Immunity to LuloHya and Lundep, the salivary spreading factors from Lutzomyia longipalpis, protects against Leishmania major infection

PLoS Pathog. 2018 May 3;14(5):e1007006. doi: 10.1371/journal.ppat.1007006. eCollection 2018 May.

Abstract

Salivary components from disease vectors help arthropods to acquire blood and have been shown to enhance pathogen transmission in different model systems. Here we show that two salivary enzymes from Lutzomyia longipalpis have a synergist effect that facilitates a more efficient blood meal intake and diffusion of other sialome components. We have previously shown that Lundep, a highly active endonuclease, enhances parasite infection and prevent blood clotting by inhibiting the intrinsic pathway of coagulation. To investigate the physiological role of a salivary hyaluronidase in blood feeding we cloned and expressed a recombinant hyaluronidase from Lu. longipalpis. Recombinant hyaluronidase (LuloHya) was expressed in mammalian cells and biochemically characterized in vitro. Our study showed that expression of neutrophil CXC chemokines and colony stimulating factors were upregulated in HMVEC cells after incubation with LuloHya and Lundep. These results were confirmed by the acute hemorrhage, edema and inflammation in a dermal necrosis (dermonecrotic) assay involving a massive infiltration of leukocytes, especially neutrophils, in mice co-injected with hemorrhagic factor and these two salivary proteins. Moreover, flow cytometry results showed that LuloHya and Lundep promote neutrophil recruitment to the bite site that may serve as a vehicle for establishment of Leishmania infection. A vaccination experiment demonstrated that LuloHya and Lundep confer protective immunity against cutaneous leishmaniasis using the Lu. longipalpis-Leishmania major combination as a model. Animals (C57BL/6) immunized with LuloHya or Lundep showed minimal skin damage while lesions in control animals remained ulcerated. This protective immunity was abrogated when B-cell-deficient mice were used indicating that antibodies against both proteins play a significant role for disease protection. Rabbit-raised anti-LuloHya antibodies completely abrogated hyaluronidase activity in vitro. Moreover, in vivo experiments demonstrated that blocking LuloHya with specific antibodies interferes with sand fly blood feeding. This work highlights the relevance of vector salivary components in blood feeding and parasite transmission and further suggests the inclusion of these salivary proteins as components for an anti-Leishmania vaccine.

Publication types

  • Research Support, N.I.H., Intramural

MeSH terms

  • Animals
  • Computer Simulation
  • Endonucleases / immunology
  • Female
  • Host-Pathogen Interactions / immunology
  • Humans
  • Hyaluronoglucosaminidase / chemistry
  • Hyaluronoglucosaminidase / immunology*
  • Insect Proteins / chemistry
  • Insect Proteins / immunology
  • Leishmania major / immunology*
  • Leishmania major / pathogenicity*
  • Leishmaniasis, Cutaneous / immunology*
  • Leishmaniasis, Cutaneous / prevention & control*
  • Mice
  • Mice, 129 Strain
  • Mice, Inbred C57BL
  • Models, Molecular
  • Neutrophils / immunology
  • Polysaccharide-Lyases / immunology
  • Psychodidae / immunology*
  • Rabbits
  • Saliva / enzymology
  • Saliva / immunology

Substances

  • Insect Proteins
  • Endonucleases
  • Hyaluronoglucosaminidase
  • Polysaccharide-Lyases
  • hyaluronate lyase

Grants and funding

This research was supported by the Intramural Research Program of the NIH, NIAID. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.