Immunogenicity and Serological Cross-Reactivity of Saliva Proteins among Different Tsetse Species

PLoS Negl Trop Dis. 2015 Aug 27;9(8):e0004038. doi: 10.1371/journal.pntd.0004038. eCollection 2015.

Abstract

Tsetse are vectors of pathogenic trypanosomes, agents of human and animal trypanosomiasis in Africa. Components of tsetse saliva (sialome) are introduced into the mammalian host bite site during the blood feeding process and are important for tsetse's ability to feed efficiently, but can also influence disease transmission and serve as biomarkers for host exposure. We compared the sialome components from four tsetse species in two subgenera: subgenus Morsitans: Glossina morsitans morsitans (Gmm) and Glossina pallidipes (Gpd), and subgenus Palpalis: Glossina palpalis gambiensis (Gpg) and Glossina fuscipes fuscipes (Gff), and evaluated their immunogenicity and serological cross reactivity by an immunoblot approach utilizing antibodies from experimental mice challenged with uninfected flies. The protein and immune profiles of sialome components varied with fly species in the same subgenus displaying greater similarity and cross reactivity. Sera obtained from cattle from disease endemic areas of Africa displayed an immunogenicity profile reflective of tsetse species distribution. We analyzed the sialome fractions of Gmm by LC-MS/MS, and identified TAg5, Tsal1/Tsal2, and Sgp3 as major immunogenic proteins, and the 5'-nucleotidase family as well as four members of the Adenosine Deaminase Growth Factor (ADGF) family as the major non-immunogenic proteins. Within the ADGF family, we identified four closely related proteins (TSGF-1, TSGF-2, ADGF-3 and ADGF-4), all of which are expressed in tsetse salivary glands. We describe the tsetse species-specific expression profiles and genomic localization of these proteins. Using a passive-immunity approach, we evaluated the effects of rec-TSGF (TSGF-1 and TSGF-2) polyclonal antibodies on tsetse fitness parameters. Limited exposure of tsetse to mice with circulating anti-TSGF antibodies resulted in a slight detriment to their blood feeding ability as reflected by compromised digestion, lower weight gain and less total lipid reserves although these results were not statistically significant. Long-term exposure studies of tsetse flies to antibodies corresponding to the ADGF family of proteins are warranted to evaluate the role of this conserved family in fly biology.

Publication types

  • Comparative Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Cattle
  • Cross Reactions
  • Insect Proteins / chemistry
  • Insect Proteins / immunology*
  • Insect Vectors / chemistry
  • Insect Vectors / classification
  • Insect Vectors / immunology*
  • Insect Vectors / physiology
  • Male
  • Mass Spectrometry
  • Mice
  • Mice, Inbred C57BL
  • Molecular Sequence Data
  • Phylogeny
  • Salivary Proteins and Peptides / chemistry
  • Salivary Proteins and Peptides / immunology*
  • Trypanosoma brucei gambiense / immunology
  • Trypanosoma brucei gambiense / physiology
  • Trypanosomiasis, Bovine / immunology
  • Trypanosomiasis, Bovine / parasitology
  • Tsetse Flies / chemistry
  • Tsetse Flies / classification
  • Tsetse Flies / immunology*
  • Tsetse Flies / physiology

Substances

  • Insect Proteins
  • Salivary Proteins and Peptides