The role of p110? PI3K in lymphoid cells has been studied extensively, showing its importance in immune cell differentiation, activation and development. Altered T cell localization in p110?-deficient mouse spleen suggested a role for p110? in non-hematopoietic stromal cells, which maintain hematopoietic cell segregation. We tested this hypothesis using p110?(WT/WT) mouse bone marrow to reconstitute lethally irradiated p110?(WT/WT) or p110?(D910A/D910A) (which express catalytically inactive p110?) recipients, and studied localization, number and percentage of hematopoietic cell subsets in spleen and lymph nodes, in homeostatic conditions and after antigen stimulation. These analyses showed diffuse T cell areas in p110?(D910A/D910A) and in reconstituted p110?(D910A/D910A) mice in homeostatic conditions. In these mice, spleen CD4(+) and CD8(+) T cell numbers did not increase in response to antigen, suggesting that a p110?(D910A/D910A) stroma defect impedes correct T cell response. FACS analysis of spleen stromal cell populations showed a decrease in the percentage of gp38(-)CD31(+) cells in p110?(D910A/D910A) mice. qRT-PCR studies detected p110? mRNA expression in p110?(WT/WT) spleen gp38(-)CD31(+) and gp38(+)CD31(+) subsets, which was reduced in p110?(D910A/D910A) spleen. Lack of p110? activity in these cell populations correlated with lower LT?R, CCL19 and CCL21 mRNA levels; these molecules participate in T cell localization to specific spleen areas. Our results could explain the lower T cell numbers and more diffuse T cell areas found in p110?(D910A/D910A) mouse spleen, as well as the lower T cell expansion after antigen stimulation in p110?(D910A/D910A) compared with p110?(WT/WT) mice.
Increased levels of NeuGc-containing gangliosides have been described in human breast cancer. A controlled Phase II clinical trial was conducted in patients with metastatic breast cancer to evaluate immunogenicity, safety and to identify evidences of biological activity of a cancer vaccine composed by NeuGcGM3 in a proteoliposome of Neisseria meningitidis together with Montanide ISA 51 as adjuvant. After first line chemotherapy, 79 women were randomized 1:1 to receive the vaccine candidate or best supportive care. All patients achieved at least stable disease to the first line therapy for the metastatic condition. Treatment consisted on 5 vaccine doses every 2 weeks and then, monthly re-immunization to complete 15 doses. Vaccination with the NeuGcGM3 based vaccine was safe and the most frequent adverse events consisted on injection site reactions, fever, arthralgia and chills. The vaccine was immunogenic and a sustained increase of both IgG and IgM antibody titters against NGcGM3 was observed after the second vaccination month. Antibodies were able to recognize the NeuGcGM3(+) murine tumor cell line L1210 and the myeloma cell line P3X63. Humoral response was specific since vaccination did not result in Neu-Acetyl GM3 or GM2-antibody response. Hyperimmune sera from vaccinated patients were able to prevent the NeuGcGM3 mediated CD4 down-modulation on T lymphocytes. In the intent to treat analysis, there was a trend toward a survival advantage for the vaccine group and this effect was significant for women bearing non-visceral metastasis. Two phase III clinical studies with this vaccine candidate are ongoing.
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