Extreme drought impacts have been underestimated in grasslands and shrublands globally

Climate change is increasing the frequency and severity of short-term (~1 y) drought events-the most common duration of drought-globally. Yet the impact of this intensification of drought on ecosystem functioning remains poorly resolved. This is due in part to the widely disparate approaches ecologists have employed to study drought, variation in the severity and duration of drought studied, and differences among ecosystems in vegetation, edaphic and climatic attributes that can mediate drought impacts. To overcome these problems and better identify the factors that modulate drought responses, we used a coordinated distributed experiment to quantify the impact of short-term drought on grassland and shrubland ecosystems. With a standardized approach, we imposed ~a single year of drought at 100 sites on six continents. Here we show that loss of a foundational ecosystem function-aboveground net primary production (ANPP)-was 60% greater at sites that experienced statistically extreme drought (1-in-100-y event) vs. those sites where drought was nominal (historically more common) in magnitude (35% vs. 21%, respectively). This reduction in a key carbon cycle process with a single year of extreme drought greatly exceeds previously reported losses for grasslands and shrublands. Our global experiment also revealed high variability in drought response but that relative reductions in ANPP were greater in drier ecosystems and those with fewer plant species. Overall, our results demonstrate with unprecedented rigor that the global impacts of projected increases in drought severity have been significantly underestimated and that drier and less diverse sites are likely to be most vulnerable to extreme drought.

Asymmetric responses of primary productivity to precipitation extremes: A synthesis of grassland precipitation manipulation experiments

Climatic changes are altering Earth's hydrological cycle, resulting in altered precipitation amounts, increased interannual variability of precipitation, and more frequent extreme precipitation events. These trends will likely continue into the future, having substantial impacts on net primary productivity (NPP) and associated ecosystem services such as food production and carbon sequestration. Frequently, experimental manipulations of precipitation have linked altered precipitation regimes to changes in NPP. Yet, findings have been diverse and substantial uncertainty still surrounds generalities describing patterns of ecosystem sensitivity to altered precipitation. Additionally, we do not know whether previously observed correlations between NPP and precipitation remain accurate when precipitation changes become extreme. We synthesized results from 83 case studies of experimental precipitation manipulations in grasslands worldwide. We used meta-analytical techniques to search for generalities and asymmetries of aboveground NPP (ANPP) and belowground NPP (BNPP) responses to both the direction and magnitude of precipitation change. Sensitivity (i.e., productivity response standardized by the amount of precipitation change) of BNPP was similar under precipitation additions and reductions, but ANPP was more sensitive to precipitation additions than reductions; this was especially evident in drier ecosystems. Additionally, overall relationships between the magnitude of productivity responses and the magnitude of precipitation change were saturating in form. The saturating form of this relationship was likely driven by ANPP responses to very extreme precipitation increases, although there were limited studies imposing extreme precipitation change, and there was considerable variation among experiments. This highlights the importance of incorporating gradients of manipulations, ranging from extreme drought to extreme precipitation increases into future climate change experiments. Additionally, policy and land management decisions related to global change scenarios should consider how ANPP and BNPP responses may differ, and that ecosystem responses to extreme events might not be predicted from relationships found under moderate environmental changes.

Can the past predict the future? Experimental tests of historically based population models

A frequently advocated approach for forecasting the population-level impacts of climate change is to project models based on historical, observational relationships between climate and demographic rates. Despite the potential pitfalls of this approach, few historically based population models have been experimentally validated. We conducted a precipitation manipulation experiment to test population models fit to observational data collected from the 1930s to the 1970s for six prairie forb species. We used the historical population models to predict experimental responses to the precipitation manipulations, and compared these predictions to ones generated by a statistical model fit directly to the experimental data. For three species, a sensitivity analysis of the effects of precipitation and grass cover on forb population growth showed consistent results for the historical population models and the contemporary statistical models. Furthermore, the historical population models predicted population growth rates in the experimental plots as well or better than the statistical models, ignoring variation explained by spatial random effects and local density-dependence. However, for the remaining three species, the sensitivity analyses showed that the historical and statistical models predicted opposite effects of precipitation on population growth, and the historical models were very poor predictors of experimental responses. For these species, historical observations were not well replicated in space, and for two of them the historical precipitation-demography correlations were weak. Our results highlight the strengths and weaknesses of observational and experimental approaches, and increase our confidence in extrapolating historical relationships to predict population responses to climate change, at least when the historical correlations are strong and based on well-replicated observations.

Outcome of clinical pregnancies after ovulation induction using metformin

The objective of this study was to review the first 50 clinical pregnancies of women with polycystic ovarian syndrome (PCOS) who had ovulation induced either with metformin alone, or in combination with clomifene. The study was confined to women with PCOS attending our infertility service. A register of clinical pregnancies was maintained of women who conceived after metformin therapy. The metformin was continued throughout the first trimester. The outcome of pregnancy was determined by individual chart review. Of the 50 women, 21 conceived with a combination of clomifene and metformin, and 29 with metformin alone. Seven women had a first trimester loss and 43 had a live birth. There were no perinatal deaths, no neonatal seizures and no congenital malformations. There were also no multiple pregnancies. The overall caesarean rate was 37%, and none of the babies had an Apgar score less than 7, at 5 min. This study found no evidence of any adverse clinical effects when metformin is continued in the first trimester of women with PCOS following ovulation induction. There was also no evidence of an increase in the rate of miscarriage or multiple pregnancy.

Cryopreserving and deglycerolizing sickle cell trait red blood cell components using an automated cell-processing system

RBC components with rare phenotypes are sometimes required for patients with sickle cell disease, and these rare components can often be found among donors with sickle cell trait. Cryopreserving RBC components from sickle cell trait donors requires a modified deglycerolization method to preserve the integrity of the RBCs. This study evaluated the feasibility of using an automated cell-processing system to cryopreserve and deglycerolize sickle cell trait donor RBC components. CP2D/AS-3 RBC components were collected from three donors with sickle cell trait. Each component was processed with an automated cell-processing system (ACP 215, Haemonetics Corp., Braintree, MA) and cryopreserved within 6 days of collection. The components were stored at -65 degrees C or less for at least 2 days and were deglycerolized using the automated cell-processing system's standard procedure. Before cryopreservation and after deglycerolization, several variables were measured. Deglycerolization resulted in recovery of 43.0, 76.5, and 67.5 percent of RBCs from the three sickle-cell-trait donor components compared with 80 percent or greater for all six control components. A small, dark red, jelly-like mass was noted in the bowl of the disposable set after deglycerolization of each of the three RBC sickle cell trait components. The osmolalities of all three sickle cell trait components were less than 400 mOsm/kg, but only one of the three was acceptable for a 14-day outdate. Freezing and deglycerolization of sickle cell trait donor RBC components with the automated cell-processing system resulted in recovery of some RBCs, but a decrease in RBC recovery was problematic. Modifications of the procedure are needed for processing sickle cell trait donor RBC components.

Isolation and characterization of canine satellite cells

Satellite cells were isolated from biopsies of the biceps femoris of adult dogs. Virtually all cells expressed muscle-specific proteins. Proliferation of satellite cells increased as the concentration of fetal calf serum (FCS) was increased from 1 to 10% of the basal medium. The addition of mitogenic growth factors resulted in greater proliferation than that of cells cultured in basal medium alone. Maximum proliferation was obtained when fibroblast growth factor-basic (FGF2) was added to the medium, but differences existed between sources or types. Proliferation did not plateau when the concentration of recombinant human FGF2 was 75 ng/ml but reached maximum levels when 50 ng/ml of bovine FGF2 or 10 ng/ml of growth hormone or insulin-like growth factor-1 were added to the medium. Proliferation of satellite cells decreased when more than 5 ng/ml of transforming growth factor-alpha was included in the medium. Exposure of canine satellite cells to chemically defined media induced greater fusion of total nuclei (ODM-34%; 4F, ITT-CF, and SFG-23%) than exposure to other treatments, such as basal medium plus 2 mg/ml of 1-beta-d-arabinofuranosylcytosine, 5% chick embryo extract, 1% horse serum (average 9% fused nuclei), or 1% FCS (2% fused nuclei). Actin, myosin, desmin, neural cell adhesion molecule, MyoD1, and myogenin were expressed by canine satellite cells, but expression of major histocompatibility complex class II antigen was not detected. Reverse transcriptase-polymerase chain reaction detected expression of messenger ribonucleic acid for interleukin-6 (IL-6), IL-15, and leukemia inhibitory factor by canine satellite cells. Collectively, these data suggest that isolated canine satellite cells display properties of other types of myogenic cells and may be useful for further study of the regulation of postnatal myogenesis.

Patterns of expression of muscle-specific markers of differentiation in satellite cell cultures: determination by enzyme-linked immunoculture assay and confocal immunofluorescent assay

Equine satellite cell clone SE-11 and ovine satellite cell clone I(1)were evaluated for expression of myosin heavy chain, myogenin, desmin, and muscle-specific actin over a 240 h period in culture. An enzyme-linked immunoculture assay (ELICA) was capable of detecting these proteins at all time points evaluated. A linear relationship was demonstrated between the natural logarithm of the absorbance values (corrected for cell number) from the ELICA and percent fusion in both SE-11 and I(1)cultures. The r(2)values for SE-11 cultures were: desmin 0.82, muscle actin 0.81, myogenin 0.78, and myosin 0.70. The r(2)values for I(1)cultures were: desmin 0.77, muscle actin 0.72, myogenin 0.70, and myosin 0.61. Our confocal results support the idea that differences exist between species in the differentiation dynamics of satellite cells. Further, these data suggest that the ELICA may be applied to previously conducted experiments, enabling additional data to be obtained with relation to muscle protein expression.

Bovine mammary immune response to an experimental intramammary infection with a Staphylococcus aureus strain containing a gene for staphylococcal enterotoxin C1

Staphylococcal enterotoxin C (SEC), a superantigen, is the most frequently expressed enterotoxin by bovine strains of Staphylococcus aureus causing mastitis. To examine the possible impact of SEC on the immune response of the bovine mammary gland, we monitored changes in lymphocyte subpopulations in mammary glands of four lactating cows after intramammary instillation of S. aureus strain Rn4220 transformed with a plasmid containing a gene coding for SEC1. Four other lactating cows received the same strain transformed with the plasmid without the SEC1 gene (positive control), and four cows were untreated (negative control). Mammary quarter milk samples for somatic cell count (SCC) analysis and determination of N-acetyl-beta-D-glucosimindase (NAGase) activity levels were collected daily for 21 d postinstillation. Flow cytometry utilizing three-color analysis was used to phenotype lymphocyte subpopulations isolated from milk samples collected on d 0, 4, 7, 11, 14, 18, and 21 postinstillation from all the cows. Milk from mammary gland halves (positive control and experimental) or all mammary quarters (negative control) was collected for flow cytometric analysis. Increased NAGase activity, SCC, and isolated S. aureus demonstrated that infection was established in mammary quarters intrammarily instilled with bacteria. There were no significant differences (P > 0.05) in the proportions of BoCD4 helper T lymphocytes or BoCD8 cytotoxic T lymphocytes between the two infected treatment groups. There was a significant day x treatment difference of the proportion of a gammadelta T cell subpopulation that did not express BoCD2, but did express the ACT2 activation molecule and a significant treatment difference of a gammadelta T cell subpopulation that expressed BoCD2, but not the ACT2 activation molecule (P < 0.05). Results do not support the hypothesis that the presence of the gene for SEC1 alters the mammary BoCD4 or BoCD8 T lymphocyte response to infection.

Isolation of bovine mammary lymphocytes for fluorescent activated flow cytometry

A detailed methodology is described for the isolation of T lymphocytes from bovine mammary gland secretions for flow cytometry. Mammary gland secretions are collected and centrifuged to separate the leukocytes from the mammary supernatant. The leukocytes are purified using a density gradient and diluted for fluorescent staining. Using tri-color fluorescent staining, the T lymphocytes are identified by monoclonal antibodies and stained with secondary antibodies. Flow cytometry is used to quantify the cellular subpopulations of the T lymphocytes. Proportional and statistical analysis of the flow cytometric data is conducted with computer software, CELLQuest and SAS.

Standardized flow cytometry gating in veterinary medicine

Gating in flow cytometry is used to select subpopulations of cells for analysis. The technique is critical for subsequent analysis in order to select the population, free of debris and unrelated cells. Accurately quantifying subpopulations in clinical cases is necessary for correct diagnosis. Human lymphocytes are selected by backgating on populations of CD45+high CD14- cells. These reagents are not available widely across species. In veterinary medicine, markers to identify lymphocytes are usually limited to T-lymphocyte, CD4, CD8, and B-lymphocyte surface antigens. A standardized gating technique using a T-lymphocyte antibody is described and is applicable across species where limited phenotype markers are available.

In vitro model of equine muscle regeneration

Equine satellite cells are responsible for muscle healing and regeneration in the mature horse. We describe the in vitro cell culture conditions required for clonal populations of equine satellite cells to undergo both proliferation and differentiation. Our hypothesis is that these in vitro conditions model regeneration of muscle and can be used to evaluate potential therapeutics. In this study, 2 areas of satellite cell response were tested: proliferation of clones induced by growth factors, and fusion induced by culture conditions. Equine satellite cell clones showed differences in their response to growth factors as well as accumulation of cellular protein concentrations. Equine satellite cells proliferate in response to both human and bovine FGF. IGF-1, a powerful mitogen of other satellite cell culture systems, was not as effective for inducing equine satellite cell proliferation. Protein concentrations were also measured in satellite cell cultures. Clones differed in cellular protein produced depending on growth conditions. Conditions inducing differentiation into myotubes was also determined for a 96 well assay and can be used to study the final stage of functioning muscle production. This in vitro model is the first step in identifying potential therapeutics to speed wound healing and promote muscle regeneration in horses.

Dietary beta-carotene stimulates cell-mediated and humoral immune response in dogs

The role of beta-carotene on immune response in domestic dogs is not known. Female Beagle dogs were fed 0, 2, 20 or 50 mg beta-carotene/d; blood was sampled at wk 0, 1, 2, 4 and 8 for analysis of the following: lymphoproliferation, leukocyte subpopulations and concentrations of interleukin-2 (IL-2), immunoglobulin (Ig)G and IgM. Delayed-type hypersensitivity (DTH) response was assessed at wk 0, 3 and 7. beta-Carotene supplementation increased plasma beta-carotene concentrations in a dose-dependent manner. Compared with unsupplemented dogs, those fed 20 or 50 mg of beta-carotene had higher CD4+ cell numbers and CD4:CD8 ratio. However, there was no treatment difference in CD8+, CD21+ and major histocompatability complex (MHC) class II+ cells. Plasma IgG, but not IgM concentration was higher in dogs fed beta-carotene throughout the study period. The DTH response to phytohemagglutinin (PHA) and vaccine was heightened in beta-carotene-supplemented dogs. beta-Carotene feeding did not influence mitogen-induced lymphocyte proliferation or IL-2 production. Immune response was impaired in dogs classified as low beta-carotene absorbers compared with similar dogs fed the same amount of beta-carotene. Therefore, dietary beta-carotene heightened cell-mediated and humoral immune responses in dogs.

Calcium oxalate stones in feline littermates

Two feline littermates were diagnosed with calcium oxalate uroliths. Both had been maintained on a commercially available dry diet with reduced magnesium and urine acidifying properties. One female littermate was diagnosed by visualising the stones by radiographs while the second littermate, also female, became blocked when one of the uroliths lodged in the urethra. Two other, unrelated cats in the household, of similar age and raised under the same conditions, did not develop calcium oxalate uroliths.

Dietary lutein stimulates immune response in the canine

The possible immuno-modulatory action of dietary lutein in dogs is not known. Female Beagle dogs (17-18-month old; 11.4+/-0.4kg body weight) were supplemented daily with 0, 5, 10 or 20mg lutein for 12 weeks. Delayed-type hypersensitivity (DTH) response to saline, phytohemagglutinin (PHA) and a polyvalent vaccine was assessed on Weeks 0, 6 and 12. Blood was sampled on Weeks 0, 2, 4, 8 and 12 to assess (1) lymphocyte proliferative response to PHA, concanavalin A (Con A), and pokeweed mitogen (PWM), (2) changes in peripheral blood mononuclear cell (PBMC) populations, (3) interleukin-2 (IL-2) production and (4) IgG and IgM production. After the completion of 12-week study, we continued to collect the blood weekly up to 17 weeks to evaluate the changes in immunoglobulin production upon first and second antigenic challenges on Weeks 13 and 15. Plasma lutein+zeaxanthin was undetectable in unsupplemented dogs but concentrations increased (P<0.05) rapidly on Week 2 in lutein-supplemented dogs. Thereafter, concentrations generally continued to increase in dose-dependent manner, albeit at a much slower rate. Dogs fed lutein had heightened DTH response to PHA and vaccine by Week 6. Dietary lutein increased (P<0.05) lymphocyte proliferative response to all three mitogens and increased the percentages of cells expressing CD5, CD4, CD8 and major histocompatibility complex class II (MHC II) molecules. The production of IgG increased (P<0.05) in lutein-fed dogs after the second antigenic challenge. Lutein did not influence the expression of CD21 lymphocyte marker, plasma IgM or IL-2 production. Therefore, dietary lutein stimulated both cell-mediated and humoral immune responses in the domestic canine.

Modulation of humoral and cell-mediated immune responses by dietary lutein in cats

The immuno-modulatory role of dietary lutein in domestic cats is unknown. Female Tabby cats (10-month old; n=56) were supplemented daily for 12 weeks with 0, 1, 5 or 10mg lutein. Blood was collected on Weeks 0, 2, 4, 8 and 12 to assess the following: (1) mitogen-induced peripheral blood mononuclear cells (PBMCs) proliferation, (2) changes in PBMC subpopulations, (3) interleukin-2 (IL-2) production and (4) plasma immunoglobulin (Ig)G production. In addition, delayed-type hypersensitivity (DTH) response to concanavalin A (Con A) or a polyvalent vaccine was performed on Weeks 0, 6 and 12. Dietary lutein increased plasma lutein concentrations in a dose-dependent manner (p<0.001) and concentrations had not reached steady state after 12 weeks of feeding in cats given 5 or 10mg lutein. Concentrations of plasma retinol and alpha-tocopherol were not influenced by diet. The DTH response to vaccine but not to Con A increased (p<0.05) in a dose-dependent manner on Week 6. Compared to control, cats fed lutein also showed enhanced Con A- and pokeweed mitogen-stimulated PBMCs proliferation. Dietary lutein also increased the percentages of CD4+ and CD21+ lymphocytes on Week 12 but had no significant effect on pan T, CD8 and MHC class II markers. Plasma IgG was higher (p<0.05) in cats fed 10mg lutein on Weeks 8 and 12. These results support the immuno-modulatory action of lutein in domestic cats.

Traditional and emerging methods for analyzing cell activity in cell culture

The selection of appropriate techniques to assay for markers of cell activity is important for obtaining optimal results in cell culture-based research. This paper is intended as a guide to many of the assays currently available and new techniques that have been recently introduced in the literature. This paper addresses both manual assay techniques, including the use of hemocytometers, phase contrast microscopy, cell staining, and the immunofluorescent antibody assay (IFA), and automated assays for cell activity, including stained optical density, proliferating cell nuclear antigen, creatine kinase assay, DNA quantification, electronic cell counting, flow cytometry, magnetic cell sorting, image analysis, chemiluminescence, radioisotope labeling, precursor incorporation, in-situ hybridization/ligand binding, and enzyme-linked immuno-culture assay (ELICA). Advantages/disadvantages and applicability of these assays to different areas of cell culture research are discussed, and guidelines for selecting an appropriate assay are suggested.

A standardized gating technique for the generation of flow cytometry data for normal canine and normal feline blood lymphocytes

Flow cytometry is becoming a commonly used technique to characterize a variety of cells. It provides a powerful application to rapidly determine the relative percentages of T-lymphocyte subsets and B-lymphocytes. The effectiveness of its application, however, is dependent on standardization, especially in a clinical setting. Application of flow cytometry to veterinary diagnostics has been limited by the unavailability of reagents and by the unstandardized characterization of normal values using antibodies not commercially available, but typically provided through the generosity of other researchers. This paper presents a standardized gating protocol, and average values and ranges observed for normal canine and feline blood lymphocytes using commercially available antibodies to cell surface markers for CD5, CD3, CD4, CD8, MHC II, and B lymphocytes. The averages for these markers on gated lymphocytes were as follows: Canine CD5 83.3%, Canine CD4 45.0%, Canine CD8 28.8%, Canine MHC II 98.0%, Canine B Cell 12.9%, Canine CD4/CD8 ratio 1.87, Feline T lymphocytes 77.3%, Feline CD4 44.5%, Feline CD8 25.7%, Feline B Cell 24.1%, Feline CD4/CD8 Ratio 1.75. Normal values were also established for a mixed breed group of dogs, and old versus young dogs. This information will provide researchers and clinicians with a standardized protocol for gating, which establishes a basis for comparison between techniques, and a measure of phenotypic percentages for flow cytometry in normal dogs and cats based on this standardization and commercially available antibodies.

Temperature dependent characteristics of a recombinant infectious hematopoietic necrosis virus glycoprotein produced in insect cells

A recombinant infectious hematopoietic necrosis virus (IHNV) glycoprotein (G protein) was produced in insect cells using a baculovirus vector (Autographa californica nuclear polyhedrosis virus). Characteristics of this protein were evaluated in relation to native viral G protein. A full-length (1.6 kb) cDNA copy of the glycoprotein gene of IHNV was inserted into the baculovirus vector under control of the polyhedrin promoter. High levels of G protein (approximately 0.5 microgram/1 x 10(5) cells) were produced in Spodoptera frugiperda (Sf9) cells following recombinant baculovirus infection. Analysis of cell lysates by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and Western blot revealed a recombinant IHNV G of slightly higher mobility on the gel than the viral G protein. Differences in mobility were abrogated by endoglycosidase treatment. When the recombinant G protein was produced in insect cells at 20 degrees C (RecGlow), immunostaining and cell fusion activity demonstrated surface localization of the protein. In contrast, when recombinant protein was produced at 27 degrees C (RecGhigh), G protein was sequestered within the cell, suggesting that at the 2 different temperatures processing differences may exist. Eleven monoclonal antibodies (MAbs) were tested by immunoblotting for reactivity to the recombinant G protein. All 11 MAbs reacted to the reduced proteins. Four MAbs recognized both RecGhigh and RecGlow under non-reducing conditions; however, 1 neutralizing MAb (92A) recognized RecGlow but failed to react to RecGhigh under non-reducing conditions. This suggests that differences exist between RecGlow and RecGhigh which may have implications in the development of a properly folded recombinant G protein with the ability to elicit protective immunity in fish.

Immunogenicity of a recombinant infectious hematopoietic necrosis virus glycoprotein produced in insect cells

A recombinant infectious hematopoietic necrosis virus (IHNV) glycoprotein (G protein), produced in Spodoptera frugiperda (Sf9) cells following infection with a baculovirus vector containing the full-length (1.6 kb) glycoprotein gene, provided very limited protection in rainbow trout Oncorhynchus mykiss challenged with IHNV. Fish were injected intraperitoneally (i.p.) with Sf9 cells grown at 20 degrees C (RecGlow) or 27 degrees C (RecGhigh) expressing the glycoprotein gene. Various antigen (Ag) preparations were administered to adult rainbow trout or rainbow trout fry. Sera collected from adult fish were evaluated for IHNV neutralization activity by a complement-dependent neutralization assay. Anti-IHNV neutralizing activity was observed in sera, but the percent of fish responding was significantly lower (p < 0.05) in comparison to fish immunized with a low virulence strain of IHNV (LV-IHNV). A small number of fish immunized with RecGlow or RecGhigh possessed IHNV G protein specific antibodies (Abs) in their serum. Cumulative mortality (CM) of rainbow trout fry (mean weight, 1 g) vaccinated by i.p. injection of freeze/thawed Sf9 cells producing RecGlow was 18% in initial trials following IHNV challenge. This level of protection was significant (p < 0.05) but was not long lasting, and neutralizing Abs were not detected in pooled serum samples. When trout fry (mean weight, 0.6 g) were vaccinated with supernatant collected from sonicated Sf9 cells, Sf9 cells producing RecGlow, or Sf9 cells producing RecGhigh, CM averaged 46%. Protection was enhanced over negative controls, but not the positive controls (2% CM), suggesting that in the first trial soluble cellular proteins may have provided some level of non-specific protection, regardless of recombinant protein expression. Although some immunity was elicited in fish, and RecGlow provided short-term protection from IHNV, Ab-mediated protection could not be demonstrated. The results suggest that recombinant G proteins produced in insect cells lack the immunogenicity associated with vaccination of fish with an attenuated strain of IHNV.

Report of the Second Equine Leucocyte Antigen Workshop, Squaw valley, California, July 1995

The final assignment of antibody clusters for leucocyte antigens and immunoglobulins, as described in detail in Sections 3 and 4, is summarized in Table 4. Together with other mAbs developed outside of ELAW II (Table 9) this pool of reagents represent a powerful array of tools for the study of equine immunity. The Second Equine Leucocyte Antigen Workshop made considerable advances in pursuing the objectives of establishing the specificities of mAbs and achieving consensus on the nomenclature for equine leucocyte and immunoglobulin molecules. Of equal importance, several productive collaborations were fostered among the participating laboratories and observers. Overall, enormous advances have been made in the past decade since mAbs specific for equine leucocyte antigens and immunoglobulins were first reported. There remains enormous scope and need for further studies of equine leucocyte antigens and immunoglobulins, both for the purposes of comparative immunology and for the good of the horse. In the future novel techniques will be required to develop reagents for specific target antigens such as the orthologues of the CD25 or CD45 isoforms. In studies of equine immunoglobulins the functional role of the IgG isotypes must be better established, reagents for IgE must be developed, and cloning of the immunoglobulin heavy chain genes will be essential if the complexities of the IgG sub-isotypes are to be elucidated. The tasks still facing the currently small group of equine immunologists throughout the world remain formidable, and will only be tackled successfully in a spirit of collaboration.

Frequency of memory cytotoxic T lymphocytes to equine infectious anemia virus proteins in blood from carrier horses

Horses with equine infectious anemia virus (EIAV) have episodes of viremia and disease; however, most eventually become inapparent carriers. A possible mechanism of control is cytotoxic T lymphocytes (CTL). To evaluate CTL in inapparent carriers with low viral loads, peripheral blood mononuclear cells (PBMC) were stimulated in vitro with autologous EIAV-infected PBMC and human IL-2 to detect memory CTL (CTLm). In initial studies, three carriers had CTLm and one of these had low-level effector CTL (CTLe). The CTLm were restricted by equine lymphocyte alloantigen-A (ELA-A) locus encoded MHC class I molecules on autologous equine kidney (EK) target cells. In addition, EK cells did not express MHC class II molecules. The CTLm frequency in PBMC from five inapparent carriers infected for 22 to 50 months was determined by limiting dilution analysis. PBMC were diluted, stimulated, and tested on EK cell targets infected with EIAV and recombinant vaccinia viruses expressing EIAV Env or Gag/Pr proteins. All five carriers had CTLm to EIAV-infected targets, while four had CTLm to targets expressing Env and four had CTLm to targets expressing Gag/Pr proteins. The CTLm frequency range was 60 to 468 per 10(6) PBMC to EIAV-infected targets, 4 to 286 to Env-expressing targets, and 25 to 190 to Gag/Pr-expressing targets. These results should facilitate the identification of epitopes recognized by predominant CTLm from horses controlling a lentivirus infection.

Cytokine RNA expression in an equine CD4+ subset differentiated by expression of a novel 46-kDa surface protein

Two monoclonal antibodies (MAb), HB65A (IgG2a) and HB86A (IgGI), recognize a unique cell surface molecule on equine T-lymphocytes. The molecule, designated EqWC4, identified by these MAbs is present on a subpopulation of CD4+ equine lymphocytes (6.3-10.2% of Arabian lymphocytes CD4+ WC4+) and a smaller population of CD8+ lymphocytes (0.5% to 1.2% of Arabian lymphocytes CD8+ WC4+). EqWC4 is absent from B-lymphocytes, granulocytes, and macrophages. Both MAbs bound to a 46-kDa protein following immunoprecipitation reactions with lysates of surface labeled thymocytes. Immunoaffinity purification using HB65A yielded two molecules of 46 kDa and 52 kDa under reducing conditions and a third 92-kDa molecule was present in nonreduced conditions. Activation by mitogen did not increase expression of EqWC4 on equine lymphocytes. Lymphocytes from Arabian, Pony, and Thoroughbred breeds showed a common distribution of EqWC4 among leukocytes. However, there were significantly fewer Pony lymphocytes bound to HB65A and HB86A when compared to Arabian and Thoroughbred breeds. Using reverse transcriptase-polymerase chain reaction (RT-PCR), magnetically enriched populations (to 80% of cells isolated) of EqWC4+ lymphocytes expressed a cytokine RNA profile dominated by -interleukin2 (IL-2) and interferon-gamma (IFN-gamma) for unstimulated cells. Upon mitogen stimulation, IL-4 was also expressed at low levels while the IL-2 levels decreased and the IFN-gamma levels increased relative to unstimulated cells. EqWC4 is similar to CD28 in molecular weight and its formation of dimers and could therefore be the equine orthologue. However, because of the differences in CD28 expression, EqWC4 probably represents a previously uncharacterized equine lymphocyte marker.

Control of equine infectious anemia virus is not dependent on ADCC mediating antibodies

Horses infected with equine infectious anemia virus (EIAV) have recurrent episodes of viremia which are eventually controlled, but the immune mechanisms have not been identified. Antibodies were detected to the surface of EIAV-infected cells within 1 month postinfection and remained for at least 3.5 years postinfection. These antibodies recognized cell surface-exposed envelope (Env) glycoproteins, but could not mediate antibody dependent cellular cytotoxicity (ADCC) using EIAV-WSU5-infected equine kidney (EK) cells as targets and peripheral blood mononuclear cells (PBMC) or polymorphonuclear cells (PMN) as effector cells. Furthermore, purified IgG antibodies from horses infected with either EIAV-WSU5 or EIAV-Wyo did not mediate ADCC of infected target cells. Armed effector cells could not be detected in infected horse blood nor could effector cells be prearmed by incubation with serum antibodies to cell surface antigens. The use of EIAV-WSU5-infected equine macrophages as target cells did not result in ADCC. In contrast, serum antibody from EHV-1 vaccinated horses and PBMC or PMN as effector cells caused ADCC of EHV-1-infected EK cells. These results indicate that ADCC is not involved in the control of EIAV in carrier horses.

Quantitative characterization of lymphocyte populations in bronchoalveolar lavage fluid and peripheral blood of normal adult Arabian horses

Bronchoalveolar lavage fluid (BALF) and peripheral blood were obtained from each of 17 adult Arabian mares and absolute numbers and relative lymphocyte proportions were determined for total T lymphocytes, using CD2 as a marker, CD4 + T lymphocytes, CD8 + T lymphocytes, CD5 + lymphocytes, and sIgM + B lymphocytes. The marked variation in BALF cell recovery resulted in wide variation in absolute values for each lymphocyte subset. The relative proportions of gated BALF lymphocytes were much less variable and provided a basis for comparison of lymphocyte subsets between the BALF and peripheral blood in normal horses. The total lymphocyte population was comprised predominantly of T cells in both BALF (83 +/- 11% CD2 + lymphocytes) and peripheral blood (70 +/- 8% CD2 + lymphocytes). There was a significantly greater percentage of total T lymphocytes and a significantly lower percentage of B lymphocytes in BALF as compared with peripheral blood collected at the same time. The increase in total T lymphocytes in BALF reflected a significantly higher percentage of CD8 + T lymphocytes in BALF (39 +/- 7%) as compared with peripheral blood (18 +/- 5%). The mean percentages of CD4 + T lymphocytes (58 +/- 13% in BALF; 62 +/- 8% in peripheral blood) and CD5 + lymphocytes (78 +/- 11% in BALF; 71 +/- 7% in peripheral blood), a population composed primarily of T lymphocytes but also including a subset of sIgM + B lymphocytes, were not significantly different between the two compartments. These normal values in Arabian mares provide a basis for detection of disease associated changes in the lymphocyte populations and for determination of effects of age and breed on lymphocyte subpopulations in the BALF and peripheral blood.

Glycoprotein B of bovine herpesvirus-1 binds heparin

Many members of the herpesvirus family have been shown to bind heparan sulfate on the surface of target cells. A previous report on bovine herpesvirus-1 (BHV-1) glycoprotein interactions indicated that only gC bound to heparin-agarose columns. In this report, we demonstrated that both gC and gB of wild-type BHV-1 bound to heparin-agarose columns and that gC-minus virus infectivity was inhibited by heparin.

Major histocompatibility complex-restricted CD8+ cytotoxic T lymphocytes from horses with equine infectious anemia virus recognize Env and Gag/PR proteins

Cytotoxic T lymphocytes (CTL) can control some viral infections and may be important in the control of lentiviruses, including human immunodeficiency virus type 1. Since there is limited evidence for an in vivo role of CTL in control of lentiviruses, dissection of immune mechanisms in animal lentiviral infections may provide needed information. Horses infected with equine infectious anemia virus (EIAV) a lentivirus, have acute plasma viremia which is terminated in immunocompetent horses. Viremic episodes may recur, but most horses ultimately control infection and become asymptomatic carriers. To begin dissection of the immune mechanisms involved in EIAV control, peripheral blood mononuclear cells (PBMC) from infected horses were evaluated for CTL to EIAV-infected cells. By using noninfected and EIAV-infected autologous equine kidney (EK) cells in 51Cr-release assays, EIAV-specific cytotoxic activity was detected in unstimulated PBMC from three infected horses. The EIAV-specific cytotoxic activity was major histocompatibility complex (MHC) restricted, as determined by assaying EIAV-infected heterologous EK targets, and was mediated by CD8+ T lymphocytes, as determined by depleting these cells by a panning procedure with an anti-CD8 monoclonal antibody. MHC-restricted CD8+ CTL in unstimulated PBMC from infected horses caused significant specific lysis of autologous EK cells infected with recombinant vaccinia viruses expressing EIAV genes, either env or gag plus 5' pol. The EIAV-specific MHC-restricted CD8+ CTL were detected in two EIAV-infected horses within a few days after plasma viremia occurred and were present after viremia was terminated. The detection of these immune effector cells in EIAV-infected horses permits further studies to determine their in vivo role.

Biosynthesis of the immunosuppressant immunomycin: the enzymology of pipecolate incorporation

Immunomycin, an immunosuppressant closely related to FK 506, contains a pipecolate residue in amide linkage with an acyl group in its polyketide backbone. An enzyme activating L-pipecolic acid has been isolated from Streptomyces hygroscopicus var. ascomyceticus, which produces immunomycin. Purification results in a monomer of 170 kDa exhibiting N-terminal heterogeneity, apparently arising from proteolysis of a single species. It is a dimer under native conditions. The reaction appears to use an aminoacyl adenylate as an intermediate in the activating reaction, as do most activating enzymes involved in nonribosomal peptide synthesis. A range of pipecolate and proline analogues act as substrates in the pyrophosphate-ATP exchange resulting from the adenylation reaction. Several analogues are inhibitors of the subsequent thioesterification of the enzyme. Antibody raised to the purified enzyme was used to follow antigen during the course of fermentation. Maximal levels of antigen are found when synthesis of immunomycin is maximal. Ten of twelve immunomycin nonproducing mutants lack detectable pipecolate-activating enzyme in Western blots. From the enzymatic characteristics, substrate specificity, and immunological properties, we propose that we have isolated the enzyme responsible for activating pipecolic acid for immunomycin biosynthesis.

Infantile free sialuria without lysosomal storage

Except for two reported patients, increased free sialic acid excretion has been associated with lysosomal storage. This is a report of a child with progressive neurologic deterioration and increased excretion of free sialic acid. Although lysosomal storage was absent, nuclear invagination or inclusions were present.

Nitrogen repression of gilvocarcin V production in Streptomyces arenae 2064

Analysis of gilvocarcin V production by Streptomyces arenae in complex and chemically defined media revealed strong nitrogen repression of antibiotic biosynthesis. Nitrogen regulation was first suggested by the observation of a 10-fold increase in gilvocarcin V production when the ammonium ion trapping agent Mg3(PO4)2.8H2O was added to complex medium. In a chemically defined medium, cell mass increased as the initial ammonium sulfate concentrations approached 7.5 mM; however, antibiotic production was strongly repressed at ammonium sulfate concentrations exceeding 1.5 mM. Repression of gilvocarcin V production at 7.5 mM ammonium sulfate was maximally reversed by adding Mg3(PO4)2.8H2O to the medium at 25 mM; specific antibiotic production attained a level 2.5-fold higher than at the nonrepressive ammonium salt concentration of 1.5 mM. Evaluation of the effects of soluble inorganic phosphate concentrations upon gilvocarcin V titers suggested that the relatively insoluble Mg3(PO4)2.8H2O must in fact serve as an ammonium ion-trapping agent, as previously reported in other fermentation systems, not as a supplementary source of phosphate for growth and antibiotic production. These studies also revealed a minor repression of antibiotic synthesis at elevated levels of soluble phosphate. Comparisons of several amino acids as nitrogen sources in a Mg3(PO4)2.8H2O-containing medium indicated that L-aspartic acid and glycine promoted the highest yields of gilvocarcin V. Metabolism of these two amino acids into precursors of the polyketide pathway for gilvocarcin V biosynthesis is postulated.

Largomycin FII chromophore component 4, a new pluramycin antibiotic

The chromophore of the antitumor chromoprotein largomycin FII is a mixture of components belonging to the pluramycin class of antitumor antibiotics. Against most organisms tested, component 4 exhibited activity equal to or greater than the major chromophore components pluramycin A and deacetylpluramycin A. Data obtained from UV, IR, 1H and 13C NMR, and from fast atom bombardment mass spectrometry were used to determine the structure of component 4 as epoxykidamycin, a new member of the pluramycin class.

Biosynthesis of fredericamycin A, a new antitumor antibiotic

Fredericamycin A (FM A), produced by a strain of Streptomyces griseus, represents a new structural class of antitumor antibiotics containing a spiro ring system. Studies on the producer organism showed that glucose in the fermentation medium is not utilized until late in the growth stage, just prior to synthesis of FM A. [14C]Glucose tracer experiments demonstrated that glucose is incorporated into FM A by catabolism to acetate. Biosynthetic enrichment of FM A with single- and double-labeled [13C]acetate showed that the entire carbon skeleton of the spiro ring system is derived from acetate. L-Methionine was shown to provide the only nonskeletal carbon in FM A, the methoxy carbon at position C-6. The direction of the polyketide chain and the position of the carbon lost during biosynthesis were established by using stable isotope experiments. A general model for FM A biosynthesis is proposed, and a possible scheme for the formation of the spiro carbon center is presented.

Structure and properties of major largomycin FII chromophore components

Largomycin FII, a protein antitumor antibiotic of molecular weight 29,300 daltons, contains a chromophore that is separable under mild denaturing conditions. The chromophore complex was found to be considerably less stable than the holoprotein towards light and heat, suggesting a protective effect of the protein on the chromophore. Separation of the chromophore into several components was achieved using high performance liquid chromatography, and the biological activity of the isolated components was determined. Data gathered from UV, IR, proton and carbon NMR, and fast atom bombardment mass spectrometry indicated that all the chromophore components belong to the pluramycin class of antitumor agents. Pluramycin A and deacetylpluramycin A were found to be the two major components.

Fredericamycin A, a new antitumor antibiotic. II. Biological properties

Fredericamycin A is a novel antibiotic produced by a soil isolate of Streptomyces griseus (FCRC-48). In vitro, fredericamycin A exhibits antibacterial, antifungal, and cytotoxic activities. In vivo, fredericamycin A exhibits very good antitumor activity against P388 mouse leukemia as well as the CD8F mammary tumor and marginal activity against B16 melanoma. Fredericamycin A failed to demonstrate any interaction with DNA and inhibited protein and RNA synthesis preferentially to DNA synthesis in Bacillus subtilis and P388 cells.

Fredericamycin A, a new antitumor antibiotic. I. Production, isolation and physicochemical properties

A new antitumor antibiotic, fredericamycin A (FCRC-A48, NSC-305263), has been isolated from a strain of Streptomyces griseus (FCRC-48). Based on its unique ultraviolet-visible spectrum, infrared spectrum, proton and carbon-13 nuclear magnetic resonance spectra and mass spectra, it is judged to be a novel acid-base indicator type of compound. Its production, isolation and physicochemical properties are discussed. The isolation, ultraviolet-visible spectrum and some biological properties of two minor components, fredericamycin B and fredericamycin C, are also described.

Separation of gentamicin C-complex into five components by Craig distribution

A gentamicin C-complex preparation was separated preparatively into five components by Craig distribution. Gentamicins C1, C2, and C1a were the major components, whereas components C2a and C2b represented only 4% of the total C-complex mixture. Paper chromatographic analysis showed that the gentamicin C2b separated by Craig distribution was identical with a gentamicin isolated from Micromonospora purpurea var. JI-33 fermentation broth and identified as 6'-N-methylgentamicin C1a. Similarly, component C2a was identical with a previously separated gentamicin component tentatively identified as the 6'-C epimer of gentamicin C2.