Mechanisms of binding of Brucella abortus to mononuclear phagocytes from cows naturally resistant or susceptible to brucellosis

During the course of bovine brucellosis, Brucella abortus adheres to and infects cells of the mononuclear phagocyte system. Potential mechanisms of binding, as measured by numbers of phagocytosed bacteria, were studied in two populations of cattle genetically resistant (R) or susceptible (S) to infection with B. abortus. Live B. abortus gained entry into cultured bovine macrophages without organism-specific opsonization. Bacterial entry into macrophages from R was inhibited by the peptide RGDS, outer membrane-peptidoglycan complex from B. abortus strain RB51, anti-LFA-1 monoclonal antibody, anti-C3 antiserum, fibronectin, purified O-antigen from B. abortus lipopolysaccharide, mannan and heat-aggregated IgG. Bacterial entry into macrophages from S was inhibited by outer membrane-peptidoglycan complex, anti-LFA-1 monoclonal antibody, O-antigen and heat-aggregated IgG. The peptide RGES did not inhibit entry into macrophages from R or S. These data support the existence of organism-related receptors on monocyte-derived macrophages for B. abortus which mediate binding in the absence of serum. Secondly, there are demonstrable differences in mechanisms of binding of B. abortus to cells from cattle genetically resistant or susceptible to infection by this organism. These findings further substantiate the importance of phagocytosis and clearance functions of the mononuclear phagocyte system in resistance to bovine brucellosis. Perpetuation of infection in susceptible cattle may occur by establishing an intracellular reservoir of viable organisms. Further studies are necessary to investigate receptor affinities, and the potential for an alternate receptor for this organism in S cattle.

Type I Keratinocyte Transglutaminase: Expression in Human Skin and Psoriasis

A 92-kD transglutaminase (TGase K), expressed in human cultured keratinocytes and stratum corneum, catalyzes a critical step in the formation of the cornified envelope of terminal differentiation. A rabbit polyclonal antibody to TGase K was used to isolate overlapping cDNA clones from a human keratinocyte cDNA expression library. The cDNA clones were sequenced and unequivocally identified as TGase K by comparison to the N-terminal amino acid sequences of two cyanogen bromide fragments from the purified enzyme. The mRNA for Tgase K is expressed in cultured keratinocytes but not in A431 squamous carcinoma cells, in fibroblasts, or in other non-epithelial tissues and cells. Although TGase K protein expression is limited to the upper layers of normal epidermis, the mRNA is generally present throughout the epidermis, suggesting the possibility of post-transcriptional regulation. Precocious expression of TGase K protein occurs in psoriasis, and quantitative Northern blot analysis of TGase K mRNA from normal and involved epidermal biopsies from psoriasis patients suggests that TGase K mRNA levels are increased in psoriatic lesions. By using quantitative laser scanning confocal microscopy (LSCM) and in situ hybridization, the increase of the TGase K mRNA was in the range of 3-7 times in the psoriatic epidermis and was significantly higher compared with normal skin and with paired adjacent skin. Quantitative LSCM provides a powerful and direct method for analysis of gene expression in skin.

SDS-soluble and peptidoglycan-bound proteins in the outer membrane-peptidoglycan complex of Brucella abortus

Outer membrane-peptidoglycan complex from Brucella abortus was separated from cytoplasmic membrane and cytosol by either sucrose density gradient fractionation or differential (rate) centrifugation of surface labeled cells disrupted by sonication without the use of detergents. The outer membrane-peptidoglycan complex had a buoyant density of 1.22 gm/ml and contained 67 labeled SDS-soluble proteins when examined by SDS-PAGE. Included were four major bands exhibiting molecular masses of 88k, 40k, 35.7k and 26k daltons corresponding to previously described group 1, 2 and 3 outer membrane proteins. Lysozyme treatment of outer membrane-peptidoglycan complex increased its buoyant density to 1.25 gm/ml and released eight additional peptidoglycan-linked proteins.

Inhibition of copper-associated erythrocyte ghost membrane lipid peroxidation by hepatic cytosolic low molecular weight proteins

Male weanling Fischer rats were injected ip once daily with either 12.5 mg/kg body weight cupric chloride or 2 ml/kg body weight saline for up to 70 days. As the hepatic cytosolic copper increased in copper-treated rats, copper bound to proteins of different molecular weights; this was determined by gel filtration chromatography. Hepatic cytosolic copper from rats treated with cupric chloride for 14 days eluted in 3 peaks. These included a 150,000 + dalton peak, a 29,000 dalton peak and an 11,000-12,800 dalton peak. In addition to these peaks, hepatic cytosolic copper from rats treated with cupric chloride for greater than or equal to 28 days also eluted in a 4th, but shorter, 6,000-7,000 dalton peak. Hepatic cytosolic copper from saline-treated rats eluted only in a single 29,000 dalton peak. Experiments using an erythrocyte ghost membrane model of copper-associated lipid peroxidation demonstrated that incubation of membranes with protein-bound copper eluted in the 11,000-12,000 dalton peak was associated with less lipid peroxidation than incubation of membranes with cupric chloride or protein-bound copper eluted in the 150,000+ dalton peak. Experimental results suggest that the ability of copper to catalyze lipid peroxidation is significantly reduced by binding with hepatic cytosolic low molecular weight proteins but not by binding with hepatic cytosolic high molecular weight proteins.

Histology and morphometry of Strongylus vulgaris-mediated equine mesenteric arteritis

Histological and morphometric evaluation of equine cranial mesenteric arteries was performed on 239 and 89 arteries, respectively. Histological examination revealed that thrombosis and the severity of inflammation varied on a seasonal basis and were directly associated with larval presence. Intimal and adventitial fibrosis were generally of greater severity than medial fibrosis. Fibrosis of the vasa vasorum was less frequent than fibrosis of the artery itself. Morphometry revealed a significant increase in intimal, adventitial and, to a lesser extent, medial area in affected as compared with normal arteries. This change was due to the accumulation of collagen and was considered to result in decreased arterial elasticity. The luminal area varied widely among affected arteries.

Induction of lymphocyte responsiveness by the outer membrane-peptidoglycan complex of rough strains of Brucella abortus

The outer membrane-peptidoglycan complex (OM-PG) from rough strains of Brucella abortus was tested for its ability to induce lymphocyte responsiveness in cattle. Six groups of heifers were immunized with varying doses and administration schedules of rough OM-PG and assayed for responsiveness of their lymphocytes in proliferation assays in vitro. All OM-PG preparations were emulsified in a commercial adjuvant for administration. Two other groups of heifers were immunized with strain 19 vaccine or adjuvant alone. Three groups of heifers received two inoculations of OM-PG antigens from a naturally-occurring rough strain at a 57-day interval. The doses of OM-PG given in these three groups were 400 micrograms, 1200 micrograms, and 4000 micrograms at each inoculation. The frequency of cows that responded in lymphocyte proliferation assays increased with the dose of OM-PG given. Two groups received single inoculations of OM-PG, either 2400 micrograms or 8000 micrograms. Although there were responsive cows in these immunization groups, their frequency was lower than in the groups receiving the same total dose in two inoculations. A sixth group of cows was inoculated with OM-PG from a rough transposon mutant of B. abortus, and the frequency of responsive cows in this immunization group was comparable to that of responsive cows immunized with the same dose of OM-PG from the spontaneous rough mutant. In comparisons of cows inoculated with strain 19 to those inoculated with OM-PG preparations, differences were observed in the relative responsiveness of their lymphocytes to whole cells and OM-PG in the in vitro lymphocyte proliferation assays. These differences suggested that lymphocytes stimulated by strain 19 vaccination have different specificities than those stimulated by immunization with OM-PG of rough mutant strains of B. abortus.

Genetic variation at the omp2 porin locus of the brucellae: species-specific markers

The omp2 locus of Brucella abortus is composed of two closely related genes (omp2a and omp2b) that encode, and potentially both express, homologous porin proteins. Genetic variation at this locus is revealed in the form of restriction-fragment-length polymorphisms which can be used to distinguish the type strains of all six Brucella species. Five of the six species contain single copies of omp2a and omp2b, whereas Brucella ovis appears to have two copies of the omp2a gene. The implications of these results with regard to the physiological functions of the omp2a and the omp2b gene products, phylogeny of the genus, and species-specific adaptation are discussed.

Immunogenicity of subcellular fractions of Brucella abortus: measurement by in vitro lymphocyte proliferative responses

Five groups of heifers were immunized with various subcellular fractions of Brucella abortus and tested for their responsiveness in lymphocyte proliferative responses in vitro. The five subcellular fractions used as immunogens were: (1) a mixture of recombinant outer membrane proteins fused to Escherichia coli beta-galactosidase, (2) a mixture of outer membrane proteins BaomI, BaomIIB1, and BaomIII1, (3) a mixture of outer membrane proteins 7.5 kDa and 8.8 kDa, (4) a complex of smooth lipopolysaccharide and proteins, and (5) a complex of outer membranes and peptidoglycan (OM-PG complex) from a rough strain. All immunogens were emulsified in adjuvant and administered twice at a 61-day interval. Two other groups of cows were included; one immunized with strain 19 and the other with adjuvant only. Strain 19 and the rough OM-PG complex induced responsiveness in lymphocyte proliferation assays in a high percentage of immunized cows. The smooth lipopolysaccharide-protein complex induced responsiveness in fewer cows. The lowest frequencies of responding cows were found in groups that received either recombinant proteins or purified protein mixtures. Based on these results, we concluded: (1) cellular immunity, as measured by in vitro lymphocyte proliferative responses, can be induced with subcellular fractions of B. abortus and (2) the more complex the immunogen, the greater the frequency of responding cows.

Enzymatic synthesis of dihydrosirohydrochlorin (precorrin-2) and of a novel pyrrocorphin by uroporphyrinogen III methylase

Uroporphyrinogen III methylase was purified from a recombinant hemB-strain of E. coli harbouring a plasmid containing the cysG gene. N-terminal analysis of this purified protein gave an amino acid sequence corresponding to that predicted from the genetic code. From the u.v./visible spectrum of the reaction catalysed by this SAM dependent methylase it was possible to observe the sequential appearance of the chromophores of a dipyrrocorphin and subsequently of a pyrrocorphin. Confirmation of this transformation was obtained from 13C-NMR studies when it was demonstrated, for the first time directly, that uroporphyrinogen is initially converted into dihydrosirohydrochlorin (precorrin-2) and then, by further methylation, into a novel trimethylpyrrocorphin.

DNA sequence and expression of the 36-kilodalton outer membrane protein gene of Brucella abortus

The cloning of the gene(s) encoding a 36-kilodalton (kDa) cell envelope protein of Brucella abortus has been previously described (T. A. Ficht, S. W. Bearden, B. A. Sowa, and L. G. Adams, Infect, Immun. 56:2036-2046, 1988). In an attempt to define the nature of the previously described duplication at this locus we have sequenced 3,500 base pairs of genomic DNA encompassing this region. The duplication represented two similar open reading frames which shared more than 85% homology at the nucleotide level but differed primarily because of the absence of 108 nucleotides from one of the two gene copies. These two genes were read from opposite strands and potentially encoded proteins which are 96% homologous. The predicted gene products were identical over the first 100 amino acids, including 22-amino-acid-long signal sequences. The amino acid composition of the predicted proteins was similar to that obtained for the Brucella porin isolated by Verstreate et al. (D. R. Verstreate, M. T. Creasy, N. T. Caveney, C. L. Baldwin, M. W. Blab, and A. J. Winter, Infect. Immun. 35:979-989, 1982) and presumably represented two copies of the porin gene, tentatively identified as omp 2a (silent) and omp 2b (expressed). The homology between the two genes extended to and included Shine-Dalgarno sequences 7 base pairs upstream from the ATG start codons. Homology at the 3' ends extended only as far as the termination codon, but both genes had putative rho-independent transcription termination sites. Localization of the promoters proved more difficult, since the canonical procaryotic sequences could not be identified in the region upstream of either gene. Promoter activity was demonstrated by ligation to a promoterless lacZ gene in pMC1871. However, only one active promoter could be identified by using this system. A 36-kDa protein was synthesized in E. coli with the promoter in the native orientation and was identical in size to the protein produced in laboratory-grown B. abortus. When the promoter-containing fragment was inverted, a 33-kDa protein was expressed. These results were consistent with the predicted sizes based on the nucleotide sequences of the open reading frames in omp 2b and omp 2a. Whether this locus contains one active and one silent or cryptic porin gene, or two active Brucella porin genes expressed under different environmental conditions, is discussed.

Lectin binding sites of cultured ovarian Sertoli cell tumors and follicular granulosa cells

A panel of seven alkaline phosphatase labeled lectins was used to probe nitrocellulose electroblots of SDS-PAGE separated proteins from a primary culture of normal ovarian granulosa cells and an ENU-induced Sertoli cell tumor cell line (SCTL-I). Several additional lectin binding proteins were observed in silver stained SDS-PAGE gels as well as with lectins in SCTL-I. Succinated concanavalin A (Suc. Con A), Ricin communis agglutinin (RCA-I), Ulex europaeus agglutinin (UEA 1), Soybean agglutinin (SBA), Dolichos biflorus agglutinin (DBA) and Peanut agglutinin (PNA) stained more intensely in SCTL-I than normal granulosa cells. The same lectins as above, labeled with fluorescein isothiocyanate (FITC), were used to study the distribution of specific binding sites of tissue cultured cells grown in chamber/slides. Both normal ovarian granulosa cells and SCT cells exhibited strong peninuclear cytoplasmic labeling with Con A UEA-1 and WGA exhibited predominantly a nuclear and granular cytoplasmic staining pattern. SBA and DBA exhibited a strong coarse granular cytoplasmic labeling in granulosa cells and moderate granular cytoplasmic in SCT cells. In granulosa cells, Golgi regions stained strongly with PNA but weakly in SCT cells. RCA-I staining was negative in both cultures. Labeling of tissue cultured cells with lectins provides more details than histological sections of lectins binding sites at cellular structural levels.

Preliminary investigations on the effects of a Strongylus vulgaris larval extract, mononuclear factors and platelet factors on equine smooth muscle cells in vitro

Factors involved in the proliferation of equine vascular smooth muscle cells were studied in vitro. The most prominent proliferative responses in cultured vascular smooth muscle cells were induced by Strongylus vulgaris larval antigen extract (LAE) and platelet-derived factors. Less significant proliferative responses were obtained with conditioned media from S. vulgaris LAE stimulated and from unstimulated equine mononuclear leukocytes. Additionally, vascular smooth muscle cells exposed to S. vulgaris LAE developed numerous perinuclear vacuoles and were more spindle-shaped than control or smooth muscle cells exposed to other factors. Equine mononuclear leukocytes exposed to LAE developed prominent morphological changes, including enlargement, clumping and increased numbers of mitotic figures.

A 36-kilodalton Brucella abortus cell envelope protein is encoded by repeated sequences closely linked in the genomic DNA

Recombinant bacteriophage expressing Brucella abortus antigens have been isolated from a lambda gt11 expression library by using antibody raised against a sodium dodecyl sulfate-polyacrylamide gel electrophoresis-purified cell envelope protein of 36 kilodaltons. Fusion products expressed by these recombinants vary in apparent molecular mass by sodium dodecyl sulfate-polyacrylamide gel electrophoresis but only slightly exceed the size of beta-galactosidase. Western blot (immunoblot) analysis of crude lysates derived from lambda gt11 lysogens indicates that the fusion products react specifically with the original antisera used for recombinant selection and selectively bind antibody directed against the 36-kilodalton cell envelope protein. Analysis of the DNA inserts from 11 independently selected recombinants reveals similar-size EcoRI fragments which range in size from 150 to 300 base pairs (bp), all of which cross-hybridize via Southern blot analysis. Three independently selected EcoRI inserts ranging in size from 200 to 270 bp have been subcloned into M13mp18 and sequenced; all three contain a common region of about 200 bp. Southern blot analysis of B. abortus genomic DNAs digested with EcoRI, PstI, or DdeI indicates the presence of two fragments which hybridize to these DNA probes while single BamHI and HindIII fragments hybridize. The absence of these sites from the internal DNA sequence of the cloned probes suggests the presence of more than one copy of these sequences within the B. abortus genome. The same DNA probes have been used to select genomic clones of approximately 20 kbp from a lambda 2001 library. The lambda 2001 recombinants contain single BamHI fragments and two PstI fragments which hybridize to these oligonucleotide probe constructed on the basis of the amino-terminal sequence of the mature gene product hybridizes to the same BamHI and PstI fragments as the lambda gt11-derived DNA probe. Although the relative positions of the oligonucleotide sequences and the lambda gt11 insert within the genes is not known, the two sequences flank a region which corresponds to at least 40% of the size of the predicted gene. Additional experimentation must be performed to determine whether these sequences represent either two complete structural genes encoding major cell envelope proteins or repetitive sequences within a single structural gene.

Protection against Brucella abortus in mice with O-polysaccharide-specific monoclonal antibodies

Mice injected with either of two monoclonal antibodies specific for the O polysaccharide of Brucella abortus prior to challenge infection had viable counts in spleens and livers significantly below those in control groups 1 and 4 weeks later. Two monoclonal antibodies specific for the porin of B. abortus failed to confer protection.

Physiology of F-pilin synthesis and utilization

Sodium dodecyl sulfate-polyacrylamide gel electrophoresis was used to study the synthesis and turnover of F-pilin in membrane preparations of Escherichia coli K-12 under conditions which have been reported to affect the production of F-pili. Incorporation of [(35)S]methionine into membrane F-pilin by cells in log phase was barely detectable at 25 degrees C, but increased with temperature. The labeled pilin band was prominent in membranes from 37 degrees C cultures and even more prominent if the growth temperature was raised to 42 degrees C. The appearance of other tra products in the membranes was similarly temperature dependent. In cultures grown in glucose minimal medium at 37 degrees C, the relative amount of membrane pilin and traT product synthesis remained unchanged from early log phase through early stationary phase; provision of glycerol or arabinose as a substitute carbon source had no obvious effect. Turnover of traT product and membrane F-pilin, as assessed in an Flac tra mutant strain which is incapable of elaborating pili, was not rapid. Both traT product and pilin subunits labeled in mid-log phase cells were still apparent in the membranes after growth of the cells to stationary phase. The relative amount of labeled pilin decreased with prolonged incubation in stationary phase, but the relative amount of traT product did not decrease even after the culture was incubated for 24 h. When wild-type Flac piliated cells were used, a similar result was obtained, but in this case, loss of F-pilin from the preparations could be acclerated by blending the cells. Although intermittent blending during culture growth caused a slow depletion of the labeled pilin pool, continuous blending resulted in the rapid disappearance of this pool from our preparations. Loss of other membrane polypeptides was not accelerated by our blending procedure, and blending did not affect the turnover of the pilin pool of the Flac tra mutant. Our data are consistent with a model in which pilin subunits are assembled transiently into pili, conserved by retraction, and made available for subsequent reassembly. Growth in 0.01% sodium dodecyl sulfate did not accelerate loss of pilin from the Flac strain compared with the Flac tra strain, and we suggest that in the presence of sodium dodecyl sulfate at this concentration, F-pili are not elaborated from cell surfaces.

A new activity in the Ftra operon which is required for F-pilin synthesis

Membrane preparations from a series of Hfr mutant strains of Escherichia coli K12 deleted in the promoter distal end of the F transfer operon were analyzed. Deletions which extended into traG, as expected, had no discernible effect on synthesis of membrane F-pilin. A more extensive deletion in strain K1777 which eliminated traH activity similarly had no effect on F-pilin synthesis. Membranes from three other TraF+ TraH- deletion strains, as well as membranes from all strains carrying deletions extending into traF or further, lacked F-pilin, however. Since traH amber mutations do not affect synthesis of membrane pilin (Moore et al. 1981 b) we conclude that a gene required for F-pilin biosynthesis is located between traF and traH. We have named this gene traQ. Further evidence for traQ and an assay for its activity was obtained by examining the products of a TraM+ TraJ+ TraA+ lambda transducing phage, KI lambda 13, in UV irradiated cells. Infection of F- cells with KI lambda 13 does not result in F-pilin synthesis. Membrane pilin is synthesized as a product of the transducing phage if an Flac or Hfr irradiated host is used, however. Mutant analysis demonstrated that this synthesis is independent of host expression of traA, traL, traE, traK, traB, traV, traW, traC, traU, traF, or traH, but dependent on expression of the traF-traH region. We interpret our data to indicate that an activity encoded by traQ is required for the conversion of traA product to F-pilin.

The effect of tra mutations on the synthesis of the F-pilin membrane polypeptide

We had previously demonstrated that several F specific polypeptide bands could be detected in the membranes of Flac, but not F- strains of Escherichia coli K12, (Moore et al. 1981). One of these polypeptides co-migrated with F-pilin protein on polyacrylamide gels. We have now analyzed 35[S]methionine labelled membrane preparations from a series of strains containing Flac tra mutant plasmids. The F-pilin polypeptide was absent from preparations of strains containing all traA mutants tested, confirming the importance of the traA gene on F-pilin biosynthesis. A polypeptide which migrate in the F-pilin position was still present, however, in membranes prepared from Flac strains carrying mutations in traL, traE, traK, traB, traV, traW, traC, traU, traF, traH or traG despite the inability of these mutants to elaborate F-pili filaments. Thus, all of these gene products may be concerned with F-pilus assembly and outgrowth rather than biosynthesis of the F-pilin subunit. The polar mutation tra-4 did, however, prevent the appearance of pilin polypeptide, indicating that at least one unidentified gene in the region between traE and traG must also be required in F-pilin biosynthesis. Our analysis also permitted the identification of a 100,000 dalton membrane protein as the product of traG. The appearance of an F specific 12,000 dalton protein was prevented by traD amber mutants. As expected, traJ mutants prevented the expression of all the tra operon products detected except the product of traT. The traT product band was reduced only to 50 - 60% of its normal intensity.

Location of an F-pilin pool in the inner membrane

Polyacrylamide gel analysis of [35S]methionine-labeled membrane preparations from Escherichia coli has revealed the presence of five polypeptides present only in the membranes of cells containing the conjugative plasmid F. In addition to the previously reported product of traT, polypeptides migrating with apparent molecular weights of 100,000, 23,500, 12,000, and 7,000 were resolved. Membrane preparations from F traJ mutants lacked these polypeptides, indicating that all of these proteins are tra gene products. The 7,000-molecular-weight polypeptide comigrated with unlabeled purified F-pilin protein. About 4 to 5% of the total radioactive label in whole membrane preparations was present in this polypeptide, indicating the existence of a substantial pool of membrane-associated F-pilin. The polypeptide could be extracted from whole membrane preparations with Triton X-100 and was found in the inner membrane fraction of membranes separated by sucrose density centrifugation.

Effect of diflubenzuron (Dimilin; TH--6040) on the hyaluronic acid concentration in chicken combs

The addition of N-[[(4-chlorphenyl)amino]carbonyl]-2,6-difluorobenzamide(diflubenzuron; Dimilin; TH-6040) up to levels of 250 ppm of the total diet of both male broilers and layers for 98 days did not affect the hyaluronic acid (HA) concentration (microgram/g tissue) in the combs. The concentration was measured at 21, 28, 42, 56, and 98 days on feed. The concentration in the combs of the layers were not significantly different at any sampling period regardless of diet. At the end of 56 days on feed, the combs of the broiler controls had a significantly (P less than .025) higher concentration than did any of the groups fed diflubenzuron. There were no differences observed at 21, 28, 42, or 98 days in the broilers. The HA concentration increased as the chickens matured and became larger; however, large variations were observed within the various groups at a given sample period.