An in-depth investigation of the microbiota and its virulence factors associated with severe udder cleft dermatitis lesions

Udder cleft dermatitis (UCD) is a skin condition affecting the anterior parts of the udder in dairy cattle. In the present study, we aimed to shed light on the microbiota in severe UCD lesions versus healthy udder skin by putting forward a taxonomic and functional profile based on a virulence factor analysis. Through shotgun metagenomic sequencing, we found a high proportion of bacteria in addition to a low abundance of archaea. A distinct clustering of healthy udder skin versus UCD lesion samples was shown by applying principal component analysis and (sparse) partial least squares analysis on the metagenomic data. Proteobacteria, Bacillota, and Actinomycetota were among the most abundant phyla in healthy udder skin samples. In UCD samples, Bacteroidota was the most abundant phylum. At genus level, Bifidobacterium spp. had the highest relative abundance in healthy skin samples, whereas Porphyromonas spp. and Corynebacterium spp. had the highest relative abundance in UCD samples. In the differential abundance analysis, Porphyromonas spp. and Bacteroides spp. were significantly differentially abundant in UCD samples, whereas Bifidobacterium spp., Staphylococcus sp. AntiMn-1, and Staphylococcus equorum were more commonly found in healthy samples. Moreover, the abundance of several treponeme phylotypes was significantly higher in lesion samples. The streptococcal cysteine protease speB was among the most abundant virulence factors present in severe UCD lesions, while a plethora of virulence factors such as the antitoxin relB were downregulated, possibly contributing to creating the ideal wound climate for the dysbiotic community. Network analysis showed healthy lesion samples had a large network ofpositive, correlations between the abundances of beneficial species such as Aerococcus urinaeequi and Bifidobacterium angulatum, indicating that the healthy skin microbiome forms an active protective bacterial network, which is disrupted in case of UCD. In UCD samples, a smaller microbial network mainly consisting of positive correlations between the abundances of Bacteroides fragilis and anaerobic Bacteroidota was exposed. Moreover, a high correlation between the taxonomic data and virulence factors was revealed, concurrently with 2 separate networks of microbes and virulence factors. One network, matching with the taxonomic findings in the healthy udder skin samples, showcased a community of harmless or beneficial bacteria, such as Bifidobacterium spp. and Butyrivibrio proteoclasticus, associated with hcnB, hcnC, relB, glyoxalase, and cupin 2. The other network, corresponding to UCD samples, consisted of pathogenic or facultative pathogenic and mainly anaerobic bacteria such as Treponema spp., Mycoplasmopsis spp., and bovine gammaherpesvirus 4, that correlated with virulence factors SpvB, fhaB, and haemagglutination activity domain-associated factor. Our results point toward a dysbiotic community with a notable decrease in diversity and evenness, with a loss of normal skin inhabitants and innocuous or useful species making way for predominantly anaerobic, facultative pathogens. The shift in the abundance of virulence factors such as fhaB and SpvB could play a role in the manifestation of a local micro-environment favorable to the microbiome associated with udder skin lesions. Lastly, the presence of specific networks between microbial species, and between microbes and virulence factors was shown.

Mycothione reductase as a potential target in the fight against Mycobacterium abscessus infections

While infections caused by Mycobacterium abscessus complex (MABC) are rising worldwide, the current treatment of these infections is far from ideal due to its numerous shortcomings thereby increasing the urge for novel drug targets. In this study, mycothione reductase (Mtr) was evaluated for its potential as a drug target for MABC infections since it is a key enzyme needed in the recycling of mycothiol, the main low-molecular-weight thiol protecting the bacteria against reactive oxygen species and other reactive intermediates. First, a Mab∆mtr mutant strain was generated, lacking mtr expression. Next, the in vitro sensitivity of Mab∆mtr to oxidative stress and antimycobacterial drugs was determined. Finally, we evaluated the intramacrophage survival and the virulence of Mab∆mtr in Galleria mellonella larvae. Mab∆mtr demonstrated a 39.5-fold reduction in IC90 when exposed to bedaquiline in vitro. Furthermore, the Mab∆mtr mutant showed a decreased ability to proliferate inside macrophages and larvae, suggesting that Mtr plays an important role during MABC infection. Altogether, these findings support the assumption of Mtr being a potential target for antimycobacterial drugs.IMPORTANCEMycobacterium abscessus complex (MABC) is a group of bacteria causing a serious public health problem worldwide due to its ability to cause progressive disease, its highly resistant profile against various antibiotics, and its lengthy treatment. Therefore, new drugs are needed to alleviate antibiotic resistance and reduce the length of the current treatment. A potential new target for new antibiotics is mycothione reductase (Mtr), an important enzyme belonging to a pathway that protects the bacteria against harmful conditions. Our research created a bacterium deficient of mtr by using advanced genetic techniques and demonstrated that mtr-deficient bacteria have a decreased ability to multiply during infection. Furthermore, we show evidence that currently used antibiotics combined with mtr deficiency can lead to a better treatment of MABC infection. Altogether, our results validate Mtr as a potential new target and suggest that Mtr plays a role during MABC infection.

Severe udder cleft dermatitis lesion transcriptomics points to an impaired skin barrier, defective wound repair and a dysregulated inflammatory response as key elements in the pathogenesis

This study is the first to investigate the transcriptomic changes occurring in severe udder cleft dermatitis lesions (UCD) in Holstein-Friesian cows. An examination of the gene expression levels in natural UCD lesions and healthy udder skin through RNA Seq-Technology provided a deeper insight into the inflammatory pathways associated with this disease. A clear distinction between the gene expression patterns of UCD lesions and healthy skin was shown in the principal component analysis. Genes coding for inflammatory molecules were upregulated such as the chemokines C-X-C motif ligand 2 (CXCL2), 5 (CXCL5) and 8 (CXCL8), and C-C motif ligand 11 (CCL11). Moreover, the genes coding for the multifunctional molecules ADAM12 and SLPI were amongst the highest upregulated ones, whereas the most downregulated genes included the ones coding for keratins and keratin-associated molecules. Predominantly inflammatory pathways such as the chemokine signaling, cytokine receptor interaction and IL-17 signaling pathway were significantly upregulated in the pathway analysis. These results point towards a fulminant, dysregulated inflammatory response concomitant with a disruption of the skin barrier integrity and a hampered wound repair mechanism in severe UCD lesions.

Comparative analysis of different nuclear transfer techniques to prevent the transmission of mitochondrial DNA variants

Prevention of mitochondrial DNA (mtDNA) diseases may currently be possible using germline nuclear transfer (NT). However, scientific evidence to compare efficiency of different NT techniques to overcome mtDNA diseases is lacking. Here, we performed four types of NT, including first or second polar body transfer (PB1/2T), maternal spindle transfer (ST) and pronuclear transfer (PNT), using NZB/OlaHsd and B6D2F1 mouse models. Embryo development was assessed following NT, and mtDNA carry-over levels were measured by next generation sequencing (NGS). Moreover, we explored two novel protocols (PB2T-a and PB2T-b) to optimize PB2T using mouse and human oocytes. Chromosomal profiles of NT-generated blastocysts were evaluated using NGS. In mouse, our findings reveal that only PB2T-b successfully leads to blastocysts. There were comparable blastocyst rates among PB1T, PB2T-b, ST and PNT embryos. Furthermore, PB1T and PB2T-b had lower mtDNA carry-over levels than ST and PNT. After extrapolation of novel PB2T-b to human in vitro matured (IVM) oocytes and in vivo matured oocytes with smooth endoplasmic reticulum aggregate (SERa) oocytes, the reconstituted embryos successfully developed to blastocysts at a comparable rate to ICSI controls. PB2T-b embryos generated from IVM oocytes showed a similar euploidy rate to ICSI controls. Nevertheless, our mouse model with non-mutated mtDNAs is different from a mixture of pathogenic and non-pathogenic mtDNAs in a human scenario. Novel PB2T-b requires further optimization to improve blastocyst rates in human. Although more work is required to elucidate efficiency and safety of NT, our study suggests that PBT may have the potential to prevent mtDNA disease transmission.

The Integrin α2β1 (GPIa/IIa)-I-Domain Inhibits Platelet-Collagen Interaction

The integrin α2β1 is a major cellular receptor for collagen. The α2subunit contains an ± 200 amino acids inserted domain (I-domain) in the N-terminal region. A certain degree of homology exists between the I-domains found in integrins, collagen and the A-domains of vWF.

The α2-I-domain encoding region (aa residues D145 to S334) was obtained by RT-PCR from mRNA of non stimulated human PBL’s. The primers were designed to introduce the necessary restriction sites for cloning of the DNA fragment in frame downstream of the malE gene, as well as a stop codon after the last triplet. The resulting construct pMAL-c2-α2-I allows the expression of the I-domain, fused to the C-terminus of maltose binding protein (mal). The α2-I-mal is purified from the bacterial extract by affinity chromatography on an amylose column.

The purified α2-I-mal has been characterized by ELISA’s. The animal bound to immobilised collagen type I in a concentration dependent manner and could be blocked by the functional monoclonal anti-α2β1 antibody 6F1.

The interaction of α2-I-mal with collagen furthermore is Mg2+- dependent since the binding was inhibited in the presence of 10 mM EDTA or 10 mM Ca2+ but sustained in the presence of 10 mM Mg2+.

Finally, α2-I-mal itself was able to inhibit adhesion of washed platelets to collagen immobilised on a microtiterplate in a dose-dependent manner (α2-I-mal IC50:0.7 μ M) as well as platelet aggregation induced by collagen type I (α2-I-mal IC50: 0.7 μM).

With these results we could confirm that the α2-I-domain represents the collagen-binding site of α2β1 and we furthermore could indicate that this domain is able to prevent platelet adhesion to collagen and collagen-induced platelet aggregation, pointing to the primordial role of α2-I-mal and hence of α2β1 in platelet-collagen interaction.

The integrin alpha 2 beta 1 (GPIa/IIa)-I-domain inhibits platelet-collagen interaction

The integrin alpha 2 beta 1 is a major cellular receptor for collagen. The alpha 2 subunit contains an +/- 200 amino acids inserted domain (I-domain) in the N-terminal region. A certain degree of homology exists between the I-domains found in integrins, collagen and the A-domains of vWF. The alpha 2-I-domain encoding region (aa residues D145 to S334) was obtained by RT-PCR from mRNA of non stimulated human PBL's. The primers were designed to introduce the necessary restriction sites for cloning of the DNA fragment in frame downstream of the malE gene, as well as a stop codon after the last triplet. The resulting construct pMAL-c2-alpha 2-I allows the expression of the I-domain, fused to the C-terminus of maltose binding protein (mal). The alpha 2-I-mal is purified from the bacterial extract by affinity chromatography on an amylose column. The purified alpha 2-I-mal has been characterized by ELISA's. The alpha 2-I-mal bound to immobilised collagen type I in a concentration dependent manner and could be blocked by the functional monoclonal anti-alpha 2 beta 1 antibody 6F1. The interaction of alpha 2-I-mal with collagen furthermore is Mg(2+)-dependent since the binding was inhibited in the presence of 10 mM EDTA or 10 mM Ca2+ but sustained in the presence of 10 mM Mg2+. Finally, alpha 2-I-mal itself was able to inhibit adhesion of washed platelets to collagen immobilised on a microtiterplate in a dose-dependent manner (alpha 2-I-mal IC50:0.7 microM) as well as platelet aggregation induced by collagen type I (alpha 2-I-mal IC50:0.7 microM). With these results we could confirm that the alpha 2-I-domain represents the collagen-binding site of alpha 2 beta 1 and we furthermore could indicate that this domain is able to prevent platelet adhesion to collagen and collagen-induced platelet aggregation, pointing to the primordial role of alpha 2-I-mal and hence of alpha 2 beta 1 in platelet-collagen interaction.

Anticoagulant repertoire of the hookworm Ancylostoma caninum

Hookworms are hematophagous nematodes that infect a wide range of mammalian hosts, including humans. There has been speculation for nearly a century as to the identity of the anticoagulant substances) used by these organisms to subvert host hemostasis. Using molecular cloning, we describe a family of potent small protein (75-84 amino acids) anticoagulants from the hookworm Ancylostoma caninum termed AcAP (A. caninum anticoagulant protein). Two recombinant AcAP members (AcAP5 and AcAP6) directly inhibited the catalytic activity of blood coagulation factor Xa (fXa), while a third form (AcAPc2) predominantly inhibited the catalytic activity of a complex composed of blood coagulation factor VIIa and tissue factor (fVIIa/TF). The inhibition of fVIIa/TF was by a unique mechanism that required the initial formation of a binary complex of the inhibitor with fXa at a site on the enzyme that is distinct from the catalytic center (exo-site). The sequence of AcAPc2 as well as the utilization of an exo-site on fXa distinguishes this inhibitor from the mammalian anticoagulant TFPI (tissue factor pathway inhibitor), which is functionally equivalent with respect to fXa-dependent inhibition of fIIa/TF. The relative sequence positions of the reactive site residues determined for AcAP5 with the homologous regions in AcAP6 and AcAPc2 as well as the pattern of 10 cysteine residues present in each of the inhibitors suggest that the AcAPs are distantly related to the family of small protein serine protease inhibitors found in the nonhematophagous nematode Ascaris lumbricoides var. suum.

An echistatin-like Arg-Gly-Asp (RGD)-containing sequence in the heavy chain CDR3 of a murine monoclonal antibody that inhibits human platelet glycoprotein IIb/IIIa function

We describe the production and biochemical characterization of the first GPIIb/IIIa-inhibiting monoclonal antibody that contains an RGD sequence in the CDR3 region of the heavy chain. Monoclonal antibodies obtained by immunizing mice with human platelets were screened using consecutive ELISAs based on human platelets and immuno-affinity-purified glycoprotein (GP) IIb/IIIa coated on microtitre plates. Out of 30 monoclonal antibodies reacting with GPIIb/IIIa, one, MA-16N7C2, potently inhibited platelet aggregation induced by ADP, thrombin, arachidonic acid, collagen, U46619, adrenaline and platelet-activating factor, whereas ristocetin-induced aggregation was unaffected. MA-16N7C2 (IgG2a) bound approximately 4 times faster to activated than to resting platelets, with a Kdcalc of 6.6nM and of 17.5nM, respectively. Equilibrium binding studies to non-activated platelets showed a Kd of 18.2nM with 41 x 10(3) binding sites per platelet. The antibody recognized GPIIb/IIIa only as a Ca(2+)-dependent complex. MA-16N7C2 blocked fibrinogen and von Willebrand factor binding to GPIIb/IIIa in a competitive manner with a Ki of 8.5nM and 13.2nM, respectively. Sequence analysis revealed a RGD-containing sequence with homology to disintegrins, in the CDR3 region of the heavy chain. That this RGD-containing sequence could be involved in the interaction of the antibody to GPIIb/IIIa was finally indicated by showing that the binding is completely and competitively inhibited by echistatin.

Pharmacokinetic and thrombolytic properties of chimeric plasminogen activators consisting of a single-chain Fv fragment of a fibrin-specific antibody fused to single-chain urokinase

The pharmacokinetic and thrombolytic properties were determined of two recombinant single-chain chimeric plasminogen activators (PA) consisting of u-PA-33k, a low-molecular weight derivative of single-chain urokinase-type PA (scu-PA) comprising amino acids Ala132 through Leu411, and of either a single-chain variable region fragment (Fv) derived from the fibrin fragment D-dimer-specific monoclonal antibody MA-15C5 (K12G0S32) or of the deglycosylated single-chain Fv fragment obtained by substitution of Asn88 with Glu (K12G2S32). Following bolus injection in hamsters, clearances of recombinant scu-PA (rscu-PA) and of K12G0S32 were similar. In contrast, clearance of K12G2S32 was fourfold slower than that of rscu-PA. The thrombolytic potency (percent lysis per u-PA administered in milligrams per kilogram body weight) and specific thrombolytic activity (percent lysis per microgram per milliliter steady-state plasma u-PA antigen level) of these compounds were studied in hamsters with an experimental pulmonary embolus consisting of a human plasma clot injected via the jugular vein. The doses of K12G0S32 and K12G2S32 required to obtain maximal rate of clot lysis were sixfold and 11-fold lower than that of rscu-PA. The steady-state u-PA-related plasma antigen levels of K12G0S32 and K12G2S32 required to obtain maximal rate of clot lysis were 10-fold and fourfold lower than that of rscu-PA. Thus, targeting of K12G0S32 to the clot surface by means of its glycosylated Fv fragment results in a 10-fold increase of its specific thrombolytic activity and sixfold increase of its thrombolytic potency as compared with those of rscu-PA. Targeting of K12G2S32 to the clot surface by means of its deglycosylated Fv fragment results in only a twofold increase of its thrombolytic activity. However, its fourfold slower clearance, combined with its twofold higher specific thrombolytic activity, results in an 11-fold increase of its thrombolytic potency over that of rscu-PA. These findings indicate that the thrombolytic potency of chimeric antibody-targeted PA may be increased by increasing the specific thrombolytic activity, reducing the clearance, or both.

Biochemical characterization of single-chain chimeric plasminogen activators consisting of a single-chain Fv fragment of a fibrin-specific antibody and single-chain urokinase

K12G0S32 is a 57-kDa recombinant single-chain chimeric plasminogen activator consisting of scFv-K12Go, a single-chain variable-region antigen-binding fragment (Fv) of the monoclonal antibody MA-15C5, which is specific for fragment D-dimer of human cross-linked fibrin, and a low-molecular-mass (33 kDa) urokinase-type plasminogen activator (u-PA-33k) containing amino acids Ala132-Leu411 (Holvoet, P., Laroche, Y., Lijnen, H. R., Van Cauwenberghe, R., Demarsin, E., Brouwers, E., Matthyssens, G. & Collen D. (1991) J. Biol. Chem. 266, 19717-19724). In addition, the Arg156-Phe157 thrombin-cleavage site in the u-PA moiety of K12G0S32 is removed by substitution of Phe157 with Asp. In the present study, the fibrinolytic potency of K12G0S32, determined in a system composed of a 125I-fibrin-labeled human plasma clot submerged in citrated plasma, was found to be only twofold higher than that of intact single-chain u-Pa (rscu-PA), but 17-fold higher than that of rscu-PA(M), a variant of rscu-PA in which the thrombin-cleavage site was removed by substitution of Phe157 with Asp. The fibrinolytic potency of K12G0S32T, with an intact thrombin-cleavage site, was 6-15-fold higher than that of rscu-PA. Conversion of 1 microM single-chain K12G0S32 or rscu-PA(M) into their two-chain derivatives with plasmin occurred at a rate of 1.0 +/- 0.15 nmol.min-1.nmol plasmin-1 and 0.85 +/- 0.074 nmol.min-1.nmol plasmin-1, compared to 14 +/- 2.3 nmol.min-1.nmol plasmin-1 and 18 +/- 2.6 nM.min-1.nmol plasmin-1 for K12G0S32T and rscu-PA, respectively. Purified fragment D-dimer of human cross-linked fibrin inhibited the fibrinolytic potency of single-chain K12G0S32T, but not of two-chain K12G0S32T, in a dose-dependent manner. Furthermore, the fibrinolytic potencies of two-chain K12G0S32 and K12G0S32T were not significantly higher than those of recombinant two-chain u-PA (rtcu-PA) or of rtcu-PA(M). These findings suggest that the 59-fold increase in fibrinolytic potency of K12G0S32T, relative to that of rscu-PA(M), is due both to targeting of the activator to the clot via the single-chain Fv fragment (sixfold increase) and to a more efficient conversion of single-chain K12G0S32T to its two-chain derivative (eightfold increase). Thus, targeting to clots by means of fibrin-specific antibodies results in a significant increase of the fibrinolytic potency of single-chain but not of two-chain u-PA.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of a recombinant single-chain molecule comprising the variable domains of a monoclonal antibody specific for human fibrin fragment D-dimer

A recombinant single-chain molecule, scFv-K12G0, containing the variable domains of the monoclonal antibody MA-15C5, specific for fragment D-dimer of human cross-linked fibrin, was constructed and expressed in Spodoptera frugiperda, Sf9, insect cells. The Arg108 carboxyl-terminal amino acid of the variable domain of the light-chain of the antibody was connected through a synthetic Ala-Gly-Gln-Gly-Ser-Ser-Val peptide linker with the Gln1 amino-terminal amino acid of the variable domain of its heavy chain. scFv-K12G0 was secreted by the infected Sf9 cells at a rate of 10 micrograms/10(6) cells within 48 h, resulting in conditioned medium with a maximal concentration of 15 mg of scFv-K12G0/liter. The molecule, purified to homogeneity by ion exchange chromatography and gel filtration, migrated as a single Mr band on reduced sodium dodecyl sulfate-gel electrophoresis. It bound to immobilized fragment D-dimer with an affinity constant of 4.0 x 10(9) M-1 (2.0 x 10(10) M-1 for intact MA-15C5). Clearing of scFv-K12G0 from the circulation in rabbits occurred with an initial half-life (t1/2 alpha) of 10 min and a clearance of 5.1 ml min-1, as compared to 90 min and 210 ml min-1 for intact MA-15C5. Nephrectomy resulted in a prolongation of t1/2 alpha to 110 min, suggesting that the rapid clearance of scFv-K12G0 occurs primarily via the kidney, presumably by glomerular filtration. The results indicate that the single-chain recombinant molecule scFv-K12G0 is secreted in functionally intact form and suggest that it may be useful for targeting of radioisotopes or plasminogen activators to blood clots in vivo.

Interaction of the Bacillus subtilis phage phi 105 repressor DNA: a genetic analysis

The Bacillus subtilis phage phi 105 repressor specifically recognizes a 14-bp operator sequence which does not exhibit 2-fold rotational symmetry. To facilitate a genetic analysis of this sequence-dependent DNA binding a B. subtilis strain was constructed in which mutations affecting the phi 105 repressor-operator interaction cause a selectable phenotype, chloramphenicol resistance. After in vivo mutagenesis, we isolated and mapped 22 different mutations in the repressor coding sequence, 15 of which are missense substitutions. These are exclusively located in the N-terminal part (positions 1-43) of the 144 residue long polypeptide. Two nonsense mutants, at positions 70 and 89, respectively, still show partial repressor activity. These data suggest that the phi 105 repressor consists of at least two independently folding structural domains, of which the N-terminal is involved in operator binding. Twelve missense mutations are clustered in a region extending from Gln-18 to Arg-37, which we propose to be the DNA-binding alpha-helix--beta-turn--alpha-helix motif, common to all lambda Cro-like repressors. The second ('recognition') helix shows significant homology with the corresponding sequence in Tn3 resolvase, and there is also a striking similarity between the phi 105 operator and the consensus sequence for a Tn3 res half-site. Based on these observations, and on the previously isolated phi 105 0c mutants, we tentatively assign some specific contacts between base pairs from the first half of a phi 105 operator site and amino acids from the repressor's 'recognition helix'.