Antigen-based
therapies (
ABTs) fail to restore normoglycemia in newly diabetic NOD mice, perhaps because too few β-cells remain by the time that ABT-induced regulatory responses arise and spread. We hypothesized that combining a fast-acting
anti-inflammatory agent with an ABT could limit pathogenic responses while ABT-induced regulatory responses arose and spread. γ-
Aminobutyric acid (
GABA) administration can inhibit
inflammation, enhance regulatory T-cell (Treg) responses, and promote β-cell replication in mice. We examined the effect of combining a prototypic ABT,
proinsulin/
alum, with
GABA treatment in newly diabetic NOD mice.
Proinsulin/
alum monotherapy failed to correct
hyperglycemia, while
GABA monotherapy restored normoglycemia for a short period. Combined treatment restored normoglycemia in the long term with apparent permanent remission in some mice.
Proinsulin/
alum monotherapy induced
interleukin (IL)-4- and IL-10-secreting T-cell responses that spread to other β-cell
autoantigens.
GABA monotherapy induced moderate
IL-10 (but not IL-4) responses to β-cell
autoantigens. Combined treatment synergistically reduced spontaneous type 1 T-helper cell responses to
autoantigens, ABT-induced
IL-4 and humoral responses, and insulitis, but enhanced
IL-10 and Treg responses and promoted β-cell replication in the islets. Thus, combining ABT with
GABA can inhibit pathogenic T-cell responses, induce Treg responses, promote β-cell replication, and effectively restore normoglycemia in newly diabetic NOD mice. Since these treatments appear safe for humans, they hold promise for
type 1 diabetes intervention.