Abstract
AbstractThe protozoan parasiteTrypanosoma evansiis responsible for causing Surra in a variety of mammalian hosts over a wide geographical area. In the absence of an effective vaccine and increasing resistance to current chemotherapeutic agents, peptidases from the S9 prolyl oligopeptidase family have been identified as potential drug and vaccine targets. In order to understand the function of these peptidases during infection, three null mutant clones for prolyl oligopeptidase (Δpop), prolyl oligopeptidase-like (Δpop-like) and oligopeptidase B (Δopb) were generated inT. evansiRoTat 1.2 parasites and used for infection of mice. Mice inoculated withT. evansi Δpop-likemutants were able to survive longer than other groups of mice inoculated withΔpop,Δopbmutants or wild-type parasites. The regression analysis of plasma from mice-infected over time usingΔpop-likemutants showed stable levels of interleukin-10 (IL-10) (non-significant slope,P= 0·171) and declining IL-1b levels (negative slope,P= 0·04) when compared with the wild-type control that demonstrated increasing levels of IL-10 and IL-1b (P< 0·01 for both). Further analysis using mouse spleen cells in anin vitro24 h incubation assay revealed that the percentage of IL-10 producing CD3 positive cells display significantly lower values when incubated withΔpop-likeparasites than the wild-type clone (P= 0·002). These results suggest that prolyl oligopeptidase-like peptidase may play a role in immune responses duringT. evansiinfections by affecting interleukin concentrations in the host.
Highlights
The mechanically transmitted protozoan parasite Trypanosoma evansi, a causative agent of the disease called Surra, is geographically the most widely distributed member of the genus Trypanosoma and infects the widest range of mammalian hosts, including buffaloes, camels, cattle, pigs, dogs, horses and goats (Holland et al 2003; Dargantes et al 2009; Desquesnes et al 2013; Salah et al 2015)
Whereas recombinant prolyl oligopeptidases (POPs) from T. brucei and T. cruzi are capable of hydrolysing proline rich native collagen, recombinant POP from Schistosoma mansoni is unable to hydrolyse substrates such as human collagens type I and IV (Bastos et al 2005, 2010; Fajtová et al 2015)
Oligopeptidase B, putative POP and prolyl oligopeptidase-like from T. b. brucei (TbbOPB, TbbPOP and TbbPOP-like; Gene IDs Tb927·11·12850, Tb927·10·8020 and Tb927·5·4300, respectively) were all included in the screen
Summary
The mechanically transmitted protozoan parasite Trypanosoma evansi, a causative agent of the disease called Surra, is geographically the most widely distributed member of the genus Trypanosoma and infects the widest range of mammalian hosts, including buffaloes, camels, cattle, pigs, dogs, horses and goats (Holland et al 2003; Dargantes et al 2009; Desquesnes et al 2013; Salah et al 2015). Parasites that die as a result of the host immune response release biologically active products that have been associated with disease symptoms (Taylor and Authié, 2004; Antoine-Moussiaux et al 2009) These toxins include enzymes such as trypanosome peptidases that hydrolyse host proteins, trypanosome phospholipases that hydrolyse red blood cell membranes and trypanosome trans-sialidases that act as important factors for virulence and anaemia (Tizard et al 1978; Antoine-Moussiaux et al 2009; Coustou et al 2012; Habila et al 2012). The study of these factors, and in particular peptidases, led to the idea of developing new anti-disease vaccines that target trypanosome products that are associated with disease symptoms (Authié, 1994; Authié et al 2001; Antoine-Moussiaux et al 2009)
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