Soluble Antigen Arrays Efficiently Deliver Peptides and Arrest Spontaneous Autoimmune Diabetes

Abstract

Antigen-specific immunotherapy (ASIT) offers a targeted treatment of autoimmune diseases that selectively inhibits autoreactive lymphocytes, but there remains an unmet need for approaches that address the limited clinical efficacy of ASIT. Soluble antigen arrays (SAgAs) deliver antigenic peptides or proteins in multivalent form, attached to a hyaluronic acid backbone using either hydrolysable linkers (hSAgAs) or stable click chemistry linkers (cSAgAs). They were evaluated for the ability to block spontaneous development of disease in a nonobese diabetic mouse model of type 1 diabetes (T1D). Two peptides, a hybrid insulin peptide and a mimotope, efficiently prevented the onset of T1D when delivered in combination as SAgAs, but not individually. Relative to free peptides administered at equimolar dose, SAgAs (particularly cSAgAs) enabled a more effective engagement of antigen-specific T cells with greater persistence and induction of tolerance markers, such as CD73, interleukin-10, programmed death-1, and KLRG-1. Anaphylaxis caused by free peptides was attenuated using hSAgA and obviated using cSAgA platforms. Despite similarities, the two peptides elicited largely nonoverlapping and possibly complementary responses among endogenous T cells in treated mice. Thus, SAgAs offer a novel and promising ASIT platform superior to free peptides in inducing tolerance while mitigating risks of anaphylaxis for the treatment of T1D.

Preclinical evaluation of a precision medicine approach to DNA vaccination in type 1 diabetes

“…Thus, reestablishing tolerance is a lengthy process in which the phenotype of specific T cells is gradually altered over repeated exposures to autoantigens. The response to pDNA-encoded p79 was similar, albeit less pronounced, to the response to p79-carrying soluble antigen arrays ( 5 ). Induction of p79-reactive CD4+ T cells with anergic (CD73+ FR4+) and suppressive (IL-10+) phenotype was seen with both approaches.…”

“…Treatment with a single InsB 9–23 (R22E) mimotope in soluble form also significantly prevented the onset of disease in NOD mice, whether it was started at 4 to 6 or 12 to 14 wk of age ( 35 ). More recently, we showed that two peptides in combination (p79 mimotope and hybrid insulin peptide [2.5HIP]) delivered by soluble antigen array starting later, at 8 wk of age, protected 70% of mice ( 5 ). Presentation of a few selected epitopes on MHC molecules displayed on nanoparticles in Pere Santamaria’s successful studies on stage 2 disease also leads to tolerance that spread to other epitopes of the same antigen or others ( 16 , 36 ).…”

“…It is possible that long-term repeated antigen exposure converts some of these anergic cells to Tregs ( 37 ). However, all epitopes delivered together may not have the same mechanism of action ( 5 ). Moreover, the limited stability of Tregs in both NOD mice and T1D patients ( 38 , 39 ) remains a major issue and it is possible that, once this population is established, continued treatment, perhaps with less frequent dosing, will be required to maintain this population.…”

“…Selected autoantigens have been administered to patients in the form of proteins or peptides via parenteral, oral, or nasal routes, or in the form of protein-encoding DNA plasmids (DNA vaccines) ( 1 , 3 ). A wide variety of delivery vehicles have been developed and tested to funnel these antigens to specific cell types and/or anatomical locations, including various micro- and nanoparticles ( 4 ) and, more recently, soluble antigen arrays ( 5 ). A DNA-based approach allows the patient’s own cells to 1) endogenously express the protein(s) of interest, which may sometimes be challenging to produce recombinantly (e.g., proinsulin), 2) apply natural posttranslational modifications (PTMs), some of which are playing a critical role in the disease process ( 6 , 7 ), and 3) possibly allow the antigen(s) to persist longer than exogenous antigens (with the exception of nanoparticles designed to achieve slow antigen release).…”

Preclinical evaluation of a precision medicine approach to DNA vaccination in Type 1 diabetes

“…Selected autoantigens have been administered to patients in the form of proteins or peptides via parenteral, oral or nasal routes, or in the form of protein-encoding DNA plasmids (DNA vaccines) (1, 3). A wide variety of delivery vehicles have been developed and tested to funnel these antigens to specific cell types and/or anatomical locations, including various micro-and nanoparticles (4), and more recently, soluble antigen arrays (5). A DNA-based approach allows the patient's own cells to (i) endogenously express the protein(s) of interest, which may sometimes be challenging to produce recombinantly (e.g.…”