Abstract
In spite of sufficient data on Neem Leaf Glycoprotein (NLGP) as a prophylactic vaccine, little knowledge currently exists to support the use of NLGP as a therapeutic vaccine. Treatment of mice bearing established sarcomas with NLGP (25 µg/mice/week subcutaneously for 4 weeks) resulted in tumor regression or dormancy (Tumor free/Regressor, 13/24 (NLGP), 4/24 (PBS)). Evaluation of CD8+ T cell status in blood, spleen, TDLN, VDLN and tumor revealed increase in cellular number. Elevated expression of CD69, CD44 and Ki67 on CD8+ T cells revealed their state of activation and proliferation by NLGP. Depletion of CD8+ T cells in mice at the time of NLGP treatment resulted in partial termination of tumor regression. An expansion of CXCR3+ and CCR5+ T cells was observed in the TDLN and tumor, along with their corresponding ligands. NLGP treatment enhances type 1 polarized T-bet expressing T cells with downregulation of GATA3. Treg cell population was almost unchanged. However, T∶Treg ratios significantly increased with NLGP. Enhanced secretion/expression of IFNγ was noted after NLGP therapy. In vitro culture of T cells with IL-2 and sarcoma antigen resulted in significant enhancement in cytotoxic efficacy. Consistently higher expression of CD107a was also observed in CD8+ T cells from tumors. Reinoculation of sarcoma cells in tumor regressed NLGP-treated mice maintained tumor free status in majority. This is correlated with the increment of CD44hiCD62Lhi central memory T cells. Collectively, these findings support a paradigm in which NLGP dynamically orchestrates the activation, expansion, and recruitment of CD8+ T cells into established tumors to operate significant tumor cell lysis.
Highlights
Immune mediated restriction of tumor growth essentially requires synchronization of several interdependent events, including activation of tolerized immune cells [1], their migration and homing [2], suppression of suppressor activities of regulatory cells [3], type 1 polarization of immune microenvironment [4], inhibition of interference of pro-tumor molecules [5], memory development to prevent recurrence [6] and normalization of tumor vasculature [7]
We have reported that Neem Leaf Glycoprotein (NLGP), a nontoxic preparation from neem (Azadirachta indica) leaf, can effectively prevent the murine tumor growth [19,20]
Mice harboring established day 7 sarcoma were left untreated or they were administered with NLGP (25 mg) weekly for 4 weeks in total
Summary
Immune mediated restriction of tumor growth essentially requires synchronization of several interdependent events, including activation of tolerized immune cells [1], their migration and homing [2], suppression of suppressor activities of regulatory cells [3], type 1 polarization of immune microenvironment [4], inhibition of interference of pro-tumor molecules [5], memory development to prevent recurrence [6] and normalization of tumor vasculature [7]. In designing effective immunotherapy [16] and to obtain better clinical outcome [14], substantial emphasis has recently been placed on the development of treatment modalities that are capable of restoring systemic and tumor infiltrated T-cell functions [17] and associated immune dysfunctions [18]
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