First analysis of the secretome of the canine heartworm, Dirofilaria immitis

James Geary,Selwyn A Headley,Charles Mackenzie,Doug Whitten,Timothy Geary,Mohamed Satti,Dalen Agnew,Nicole Madrill,Yovany Moreno

doi:10.1186/1756-3305-5-140

Abstract

BackgroundThe characterization of proteins released from filariae is an important step in addressing many of the needs in the diagnosis and treatment of these clinically important parasites, as well as contributing to a clearer understanding of their biology. This report describes findings on the proteins released during in vitro cultivation of adult Dirofilaria immitis , the causative agent of canine and feline heartworm disease. Differences in protein secretion among nematodes in vivo may relate to the ecological niche of each parasite and the pathological changes that they induce.MethodsThe proteins in the secretions of cultured adult worms were run on Tris-Glycine gels, bands separated and peptides from each band analysed by ultra mass spectrometry and compared with a FastA dataset of predicted tryptic peptides derived from a genome sequence of D. immitis. ResultsThis study identified 110 proteins. Of these proteins, 52 were unique to D. immitis . A total of 23 (44%) were recognized as proteins likely to be secreted. Although these proteins were unique, the motifs were conserved compared with proteins secreted by other nematodes.ConclusionThe present data indicate that D. immitis secretes proteins that are unique to this species, when compared with Brugia malayi. The two major functional groups of molecules represented were those representing cellular and of metabolic processes. Unique proteins might be important for maintaining an infection in the host environment, intimately involved in the pathogenesis of disease and may also provide new tools for the diagnosis of heartworm infection.

Highlights

The characterization of proteins released from filariae is an important step in addressing many of the needs in the diagnosis and treatment of these clinically important parasites, as well as contributing to a clearer understanding of their biology
D. immitis has been controlled through several different strategies, the most successful has been the prophylactic administration of a range of drug combinations and administration schedules, most usually involving tablets or topical preparations containing a macrocyclic lactone (ML) anthelmintic to uninfected dogs and cats to protect them by killing infective L3 larvae and developing L4 larvae [3]; drugs in this class of agents are microfilaricidal
The present study describes the secretome of D. immitis, as distinct from that of B. malayi, which resides in a different niche in the mammalian host

Summary

Introduction

The characterization of proteins released from filariae is an important step in addressing many of the needs in the diagnosis and treatment of these clinically important parasites, as well as contributing to a clearer understanding of their biology. This report describes findings on the proteins released during in vitro cultivation of adult Dirofilaria immitis, the causative agent of canine and feline heartworm disease. Infections with small numbers of adult D. immitis may be asymptomatic and have limited pathological effects; high adult worms loads usually cause exercise intolerance, a wet cough and lethargy in D. immitis has been controlled through several different strategies, the most successful has been the prophylactic administration of a range of drug combinations and administration schedules, most usually involving tablets or topical preparations containing a macrocyclic lactone (ML) anthelmintic to uninfected dogs and cats to protect them by killing infective L3 larvae and developing L4 larvae [3]; drugs in this class of agents are microfilaricidal. A course of arsenical drugs, such as the currently preferred malarsomine, is adulticidal, this regimen is not without risk to the animal due to the hepato- and nephron-toxicity of these compounds [7,8]; ‘slow-kill’ strategies for use of MLs in infected dogs have been developed [9], and the potential for anti-Wolbachia treatment options to reduce transmission and pathological effects following adulticidal therapy is promising [10,11]

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Discussion

Conclusion