Circulating regulatory (CD4+CD25+FOXP3+) T cells decrease in breast cancer patients after vaccination with an Ii-Key-modified class II HER2/ neu peptide (AE37)

• Published in: Cancer research (Chicago, Ill.) Vol. 69; no. 2_Supplement; p. 3134
• Main Authors: Gates, JD, Benavides, LC, Carmichael, MG, Hueman, MT, Holmes, JP, Khoo, S, Stojadinovic, A, von Hofe, E, Ponniah, S, Peoples, GE
• Format: Journal Article
• Language: English
• Published: 15.01.2009
• ISSN: 0008-5472; 1538-7445
• DOI: 10.1158/0008-5472.SABCS-3134

Abstract Abstract #3134 Background: CD4+CD25+FOXP3+ regulatory T cells (Tregs) have been implicated in the suppression of immune responses against various tumors. To monitor the potential induction of Tregs in breast cancer (BrCa) patients receiving a modified HLA Class II HER2/neu peptide (AE37) vaccine in a clinical trial, we have analyzed peripheral blood lymphocytes (PBL) from vaccinated patients for the presence of Tregs and correlated our findings with ex vivo immune assays and in vivo delayed type hypersensitivity (DTH) responses to the vaccine. Methods: Fifteen BrCa patients have completed 6 monthly injections of the AE37+GM-CSF vaccine in a dose escalation safety study. The AE37 peptide consists of a HER2/neu peptide (776-790) linked to the Ii-Key moiety of the HLA Class II-associated invariant chain, which enhances epitope interaction with the Class II molecule. PBL obtained pre- and post-vaccination were stained with anti-CD4/CD25 (n=15) and FOXP3 (n=9) antibodies (PCH101 and 236A/E7) and analyzed by flow cytometry. Cells were also stimulated ex vivo with AE37 peptide to measure IFN-γ ELISPOT, proliferation (3H-thymidine-cpm) and cytokine secretion (TGF-β). DTH responses to the AE37 peptide pre- and post-vaccination were also recorded. Results: The mean CD4+ and CD4+CD25+ T cell populations for all patients (n=15) did not change from pre- to post-vaccination (CD4+ = 52.3+3.3% vs. 50.5+3.9%, p=0.6; CD4+CD25+ = 1.9+0.2% vs. 2.4+0.5%, p=0.2). Tregs (CD4+CD25+FOXP3+) were reduced in all 9 patients tested pre- to post-vaccination for both FOXP3 antibodies (Ab) (FOXP3 Ab1 = 2.1+0.2% vs. 1.1+0.1%, p=0.002; FOXP3 Ab2 = 2.0+0.2% vs. 1.0+0.2%, p=0.0009). There was no difference in pre- to post-vaccination levels of TGF-β (2720+582 pg/ml vs. 3387+848 pg/ml; p=0.9). AE37-specific proliferative responses increased from pre- to post-vaccination (34+23cpm vs. 6427+1431 cpm; p<0.001). ELISPOT demonstrated an increased response from pre- to long term (6-12mo.) post-vaccination (Median – 2 vs. 34 spots/106 cells; p=0.003). DTH responses increased in all patients from pre- to post-vaccination (3.6+1.4 mm vs. 56.0+9.4 mm; p<0.0001), and there appeared to be an inverse relationship between the degree of Treg reduction and the size of DTH response to AE37 (R2=0.83).
 Discussion: The novel AE37 HER2/neu peptide vaccine does not result in increased levels of Tregs. Furthermore, the reduced levels of Tregs in vaccinated patients appear to be associated with more robust responses in ex vivo immune assays and in vivo DTH reactions suggesting that the AE37 vaccine may be clinically useful. Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3134.