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Plant-based vaccines for oral delivery of type 1 diabetes-related autoantigens: Evaluating oral tolerance mechanisms and disease prevention in NOD mice

View Article: PubMed Central - PubMed

ABSTRACT

Autoantigen-specific immunological tolerance represents a central objective for prevention of type 1 diabetes (T1D). Previous studies demonstrated mucosal antigen administration results in expansion of Foxp3+ and LAP+ regulatory T cells (Tregs), suggesting oral delivery of self-antigens might represent an effective means for modulating autoimmune disease. Early preclinical experiments using the non-obese diabetic (NOD) mouse model reported mucosal administration of T1D-related autoantigens [proinsulin or glutamic acid decarboxylase 65 (GAD)] delayed T1D onset, but published data are conflicting regarding dose, treatment duration, requirement for combinatorial agents, and extent of efficacy. Recently, dogma was challenged in a report demonstrating oral insulin does not prevent T1D in NOD mice, possibly due to antigen digestion prior to mucosal immune exposure. We used transplastomic plants expressing proinsulin and GAD to protect the autoantigens from degradation in an oral vaccine and tested the optimal combination, dose, and treatment duration for the prevention of T1D in NOD mice. Our data suggest oral autoantigen therapy alone does not effectively influence disease incidence or result in antigen-specific tolerance assessed by IL-10 measurement and Treg frequency. A more aggressive approach involving tolerogenic cytokine administration and/or lymphocyte depletion prior to oral antigen-specific immunotherapy will likely be required to impart durable therapeutic efficacy.

No MeSH data available.


(A) Continuous oral treatment with tobacco leaves expressing 500 μg GAD (gray, short dash), 250 μg CTB-hpINS (black, short dash), or the combination of both (gray, solid line), were compared to untreated (black, solid line) or WT control tobacco-treated animals (black, long dash), P = 0.24 (Log-rank test). (B) Animals experiencing catastrophic failure (black), non-catastrophic failure (gray), or no failure (those animals that survived to 32 weeks of age, white) are represented P = 0.08 (Chi-square test). T1D incidence did not differ between Phase 1 (dashed lines, treatment duration: 10 weeks) and Phase 2 (solid lines, treatment duration: ongoing through study endpoint) for (C) CTB-hpINS, (D) GAD, and (E) WT tobacco-treated animals P = 0.97, P = 0.96, and P = 0.32, respectively (Log-rank test). Number of animals (n) per group is indicated in the figure.
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f3: (A) Continuous oral treatment with tobacco leaves expressing 500 μg GAD (gray, short dash), 250 μg CTB-hpINS (black, short dash), or the combination of both (gray, solid line), were compared to untreated (black, solid line) or WT control tobacco-treated animals (black, long dash), P = 0.24 (Log-rank test). (B) Animals experiencing catastrophic failure (black), non-catastrophic failure (gray), or no failure (those animals that survived to 32 weeks of age, white) are represented P = 0.08 (Chi-square test). T1D incidence did not differ between Phase 1 (dashed lines, treatment duration: 10 weeks) and Phase 2 (solid lines, treatment duration: ongoing through study endpoint) for (C) CTB-hpINS, (D) GAD, and (E) WT tobacco-treated animals P = 0.97, P = 0.96, and P = 0.32, respectively (Log-rank test). Number of animals (n) per group is indicated in the figure.

Mentions: There was a 22% difference in the proportion of diabetic mice between those autoantigen-treated and WT-treated animals (Fig. 3A); however, the study was not sufficiently powered to detect a difference less than 50%, an effectiveness in line with previous oral antigen studies in NOD mice. Thus, T1D incidence and progression did not differ significantly between NOD mice that received oral autoantigen therapy (either alone or in combination). Compared to tobacco-treated animals (including WT), untreated mice had a more dramatic onset of diabetes with at least one of the two consecutive diagnostic BGVs exceeding 400 mg/dL in the majority of those animals (Figs 3B, S2A–E). The CTB-hpINS fed group showed the lowest rate of severity, with 11% (n = 1/9) mice showing >400 mg/dL diagnostic BGV (Fig. 3B). In the previously reported study19, none of the untreated mice showed >400 mg/dL BGV at any point, though those animals were sacrificed prior to expected time of peak T1D incidence.


Plant-based vaccines for oral delivery of type 1 diabetes-related autoantigens: Evaluating oral tolerance mechanisms and disease prevention in NOD mice
(A) Continuous oral treatment with tobacco leaves expressing 500 μg GAD (gray, short dash), 250 μg CTB-hpINS (black, short dash), or the combination of both (gray, solid line), were compared to untreated (black, solid line) or WT control tobacco-treated animals (black, long dash), P = 0.24 (Log-rank test). (B) Animals experiencing catastrophic failure (black), non-catastrophic failure (gray), or no failure (those animals that survived to 32 weeks of age, white) are represented P = 0.08 (Chi-square test). T1D incidence did not differ between Phase 1 (dashed lines, treatment duration: 10 weeks) and Phase 2 (solid lines, treatment duration: ongoing through study endpoint) for (C) CTB-hpINS, (D) GAD, and (E) WT tobacco-treated animals P = 0.97, P = 0.96, and P = 0.32, respectively (Log-rank test). Number of animals (n) per group is indicated in the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC5304332&req=5

f3: (A) Continuous oral treatment with tobacco leaves expressing 500 μg GAD (gray, short dash), 250 μg CTB-hpINS (black, short dash), or the combination of both (gray, solid line), were compared to untreated (black, solid line) or WT control tobacco-treated animals (black, long dash), P = 0.24 (Log-rank test). (B) Animals experiencing catastrophic failure (black), non-catastrophic failure (gray), or no failure (those animals that survived to 32 weeks of age, white) are represented P = 0.08 (Chi-square test). T1D incidence did not differ between Phase 1 (dashed lines, treatment duration: 10 weeks) and Phase 2 (solid lines, treatment duration: ongoing through study endpoint) for (C) CTB-hpINS, (D) GAD, and (E) WT tobacco-treated animals P = 0.97, P = 0.96, and P = 0.32, respectively (Log-rank test). Number of animals (n) per group is indicated in the figure.
Mentions: There was a 22% difference in the proportion of diabetic mice between those autoantigen-treated and WT-treated animals (Fig. 3A); however, the study was not sufficiently powered to detect a difference less than 50%, an effectiveness in line with previous oral antigen studies in NOD mice. Thus, T1D incidence and progression did not differ significantly between NOD mice that received oral autoantigen therapy (either alone or in combination). Compared to tobacco-treated animals (including WT), untreated mice had a more dramatic onset of diabetes with at least one of the two consecutive diagnostic BGVs exceeding 400 mg/dL in the majority of those animals (Figs 3B, S2A–E). The CTB-hpINS fed group showed the lowest rate of severity, with 11% (n = 1/9) mice showing >400 mg/dL diagnostic BGV (Fig. 3B). In the previously reported study19, none of the untreated mice showed >400 mg/dL BGV at any point, though those animals were sacrificed prior to expected time of peak T1D incidence.

View Article: PubMed Central - PubMed

ABSTRACT

Autoantigen-specific immunological tolerance represents a central objective for prevention of type 1 diabetes (T1D). Previous studies demonstrated mucosal antigen administration results in expansion of Foxp3+ and LAP+ regulatory T cells (Tregs), suggesting oral delivery of self-antigens might represent an effective means for modulating autoimmune disease. Early preclinical experiments using the non-obese diabetic (NOD) mouse model reported mucosal administration of T1D-related autoantigens [proinsulin or glutamic acid decarboxylase 65 (GAD)] delayed T1D onset, but published data are conflicting regarding dose, treatment duration, requirement for combinatorial agents, and extent of efficacy. Recently, dogma was challenged in a report demonstrating oral insulin does not prevent T1D in NOD mice, possibly due to antigen digestion prior to mucosal immune exposure. We used transplastomic plants expressing proinsulin and GAD to protect the autoantigens from degradation in an oral vaccine and tested the optimal combination, dose, and treatment duration for the prevention of T1D in NOD mice. Our data suggest oral autoantigen therapy alone does not effectively influence disease incidence or result in antigen-specific tolerance assessed by IL-10 measurement and Treg frequency. A more aggressive approach involving tolerogenic cytokine administration and/or lymphocyte depletion prior to oral antigen-specific immunotherapy will likely be required to impart durable therapeutic efficacy.

No MeSH data available.