Reproduction of contagious caprine pleuropneumonia reveals the ability of convalescent sera to reduce hydrogen peroxide production in vitro

Abstract

Contagious caprine pleuropneumonia (CCPP), caused by Mycoplasma capricolum subsp. capripneumoniae is a severe disease widespread in Africa and Asia. Limited knowledge is available on the pathogenesis of this organism, mainly due to the lack of a robust in vivo challenge model and the means to do site-directed mutagenesis. This work describes the establishment of a novel caprine challenge model for CCPP that resulted in 100% morbidity using a combination of repeated intranasal spray infection followed by a single transtracheal infection employing the recent Kenyan outbreak strain ILRI181. Diseased animals displayed CCPP-related pathology and the bacteria could subsequently be isolated from pleural exudates and lung tissues in concentrations of up to 109 bacteria per mL as well as in the trachea using immunohistochemistry. Reannotation of the genome sequence of ILRI181 and F38T revealed the existence of genes encoding the complete glycerol uptake and metabolic pathways involved in hydrogen peroxide (H2O2) production in the phylogenetically related pathogen M. mycoides subsp. mycoides. Furthermore, the expression of L-α-glycerophosphate oxidase (GlpO) in vivo was confirmed. In addition, the function of the glycerol metabolism was verified by measurement of production of H2O2 in medium containing physiological serum concentrations of glycerol. Peroxide production could be inhibited with serum from convalescent animals. These results will pave the way for a better understanding of host–pathogen interactions during CCPP and subsequent vaccine development.Electronic supplementary materialThe online version of this article (10.1186/s13567-019-0628-0) contains supplementary material, which is available to authorized users.

Contagious Bovine and Caprine Pleuropneumonia: a research community’s recommendations for the development of better vaccines

“…This model is based on a combination of two subsequent inoculations of aerosols of cultures into the nasal cavity of goats followed by a trans-tracheal inoculation. Morbidity of 100% and a mortality of 50-60% was seen in infected animals, closely mimicking natural infection 49 . Improvements of the challenge model are possible, including titration of the challenge dose, use of an aerosol chamber for infection as has been used for experimental infections with other Mycoplasma species 51,52 , and whether either the aerosol or the trans-tracheal inoculations are dispensable to allow simplification of the procedure.…”

“…A common feature of these models is the intratracheal inoculation of a Mycoplasma culture using a tube that is inserted via the nasal or oral cavity while the animal is standing or in lateral recumbency. In the past, fresh cultures were used for inoculation, however, it has now been demonstrated that frozen stock cultures work well for both pathogens 60,49 . The instillation of a solution of agar after inoculation of the mycoplasma broth culture has been show to be dispensable 60 .…”

“…We suggest performing adoptive transfer experiments with purified antibodies from convalescent, diseased, and healthy animals to animals that are subsequently infected experimentally. Such activities should be initiated with CCPP, as the infection model is well established, and large amounts of sera have been collected from convalescent animals at necropsy during a recent trial 49 . If the adoptively transferred antibodies are protective, we can focus on characterization of the spectrum of specificities of the antibodies using bead-based assays and bioinformatic network analysis of B-cell responses in protected animals.…”

“…But which challenge models are available? For CCPP, of late a novel challenge model has recently been reported 49 , based on the recent Kenyan outbreak strain ILRI181 50 . This model is based on a combination of two subsequent inoculations of aerosols of cultures into the nasal cavity of goats followed by a trans-tracheal inoculation.…”

An alternative caprine infection model for Mycoplasma mycoides

“…It is against this background that this work reports the use of an invivo experiment, comparing a wild type (Mmc GM12) and Mmc 1.1 delta 68 strains to ascertain whether the mutant after target specific edits led to attenuation. This alternative method was adopted with modifications for other ruminant Mycoplasma in-vivo work by Jores et al (2018) and Liljander et al (2019), with infection success observed.…”