Characterization of Campylobacter concisus hemolysins

Campylobacter concisus is an opportunistic pathogen commonly found in the human oral cavity. It has also been isolated from clinical sources including gastroenteritis cases. Both secreted and cell-associated hemolytic activities were detected in C. concisus strains isolated from children with gastroenteritis. The secreted hemolytic activity of C. concisus strains was labile and was detected in variable levels from fresh-culture filtrates only. In addition, another secreted hemolysin/cytotoxin with a molecular weight <10 kDa was detected in a single C. concisus strain (RCH 12). A C. concisus genomic library, constructed from strain RCH 3 in Escherichia coli XL1-Blue, was screened for hemolytic clones. Subcloning and sequence analysis of selected hemolytic clones identified ORFs for genes that enhance hemolytic activity but do not appear to be related to any known hemolysin genes found in Gram-negative bacteria. In a previous study, a stable cell-associated hemolysin was identified as an outer-membrane phospholipase A (OMPLA) encoded by the pldA gene. In this study, we report cloning of the pldA gene of the clinical strain C. concisus RCH 3 and the complementation of phospholipase A activity in an E. coli pldA mutant.

Identification of a gene for an ancient cytokine, interleukin 15-like, in mammals; interleukins 2 and 15 co-evolved with this third family member, all sharing binding motifs for IL-15Rα

Interleukins 2 and 15 (IL-2 and IL-15) are highly differentiated but related cytokines with overlapping, yet also distinct functions, and established benefits for medical drug use. The present study identified a gene for an ancient third IL-2/15 family member in reptiles and mammals, interleukin 15-like (IL-15L), which hitherto was only reported in fish. IL-15L genes with intact open reading frames (ORFs) and evidence of transcription, and a recent past of purifying selection, were found for cattle, horse, sheep, pig and rabbit. In human and mouse the IL-15L ORF is incapacitated. Although deduced IL-15L proteins share only ~21 % overall amino acid identity with IL-15, they share many of the IL-15 residues important for binding to receptor chain IL-15Rα, and recombinant bovine IL-15L was shown to interact with IL-15Rα indeed. Comparison of sequence motifs indicates that capacity for binding IL-15Rα is an ancestral characteristic of the IL-2/15/15L family, in accordance with a recent study which showed that in fish both IL-2 and IL-15 can bind IL-15Rα. Evidence reveals that the species lineage leading to mammals started out with three similar cytokines IL-2, IL-15 and IL-15L, and that later in evolution (1) IL-2 and IL-2Rα receptor chain acquired a new and specific binding mode and (2) IL-15L was lost in several but not all groups of mammals. The present study forms an important step forward in understanding this potent family of cytokines, and may help to improve future strategies for their application in veterinarian and human medicine.