Neutropenic Mice Provide Insight into the Role of Skin-Infiltrating Neutrophils in the Host Protective Immunity against Filarial Infective Larvae

PLoS Negl Trop Dis. 2016 Apr 25;10(4):e0004605. doi: 10.1371/journal.pntd.0004605. eCollection 2016 Apr.

Abstract

Our knowledge and control of the pathogenesis induced by the filariae remain limited due to experimental obstacles presented by parasitic nematode biology and the lack of selective prophylactic or curative drugs. Here we thought to investigate the role of neutrophils in the host innate immune response to the infection caused by the Litomosoides sigmodontis murine model of human filariasis using mice harboring a gain-of-function mutation of the chemokine receptor CXCR4 and characterized by a profound blood neutropenia (Cxcr4(+/1013)). We provided manifold evidence emphasizing the major role of neutrophils in the control of the early stages of infection occurring in the skin. Firstly, we uncovered that the filarial parasitic success was dramatically decreased in Cxcr4(+/1013) mice upon subcutaneous delivery of the infective stages of filariae (infective larvae, L3). This protection was linked to a larger number of neutrophils constitutively present in the skin of the mutant mice herein characterized as compared to wild type (wt) mice. Indeed, the parasitic success in Cxcr4(+/1013) mice was normalized either upon depleting neutrophils, including the pool in the skin, or bypassing the skin via the intravenous infection of L3. Second, extending these observations to wt mice we found that subcutaneous delivery of L3 elicited an increase of neutrophils in the skin. Finally, living L3 larvae were able to promote in both wt and mutant mice, an oxidative burst response and the release of neutrophil extracellular traps (NET). This response of neutrophils, which is adapted to the large size of the L3 infective stages, likely directly contributes to the anti-parasitic strategies implemented by the host. Collectively, our results are demonstrating the contribution of neutrophils in early anti-filarial host responses through their capacity to undertake different anti-filarial strategies such as oxidative burst, degranulation and NETosis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Disease Models, Animal
  • Filariasis / parasitology*
  • Filariasis / pathology*
  • Filarioidea / growth & development
  • Filarioidea / immunology*
  • Immunity, Innate*
  • Larva / growth & development
  • Larva / immunology
  • Leukocyte Reduction Procedures
  • Mice
  • Neutrophils / immunology*
  • Receptors, CXCR4 / genetics
  • Receptors, CXCR4 / metabolism
  • Skin / parasitology*
  • Skin / pathology*

Substances

  • CXCR4 protein, mouse
  • Receptors, CXCR4

Grants and funding

This work was supported by a DIM Malinf (Domaine d'Intérêt Majeur, Maladies Infectieuses) from the Conseil Régional d'Ile-de-France, by the European Commission (grant No. 242121, EPIAF), and the European Research Area Network (ERA-NET 2011: Rare-013-01 WHIM-Thernet). FB and GSL are members of the Laboratory of Excellence in Research on Medication and Innovative Therapeutics supported by a grant from ANR (Investissements d’Avenir -ANR-10-LABX-0033-LERMIT). NP is a recipient of a DIM Malinf post-doctoral grant. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.