Activity of the HMGB1-derived immunostimulatory peptide Hp91 resides in the helical C-terminal portion and is enhanced by dimerization

Abstract

We have previously shown that an 18 amino acid long peptide, named Hp91, whose sequence corresponds to a region within the endogenous protein HMGB1, activates dendritic cells (DCs) and acts as adjuvant in vivo by potentiating Th1-type antigen-specific immune responses. We analyzed the structure-function relationship of the Hp91 peptide to investigate the amino acids and structure responsible for immune responses. We found that the cysteine at position 16 of Hp91 enabled formation of reversible peptide dimmers, monomer and dimmer were compared for DC binding and activation. Stable monomers and dimers were generated using a maleimide conjugation reaction. The dimer showed enhanced ability to bind to and activate DCs. Furthermore, the C-terminal 9 amino acids of Hp91, named UC1018 were sufficient for DC binding and Circular dichroism showed that UC1018 assumes an alpha-helical structure. The ninemer peptide UC1018 induced more potent antigen-specific CTL responses in vivo as compared to Hp91 and it protected mice from tumor development when used in a prophylactic vaccine setting. We have identified a short alpha helical peptide that acts as potent adjuvant inducing protective immune responses in vivo.

Secretion of dengue virus envelope protein ectodomain from mammalian cells is dependent on domain II serotype and affects the immune response upon DNA vaccination

“…In addition, antigens presented in a dimeric structure were shown to have enhanced abilities to bind and activate relevant receptors on the surface of immune cells, including B-cells, which could be important for inducing stronger immune responses (Saenz et al, 2014). When analysing dimerization properties of sE and DI/DII proteins, we found that secretory sE (serotypes 3 and 4) were capable of forming stable dimers (approximately 20 % of secreted sE), in agreement with previous reports .…”

Engineering of a self-adjuvanted iTEP-delivered CTL vaccine

“…They have also been used to deliver CTL vaccine, and the vaccine potency was exaggerated by loading with immunogenic adjuvant, in this case the H 100 peptide, to trigger a desired immune response. The H 100 peptide is specifically suitable in our system because: 1) H 100 is a proven TLR4 agonist and inflammatory mediator [39,40] . 2) It is easily fused at a desired position of the iTEPs and readily produced by a recombinant approach.…”

“…Deletion and overlapping analysis of H 91 showed that H91-98, H94-101, or H97-104 did not bind or induce DCs to release IL-6. Only H91-108 (H 91 ) or H100-108 (H 100 ) had the DC stimulatory function, and the effect of H 100 was even stronger than that of H 91 [40] . It is noteworthy that a cysteine (C106 of HMGB1) is present in both H 91 and H 100 but not in the other non-functional HMGB1-derived peptides.…”

“…The helical C-terminal portion of H 91 , a peptide corresponding to amino acids 100-108 of HMGB1 and thus was named as H 100 , was responsible for its immunostimulatory function. H 100 with N-terminal biotin modification induced a more potent antigen-specific CTL response than H 91 and delayed tumor development in a prophylactic vaccine setting [40] .…”

Triggered Immune Response Induced by Antigenic Epitopes Covalently Linked with Immunoadjuvant-Pulsed Dendritic Cells as a Promising Cancer Vaccine

“…Saenz and his group demonstrated that HP91 could function as adjuvant in vivo through potentiating cellular and humoral immune responses [10]. Further studies showed that the region of HP91 which is responsible for its immunostimulatory function is located in the C-terminal, a peptide corresponding to amino acids 100-108 of HMGB1 [10,11]. In this study, we denoted this short peptide as HB 100-108 .…”