Effect of rCaIFN-γ pretreatment on propofol-isoflurane suppression of NK cytotoxic activity in the peripheral blood of dogs.

In dogs, natural killer (NK) cell cytotoxic activity, which is an index of antitumor immunity, decreases after general anesthesia. In this study, we examined whether the decrease in NK cytotoxic activity can be controlled with interferon-gamma (IFN-γ) treatment. Beagles were divided into 2 groups: a treated group (n = 6) that received recombinant canine IFN-γ (rCaIFN-γ) and an untreated control group (n = 6). Blood samples were taken before and at 24, 120, and 192 hours after anesthesia. NK cytotoxic activity toward canine thyroid cancer cells was measured in isolated lymphocytes with the Rose Bengal assay. The decrease in NK cytotoxic activity after anesthesia was significantly inhibited by administration of rCaIFN-γ before propofol-isoflurane anesthesia. Further studies are necessary to evaluate the clinical implications of rCaIFN-γ treatment in tumor recurrence and morbidity.

Enhancement of anti-tumor immune responses by transfection of IFNγ gene into tumor using a novel type synthetic vector.

The existence of Th1 responses in a tumor microenvironment elicits a better prognosis for the patients. Transfection of Th1 polarizing cytokines, such as IFNγ, into tumor cells is an effective way to set up an appropriate microenvironment. Using a novel type synthetic vector composed of polyamidoamine dendrons, we transfected canine IFNγ gene into canine tumor cell lines, and examined direct and indirect effects of dendritic cells (DCs) against tumor growth in vitro. A cloned canine IFNγ gene expressed functional protein that induces maturation of DCs. When the canine IFNγ gene was transfected into canine tumor cell lines using the synthetic vector, most cells secreted canine IFNγ. Secretion of IFNγ reduced with time, but was maintained for 48h. DCs incubated with the IFNγ-transfected tumor cells exhibited greater suppressive activity and induced significantly higher cytotoxic activity against the tumor cells, relative to those incubated with untransfected tumor cells and comparable dose of IFNγ. Successful transfection of IFNγ by the synthetic vector efficiently enhanced the anti-tumor immune function of DCs, and sets up a suitable microenvironment for improvement in tumor therapy.

Characterization of Fusobacterium necrophorum isolated from llama and alpaca.

Fusobacterium necrophorum, a Gram-negative, anaerobic bacterium, is an opportunistic animal and human pathogen that causes a variety of infections termed necrobacillosis. There are 2 subspecies of F. necrophorum (subsp. necrophorum and subsp. funduliforme) that differ morphologically and biochemically and in virulence. Leukotoxin, a secreted protein, is considered to be the major virulence factor. In camelids, F. necrophorum causes a variety of infections, generally involving the lips, tongue, pharynx, interdigital spaces, foot pad, larynx, mandible, or maxillary bones. The objective of the current study was to characterize the presumptive Fusobacterium isolates from a variety of necrotic infections in llama (Lama glama) and alpaca (Vicugna pacos) and determine whether the strains possess leukotoxin activities. A total of 7 isolates from alpaca and 2 isolates from llama were characterized. Based on growth characteristics in broth culture, and biochemical and polymerase chain reaction analyses, all 9 isolates belonged to subsp. necrophorum and possessed the putative hemagglutinin gene. Western blot analysis with antileukotoxin antibodies raised in rabbit showed the presence of leukotoxin protein in the culture supernatant of all isolates. Furthermore, flow cytometry of the culture supernatants demonstrated cytotoxicity to bovine and alpaca polymorphonuclear leukocytes (PMNs). The extent of cytotoxicity to either alpaca or bovine PMNs differed among camelid strains. The cytotoxicity of many of the camelid strains was higher (P < 0.05) toward alpaca PMNs compared to bovine PMNs. Fusobacterium necrophorum isolates from llama and alpaca are similar to bovine isolates, and leukotoxin may be a major virulence factor.

Comparison between intestinal and non-mucosal immune functions of rainbow trout, Oncorhynchus mykiss.

Since mucosal surfaces represent major portals of entry for pathogens, its associated immune system is important to protect the organism. In this paper, we compared at the cellular and molecular levels intestinal leukocyte suspensions with their head kidney (HK) or peripheral blood (PBL) counterparts to highlight characteristics of intestinal immune functions in healthy rainbow trout. These studies show that intestinal phagocytes are less activated by yeast cells but when they are activated they can ingest as many yeast cells as their HK counterparts. A natural cytotoxic activity could be detected which is twice higher in intestinal than in HK leukocyte preparations. This natural cytotoxic activity is correlated with the expression of transcripts encoding the natural killer enhancement factor (NKEF). Intestinal leukocytes did not respond to an in vitro mitogenic stimulation performed under classical culture conditions. And finally, a high expression of CD8α transcripts was observed in gut leukocyte preparations, suggesting that the intestine could contain a high proportion of T cells expressing the αα homodimeric form of CD8. This kind of comparison on nonimmunized fish provides better knowledge on basal immune functions in the intestine to, analyze later on, immune responses induced by an antigenic stimulation.

Research of Salmonella spp. and evaluation of pathogenicity, cytotoxicity of Escherichia coli isolates proceeding from sparrows (Passer domesticus) / Pesquisa de Salmonella spp. e avaliação da patogenicidade, citotoxidade de isolados de Escherichia coli procedentes de pardais (Passer domesticus)

The aim of this study was to research the occurrence of Salmonella spp. and Escherichia coli in feces samples of sparrows, as well as to identify the pathogenicity, cytotoxicity and sensitivity profile of the isolates to antimicrobial use. Two hundred and twenty eight sparrows were captured in eight farms. The in vitro pathogenicity test was performed by the isolates culture on congo red-magnesium oxalate Agar, whilst the in vivo pathogenicity test was performed in one day-old chicks. In order to study the cytotoxic effects of indicators, samples were inoculated into Vero cells. The results obtained for Escherichia coli isolation confirmed the presence of this microorganism in 30 (13.2%) of the evaluated samples. Out of those isolates, 10 (33.3%) presented the capacity of absorbing ongo red. As for in vivo pathogenicity a 68.0% of mortality rate of the evaluated samples was observed. Out of 20 isolates tested for cytotoxin production, none of them presented cytotoxic effect in the Vero cells. The Salmonella spp was isolated only in one sample (0.04%), and it was identified as Salmonella enterica subspecies houtenae. Results obtained through this research indicate the need for new studies to identify other virulence factors of E. coli samples and to delineate the phylogenetic profile of the isolates in order to establish a relation with colibacillosis outbreaks in chickens and broilers in the studied region, as well as to analyze the critical points in the aviculture productive chain to identify the source of Salmonella enterica subspecies houtenae.

Objetivou-se com este estudo pesquisar a ocorrência de Salmonella spp. e Escherichia coli em amostras de fezes de pardais, além de avaliar a patogenicidade, citotoxicidade e perfil de sensibilidade dos isolados frente a antimicrobianos. Foram capturados 228 pardais em oito granjas. O teste de patogenicidade in vitro foi realizado por meio do cultivo dos isolados em ágar oxalato de magnésio acrescido de vermelho de congo, enquanto o teste de patogenicidade in vivo foi realizado em pintos de um dia. Para o estudo dos indicadores dos efeitos citotóxicos, as amostras foram inoculadas em células Vero. Os resultados obtidos quanto ao isolamento de Escherichia coli confirmaram a presença deste microorganismo em 30 (13,2%) amostras analisadas. Destes isolados, dez (33,3%) apresentaram capacidade de absorção do vermelho congo. Quanto à patogenicidade in vivo observou-se uma taxa de mortalidade de 68,0% das amostras analisadas. Dos 20 isolados testados quanto à produção de citotoxina, nenhum apresentou efeito citotóxico nas células Vero. Obteve-se o isolamento de Salmonella spp. em apenas uma amostra (0,04%), sendo tipificada em Salmonella enterica subespécie houtenae. Os resultados obtidos nesta pesquisa indicam a necessidade da realização de novos estudos para identificar outros fatores de virulência das amostras de E. coli e traçar o perfil filogenético dos isolados para estabelecer uma relação com surtos de colibacilose em galinhas e frango de corte na região estudada, além de analisar os pontos críticos na cadeia produtiva da avicultura para identificar a origem da Salmonella enterica subespécie houtenae.

Caracterização molecular e fenotípica de estirpes de Escherichia coli produtoras de shiga-toxina (STEC) não-O157 de fezes e carcaças bovinas / Molecular and phenotypic characterization of shiga toxin producing Escherichia coli (STEC) non-O157 strains from bovine feces and carcass

Foram coletados 100 suabes retais e 100 suabes de carcaças bovinas em matadouros do estado de São Paulo, e um total de 326 estirpes de E. coli foram identificadas, sendo 163 de amostras retais e 163 de amostras de carcaça. Todos os isolados submetidos à PCR para detecção dos genes das toxinas Stx1 e Stx2 foram identificados como não-O157 e fenotipados pelo teste da citotoxicidade em células Vero. Das 26 estirpes que apresentaram apenas o gene stx1, das 56 que apresentaram apenas o gene stx2 e das 30 estirpes que apresentaram ambos os genes, 17 (65,4%), 42 (75%) e 22 (73,3%), respectivamente, foram positivas ao teste de citotoxicidade. Não houve diferença estatística entre os três perfis genéticos e na positividade ao teste de citotoxicidade. Os resultados mostram a alta frequência de expressão dos fatores de virulência das STEC de bovinos.

In the present study 100 rectal and 100 carcass swabs were collected from bovines at slaughterhouses in São Paulo state, and the total of 326 E. coli strains were identified (163 from rectal samples and 163 from carcass samples). All the isolates were submitted to PCR for Stx1 and Stx2 toxin gene detection and all strains were identified as non-O157 and phenotyped by the citotoxicity test in Vero cells. Out of 26 strains that presented only the stx1 gene, 56 that presented only the stx2 gene and 30 that presented both genes, 17 (65.4%), 42 (75%) and 22 (73.3%), respectively, were positive for the citotoxicity test. There was no statistically significant difference among these three toxinotyping profiles and positivity in the citotoxicity test, but the results show high frequency of virulence factor expression of bovine.

Immunological responses to Clostridium perfringens alpha-toxin in two genetically divergent lines of chickens as influenced by major histocompatibility complex genotype.

Chickens genetically selected for low (LA) or high (HA) antibody response to SRBC displayed a correlated change in MHC, so that LA chickens were 96% B13 and HA chickens were 96% B21. The LA line appears to be less susceptible to invasion by extracellular pathogens, whereas HA chickens are more resistant to infection by intracellular organisms. Resistance to Clostridium perfringens is one instance in which the lines do not follow their established trend of pathogen susceptibility, where during a clinical outbreak of necrotic enteritis, B21B21 genotypes experienced significantly less mortality than B13B13 genotypes. A study was carried out to assess immunological differences between LA and HA lines during exposure to C. perfringens α-toxin. Peripheral blood mononuclear cells were isolated from each genetic line, cultured with or without lipopolysaccharide (4 h), and exposed to varying concentrations of α-toxin (1; 10; 100; and 1,000 U/L) for 2 and 4 h. Evaluation of cellular proliferation, percentage of cytotoxicity, and immunological gene expression was carried out in a series of experiments. Cells isolated from HA chickens had significantly increased proliferation than those from LA chickens at low toxin levels (1 and 10 U/L) and significantly decreased proliferation at high toxin levels (100 and 1,000 U/L). Following exposure to lipopolysaccharide, the percentage of cytotoxicity was higher for LA than HA cells. In both assays, HA cells displayed superior performance following lipopolysaccharide-stimulation. Gene expression analysis of immune transcripts by quantitative real-time PCR revealed significantly upregulated expression of interferon (IFN)-γ, interleukin (IL)-8, IL-13 (2 h), IL-15, and CXCLi1 (4 h) in HA than LA chickens. Cells isolated from the LA line displayed significantly elevated expression of IL-2, IL-10, IL-13 (4 h), IL-16, IL-18, inducible nitric oxide synthase (iNOS), CXCLi1 (2 h), and lipopolysaccharide-induced tumor necrosis factor-α factor (LITAF) compared with the HA line. Clearly, these 2 genetic lines display highly divergent immune responses in regards to C. perfringens toxin exposure.

Evaluating antigen-specific cytotoxicity of CD8+ T cells in fish by granzyme B-like activity.

Granzyme B plays an important role in granule-mediated apoptosis by CTL. It is a well characterized component of the cytolytic machinery in mammals and a candidate for the evaluation of cytotoxic activity of CTL as an alternative to conventional cytotoxicity assay. In this study, we examined the effects of granzyme inhibitors to assess the characteristics of fish granzymes in terms of substrate specificity and the involvement of granzyme B-like in the cytotoxic response. 3,4-dichloroisocoumarin (DCI), which inhibit the activity of serine protease including all members of the granzyme family, markedly suppressed the cytotoxic activity of CTL. However, CTL-mediated cytotoxicity was significantly but not completely suppressed by the addition of carbobenzyloxy-Ile-Glu-Thr-Asp-fluoromethyl ketone (Z-IETD-FMK) that specifically blocks granzyme B activity. These results suggest that additional serine proteases as well as granzyme B-like are involved in cytotoxicity of CTL in fish. We further compared cytotoxicity with the granzyme B-like hydrolytic activity against fluorogenic substrate acetyl-Ile-Glu-Thr-Asp-4-methylcoumaryl-7-amide (Ac-IETD-MCA) and found that granzyme B-like activity correlated well with the cytotoxicity of CTL in ginbuna crucian carp. Present results suggest that the granzyme activity assays is useful to assess cytotoxic activity of CTL in fish in which genetic information on granzymes and specific tools for cytotoxicity assay are not available because of well conserved catalytic triad residues and substrate binding sites in granzyme B throughout vertebrates.

Hemolysin EthA in Edwardsiella tarda is essential for fish invasion in vivo and in vitro and regulated by two-component system EsrA-EsrB and nucleoid protein HhaEt.

Edwardsiella tarda is a Gram-negative pathogen for hemorrhagic septicemia in fish. Recently, two-component system (TCS) EsrA-EsrB in E. tarda has been found to play key roles in regulating type III secretion system (TTSS) and type VI secretion system (T6SS). In this study, a markedly attenuated ΔesrB mutant was investigated to exhibit enhanced cell-invasion capability, as well as the increased cytotoxicity of its extracellular products (ECPs). Compared with the parental strain, the ΔesrB mutant unexpectedly displayed the significantly increased hemolytic activity, and the restoration of hemolysin production was observed in the complemented strain esrB(+). A hemolysis-associated 147 kDa protein, EthA, was found to be up-regulated in the ECPs of ΔesrB. The deletion of ethA gene in E. tarda wild type and ΔesrB strains drastically decreased their capacities in internalization of epithelial papilloma of carp (EPC) cells. These results indicated that the increased production of EthA was responsible for the enhanced cell-invasion related capabilities in ΔesrB. Furthermore, the expression of EthA in ΔesrB exhibited a temperature-induced manner, and a nucleoid protein Hha(Et) was identified to mediate ethA expression by directly binding to its promoter. These results demonstrated that the virulence determinant EthA was fully required for invasion abilities of E. tarda and was subjected to the control of a complicated and precisely regulated network primed for its invasion, colonization and infection process in fish.

T lymphocyte proliferative capacity and CD4+/CD8+ ratio in primiparous and pluriparous lactating cows.

T cells play a central role in specific immunity; their populations and phenotypes could be affected by number of lactation in high-yielding dairy cows. To investigate the effects of parity on the dynamics of T lymphocytes, lymphoproliferative capacity, T lymphocyte subsets and CD4+/CD8+ ratio were studied in peripheral blood of primiparous and pluriparous dairy cows during mid-late lactation. A non-radioactive technique was also adapted for a detailed lymphoproliferation assay. Compared with the primiparous cows, the pluriparous cows exhibited weaker lymphoproliferative activity, larger number of CD4+ cells and substantially greater CD4+/CD8+ ratio in their blood circulation. The increase of the CD4+/CD8+ ratio in the blood of pluriparous dairy cows was mainly due to the rise in the proportion of CD4+ cells and decline in the proportion of CD8+ cells. This increase of the CD4+/CD8+ ratio coincided with the decrease of mitogen-induced proliferation capacity of T lymphocytes. Of four lymphocyte divisions or generations during the lymphoproliferation assay, maximal lymphocyte proliferation capacity at generation 3 in primiparous cows was markedly greater than in pluriparous cows. With an alternatively safer, faster and more reproducible assay (compared with 3H-thymidine scintillation assay) we showed for the first time that aging in dairy cows leads to a decreased mitogen-induced lymphoproliferation and disturbed proportion between CD4+ and CD8+ T cells. This CD4+-CD8+ imbalance together with diminished lymphoproliferative capacity may lead to a weaker T cytotoxic-mediated immunity and increased susceptibility to infectious diseases in pluriparous lactating cows. Our study also emphasizes further application of the methods in farm animals.

Phenotypic analysis and effects of sequential administration of activated canine lymphocytes on healthy beagles.

We attempted to accumulate the basic data for evaluation of activated lymphocyte therapy for small animal medicine. The peripheral blood mononuclear cells (PBMCs) collected from healthy dogs were activated using anti-CD3 antibody and human recombinant (hr) interleukin (IL)-2 and reactivated using hr interferon (IFN)-alpha and hr IL-2. The property of obtained cells was compared with PBMCs. The number of cells was shown to have increased approximately>50 -fold by cultivation. The proportion of CD8+ cells was significantly increased, the cytotoxicity of the cultured cells was revealed to have been reinforced. Additionally, CD56 mRNA levels tended to have increased. The cells obtained by this method were confirmed to be activated lymphocytes. Furthermore, we investigated the effects of sequential administration of the obtained cells to healthy dogs. By sequential administration of the activated lymphocytes, the cell proliferative activity, proportion of CD4+ cells and CD8+ cells, and serum IFN-gamma concentration were shown to have increased, and no severe adverse effects were observed. Consequently, activated lymphocytes could be induced using anti-CD3 antibody and IL-2 in healthy dogs, and sequential administration of activated lymphocytes reinforced the recipient's immunity.

Orientation of bovine CTL responses towards PIM, an antibody-inducing surface molecule of Theileria parva, by DNA subunit immunization.

East Coast fever, an acute lymphoproliferative disease of cattle, is caused by the apicomplexan parasite Theileria parva. Protective immunity is mediated by CD8(+) cytotoxic T lymphocytes directed against schizont-infected cells. The polymorphic immunodominant molecule, although an antibody-inducing surface molecule of the schizont, has been hypothesized to play a role in protective immunity. In order to evaluate the immunogenicity of PIM for inducing CTL, cattle were immunized with PIM in isolation from other T. parva antigens, forcing the presentation of PIM-derived epitopes on the MHC class I molecules. Although parasite-specific cytotoxicity was induced in both vaccinated animals, their immune response was clearly different. One animal generated MHC-restricted parasite-specific CTL against PIM while the other calf exhibited a strong PIM-specific proliferative response but non-MHC-restricted parasite-specific cytotoxicity. Only calf 1 survived a lethal sporozoite challenge. This DNA immunization technique with an antigen in isolation of CTL-immunodominant antigens might open possibilities for directing CTL responses against predefined antigens, such as strain cross-reacting CTL antigens.

Attenuated cytokine responses in porcine lymph node cells stimulated with CpG DNA are associated with low frequency of IFNalpha-producing cells and TLR9 mRNA expression.

The immune stimulatory effects of synthetic CpG DNA, on porcine peripheral blood mononuclear cells (PBMC) have been reported, but little is known about CpG-induced responses in other lymphoid tissues of pigs. We investigated innate immune responses induced by CpG DNA in cells from blood, lymph nodes (LN) and spleens of pigs. Porcine PBMC and lymph node cells (LNC) were stimulated in vitro with three classes (A-, B- and C-class) of CpG oligodeoxynucleotides (ODNs), and a non-CpG control ODN. All three classes of CpG ODNs induced significant production of IFNalpha, TNFalpha, IL-1, IL-6 and IL-12 in PBMC. In contrast, in LNC, only IL-12 was stimulated by all three classes of CpG ODNs, while IFNalpha, and IL-6 were induced by A- and C-class ODNs. No TNFalpha was induced in LNC by any of the ODNs. Significant lymphocyte proliferation was induced in PBMC by all three classes of CpG ODNs and non-CpG control. However, in LNC, B- and C-class ODNs induced significant proliferation, while no proliferation was seen with A-class and non-CpG control ODN. All three classes of ODNs induced NK-like cytotoxicity in PBMC and spleen cells, but were less effective in inducing NK cytotoxicity in LNC. We then investigated the reasons for the relatively poor CpG-induced responses in LNC. Our investigations revealed that LNC had a lower frequency of IFNalpha-secreting cells and expressed low levels of TLR9 mRNA compared to PBMC. We conclude that the lower number of IFNalpha-secreting cells and receptor expression may contribute to the attenuated responses in LNC following stimulation with CpG ODN.

Contribution of MX dynamin, oligoadenylate synthetase, and protein kinase R to anti-paramyxovirus activity of type 1 interferons in vitro.

OBJECTIVE: To determine the contribution of MX dynamin, oligoadenylate synthetase (OAS), and double-stranded RNA-dependent protein kinase R (PKR) to the antiviral effects of type 1 interferons (IFNs) against bovine parainfluenza-3 virus (PI-3V) infection of Vero cells. SAMPLE POPULATION: Vero cell cultures. PROCEDURES: PI-3V yield was first compared between control and transfected type 1 IFNs-incompetent Vero cells expressing recombinant OAS or MX proteins. Afterwards, phosphorylation of eukaryotic initiation factor 2 alpha (eIF2alpha) was used to scale the degree of PKR activation upon infection of Vero cells by PI-3V. RESULTS: Overexpression of OAS did not result in significantly decreased viral replication. Phosphorylated eIF2alpha forms, the hallmark of PKR activation, were not increased in IFNalpha-primed infected Vero cells. Although human MXA contributed to partial blockade of replication of bovine PI-3V, the antiviral effect was not as strong as that of IFNalpha. CONCLUSIONS AND CLINICAL RELEVANCE: The powerful anti-Paramyxovirus activity of type 1 IFNs is mediated by noncanonic pathways.

A novel culture method of canine peripheral blood lymphocytes with concanavalin a and recombinant human interleukin-2 for adoptive immunotherapy.

This study was designed to develop a novel culture method for the efficient proliferation of canine peripheral blood lymphocytes (cPBL) for adoptive immunotherapy. When cPBL were cultured in the presence of concanavalin A (Con A), proliferation of cPBL was induced and expression of interleukin-2 receptor (IL-2R) which enables to respond to exogenously added IL-2 was upregulated. And then, when cPBL were cultured with recombinant human interleukin-2 (rhIL-2) in addition to Con A, proliferation was accelerated and increased to about 10-fold after 1 week. The phenotypic analysis showed that the main population of the cultured cPBL was consisted of CD8+ positive lymphocytes. Among them, CD4+CD8+ double positive (DP) lymphocytes had significantly increased, and the ratio of CD4+ single positive (SP) lymphocytes to CD8+ SP lymphocytes (CD4+SP/CD8+SP) was decreased as compared to before culturing. To evaluate the cytotoxic activity of cPBL cultured with Con A and rhIL-2, furthermore, cytotoxic assay was carried out against xenogeneic melanoma cell line (MeWo), which resulted in MHC-unrestricted cytokilling. These results suggest that the culture method of cPBL by the use of Con A and rhIL-2 may be useful for generating lymphokine activated killer cells, and also this may be beneficial for adoptive immunotherapy of tumor-bearing dogs.

Transfection of non-susceptible cells with Ovis aries recombinant lymphocyte function-associated antigen 1 renders susceptibility to Mannheimia haemolytica leukotoxin.

Mannheimia haemolytica is an important etiological agent of pneumonia in domestic sheep (DS, Ovis aries). Leukotoxin (Lkt) produced by this organism is the principal virulence factor responsible for the acute inflammation and lung injury characteristic of M. haemolytica caused disease. Previously, we have shown that the leukocyte-specific integrins, beta(2) integrins, serve as the receptor for Lkt. Although it is certain that CD18, the beta subunit of beta(2) integrins, mediates Lkt-induced cytolysis of leukocytes, it is not clear whether CD18 of all three beta(2) integrins, LFA-1, Mac-1 and CR4, mediates Lkt-induced cytolysis of DS leukocytes. Since polymorphonuclear leukocytes, which express all three beta(2) integrins, are the leukocyte subset that is most susceptible to Lkt, we hypothesized that all three beta(2) integrins serve as the receptor for Lkt. The objective of this study was to determine whether DS LFA-1 serves as a receptor for M. haemolytica Lkt. We cloned the cDNA for DS CD11a, the alpha subunit of LFA-1, and co-transfected it along with the previously cloned cDNA for DS CD18, into a Lkt-non-suceptible cell line. Transfectants stably expressing DS LFA-1 were bound by Lkt. More importantly, Lkt lysed the DS LFA-1 transfectants in a concentration-dependent manner. Pre-incubation of Lkt with a Lkt-neutralizing monoclonal antibody (MAb), or pre-incubation of transfectants with MAbs specific for DS CD11a or CD18, inhibited Lkt-induced cytolysis of the transfectants. Exposure of LFA-1 transfectants to low concentrations of Lkt resulted in elevation of intracellular [Ca(2+)](i). Taken together, these results indicate that DS LFA-1 serves as a receptor for M. haemolytica Lkt.

Effect of heat-inactivated fish and non-fish derived probiotics on the innate immune parameters of a teleost fish (Sparus aurata L.).

The in vitro effects of four heat-inactivated bacterial species on the cellular innate immune responses of the gilthead seabream (Sparus aurata L.) were investigated. Head-kidney leucocytes were isolated and incubated for 30 min with two bacteria isolated from seabream skin (Pdp11 and 51M6; members of the Vibrionaceae and in the genus Shewanella) and two bacteria used as probiotics in humans and cattle (Lactobacillus delbrüeckii subsp. lactis and Bacillus subtilis) at 5 x 10(5), 5 x 10(6) or 5 x 10(7)CFU/ml. After incubation, different cellular innate immune parameters (leucocyte peroxidase content, phagocytosis, respiratory burst activity and cytotoxicity) were evaluated. The leucocyte peroxidase content was significantly higher after incubation with 51M6 at 5 x 10(7)CFU/ml. Head-kidney phagocytes were able to engulf the four bacterial species in all four cases, L. delbrüeckii subsp. lactis and B. subtilis being the most actively phagocytized. The incubation of seabream leucocytes with 51M6, L. delbrüeckii subsp. lactis and B. subtilis resulted in a great increase in respiratory burst activity. Cytotoxic activity was generally stimulated in a dose-dependent manner, the enhancement obtained with 5 x 10(7)CFU/ml being statistically significant. The usefulness of in vitro assays for screening and selecting candidate probiotic bacteria, as well as for optimising their effective dose, is discussed in relation with their immune-modulatory properties.

Genotyping of Toll-like receptor 4, myeloid differentiation factor 2 and CD-14 in the horse: an investigation into the influence of genetic polymorphisms on the LPS induced TNF-alpha response in equine whole blood.

The inter- and intra-species differences in the response to lipopolysaccharides (LPS) are well recognised in mammalian species. It has been hypothesized that these differences can be attributed to genetic polymorphisms in the components involved in LPS signal transduction. These components include the cluster of differentiation factor 14 (CD-14), a membrane bound protein on the surface of mononuclear cells that recognises LPS and a receptor complex consisting of Toll-like receptor-4 (TLR-4) and myeloid differentiation factor-2 (MD-2). Sequencing of these three proteins in humans and mice revealed that all three are susceptible to polymorphic alterations, influencing the response to LPS. Previous experiments in the horse showed large inter-individual variations in the response to LPS. With the aim to assess this inter-individual variation, we performed a whole blood assay in 10 healthy horses as a functional assay to study the responsiveness to LPS. In 3 out of the 10 horses, LPS-induced TNF-alpha production was significantly lower compared to the overall mean. Subsequently the entire cDNA sequence encoding for the TLR-4, MD-2 and CD-14 protein was documented for each horse. Although mutations were observed in the sequence of TLR-4, these could not be related to an altered response to LPS in the concentration used in this study, as determined in the whole blood assay. Despite the various mutations found in the TLR-4 receptor protein, no alterations could be found in either the MD-2 or CD-14 gene, which are obviously more conserved structures.

Modulation of juvenile brook trout (Salvelinus fontinalis) cellular immune system after Aeromonas salmonicida challenge.

In fish, the first line of defence against infectious microorganisms is based on non-specific cellular immune mechanisms (innate immunity). In this study, we measured the non-specific immune parameters (natural cytotoxic cells (NCC) activity, lymphoproliferation, percentage of phagocytosis and phagocytic activity) in brook trout (Salvelinus fontinalis) infected by a virulent strain of Aeromonas salmonicida. Eight days post-infection, the mortality of infected fish reached 70%. A transient immunostimulation of the NCC activity was noticed 24h post-infection, but there was no significant difference at 48 h. Then, infection of brook trout with A. salmonicida induced a biphasic immune response. At 24h post-infection, lymphoproliferation was drastically depressed but returned to control level at 96 h. A slight increase in the percentage of phagocytosis and the phagocytic activity was noticed throughout the experiment. Conversely the cell mortality was significantly higher in infected fish compared to control. The modulation of immunological parameters might reveal important clues on how innate immunity might protect fish from bacterial infections.

Different sensitivity of carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss) to the immunomodulatory effects of UVB irradiation.

In order to study the sensitivity of two fish species, carp (Cyprinus carpio) and rainbow trout (Oncorhynchus mykiss), to the immunomodulatory effects of ultraviolet B (UVB) radiation, the fish were exposed to a single UVB dose of 50, 250, 500 or 1,000 mJ cm(-2). These species represent different phylogenetic groups of fish, and they differ also in their behaviour inhabitating often dark and turbid (carp) or clear and transparent waters (salmonids). Immune responses were studied on day 1 post-irradiation. Unexposed fish, and fish exposed to radiation depleted of UV wavelengths served as controls. UVB irradiation markedly enhanced the blood respiratory burst and cytotoxic activity in carp, but in the head kidney these parameters were significantly suppressed. Rainbow trout respiratory burst was affected only after exposure with the highest dose of UVB. Lymphopenia and granulophilia were noted in both fish blood after exposure. This study indicates that UVB irradiation modulates immune functions in both fish species studied, and that rainbow trout is more tolerant than carp against UVB. Fish are clearly adapted to the environmental UVB levels prevailing in their usual living habitats, but are also a target of undesired effects of UVB on immune functions whenever exposed to increased radiation levels.