Prophylactic immune tolerance induced by changing the ratio of antigen-specific effector to regulatory T cells.
BACKGROUND
Gene and protein replacement therapies for inherited protein deficiencies such as hemophilia or lysosomal storage disorders are limited by deleterious immune responses directed against their respective therapeutic proteins. Therefore, the development of protocols preventing such responses is key to providing successful long-term therapy.


OBJECTIVE
We sought to develop a protocol, utilizing a drug/peptide cocktail, that would effectively shift the antigen-specific CD4+ T-cell population, tipping the balance from effector T cells (Teffs) towards regulatory T cells (Tregs).


METHODS
Treg-deficient (DO11.10-tg Rag2(-/-)) BALB/c mice were used to screen for an optimal protocol addressing the aforementioned goal and to study the mechanisms underlying in vivo changes in T-cell populations. Muscle-directed gene transfer to hemophilia B mice was also performed in order to test the optimal protocol in a therapeutically relevant setting.


RESULTS
Specific antigen administration (4-week repeated dosing) combined with rapamycin and interleukin-10 led to substantial reductions in Teffs, via activation-induced cell death, and induced CD4+CD25+FoxP3+ Tregs to a large extent in multiple organs. The proportion of apoptotic T cells also increased over time, whereas Teffs and Tregs were differentially affected. When applied to a model of protein deficiency (gene therapy for hemophilia B), the protocol successfully prevented inhibitor formation, whereas non-specific immunosuppression was only marginally effective.


CONCLUSIONS
It is feasible to provide a short-term, prophylactic protocol allowing for the induction of immune tolerance. This protocol may provide a marked advance in efforts seeking to improve clinical outcomes in disorders involving therapeutic protein replacement.
Nayak
S
S
Department of Pediatrics, University of Florida, Gainesville, FL 32610, USA.
Cao
O
O
Hoffman
B E
BE
Cooper
M
M
Zhou
S
S
Atkinson
M A
MA
Herzog
R W
RW
D000818:Animals; D000941:Antigens / Q000737:chemistry*; D015496:CD4-Positive T-Lymphocytes / Q000166:cytology; D005164:Factor IX / Q000235:genetics*; D051858:Forkhead Transcription Factors / Q000096:biosynthesis; D015316:Genetic Therapy / Q000379:methods*; D006467:Hemophilia A / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D007108:Immune Tolerance; D016753:Interleukin-10 / Q000378:metabolism; D053645:Interleukin-2 Receptor alpha Subunit / Q000096:biosynthesis; D051379:Mice; D008807:Mice, Inbred BALB C; D008809:Mice, Inbred C3H; D020123:Sirolimus / Q000494:pharmacology*; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*
D000941:Antigens; C418974:FOXP3 protein, human; D051858:Forkhead Transcription Factors; D053645:Interleukin-2 Receptor alpha Subunit; D016753:Interleukin-10; D005164:Factor IX; D020123:Sirolimus