Tropentag, September 17 - 19, 2013 in Stuttgart-Hohenheim "Agricultural development within the rural-urban continuum"

Are Capsule Polysaccharides of Mycoplasma Pathogens Affecting Ruminants in Africa Novel Vaccine Targets?

¹International Livestock Research Institute (ILRI), Biotechnology-Improving Livestock Disease Control, Kenya
²J. Craig Venter Institute, Synthetic Biology, United States of America
³University of Alberta, Alberta Glycomics Center, Canada

Abstract

Contagious bovine pleuropneumonia (CBPP) caused by Mycoplasma mycoides subsp. mycoides (Mmm) is one of the most important livestock diseases in sub-Saharan Africa. CBPP impacts health and poverty of livestock-dependent people through decreased animal productivity, reduced food supply, and the cost of control measures. Additionally, CBPP is a barrier to trade in many African countries and this reduces the value of livestock and the income of many value chain stakeholders.
Presently control of CBPP relies mainly on a live vaccine of limited efficacy and duration of immunity. Vaccines with better efficacy are necessary for control and eradication programmes within all African regions.
To date, our understanding of pathogenicity of the Mycoplasma mycoides is rather limited, since neither toxins nor colonisation factors have been identified. Up to now a long-lasting protective immune response could not be induced experimentally. Mycoplasma mycoides has a polysaccharide capsule that is likely to protect the pathogen from the host's immune responses. Full genome sequencing and in silico analysis of Mycoplasma mycoides isolates revealed a set of conserved genes involved in polysaccharide biosynthesis. A series of complementation assays and transposon mutagenesis experiments confirmed their function and highlighted the importance of these genes for survival of the pathogen, respectively.
Vaccines based on capsular polysaccharides are today available against Streptococcus pneumoniae, Neisseria meningitidis, Haemophilus influenzae type B and typhoid fever, and we are investigating the possibility of using the polysaccharides from the Mycoplasma capsule as a vaccine target. To this end, we are characterising the capsule using NMR technology.
We are investigating the role of Mycoplasma polysaccharides by mutagenesis of proteins involved in polysaccharide biosynthesis. Therefore we are using synthetic genomics via codon pair alteration, in order to decrease expression/abundance of the encoded enzymes. These mutants allow us to finally gauge the role of the capsule polysaccharides in host pathogen interactions using adhesion or in vivo experiments. The capsule of the resulting mutants will then be characterised, and the phenotypes will be tested in vitro and subsequently in vivo.

Keywords: Capsule, carbohydrates, CBPP, Contagious Bovine Pleuropneumonia, mycoplasma, polysaccharide, vaccine

Contact Address: Elise Schieck, International Livestock Research Institute (ILRI), Biotechnology-Improving Livestock Disease Control, Nairobi, Kenya, e-mail: elisesgmail.com