a Molecular Platform for Adjuvant-Free Vaccine Delivery

Abstract

Protein-based vaccine development faces the difficult challenge of finding robust yet non-toxic adjuvants suitable for humans. Here, using a molecular engineering approach, we have developed a molecular platform for generating self-adjuvanting immunogens that do not depend on exogenous adjuvants for induction of immune responses. These are based on the concept of Immune Complex Mimics (ICM), structures that are formed between an oligomeric antigen and a monoclonal antibody (mAb) to that antigen. In this way, the roles of antigens and antibodies within the structure of immune complexes are reversed, so that a single monoclonal antibody, rather than polyclonal sera or expensive mAb cocktails can be used. We tested this approach in the context of Mycobacterium tuberculosis (MTB) infection by linking the highly immunogenic and potentially protective Ag85B with the oligomeric Acr (alpha crystallin, HspX) antigen. When combined with an anti-Acr monoclonal antibody, the fusion protein formed ICM which bound to C1q component of the complement system and were readily taken up by antigen-presenting cells in vitro. ICM induced a strong Th1/Th2 mixed type antibody response, which was comparable to cholera toxin adjuvanted antigen, but only moderate levels of T cell proliferation and IFN-γ secretion. Unfortunately, the systemic administration of ICM did not confer statistically significant protection against intranasal MTB challenge, although a small BCG-boosting effect was observed. We conclude that ICM are capable of inducing strong humoral responses to incorporated antigens and may be a suitable vaccination approach for pathogens other than MTB, where antibody-based immunity may play a more protective role.

Amino-functionalized poly(L-lactide) lamellar single crystals as a valuable substrate for delivery of HPV16-E7 tumor antigen in vaccine development

“…However, the induction of specific IgMs could play an important role by forming immune complexes with the antigen and acting like a self-adjuvant. 38 In our experiments, E7-specific IgG isotyping showed a pattern indicative of a mixed Th1/Th2 immune response. A significant cell-mediated immune response was also detected by IFN-γ ELISPOT assay in all mice groups analyzed.…”

Mucosal delivery of antigen‐coated nanoparticles to lungs confers protective immunity against tuberculosis infection in mice

“…Recombinant Ag85B was expressed from pET15bAg85B (construct #1) generated as described previously [32] and HBHA was expressed from pET24b-HBHA [33]. To generate rAg85B-HBHA, the Ag85B-encoding gene was amplified by PCR using Taq1 polymerase, pET15b-Ag85B as a template and the primers 5 -CAG GAT CCC ATA TGT TCT CTC GTC CTG GTT TG -3 (NdeI; For) and 5 -AAA GCG GAT CCA CCG CCT GCG GCC GCA CCT GCT CCC AAA GAA GAT TGA AGA TC 3 (BamHI, NotI; Rev).…”

Plant‐derived recombinant immune complexes as self‐adjuvanting TB immunogens for mucosal boosting of BCG

“…In the first assay, we tested whether the TB‐RICs could bind to C1q component of the complement by ELISA, as described in Supporting Data S1. As shown in Figure b, the RICs bound to C1q in a concentration‐dependent manner, as did immune complex mimics (ICM) (positive control (Pepponi et al ., )), while wild‐type plant extract showed no binding. The TBG65 mAb alone also does not bind to C1q above the background level (not shown, but reported previously in (Pepponi et al ., )).…”

“…(c) Detection of Acr in recombinant proteins by Western blotting under nonreducing conditions; Lane 1, wild‐type plant; lane 2, recombinant Acr from E. coli (multiple molecular forms are indicated); lane 3, mini‐RICs (only Acr but no Ag85B, indicating a protein band of the correct anticipated Mt of approximately 180–190 kD a); lane 4, TB‐RICs (the higher molecular band of approximately 250–270 kD a is consistent with the whole molecule, while the smaller band of 110 kD a most likely represents dissociated heavy chain‐Ag85B‐Acr). (d) Detection of Ag85B in TB‐RICs by Western blotting under reducing and nonreducing conditions; lanes 1 and 2, TB‐RICs (nonreducing and reducing conditions, respectively); lane 3, recombinant Acr‐Ag85B from E. coli [50 kD a, generated as previously described (Pepponi et al ., )]; lane 4, wild‐type plant (nonspecific 60 kD a protein band cross‐reactive with anti‐Ag85B antibodies appears in all extracts). (e) Purified TB‐RICs.…”