Biomedical subjects

Tracey J Coffey

Publications and source records attributed to Tracey J Coffey.

9 recordsLinked to original sources

PubMed2006

Pattern recognition receptors in companion and farm animals - the key to unlocking the door to animal disease?

The innate immune system is essential for host defence and is responsible for early detection of potentially pathogenic microorganisms. Upon recognition of microbes by innate immune cells, such as macrophages and dendritic cells, diverse signalling pathways are activated that combine to define inflammatory responses that direct sterilisation of the threat and/or orchestrate development of the adaptive immune response. Innate immune signalling must be carefully controlled and regulation comes in part from interactions between activating and inhibiting signalling receptors. In recent years, an increasing number of pattern recognition receptors (PRRs), including C-type lectin receptors and Toll-like receptors (TLRs), has been described that participate in innate recognition of microbes, especially through the so called pathogen-associated molecular patterns (PAMPs). Recent studies demonstrate strong interactions between signalling through these receptors. Whereas useful models to study these receptors in great detail in the murine and human system are now emerging, relatively little is known regarding these receptors in companion and farm animals. In this review, current knowledge regarding these receptors in species of veterinary relevance is summarised.

Animals↗

PubMed2006

Multilocus-sequence typing analysis reveals similar populations of Streptococcus uberis are responsible for bovine intramammary infections of short and long duration.

Multilocus-sequence typing (MLST) was used to analyse Streptococcus uberis isolates from a single herd associated with long duration (50-260 days) and rapidly cleared (less than 1 month) bovine intramammary infections to determine whether the bacterial type had any impact on the duration of infection. Most chronic infections (24 of 33) were due to continuous infection of the mammary quarter with the same sequence type, and infections were found to persist for many months. The remaining quarters were re-infected with a different sequence type within a single lactation. No particular sequence type or clonal complex (lineage) was associated with persisting infections, indicating that the outcome of intramammary infections with S. uberis is more likely to be dependent on host factors than on inter-strain differences. Analysis of these strains alongside others obtained from the same herd at a later date revealed the shift in the predominant genotypes with time.

Alleles↗

PubMed2006

Expression of TOLL-like receptors (TLR) by bovine antigen-presenting cells-potential role in pathogen discrimination?

Invading pathogens are controlled by the innate and adaptive arms of the immune system. Adaptive immunity, mediated by B and T lymphocytes, recognises pathogens via high affinity receptors. However, the establishment of a primary adaptive immune response is not rapid enough to eradicate invading microorganisms as it involves cell proliferation, gene activation and protein synthesis. More rapid defence mechanisms are provided by innate immunity, which recognises invading pathogens by germ-line-encoded pattern recognition receptors. Recent evidence shows that this recognition can mainly be attributed to the family of TOLL-like receptors (TLR). Binding of pathogen-associated molecular patterns to TLR induces the production of reactive oxygen and nitrogen intermediates, pro-inflammatory cytokines, and up-regulates expression of co-stimulatory molecules, subsequently initiating the adaptive immunity. In this paper, we will discuss the current knowledge with regards to the TLR, and in particular the bovine family of TLR. In addition, we will show the expression of TLR mRNA in bovine antigen-presenting cell subsets, summarise the discovery and the critical roles of TLR2 in host defence against Mycobacteria, and provide evidence for a mycobacteria species-specific response of bovine macrophages.

Animals↗

PubMed2006

First insights into the evolution of Streptococcus uberis: a multilocus sequence typing scheme that enables investigation of its population biology.

Intramammary infection with Streptococcus uberis is a common cause of bovine mastitis throughout the world. Several procedures to differentiate S. uberis isolates have been proposed. However, all are prone to interlaboratory variation, and none is suitable for the description of the population structure. We describe here the development of a multilocus sequence typing (MLST) scheme for S. uberis to help address these issues. The sequences of seven housekeeping gene fragments from each of 160 United Kingdom milk isolates of S. uberis were determined. Between 5 and 17 alleles were obtained per locus, giving the potential to discriminate between 1.3 x 10(7) sequence types. In this study, 57 sequence types (STs) were identified. Statistical comparisons between the maximum-likelihood trees constructed by using the seven housekeeping gene fragments showed that the congruence was no better than that between each tree and trees of random topology, indicating there had been significant recombination within these loci. The population contained one major lineage (designated the ST-5 complex). This dominated the population, containing 24 STs and representing 112 isolates. The other 33 STs were not assigned to any clonal complex. All of the isolates in the ST-5 lineage carried hasA, a gene that is essential for capsule production. There was no clear association between ST or clonal complex and disease. The S. uberis MLST system offers researchers a valuable tool that allows further investigation of the population biology of this organism and insights into the epidemiology of this disease on a global scale.

Animals↗

PubMed2006

Application of Streptococcus uberis multilocus sequence typing: analysis of the population structure detected among environmental and bovine isolates from New Zealand and the United Kingdom.

We recently developed a multilocus sequence typing (MLST) scheme to differentiate S. uberis isolates and facilitate an understanding of the population biology of this pathogen. The scheme was initially used to study a collection of 160 bovine milk isolates from the United Kingdom and showed that the majority of isolates were from one clonal complex (designated the ST-5 complex). Here we describe the MLST analysis of a collection of New Zealand isolates. These were obtained from diverse sources, including bovine milk, other bovine anatomical sites, and environmental sources. The complete allelic profiles of 253 isolates were determined. The collection was highly diverse and included 131 different sequence types (STs). The New Zealand and United Kingdom populations were distinct, since none of the 131 STs were represented within the previously studied collection of 160 United Kingdom S. uberis isolates. However, seven of the STs were members of the ST-5 clonal complex, the major complex within the United Kingdom collection. Two new clonal complexes were identified: ST-143 and ST-86. All three major complexes were isolated from milk, other bovine sites, and the environment. Carriage of the hasA gene, which is necessary for capsule formation, correlated with clonal complex and isolation from clinical cases of mastitis.

Alleles↗

PubMed2004

Hyperinvasive neonatal group B streptococcus has arisen from a bovine ancestor.

The genetic relatedness and evolutionary relationships between group B streptococcus (GBS) isolates from humans and those from bovines were investigated by phylogenetic analysis of multilocus sequence typing data. The collection of isolates consisted of 111 GBS isolates from cows with mastitis and a diverse global collection of GBS isolates from patients with invasive disease (n = 83) and carriers (n = 69). Cluster analysis showed that the majority of the bovine isolates (93%) grouped into one phylogenetic cluster. The human isolates showed greater diversity and clustered separately from the bovine population. However, the homogeneous human sequence type 17 (ST-17) complex, known to be significantly associated with invasive neonatal disease, was the only human lineage found to be clustered within the bovine population and was distinct from all the other human lineages. Split decomposition analysis revealed that the human isolate ST-17 complex, the major hyperinvasive neonatal clone, has recently arisen from a bovine lineage.

Animals↗

PubMed2003

Lack of TNF alpha supports persistence of a plasmid encoding the bovine leukaemia virus in TNF(-/-) mice.

Tumour necrosis factor (TNF) is well recognised for its role in mediating innate immune responses. However, the mechanisms of TNF that influence the adaptive immune response to viral infections are poorly understood. Over recent years, there has been evidence to suggest a role for TNF in the early phase of infection of ruminants with bovine leukaemia virus (BLV). In this study, we infected TNF(-/-) mice with a plasmid encoding infectious BLV to further elucidate the role of TNF in BLV infection. TaqMan quantitative PCR showed that proviral DNA was present in genomic DNA isolated from spleen cells of TNF(-/-) mice 4 weeks post-infection, whereas it was not detected in wild-type mice. We were not able to detect differences in serum IgM or IgG levels between the TNF(-/-) and wild-type mice, or antibodies to BLV after this short period. In showing that the lack of TNF enables the plasmid encoded BLV to persist longer, and therefore rendering the mice more susceptible to an infection with BLV, the data suggest an important defence function of TNF in the early phase of BLV infection.

Animals↗

PubMed1999

Molecular and genetic characterization of the capsule biosynthesis locus of Streptococcus pneumoniae type 23F.

The authors have previously reported the nucleotide sequence of the 5' and 3' portions of the Streptococcus pneumoniae type 23F capsular polysaccharide biosynthesis locus (cps23f) (from dexB to cps23fB and from cps23fL to aliA). These regions of cps23f were very similar to the sequence reported for cps19f, the capsule locus of S. pneumoniae type 19F. However, Southern hybridization analysis indicated that no other genes closely related to cps19f are present in the cps23f locus. In this study long-range PCR was used to amplify and clone the section of the S. pneumoniae type 23F capsule locus between cps23fB and cps23fL. This region is 13 kb in size and contains 12 new ORFs, designated cps23fC-E, I, J, and T-Z. Functions are proposed for all of the protein products, including functional homologues of Cps19fC-E, Cps19fI and Cps19fJ. A biosynthetic pathway for type 23F capsular polysaccharide is also proposed.

Amino Acid Sequence↗

PubMed1999

Serotype 14 variants of the Spanish penicillin-resistant serotype 9V clone of Streptococcus pneumoniae arose by large recombinational replacements of the cpsA-pbp1a region.

The high prevalence of penicillin resistance among Streptococcus pneumoniae isolates from Uruguay has been associated with the emergence of a penicillin-resistant clone of serotype 14. Isolates of this clone were identical by multilocus sequence typing to members of the Spanish penicillin-resistant serotype 9V clone and possessed indistinguishable forms of the penicillin-binding protein 2b and 2x genes. Their pbp1a genes were also identical, except at the 3' end. The serotype 14 isolates were shown to be a variant of the Spanish serotype 9V clone which arose by a 22.2 kb recombinational replacement that introduced the capsular biosynthetic locus, and part of the neighbouring pbp1a gene, from a serotype 14 isolate. One end of the recombinational replacement was within the first gene of the capsular polysaccharide operon, cpsA, as the sequence of the upstream dexB gene, through most of cpsA, was identical in the penicillin-resistant serotype 9V and 14 isolates, but the sequences differed in the rest of cpsA and in cpsB. The other recombinational junction was at the end of the divergently transcribed pbp1a gene, which is approximately 11.6 kb downstream of the capsular biosynthetic locus. Isolates of this serotype variant were also detected in Spain and Denmark. Penicillin-resistant serotype 14 isolates from Poland were also closely related to the penicillin-resistant serotype 9V clone, but have emerged independently, as one end of the recombinational replacement was upstream of dexB and the other was within pbp1a, but at a different position from that in the serotype 14 variants from Uruguay, Spain and Denmark. Serotype 14 variants of the Spanish serotype 9V clone have therefore arisen on more than one occasion by large recombinational replacements that extend from the start of the cps region into the pbp1a gene.

Bacterial Capsules↗