Dataset Information

Interaction between M-like protein and macrophage thioredoxin facilitates antiphagocytosis for Streptococcus equi ssp. zooepidemicus.

ABSTRACT: Streptococcus equi ssp. zooepidemicus (S. zooepidemicus, S.z) is one of the common pathogens that can cause septicemia, meningitis, and mammitis in domesticated species. M-like protein (SzP) is an important virulence factor of S. zooepidemicus and contributes to bacterial infection and antiphagocytosis. The interaction between SzP of S. zooepidemicus and porcine thioredoxin (TRX) was identified by the yeast two-hybrid and further confirmed by co-immunoprecipitation. SzP interacted with both reduced and the oxidized forms of TRX without inhibiting TRX activity. Membrane anchored SzP was able to recruit TRX to the surface, which would facilitate the antiphagocytosis of the bacteria. Further experiments revealed that TRX regulated the alternative complement pathway by inhibiting C3 convertase activity and associating with factor H (FH). TRX alone inhibited C3 cleavage and C3a production, and the inhibitory effect was additive when FH was also present. TRX inhibited C3 deposition on the bacterial surface when it was recruited by SzP. These new findings indicated that S. zooepidemicus used SzP to recruit TRX and regulated the alternative complement pathways to evade the host immune phagocytosis.

SUBMITTER: Ma Z

PROVIDER: S-EPMC3288065 | biostudies-literature | 2012

REPOSITORIES: biostudies-literature

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Interaction between M-like protein and macrophage thioredoxin facilitates antiphagocytosis for Streptococcus equi ssp. zooepidemicus.

Ma Zhe Z Zhang Hui H Zheng Junxi J Li Yue Y Yi Li L Fan Hongjie H Lu Chengping C

PloS one 20120227 2

Streptococcus equi ssp. zooepidemicus (S. zooepidemicus, S.z) is one of the common pathogens that can cause septicemia, meningitis, and mammitis in domesticated species. M-like protein (SzP) is an important virulence factor of S. zooepidemicus and contributes to bacterial infection and antiphagocytosis. The interaction between SzP of S. zooepidemicus and porcine thioredoxin (TRX) was identified by the yeast two-hybrid and further confirmed by co-immunoprecipitation. SzP interacted with both redu ...[more]

PMID: 22384152

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Project description:Streptococcus equi subsp. zooepidemicus (SEZ) has a wide host spectrum, including humans and domestic animals. The SEZ-caused swine streptococcicosis outbreak has occurred in several countries, and the swine-isolated strains usually have specific S. zooepidemicus M-like (szm) gene types. In this study, we found that the production of this specific szm gene (SzM protein) was an effective vaccine candidate. It could provide better protection with a 7-day interval immune procedure than the traditional vaccine strain ST171 and attenuate the strain ΔsezV against swine-isolated hypervirulent SEZ infections. According to this outcome, we developed monoclonal antibodies (McAbs) targeting the variable and conserved regions of this SzM protein, respectively. These McAbs all belong to the IgG1 isotype with a κ type light chain and have opsonophagocytic activity rather than agglutination or complement activation functions. We estimated the protection efficiency of the McAbs with 3 different passive immunotherapy programs. The anti-conserved region McAb can provide effective protection against swine-isolated SEZ infections with only the inconvenient immunotherapy program. It also partially works in preventing infection by other SEZ strains. In contrast, the anti-variable region McAb is only adapted to protect the host against a specific szm type SEZ strain isolated from pigs, but it is flexible for different immunotherapy programs. These data provide further information to guide the development of derived, genetically engineered McAbs that have potential applications in protecting hosts against swine-isolated, hypervirulent SEZ infections in the future. IMPORTANCE The swine-isolated SEZ, with its specific szm gene sequence, has impacted the pig feeding industry in China and North America and has led to serious economic loss. Though the SzM protein of SEZ has been proven to be an effective vaccine in preventing infection, most previous studies focused on horse-isolated strains, which have different szm gene types compared to swine-isolated strains. In this study, we developed the McAbs targeting the conserved and variable regions of this SzM protein from the swine-isolated hypervirulent strains and evaluated their protection efficiency. Our research provided information for the development of chimeric McAbs or other genetically engineered McAbs that have potential applications in protecting pigs against hypervirulent SEZ infections in the future.

Project description:BACKGROUND: Streptococcus equi ssp. equi is the causative agent of 'Strangles' in horses. This is a debilitating condition leading to economic loss, yard closures and cancellation of equestrian events. There are multiple genotypes of S. equi ssp. equi which can cause disease, but to date there has been no systematic study of strains which are prevalent in Ireland. This study identified and classified Streptococcus equi ssp. equi strains isolated from within the Irish equine industry. RESULTS: Two hundred veterinary isolates were subjected to SLST (single locus sequence typing) based on an internal sequence from the seM gene of Streptococcus equi ssp equi. Of the 171 samples which successfully gave an amplicon, 162 samples (137 Irish and 24 UK strains) gave robust DNA sequence information. Analysis of the sequences allowed division of the isolates into 19 groups, 13 of which contain at least 2 isolates and 6 groups containing single isolates. There were 19 positions where a DNA SNP (single nucleotide polymorphism) occurs, and one 3 bp insertion. All groups had multiple (2-8) SNPs. Of the SNPs 17 would result in an amino acid change in the encoded protein. Interestingly, the single isolate EI8, which has 6 SNPs, has the three base pair insertion which is not seen in any other isolate, this would result in the insertion of an Ile residue at position 62 in that protein sequence. Comparison of the relevant region in the determined sequences with the UK Streptococcus equi seM MLST database showed that Group B (15 isolates) and Group I (2 isolates), as well as the individual isolates EI3 and EI8, are unique to Ireland, and some groups are most likely of UK origin (Groups F and M), but many more probably passed back and forth between the two countries. CONCLUSIONS: The strains occurring in Ireland are not clonal and there is a considerable degree of sequence variation seen in the seM gene. There are two major clades causing infection in Ireland and these strains are also common in the UK.

Project description:The pathogen Streptococcus equi subsp. zooepidemicus is associated with a wide range of animals, including humans, and outbreaks frequently occur in pigs, equines, and goats. Thus far, few studies have assessed interactions between the host immune system and S. equi subsp. zooepidemicus and how these interactions explain the wide host spectrum of S. equi subsp. zooepidemicus Neutrophils, the first line of innate immunity, possess a defense mechanism called neutrophil extracellular traps (NETs), which primarily consist of DNA and granule proteins that trap bacteria via charge interactions. Extracellular nucleases play important roles in the degradation of the DNA backbone of NETs. Here, two related extracellular nucleases, nuclease and 5'-nucleotidase (named ENuc and 5Nuc, respectively, in this study), were identified as being encoded by the SESEC_RS04165 gene and the SESEC_RS05720 gene (named ENuc and 5Nuc, respectively), and three related gene deletion mutant strains, specifically, the single-mutant ΔENuc and Δ5Nuc strains and the double-mutant ΔENuc Δ5Nuc strain, were constructed. The ΔENuc and Δ5Nuc single-mutant strains and the ΔENuc Δ5Nuc double-mutant strain demonstrated lower virulence than wild-type S. equi subsp. zooepidemicus when the mouse survival rate was evaluated postinfection. Furthermore, wild-type S. equi subsp. zooepidemicus more frequently traversed the bloodstream and transferred to other organs. Wild-type S. equi subsp. zooepidemicus induced fewer NETs and was able to survive in NETs, whereas only 40% of the ΔENuc Δ5Nuc double-mutant cells survived. S. equi subsp. zooepidemicus degraded the NET DNA backbone and produced deoxyadenosine, primarily through the action of ENuc and/or 5Nuc. However, the double-mutant ΔENuc Δ5Nuc strain lost the ability to degrade NETs into deoxyadenosine. Deoxyadenosine decreased RAW 264.7 cell phagocytosis to 40% of that of normal macrophages. Streptococcus equi subsp. zooepidemicus causes serious bacteremia in its hosts. However, little is known about how S. equi subsp. zooepidemicus interacts with the host innate immune system, particularly innate cells found in the blood. S. equi subsp. zooepidemicus is capable of evading NET-mediated killing via the actions of its potent extracellular nucleases, ENuc and 5Nuc, which directly degrade the NET DNA backbone to deoxyadenosine. In previous studies, other pathogens have required the synergism of nuclease and 5'-nucleotidase to engage in this self-protective process; however, ENuc and 5Nuc both possess nuclease activity and 5'-nucleotidase activity, highlighting the novelty of this discovery. Furthermore, deoxyadenosine impairs phagocytosis but not the intracellular bactericidal activity of macrophages. Here we describe a novel mechanism for S. equi subsp. zooepidemicus extracellular nucleases in NET degradation, which may provide new insights into the pathogen immune evasion mechanism and the prevention and treatment of bacterial disease.

Dataset Information

Interaction between M-like protein and macrophage thioredoxin facilitates antiphagocytosis for Streptococcus equi ssp. zooepidemicus.

Publications

Interaction between M-like protein and macrophage thioredoxin facilitates antiphagocytosis for Streptococcus equi ssp. zooepidemicus.

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