Scientific Publications by FDA Staff

Infect Immun 2015 Oct;83(10):3800-15

Genetically modified live attenuated L.donovani parasites induce innate immunity through classical activation of macrophages that direct Th1 response in mice.

Bhattacharya P, Dey R, Dagur PK, Kruhlak M, Ismail N, Debrabant A, Joshi AB, Akue A, Kukuruga M, Takeda K, Selvapandiyan A, McCoy JP Jr, Nakhasi HL

Visceral Leishmaniasis (VL) causes significant mortality and there is no effective vaccine. Previously, we have shown that, genetically modified Leishmania donovani parasites, hereafter described as live attenuated parasites, induced host protective adaptive immune response in various animal models. In this study, we demonstrate innate immune response upon infection with live attenuated parasites in macrophages from BALB/c mice both in vitro and in vivo. In vitro infection of macrophages with live attenuated parasites induced significantly higher production of pro-inflammatory cytokines (TNF-a, IL-12, IFN-¿, IL-6), chemokines (MCP-1/CCL-2, MIP-1a/CCL-3, IP-10), ROS and nitric oxide concomitantly reducing anti-inflammatory cytokine (IL-10) and arginase-1 activity compared to infection with wild type L. donovani (LdWT) parasites suggesting dominant classically activated/M1 macrophage response which in turn helps in presenting antigen to T cell as observed by robust CD4+T cell activation in vitro. Similarly, parasitized splenic macrophages from live attenuated parasite infected mice also demonstrated induction of M1 macrophage phenotype as indicated by up regulation of IL-1ß, TNF- a, IL-12, and iNOS2 and down regulation of genes associated with the M2 phenotype i.e. IL-10, YM1, Arg-1 and MRC-1 compared to LdWT infected mice. Furthermore, ex-vivo antigen presentation assay showed macrophages from live attenuated parasite infected mice induced higher IFN-¿ and IL-2 but significantly less IL-10 production by OVA specific CD4+T cells resulting in proliferation of Th1 cells. These data suggest that infection with live attenuated parasite promotes a state of classical activation (M1 dominant) in macrophages, leading to the generation of protective Th1 responses in BALB/c mice.