Combined neutralization of interferon gamma and tumor necrosis factor alpha induces IL-4 production but has no direct additive impact on parasite burden in splenic cultures of human visceral leishmaniasis

Abstract

Immune activating cytokines Interferon (IFN)-γ and Tumor necrosis factor (TNF)-α are known to activate macrophages for killing of Leishmania parasite. IFN-γ provides therapeutic potential while TNF-α has been recognized to mediate protection in visceral model of infection. In the present study we investigated whether combination of IFN-γ and TNF-α has better therapeutic strength than individually using one of these cytokines in Visceral Leishmaniasis (VL) patients. We performed combined blockade of IFN-γ and TNF-α in VL splenic biopsies and demonstrated it’s impact on number of viable amastigotes and cytokine production. Additionally, selective depletion of splenic cell subsets was performed to establish the cellular sources of IFN-γ and TNF-α. Treatment of splenic aspirate cells with combination of anti-IFN-γ and anti-TNF-α monoclonal antibodies for 72 hours enabled no direct additive impact of these cytokines on parasite replication and IL-10 secretion, but IL-4 production was induced. Further assessment of splenic biopsies put forward CD4+ T cells as a source of IFN-γ whereas CD14+ cells contribute towards TNF-α production. Overall our results suggest, the interplay of pro-inflammatory cytokines IFN-γ derived from CD4+T lymphocytes and TNF-α from CD14+ cells has no direct additive impact on parasite replication but induces IL-4 production. Our data does not support direct targeting of IFN-γ and TNF-α for combination therapy but targeting these cytokines as an adjuvant in patients with exaggerated tissue inflammatory responses can have favourable patient outcome. © 2018 Singh, Sundar. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.