Identification of a novel chemokine (CCL28), which binds CCR10 (GPR2).

We report the identification and characterization of a novel CC chemokine designated CCL28 and its receptor CCR10, known previously as orphan G-protein-coupled receptor GPR2. Human and mouse CCL28 share 83% identity at the amino acid and 76% at the nucleic acid levels. We also identified the mouse homologues of CCL28 and of CCR10, which map to mouse chromosomes 13 and 11, respectively. CCL28 is expressed in a variety of human and mouse tissues, and it appears to be predominantly produced by epithelial cells. Both human and mouse CCL28 induce calcium mobilization in human and mouse CCR10-expressing transfectants. CCL28 desensitized the calcium mobilization induced in CCR10 transfectants by CCL27, indicating that these chemokines share this new chemokine receptor. In vitro, recombinant human CCL28 displays chemotactic activity for resting CD4 or CD8 T cells.

The CC chemokine receptor-7 ligands 6Ckine and macrophage inflammatory protein-3 beta are potent chemoattractants for in vitro- and in vivo-derived dendritic cells.

Dendritic cell migration to secondary lymphoid tissues is critical for Ag presentation to T cells necessary to elicit an immune response. Despite the importance of dendritic cell trafficking in immunity, at present little is understood about the mechanisms that underlie this phenomenon. Using a novel transwell chemotaxis assay system, we demonstrate that the CC chemokine receptor-7 (CCR7) ligands 6Ckine and macrophage inflammatory protein (MIP)-3 beta are selective chemoattractants for MHC class IIhigh B7-2high bone marrow-derived dendritic cells at a potency 1000-fold higher than their known activity on naive T cells. Furthermore, these chemokines stimulate the chemotaxis of freshly isolated lymph node dendritic cells, as well as the egress of skin dendritic cells ex vivo. Because these chemokines are expressed in lymphoid organs and 6Ckine has been localized to high endothelial venules and lymphatic endothelium, we propose that they may play an important role in the homing of dendritic cells to lymphoid tissues.

Molecular cloning and functional characterization of human MIP-1 delta, a new C-C chemokine related to mouse CCF-18 and C10.

We have isolated a novel human C-C chemokine, MIP-1 delta from a human fetal spleen cDNA library. The human MIP-1 delta cDNA has an unusually long 400-bp 5-prime untranslated region and a predicted 113-amino acid protein of 10 kDa. The coding sequence contains a signal peptide of 21 amino acids, indicating that the mature protein has 92 amino acids (8 kDa). Recombinant human MIP-1 delta produced by transfected human embryonic kidney 293 cells produced an 8-kDa protein, which confirmed the presence of a signal peptide. Compared with other human C-C chemokines, human MIP-1 delta shows the highest homology with human HCC-1, CK beta-8, murine C10, and CCF18 (MIP-1 gamma). The human MIP-1 delta gene is localized on chromosome 17 where most of the C-C chemokine superfamily is located. Human MIP-1 delta is expressed in T and B lymphocytes, NK cells, monocytes, and monocyte-derived dendritic cells, but not in bone marrow-derived dendritic cells. Its expression can be induced by other proinflammatory cytokines in monocytes and dendritic cells. Human MIP-1 delta is chemotactic for T cells and monocytes, but not for neutrophils, eosinophils, or B cells. Human MIP-1 delta induced calcium flux in human CCR1-transfected cells.

RANTES-induced T cell activation correlates with CD3 expression.

The chemokine RANTES induces a unique biphasic cytoplasmic Ca2+ signal in T cells. The first phase of this signal, similar to that of other chemokines, is G-protein mediated and chemotaxis associated. The second phase of this signal, unique to RANTES and evident at concentrations greater than 100 nM, is tyrosine kinase linked and results in a spectrum of responses similar to those seen with antigenic stimulation of T cells. We show here that certain jurkat T cells responded to RANTES solely through this latter pathway. A direct correlation between the RANTES-induced second phase response and CD3 expression was demonstrated in these cells. Sorting the Jurkat cells into CD3(high) and CD3(low) populations revealed that only the CD3(high) cells were responsive to RANTES. Furthermore, stimulation of these Jurkat cells with anti-CD3 mAb significantly depresses their subsequent response to RANTES. While a RANTES-specific chemokine receptor is expressed at a low level on these Jurkat cells, the RANTES-induced activation is dependent on the presence of the TCR. Thus, stimulation through TCR may partially account for RANTES' unique pattern of signaling in T cells.

Chemokine receptor CCR3 function is highly dependent on local pH and ionic strength.

The CC chemokine receptor 3 (CCR3) plays an important role in the regulation of the migration of eosinophils, a leukocyte population involved in many inflammatory pathologies including asthma. CCR3 binds to the CC chemokine eotaxin, a promigratory cytokine originally isolated as the key component in a model of eosinophil-induced airway inflammation. We show here that eotaxin/CCR3 binding interactions exhibit a marked sensitivity to relatively small changes in the extracellular environment. In particular, modest variations in the pH and the level of sodium chloride over a range of physiologic and near physiologic conditions had dramatic effects on eotaxin binding and CCR3-mediated cytoplasmic Ca2+ mobilization. These biochemical indices were reflected at the functional level as well; small changes in pH and salt also resulted in striking changes in the migration of primary human eosinophils in vitro. These results reveal that relatively small perturbations in extracellular buffer conditions can yield widely disparate interpretations of CCR3 ligand binding and affinities and suggest that modulation of the tissue microenvironment might be utilized to control the affinity and efficacy of chemokine-mediated cell migration.

Characterization of transgenic pigs expressing functionally active human CD59 on cardiac endothelium.

The critical shortage of human donor organs has generated interest in the potential for porcine to human xenotransplantation. The initial immunological barrier to xenotransplantation is hyperacute rejection, which is mediated by xenoreactive antibodies and complement, and results in rapid and irreversible tissue destruction. While endogenous complement regulatory proteins (CRPs) protect cells from injury caused by autologous complement, they are relatively species specific and most likely ineffectual in this setting. This has led to the hypothesis that expression of human CRPs in transgenic pigs may affect susceptibility to complement-mediated tissue injury in a porcine-to-human xenograft. Using specific lines of transgenic pigs that express low levels of human CD59, a CRP that acts at the terminal stage of the complement cascade, we present evidence that shows that the human CD59 protein inhibits membrane attack complex assembly and reduces tissue damage when the heart is transplanted to a baboon. Examination by immunohistochemistry of transgenic porcine hearts after transplantation revealed markedly reduced deposition of C5b and MAC, but a similar level of C3 deposition as compared with transplanted control hearts. This finding supports the concept that the species specific function of CRPs contributes to the humoral barrier to xenotransplantation and, given the low level of human CD59 protein expression in the porcine heart, argues that the human protein contributes a unique rather than an additive function in regulation of complement in a xenogeneic setting.

Human CD59 expressed in transgenic mouse hearts inhibits the activation of complement.

Porcine-to-human xenotransplantation offers a potential solution to the critical shortage of human organs. The major immunological barrier to xenotransplantation between these species is a rapid rejection process mediated by preformed natural antibodies and complement. Xenogeneic organ grafts are especially susceptible to complement mediated injury because complement regulatory proteins, which ordinarily protect cells from inadvertent injury during the activation of complement, function poorly in regulating activation of heterologous complement. Removal of xenoreactive antibodies or systemic inhibition of complement activity has been shown to prolong graft survival. As an alternative to the systemic inhibition of complement activity, we have established a model system using transgenic animals to test whether the expression of human membrane bound complement regulatory proteins on mouse endothelial cells can inhibit the activation of human complement. CD59, which acts at the terminal stage of complement activation by inhibiting the formation of the membrane attack complex, was used as a paradigm for this model. A CD59 construct containing the putative CD59 gene promoter linked to the CD59 coding region was used to demonstrate expression of the human CD59 protein in various tissues of transgenic mice, including endothelial cells in the heart. In addition, we show that the transgenic CD59 protein is biologically active as determined by the ability to inhibit the formation of membrane attack complex in transgenic mouse hearts perfused ex vivo with human plasma. These results demonstrate that expression of membrane bound complement regulatory proteins can achieve complement inhibition in a xenogeneic organ and suggest that this approach may be useful for successful xenotransplantation between discordant species.

Regulation of growth hormone receptor and binding protein expression in domestic species.

Growth hormone receptor (GHR) expression has been analyzed at the RNA level. In the rat, relative expression of the RNA species encoding the GHR and the GH-binding protein (GHBP) appears to be sensitive to endocrine status. Full-length GHR cDNA clones from ovine, porcine, and chicken were used as probes to investigate the existence of unique RNAs for GHBPs in these species. In the sheep and pig, only a single, approximately 4.5-kb RNA is apparent. Although quite high levels of GH binding activity are found in pig serum, a variety of methods failed to isolate a separate GHBP message, suggesting that porcine GHBP is produced via a mechanism different from that which is known for rat. One class of chicken GHR cDNA, resulting from alternative use of a splice acceptor 17 bases upstream of the intron 6/Exon 7 junction, is also presented.

A functional polyadenylation signal is embedded in the coding region of chicken growth hormone receptor RNA.

A study of chicken GH receptor (cGHR) expression has revealed that the two major liver and skeletal muscle transcripts of the cGHR are developmentally expressed. Expression of the larger (4.7 kilobases) transcript increases with age. The smaller transcript (0.7 kilobases) is a truncation product, resulting from alternative usage of a functional polyadenylation [poly(A)] signal embedded in the coding sequence. The extent to which alternative cleavage and polyadenylation occur displays some tissue and sex specificity. Cleavage and polyadenylation occur down-stream of the AATAAA portion of the poly(A) signal (cGHR positions 304-309) and up-stream of a GT-rich sequence. The truncated transcript appears to be translated, based on its association in vivo with polyribosomes, although the physiological role of the putative protein product of this truncated transcript is as yet unknown. Three other avian species (quail, turkey, and duck) also show a polyadenylated truncation of the GHR message due to a poly(A) signal at the same location in the coding sequence. In cell culture expression, mutation of AATAAA to AACAAG prevents production of the truncated transcript. In a chimeric construct, the signal and neighboring sequence from the cGHR are sufficient to confer cleavage and polyadenylation upon the rat GHR, a gene that otherwise lacks the internal poly(A) signal. Alternative polyadenylation within the coding region of a structural gene is discussed as a heretofore unknown means of post-transcriptional regulation of a gene product.

Lysostaphin: immunogenicity of locally administered recombinant protein used in mastitis therapy.

A recombinant bactericidal protein, recombinant lysostaphin (r-lysostaphin), that may be useful as an intramammary therapeutic for Staphylococcus aureus mastitis in dairy cattle, was evaluated for immunogenicity to various hosts. Although immunogenicity could be demonstrated in a variety of other species when administered parenterally, oral administration failed to elicit a significant immunological response. Similarly, intramammary infusion of r-lysostaphin failed to elicit significant serum titers in the bovine until 18-21 infusions were administered (total administered dose of 2-3 g of protein). Antibody titers from dairy cattle which did develop an immune response were predominantly of the IgG1 subclass. Dairy cattle with significant anti-lysostaphin titers showed no deleterious symptoms (anaphylaxis, etc.) upon subsequent infusion, and these titers did not effect the in vitro bacteriostatic activity of r-lysostaphin. Intramammary infusion of r-lysostaphin does not elicit any observable effects on the host animal or on the potential efficacy of the recombinant molecule. Intramammary recombinant proteins may be suitable effective and safe infusion products that provide an alternative to classical antibiotic therapy.

Lysostaphin: use of a recombinant bactericidal enzyme as a mastitis therapeutic.

A recombinant mucolytic protein, lysostaphin, was evaluated as a potential intramammary therapeutic for Staphylococcus aureus mastitis in dairy cattle. Lysostaphin, a product of Staphylococcus simulans, enzymatically degrades the cell wall of Staphylococcus aureus and is bactericidal. Thirty Holstein-Freisian dairy cattle in their first lactation were infected with Staphylococcus aureus (Newbould 305, ATCC 29740) in all quarters. Infections were established and monitored for somatic cell counts and Staphylococcus aureus colony-forming units 3 wk prior to subsequent treatment. Infected animals were injected through the teat canal with a single dose of recombinant lysostaphin (dose response 1 to 500 mg) or after three successive p.m. milkings with 100 mg of recombinant lysostaphin in 60 ml of sterile phosphate-buffered saline. Animals were considered cured if the milk remained free of Staphylococcus aureus for a total of 28 milkings after last treatment. Kinetic analysis of immunologically active recombinant lysostaphin demonstrated that a minimum bactericidal concentration was maintained in the milk for up to 36 to 48 h after a single infusion of 100 mg of recombinant lysostaphin. The cure rate of quarters receiving recombinant lysostaphin (100 mg in sterile phosphate-buffered saline, administered over three consecutive p.m. milkings) was 20% compared with 29% for sodium cephapirin in saline and 57% for a commercial antibiotic formulation, respectively. An improved formulation of recombinant lysostaphin may prove to be an effective alternative to antibiotic therapy for bovine mastitis.

Changes in the bovine teat canal during the nonlactating period and early lactation, as measured by teat canal impressions.

Changes in dimensions of impressions of the lumen of the teat canals of 13 cows were examined at 17 intervals during the nonlactating period and early lactation. Impressions were made of teats of 2 diagonally opposed quarters of each cow, using dental impression material. Impression length was measured and cross sections of the impressions at the proximal (distal to Furstenburg rosette), distal (proximal to the teat orifice), and middle (midway between the 2), portions of the teat canal were prepared. Cross sections were photographed and enlarged, and circumference and area were determined by use of planimetry. Effects of making repeated impressions during the nonlactating period and early lactation on new infection rates and somatic cell counts were also assessed. Mean length of teat canal impressions decreased between days 0 and 3 of involution and during the prepartum periods. Depending on the level from which they were taken, cross-sectional areas of impressions tended to increase or increased significantly during the period of involution and again in the prepartum period. Significant changes in cross-sectional area were not observed during early lactation. Changes in circumference of proximal, middle, and distal cross sections followed trends similar to area measurements, but were more variable and differences were less statistically significant. On the basis of our findings, we suggest that heightened susceptibility to new infection during mammary involution and the prepartum period may be attributable, in part, to changes in the patency of the teat canal. Making impressions repeatedly throughout the nonlactating period and early lactation did not affect the number of new intramammary infections.

Effects of supplemental vitamin A or beta-carotene during the dry period and early lactation on udder health.

Effects of vitamin A or beta-carotene supplementation during the dry period and early lactation on the frequency of new intramammary infection and clinical mastitis and on SCC and milk yield were examined. Eighty-two Holstein cows were randomly assigned to one of three groups: 1) 50,000 IU/d of vitamin A per cow (approximately equivalent to 1978 NRC recommended daily intake for dairy cows); 2) 170,000 IU/d of vitamin A per cow; or 3) 50,000 IU/d of vitamin A plus 300 mg of beta-carotene per cow. Cows were supplemented during the 2 wk before drying off, throughout the dry period, and for the first 6 wk of lactation. Concentrations of serum vitamin A did not differ among treatment groups but tended to decrease for all treatment groups from 14 d before drying off to calving. After calving, serum vitamin A tended to increase in all groups through wk 6 of lactation. Serum beta-carotene tended to be higher in beta-carotene-supplemented cows at dry-off, in the early dry period, and again during lactation. Serum beta-carotene decreased sharply in all groups during the prepartum period. The frequency of clinical mastitis and of new intramammary infection during the dry period, near parturition, and for the first 6 wk of lactation did not differ among treatment groups. The percentage of quarters newly infected over the entire trial was 26.8 in the control, 25.0 in the high vitamin A, and 30.6 in the beta-carotene group. Pathogens isolated most frequently were coagulase-negative staphylococci, streptococci other than Streptococcus agalactiae, and coliforms.(ABSTRACT TRUNCATED AT 250 WORDS)

Quantitative and qualitative properties of host polymorphonuclear cells during experimentally induced Staphylococcus aureus mastitis in cows.

Polymorphonuclear cells have a critical role in the pathogenesis of bovine mastitis. We have documented that experimentally induced Staphylococcus aureus mastitis is associated with cyclic increase and decrease in the quantity of viable bacteria shed in the milk. Concomitant with this cycling of bacteria is an inverse cycling of the hosts cells within the milk. Such somatic cells were determined to be greater than or equal to 95% polymorphonuclear cells. The quality of these cells was evaluated by measuring their relative efficiency of bacterial killing and phagocytosis at various times during an infection. Host polymorphonuclear cells had as much as 10,000-fold variation in the bactericidal failure rate for staphylococci during cell cycling. The most efficient bactericidal effect was observed at or near the peak of the somatic cell count (SCC). The ability of these cycling cells to ingest fluorescent beads was also quantitated by use of flow cytometry. The percentage of phagocytic polymorphonuclear cells that ingested fluorescent latex beads ranged from 15 to 80% of the total cell population during cell cycling, and tended to be optimal at or near peak SCC. In addition, the average number of beads ingested varied between 1 and 2 particles/polymorphonuclear cell, with as many as 17% of the phagocytic cells ingesting 4 or more beads at maximal efficiency. Polymorphonuclear cells from quarters infected with S aureus varied quantitatively (total SCC) and qualitatively (bactericidal activity and phagocytic ability) during the course of an infection. Not only is the quantity of host's phagocytic cells in the mammary gland central to the defense mechanism against infection, but the biological activation state appears to be equally important. The role of these cells in the pathogenesis of a cycling infection is presented in a model to explain the cyclic nature of mastitis.

Phytohemagglutinin alters cell morphology and decreases prolactin production in GH cells.

Phytohemagglutinin (PHA) produced morphological and functional alterations in a clonal strain of rat pituitary tumor cells (GH4C1). Addition of PHA (2-5 micrograms/ml) results in a decrease in the proportion of elongated cells from 20% in control cell cultures to less than 10% in the presence of PHA. This effect can be observed after exposure of cells to PHA for 2-3 h and requires 4 days to be reversed after removing PHA from the culture medium. A specialized cell function, the production of the peptide hormone prolactin (PRL), is also affected by PHA treatment. Exposure of cells to 2 micrograms/ml PHA results in greater than 50% inhibition of PRL production. The above effects of PHA occur without any apparent alteration in total protein per culture dish, the rate of protein synthesis or the overall growth characteristics of the cells.