TNF signalling drives expansion of bone marrow CD4+ T cells responsible for HSC exhaustion in experimental visceral leishmaniasis

Abstract

Visceral leishmaniasis is associated with significant changes in hematological function but the mechanisms underlying these changes are largely unknown. In contrast to naïve mice, where most long-term hematopoietic stem cells (LT-HSCs; LSK CD150+ CD34- CD48- cells) in bone marrow (BM) are quiescent, we found that during Leishmania donovani infection most LT-HSCs had entered cell cycle. Loss of quiescence correlated with a reduced self-renewal capacity and functional exhaustion, as measured by serial transfer. Quiescent LT-HSCs were maintained in infected RAG2 KO mice, but lost following adoptive transfer of IFNγ-sufficient but not IFNγ-deficient CD4+ T cells. Using mixed BM chimeras, we established that IFNγ and TNF signalling pathways converge at the level of CD4+ T cells. Critically, intrinsic TNF signalling is required for the expansion and/or differentiation of pathogenic IFNγ+CD4+ T cells that promote the irreversible loss of BM function. These findings provide new insights into the pathogenic potential of CD4+ T cells that target hematopoietic function in leishmaniasis and perhaps other infectious diseases where TNF expression and BM dysfunction also occur simultaneously.

Establishment, optimisation and quantitation of a bioluminescent murine infection model of visceral leishmaniasis for systematic vaccine screening

“…Immunocompromised Rag1 and Rag2-deficient mice have been useful models to isolate and study components of host immunity to VL, as well as a source of ex vivo amastigotes [25][26][27][28] . To determine the virulence of transgenic L. donovani in immunodeficient Rag1 knockout mice, they were infected intravenously with 10 8 stationary phase promastigotes and the infection followed by in vivo imaging ( Fig.…”

“…This is followed by a delayed but progressive increase in parasite burden within the spleen accompanied by splenomegaly; unlike the liver, however, spleen infections are persistent and indefinitely maintained. Genetically modified immuno-compromised mice such as Rag1 and Rag2-deficient mice have also been used successfully as models for VL and unlike the BALB/c strain, these mice more closely reflect human disease pathology since they do not clear parasites from the liver [25][26][27][28] . Uses of these immunodeficient animals, however, are generally limited to studies involving drug trials or in vivo parasite propagation since they are incapable of generating adaptive immune responses.…”

CD4+ T Cells Alter the Stromal Microenvironment and Repress Medullary Erythropoiesis in Murine Visceral Leishmaniasis

“…Cotterell et al demonstrated that chronic VL in BALB/c mice results in an increase of hematopoietic progenitors in the spleen and the BM (25), and that BM stromal macrophage-derived cells may become more supportive of myelopoiesis after infection with L. donovani in vitro , due to increased secretion of GM-CSF and TNF (26). More recently, alterations in the HSC compartment have been described that might contribute both to ongoing VL-associated immunosuppression (27) and to long term hematopoietic competence (28).…”

Association between Insulin-Like Growth Factor-I Levels and the Disease Progression and Anemia in Visceral Leishmaniasis

“…Few studies have explored the role of cytokines/growth factors in the canine bone marrow, which may contribute to VL anemia. 5,7 Thus, we evaluated IGF-I, TNF-α, and IFN-γ expression in the bone marrow of dogs with VL.…”

“…3 The effects of some growth factors/cytokines in the bone marrow have also been studied in experimental VL. 3,[5][6][7] Among growth factors, insulin-like growth factor-I (IGF-I) has been implicated in hematopoiesis, 8 and many studies have demonstrated that the growth hormone/IGF-I/IGF-binding protein 3 (IGFBP-3) axis can be downregulated during infections/immune responses through pro-inflammatory cytokine effects. 9 During active VL, intense immune inflammatory activation occurs with an overproduction of pro-inflammatory cytokines, 10 including interferon-gamma (IFN-γ) and tumor necrosis factor alpha (TNF-α).…”