Studies on the haemolytic complement of the dromedary camel (Camelus dromedarius). I. Classical pathway haemolytic activity in serum

Deiminated proteins in extracellular vesicles and serum of llama (Lama glama)-Novel insights into camelid immunity

Peptidylarginine deiminases (PADs) are phylogenetically conserved calcium-dependent enzymes which post-translationally convert arginine into citrulline in target proteins in an irreversible manner, causing functional and structural changes in target proteins. Protein deimination causes generation of neo-epitopes, affects gene regulation and also allows for protein moonlighting. Furthermore, PADs have been found to be a phylogenetically conserved regulator for extracellular vesicle (EVs) release. EVs are found in most body fluids and participate in cellular communication via transfer of cargo proteins and genetic material. In this study, post-translationally deiminated proteins in serum and serum-EVs are described for the first time in camelids, using the llama (Lama glama L. 1758) as a model animal. We report a poly-dispersed population of llama serum EVs, positive for phylogenetically conserved EV-specific markers and characterised by TEM. In serum, 103 deiminated proteins were overall identified, including key immune and metabolic mediators including complement components, immunoglobulin-based nanobodies, adiponectin and heat shock proteins. In serum, 60 deiminated proteins were identified that were not in EVs, and 25 deiminated proteins were found to be unique to EVs, with 43 shared deiminated protein hits between both serum and EVs. Deiminated histone H3, a marker of neutrophil extracellular trap formation, was also detected in llama serum. PAD homologues were identified in llama serum by Western blotting, via cross reaction with human PAD antibodies, and detected at an expected 70 kDa size. This is the first report of deiminated proteins in serum and EVs of a camelid species, highlighting a hitherto unrecognized post-translational modification in key immune and metabolic proteins in camelids, which may be translatable to and inform a range of human metabolic and inflammatory pathologies.

A hemolysis-hemagglutination assay for characterizing constitutive innate humoral immunity in wild and domestic birds

Methods to assess immunocompetence requiring only a single sample are useful in comparative studies where practical considerations prevent holding or recapturing individuals. The assay for natural antibody-mediated complement activation and red blood cell agglutination described here, requiring approximately 100 microl of blood, is highly repeatable. The effects of complement deactivation, 2-mercaptoethanol (2-ME), age, and lipopolysaccharide (LPS)-induced sickness response were examined to validate comparisons among diverse avian species. Complement deactivation by heating significantly reduces lysis and treatment with 2-ME reduces both lysis and agglutination. Lysis and agglutination both increase with age in chickens; LPS treatment does not influence these variables in 11-week-old chickens. In a comparison of 11 species, both lysis (0.0-5.3 titers) and agglutination (1.8-8.0 titers) vary significantly among species. Accordingly, this assay can be used to compare constitutive innate humoral immunity among species and with respect to age, sex, and experimental treatments within populations.

Changes in classical pathway complement activity in dromedary camels experimentally infected with Trypanosoma evansi

The complement system is known to have important effector functions in immune responses. However, its role in camel trypanosomosis has not been determined. The present study was undertaken to evaluate haemolytic complement activity in Trypanosoma evansi-infected and uninfected camels. Five dromedary camels were experimentally infected with T. evansi and classical pathway haemolytic complement activity was assayed. Parasitaemia and packed cell volume were also monitored. Following infection, classical pathway haemolytic complement showed a slight initial increase (7%) in all the camels. The amounts later dropped as the infection progressed and correlated negatively with parasitaemia. Haemolytic complement recovered following elimination of trypanosomes by treatment with melarsomine. Treatment of uninfected camels had no effect on complement. This study has demonstrated that complement concentration increases in the initial phase of infection followed by a drop as the infection progresses towards chronicity. In addition, the study has shown that activation of the classical complement pathway occurs in camels infected with T. evansi. Complement could therefore be involved in the in vivo control of parasitaemia in dromedary camels infected with T. evansi. Decreased complement levels in this species could lead to immunosuppression, widely reported in animal trypanosomosis.