Lymphocytes influence Leishmania major pathogenesis in a strain-dependent manner

PLoS Negl Trop Dis. 2019 Nov 18;13(11):e0007865. doi: 10.1371/journal.pntd.0007865. eCollection 2019 Nov.

Abstract

Cutaneous leishmaniasis (CL) is the most common form of leishmaniasis and is caused by several species of Leishmania parasite. Clinical presentation of CL varies from a self-healing infection to a chronic form of the disease determined by the virulence of infecting Leishmania species and host immune responses to the parasite. Mouse models of CL show contradictory roles of lymphocytes in pathogenesis, while acquired immune responses are responsible for host protection from diseases. To reconcile the inconclusive roles of acquired immune responses in pathogenesis, we infected mice from various genetic backgrounds with two pathogenic strains of Leishmania major, Friedlin or 5ASKH, and assessed the outcome of the infections. Our findings showed that the genetic backgrounds of L. major determine the impact of lymphocytes for pathogenesis. In the absence of lymphocytes, L. major Friedlin induced the lowest inflammatory reaction and pathology at the site of infection, while 5ASKH infection induced a strong inflammatory reaction and severe pathology. Lymphocytes ameliorated 5ASKH mediated pathology, while it exacerbated pathology during Friedlin infection. Excess inflammatory reactions, like the recruitment of macrophages, neutrophils, eosinophils and production of pro-inflammatory cytokines, together with uncontrolled parasite growth in the absence of lymphocytes during 5ASKH infection may induce severe pathology development. Taken together our study provides insight into the impact of differences in the genetic background of Leishmania on CL pathogenesis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adaptive Immunity
  • Animals
  • Disease Models, Animal
  • Female
  • Host-Pathogen Interactions
  • Leishmania major / genetics
  • Leishmania major / growth & development*
  • Leishmania major / immunology*
  • Leishmaniasis, Cutaneous / immunology*
  • Leishmaniasis, Cutaneous / pathology*
  • Lymphocytes / immunology*
  • Mice, Inbred BALB C

Grants and funding

This work was supported by the Joint Usage/Research Center on Tropical Disease, Institute of Tropical Medicine (NEKKEN), Nagasaki University (to RN, SH), the Global Health Innovative Technology (GHIT) Fund, Japan [G2015-115] (to AS, HN, SH), the Global Leadership Program, Nagasaki University (to AM, RN, SH) and JSPS KAKENHI [18H02649](to YG). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.