Salmonella enteritidis immune leukocyte-stimulated soluble factors: effects on increased resistance to Salmonella organ invasion in day-old Leghorn chicks

Dietary supplementation with vitamin C ameliorates the adverse effects of Salmonella Enteritidis-challenge in broilers by shaping intestinal microbiota

Salmonella Enteritidis (SE) infection is not only a leading cause of poor production performance and compromised animal welfare in broilers but also a potential threat to public health. Two experiments were conducted to evaluate the effects of dietary supplemental vitamin C (VC) on SE challenged-broilers. In experiment 1, one hundred eighty 1-day-old Arbor Acre broilers were randomly allocated into 3 treatments, with 0, 500, or 1,000 mg/kg VC included in the diet. In experiment 2, dietary VC at 0 or 500 mg/kg, with or without SE challenge was applied in a 2 × 2 factorial arrangement in 6 randomized complete blocks. In experiment 1, addition with 500 mg/kg VC increased BW and infectious bursal disease (IBD) titer of broilers on 35 D (P < 0.05), whereas 1,000 mg/kg VC had no effects on the IBD titer (P > 0.05) compared with the control group. In experiment 2, SE challenge depressed BW on 11 and 21 D (P < 0.05 and P = 0.088, respectively), whereas increased mortality and hepatic bacterial translocation (P < 0.05) on 21 D. Further, SE challenge resulted in lower villus height in jejunum, lower microbial richness, and diversity, whereas higher abundance of Enterobacteriaceae in cecum (P < 0.05). Importantly, supplementation with VC increased BW on both 21 and 35 D (P < 0.05 and P = 0.088, respectively) and enhanced the intestinal health by improving villus morphology and microbial structure as indicated by higher cecal microbial richness and Firmicutes to Bacteroidetes ratio, while lower abundance of Enterobacteriaceae (P < 0.05). In addition, birds fed with 500 mg/kg VC in the diet had significantly increased jejunal secretory immunoglobulin A levels, T lymphocytes stimulation index, and serum total antioxidant capability compared with groups without VC (P < 0.05). In conclusion, SE challenge induced lower production performance and higher mortality in broilers. However, dietary supplementation with VC ameliorated SE-caused damage in broilers by improving the intestinal health, partly mediated by shaping the structure of cecal microbiota.

Protection against salmonella typhimurium, salmonella gallinarum, and salmonella enteritidis infection in layer chickens conferred by a live attenuated salmonella typhimurium strain

In the present study, we investigated the protection conferred by a live attenuated Salmonella enterica serovar Typhimurium (ST) strain against Salmonella Typhimurium, Salmonella Gallinarum (SG), and Salmonella Enteritidis (SE) infection in layer chickens. Birds were orally primed with the attenuated ST strain at 7 days of age and then boosted at 4 weeks post prime immunization (PPI). Sequential monitoring of plasma IgG and mucosal secretory IgA (sIgA) levels revealed that inoculation with ST induced a significant antibody response to antigens against ST, SE, and SG. Moreover, significant lymphoproliferative responses to the 3 Salmonella serovars were observed in the immunized group. We also investigated protection against virulent ST, SE, and SG strain challenge. Upon virulent SG challenge, the immunized group showed significantly reduced mortality compared to the non-immunized group. The reduced persistence of the virulent ST and SE challenge strains in the liver, spleen, and cecal tissues of the immunized group suggests that immunization with the attenuated ST strain may not only protect against ST infection but can also confer cross protection against SE and SG infection.

Increased lymphocyte subpopulations and macrophages in the ovaries and oviducts of laying hens infected withSalmonella entericaserovar Enteritidis

Salmonella enterica serovar Enteritidis (SE) is a causative agent for human food poisoning cases throughout the world. The ovaries and the oviducts of the laying hens are the major sites of SE colonization from which vertical transmission to eggs occurs. In this study, Salmonella-induced changes in T lymphocytes, B lymphocytes and macrophages in the ovaries and oviducts were assessed after primary and secondary experimental inoculations of laying hen with SE. Statistically significant increases in the numbers of T cells (both CD4+ and CD8+) and macrophages were observed 7 to 14 days after primary inoculation, followed by a peak in B-cell numbers from the 14th day post-primary inoculation onwards in the secretory areas of the oviducts. The peak in lymphocyte numbers immediately preceded a decline in the rate of SE recovery from the reproductive tract beginning at day 14. The correlation of decreased Salmonella recovery with elevated lymphocyte and macrophage numbers strongly suggests that local cell-mediated immunity is involved in controlling SE injection in the ovaries and oviducts.

The effects of the BT/TAMUS 2032 cationic peptides on innate immunity and susceptibility of young chickens to extraintestinal Salmonella enterica serovar Enteritidis infection

The BT/TAMUS 2032 (BT) cationic peptides are a group of related cationic peptides produced by a Gram-positive bacterium. Cationic amphiphilic peptides have been found to stimulate or prime the innate immune responses in mammals. The innate immune system of poultry is functionally inefficient during the first week post-hatch enabling pathogens such as Salmonella enterica serovar Enteritidis (SE) to invade and colonize the visceral organs of these immature birds. The objective of the present study was to evaluate the effect of BT as an immunostimulator of the innate immune response of young chickens. BT, provided as a feed additive at three different concentrations (12, 24, or 48 ppm) for 4 days post-hatch, significantly increased protection against SE organ invasion in a concentration-dependent manner. The functional efficiency of heterophils, the avian equivalent to mammalian neutrophils, isolated from chickens fed the BT rations at the three concentrations was significantly up-regulated when compared to heterophils isolated from chickens fed a control starter ration as determined with an array of functional assays. Phagocytosis, oxidative burst, and degranulation were all significantly increased in a concentration-dependent manner in heterophils isolated from chickens fed the BT diets. This is the first report of bacterial cationic peptides inducing the up-regulation of the avian innate immune response and providing protection against extraintestinal Salmonella infections. The significance of these data is that the orally delivered cationic peptides stimulate the innate response at a time of immunologic inefficiency and increased susceptibility to bacterial infections (first week post-hatch). Because of the nonspecific nature of the innate response, we speculate that BT given as a feed additive during the first week post-hatch could provide increased protection against a variety of bacterial pathogens.

Salmonella carrier state in chicken: comparison of expression of immune response genes between susceptible and resistant animals

Asymptomatic Salmonella enterica serovar Enteritidis carrier state in poultry has serious consequences on food safety and public health due to the risks of food poisoning following consumption of contaminated products. An understanding the mechanisms of persistence of Salmonella in the digestive tract of chicken can be achieved by a better knowledge of the defects in the control of infection in susceptible versus resistant animals. The gene expression of innate immune response factors including anti-microbial molecules, inflammatory and anti-infectious cytokines was studied in the caecal lymphoid tissue associated with the carrier state. Expression levels of these genes were assessed by real-time PCR and were compared in two inbred lines of chickens differing in resistance to the carrier state following oral inoculation of S. enterica serovar Enteritidis at 1 week of age. No correlation was observed between resistance/susceptibility to caecal carrier state and level of interleukin (IL)-1beta, IL-8, IL-18, inducible NO synthase (iNOS) and natural resistance associated macrophage protein 1 (NRAMP1). A high baseline level of defensin gene expression was recorded in young animals from the susceptible line. In contrast, a significantly low expression of interferon-gamma (IFN-gamma) gene was observed in these susceptible infected animals in comparison to resistant ones and healthy counterparts. IFN-gamma expression level represents a valuable indication of immunodeficiency associated with persistence of Salmonella in the chicken digestive tract, and IFN-gamma thus represents a factor to consider in the development of prophylactic measures for the reduction of Salmonella carrier state.

rP33 activates bacterial killing by chicken peripheral blood heterophils

The protection of poultry from infection by Salmonella is of major concern with regard to human health because Salmonella is a common bacterial cause of foodborne diseases, and protection without the use of antibiotics is preferable in order to avoid possible complications involving antibiotic resistance. Salmonella immune lymphokine (SILK), produced by stimulated splenic T cells from Salmonella Enteritidis-immunized chickens, has been shown to confer protection against Salmonella infection on day-old chicks without the use of antibiotics. This protection results from the potentiation of an immune response following treatment with SILK. This study was undertaken to analyze a component of SILK, identified as P33, that is the product of the chicken mim-1 gene. A recombinant derivative expressing a domain of P33 (rP33) has been shown to be chemotactic for heterophils and is therefore instrumental in eliciting the immune response characteristic of SILK-induced protection against Salmonella infection in chicks. We report here that rP33 possesses the ability to activate antimicrobial responses from heterophils. The killing of Salmonella Enteritidis by heterophils was increased by in vitro treatment of the cells with rP33. Treatment with rP33 also stimulated the degranulation of heterophils but did not induce an oxidative burst or upregulate phagocytosis. These results indicate that P33 is an active component of SILK, conferring protection against Salmonella Enteritidis by augmenting the antimicrobial activities of heterophils.

Resistance to Velogenic Newcastle Disease Virus in Leghorn Chickens by Use of Prophylactic Lymphokines

A group of 1-day-old commercial leghorn chickens was prophylactically treated with lymphokines obtained from lymphocyte cultures of chickens previously infected with Salmonella enteritidis (S. enteritidis-immune lymphokines [SE-ILK]) with the objective to investigate the effect of SE-ILK on development of Newcastle disease (ND) infection caused by Chimalguacan strain, a Mexican velogenic ND virus (vNDV). Clinical signs, histologic lesions, and hemagglutination-inhibition (HI) serum titers were compared with four other groups, namely, chickens without SE-ILK treatment with virus challenge; with SE-ILK without virus challenge; with nonimmune lymphokine (NILK) treatment and virus challenge; with lymphokine treatment and no virus challenge. SE-ILK was administered intraperitoneally in a dose of 0.5 ml/chicken and was followed 30 min later with the challenge of vNDV in a dose of 10(7.6) 50% embryo lethal dose/ml per bird. Birds were observed during 21 days of postchallenge. Detection of histologic changes and virus isolation procedures were carried out on the third, seventh, 14th, and 21st postinoculation days. HI tests were performed first before treatment and later on the days of histologic sample collection except on the third postinoculation day. Results showed that SE-ILK administration conferred resistance to the chickens because: 1) it significantly diminished the severity of ND infection by inhibiting appearance of clinical signs (P < 0.001), lesions (P < 0.005), and histopathologic changes (P < 0.005); 2) it decreased vNDV isolation rate from the organs (P < 0.001), and 3) it potentialized and even accelerated (P < 0.005) primary immune response by antibodies in the presence of vNDV.

Dynamics of a protective avian inflammatory response: the role of an IL-8-like cytokine in the recruitment of heterophils to the site of organ invasion by Salmonella enteritidis

Increased resistance to Salmonella enteritidis (SE) organ infectivity in chickens can be conferred by the prophylactic administration of SE-immune lymphokines (ILK). Resistance is associated with an enhanced heterophilic accumulation within 4 h of ILK injection. In these studies, the role of IL-8 in ILK-mediated heterophil recruitment during SE infections in young chickens was investigated. Heterophil accumulation was enhanced 2-4 h after the i.p. injection of both ILK and SE (ILK/SE) when compared to the control chicks. An i.p. injection of a rabbit polyclonal anti-human IL-8 antibody significantly (P < 0.01) reduced the accumulation of heterophils in the peritoneum after the injection of ILK/SE. Injections of preimmune rabbit IgG had no effect on peritoneal heterophil numbers. Within 2 h of injection of ILK/SE, a ten-fold increase in heterophil chemotactic activity was found in the peritoneal lavage fluid from these chicks compared to the saline control chicks. Pretreatment, with the anti-IL-8 antibody, of the peritoneal lavage fluids collected from the ILK/SE-treated chicks dramatically reduced this heterophil chemotactic activity. Treatment of the lavage fluids from all groups with preimmune IgG had no effect on heterophil chemotaxis. Additionally, pretreatment of ILK with the anti-human IL-8 antibody had no effect on heterophil chemotaxis. The results from these experiments suggest that IL-8 is produced locally by the host in response to both the SE infection and the ILK. With these studies, it was established that IL-8 is a major chemotactic factor produced by the host, which aids in mediating the ILK/SE-induced recruitment of heterophils to the site of SE invasion.

Vaccines against the avian enteropathogens Eimeria, Cryptosporidium and Salmonella

The worldwide poultry industry provides a substantial proportion of the nutritional requirement of the human population. To keep pace with the increasing demand for the high-quality, low-cost protein source that poultry provides, intensive rearing practices have been developed within the past few decades. For example, chickens are housed routinely in crowded environments under adverse conditions, and genetic strains have been selected for rapid growth, high protein-to-fat content and superior egg-laying characteristics. A major negative consequence of these practices has been an increase in the incidence of diseases. Enteric diseases in particular have emerged as a major problem threatening the future viability of the poultry industry. A variety of methods have been used to combat avian diseases in the commercial setting, including improved farm management practices, the use of antibiotic drugs, the selection of disease-resistant strains of chickens, and the manipulation of the chicken's immune system. In the latter category, the development of vaccines against the major avian diseases has become a priority in the poultry industry. This review will highlight recent progress in vaccine development against three major avian enteric pathogens: Eimeria, Cryptosporidium and Salmonella.

Prophylactic administration of immune lymphokine derived from T cells of Salmonella enteritidis-immune pigs. Protection against Salmonella choleraesuis organ invasion and cecal colonization in weaned pigs

Experiments involving 132 weaned piglets were conducted to evaluate the efficacy of a Salmonella enteritidis-immune lymphokine (PILK) derived from the T cells of Salmonella enteritidis (SE)-immunized pigs to protect weaned piglets from Salmonella choleraesuis (SC) infection. Fourteen-to-seventeen day-old piglets were weaned and randomly placed into 1 of 5 groups: (1) noninfected controls, (2) PILK 3X noninfected, (3) SC infected controls, (4) PILK 1X SC infected, and (5) PILK 3X SC infected. PILK was given orally either one time (PILK 1X) or three times (PILK 3X) over 14 days. One hour after the first PILK administration on day 0, piglets were orally challenged with 10(7) cfu of SC. Weights were recorded on day 0, day 7, and day 14. On day 14, pigs in groups 3, 4, and 5 were sacrificed and organs and lymph tissue were cultured for the presence of SC. Three replicates of this experiment were pooled and anlayzed. A significant reduction in the number of pigs positive for SC in the liver, lung, and spleen was found in group 5 (PILK 3X) when compared to group 3 (inf. cont. p < 0.001[). The number of SC positive cecal contents was dramatically reduced in group 5 group when compared to group 3, with the PILK 3X group showing 13% positive pigs versus 55.2% in the infected controls (p < 0.05). Weight gain over the 14 day study in the infected PILK 3X group (group 5) was found to be comparable to the gain observed in the group 1 (noninfected controls). The pigs receiving PILK 3X (group 2) with no SC challenge gained significantly more weight than all other groups, including the noninfected controls (group 1 p < 0.05[). The results of these experiments indicate that PILK protects against SC infection in weaned pigs while enhancing performance in the presence of an SC infection.

Enhancement of phagocytosis and bacterial killing by heterophils from neonatal chicks after administration of Salmonella enteritidis-immune lymphokines

During the first week post-hatch, chickens demonstrate an increased susceptibility to infection by bacteria such as Salmonella. The purpose of the present study was to evaluate the effects of immune lymphokines on phagocytosis and killing activities of heterophils in chicks during the first 1-7 days of life. Lymphokines isolated from chicken splenic T-cells harvested from Salmonella enteriditis (SE)-hyperimmunized hens (SE-ILK), have in past experiments, demonstrated augmentation of heterophil activity in day-of-hatch chicks resulting in protection from SE organ invasion. The present experiments reveal significant increases (p<0.05) in heterophil phagocytosis and killing when comparing chicks treated with SE-ILK to control groups in vitro. In SE-ILK-treated groups, a two-fold or greater increase is noted in heterophil phagocytosis within I h of incubation as compared to controls. Heterophils isolated from 1-day-old and 4-day-old chicks treated with SE-ILK killed significantly greater numbers (p<0.05) of SE than heterophils isolated from control groups. By Day 7 post-hatch, significance is not noted in the killing activity of heterophils from treated groups when compared to control groups. However, heterophils from SE-ILK groups continue to kill greater numbers of SE than control groups. These data support SE-ILK augmentation results in an enhanced heterophil function in chicks during the greatest period of susceptibility to Salmonella invasion.

T lymphocytes, B lymphocytes, and macrophages in the ovaries and oviducts of laying hens experimentally infected with Salmonella enteritidis

Subsets of T lymphocytes, B lymphocytes, and macrophages in the ovaries and oviducts of laying hens were enumerated by immunohistochemistry after intravenous inoculation with Salmonella enteritidis. Almost all T cell subsets in the ovaries and different regions of the oviduct increased in number at 7 days post-inoculation and reached a peak by day 10. This T cell surge was followed by a peak in B cell numbers at day 14. The number of macrophages declined initially but recovered to preinoculation levels by day 21. At day 21, the numbers of T and B cells also returned to normal levels, except for IgG+ B cells in the infundibulum, isthmus, and vagina where they remained consistently elevated. The T and B cell proliferation at 10-14 days post-inoculation immediately preceded a decline in the number of S. enteritidis positive tissues from infected hens beginning at day 14 suggesting that these lymphocytes play a major role in the local immune response to S. enteritidis. The Salmonella-oviduct model will be useful for future studies on local immunity to various infectious agents.

Lymphokine-augmented activation of avian heterophils

Heterophils are important mediators of innate resistance in poultry, especially in young birds that have not yet developed an acquired immune response. Invasion of the intestinal mucosa by Salmonella spp. initiates the recruitment of large numbers of heterophils to the lamina propria. Thus, the heterophilic response can control, but not eliminate, bacterial numbers in the bird until development of acquired immunity. Unfortunately, chicks and turkey poults are highly susceptible to Salmonella infections during the first 4 d posthatch due to the functional immaturity of both the innate and acquired immune systems. We have previously shown that the administration of Salmonella enteritidis (SE)-immune lymphokines (ILK) into either 18-d-old developing embryos or day-of-hatch chicks and poults conferred increased resistance to SE organ invasion. In this review, we present evidence that the protection induced by ILK is mediated by vigorous recruitment and activation of heterophils. These activated heterophils migrate rapidly to the site of bacterial invasion where they phagocytize and kill the SE. Specifically, in vitro studies demonstrate an enhancement of functional activities of the heterophils including chemotaxis, adherence, phagocytosis, and bacterial killing. In addition, during the activation process, membrane expression of adhesion molecules rapidly changes from L-selectins to beta2 integrins (CB11b/CD18) on the cells that become activated. These results further demonstrate the validity of preventive activation in poultry to induce the migration of large numbers of activated phagocytic cells to the site of infection by a pathogenic organism. Importantly, this immunopotentiation of the inflammatory response by ILK, as described here, induces the functional maturation of heterophils during the first 4 d posthatch.

Ontogeny of the phagocytic and bactericidal activities of turkey heterophils and their potentiation by Salmonella enteritidis-immune lymphokines

Heterophils, the functional equivalent to the mammalian neutrophil, are important mediators of natural resistance against invasive pathogens in poultry. Young poultry are susceptible to pathogens, such as Salmonella enteritidis, during the first week post-hatch. No studies have evaluated the ontogeny of heterophil function in turkeys during the first few weeks post-hatch. Previous studies from our laboratory have shown day-old poults were protected against S. enteritidis organ invasion following immunoprophylactic administration of chicken S. enteritidis immune lymphokines. Therefore, the objective in the present study was to characterize the development of phagocytosis and bacterial killing by turkey heterophils during the first 3 weeks of life and to compare the effect of immune lymphokines on the development of heterophil phagocytosis and killing during the first 3 weeks post-hatch. Both functional phagocytosis and killing activities were age-dependent events. During the first 1-7 days post-hatch, little functional activity was demonstrated which apparently is associated with susceptibility. Optimal heterophil phagocytosis and killing activities were reached 14-21 days post-hatch. Administration immune lymphokines significantly potentiated phagocytosis (P < 0.01) and killing (P < 0.001) by turkey heterophils. In fact, immune lymphokine administration to 1-7-day-old poults augmented phagocytosis and killing activities of heterophils equivalent to levels found in functionally mature 14-21-day-old poults. These results demonstrate the ontogeny of the functional activity of the turkey heterophil is an age-related phenomenon, with inefficient phagocytosis and killing during the first week post-hatch. Prophylactic administration of immune lymphokines significantly potentiated the functional activity of the heterophil poults during the first 3 weeks of life. Most importantly the administration of immune lymphokines enhanced the functional activity of heterophils from 1-7-day-old poults to levels comparable to that of an immunologically mature bird.

Neutralization of G-CSF inhibits ILK-induced heterophil influx: granulocyte-colony stimulating factor mediates the Salmonella enteritidis-immune lymphokine potentiation of the acute avian inflammatory response

Hematopoietic colony stimulating factors (CSF) regulate the growth and development of phagocytic cell progenitors and also augment functional activation of phagocytes. Granulocyte-CSF (G-CSF) is the CSF that acts specifically upon granulocyte progenitor cells and mature granulocytes. We have shown that lymphokines (ILK) from T cells of birds immunized against Salmonella enteritidis (SE) induce a granulocytic (PMN) inflammatory response in chicks challenged with SE. This inflammatory response was characterized by: (a) a dramatic emigration of granulocytic cells from the bone marrow into the peripheral blood, (b) an enhancement of the biological functions of the circulating PMNs, and (c) a directed influx of these activated PMNs to the site of bacterial invasion. In the current study, we determined the presence of G-CSF in ILK by Western blot analysis using a goat polyclonal antihuman G-CSF antibody (Ab). Using this Ab, we then evaluated the role of G-CSF in the ILK-induced protective inflammatory response in chickens against SE. Pretreatment of ILK with the Ab totally abolished the colony-stimulating activity of the ILK. Furthermore, Ab treatment of ILK resulted in: (a) an elimination of the ILK-induced peripheral blood heterophilia with a dramatic inhibition of ILK-mediated protection against SE organ invasion and (b) an elimination of accumulation of inflammatory PMNs in the peritoneum with subsequent decrease in the survival rate of chicks challenged i.p. with SE. Taken together these studies demonstrate for the first time the contribution of G-CSF to avian PMN activation and the immunoprophylaxis of SE infection by ILK in neonatal chickens.

Characterisation of colony-stimulating activity in the avian T cell-derived factor, Salmonella enteritidis-immune lymphokine

This investigation was designed to characterise the specific cytokine activity from the conditioned medium of concanavalin A-stimulated avian T cells derived from Salmonella enteritidis-immune chickens, S enteritidis-immune lymphokine (ILK). Studies were designed to determine first, whether colony-stimulating activity was present in ILK, second, the type(s) of colonies from the bone marrow that were supported in vitro by the potential colony-stimulating factors in ILK and, third, whether colony-stimulating activity was present in serum from chicks treated with ILK and challenged with S enteritidis, and to use physicochemical treatment as a means of identifying the potential colony-stimulating factor(s) in ILK. Both ILK alone and serum from chicks treated with ILK and challenged with S enteritidis caused significant increases in the number of colony-forming units (CFU) from the bone marrow in vitro. After 10 days of incubation, ILK alone supported the in vitro growth of granulocytic bone marrow colonies. The colony-stimulating activity from serum derived from chicks treated with ILK and challenged with S enteritidis peaked two hours after the challenge. When ILK was either heated at 100 degrees C or treated with trypsin or acid and then injected into chicks, all the chicks responded with significant increases in circulating polymorphonuclear leucocytes (PMNs). However, when assayed for in vitro colony-stimulating activity, only trypsinisation destroyed the activity in ILK. The results indicate that a colony-stimulating factor which preferentially supported the growth of granulocytic bone marrow colonies was present in ILK and that the factor was stable to heat and acid but sensitive to trypsin.

Interaction of dexamethasone and Salmonella enteritidis immune lymphokines on Salmonella enteritidis organ invasion and in vitro polymorphonuclear leukocyte function

We used an anti-inflammatory dose of dexamethasone (DEX) and Salmonella enteritidis (SE)-immune lymphokines (ILK) followed by oral SE challenge to chicks to determine the effects of these treatments on SE organ invasion and in vitro function of PMNs derived from peripheral blood. Endpoints included percent protection against SE organ invasion, numbers of peripheral blood PMNs, and in vitro PMN adherence, chemotaxis, and SE killing. SE organ invasion was significantly reduced in chicks treated with either ILK alone or DEX + ILK compared to controls. Chicks treated with either DEX alone or DEX + ILK responded with a significant increase in numbers of peripheral blood PMNs as compared to controls, while numbers of PMNs in the peripheral blood from chicks treated with ILK alone were not significantly increased. PMN adherence and percent SE killing by PMNs derived from chicks treated with either ILK alone or DEX + ILK were significantly increased compared to controls. Chemotaxis of PMNs derived from chicks treated with either ILK alone or DEX alone significantly increased 2-fold over control levels. Interestingly, chemotaxis of PMNs derived from chicks that received DEX + ILK was similar to controls. Generally, ILK abated the anti-inflammatory effects of DEX on PMNs in these assays, except for chemotaxis. We interpret these data to suggest that ILK may confer protection to chicks against the early phase of SE organ invasion by inducing an inflammatory response predominated by activated PMNs.

In ovo administration of Salmonella enteritidis-immune lymphokines confers protection to neonatal chicks against Salmonella enteritidis organ infectivity

We previously reported that the prophylactic, intraperitoneal administration of supernatants from concanavalin A-stimulated T cells derived from Salmonella enteritidis (SE)-immune White Leghorn hens (i.e., SE-immune lymphokines or ILK), conferred protection to neonatal White Leghorn chicks against SE organ invasion. In the present study, we evaluated the effects of in ovo administration of ILK on hatchability, hatch weight, in vitro bactericidal activity of heterophils, and protection against SE organ invasion in neonatal White Leghorn chicks. On Day 18 of embryogenesis, injections were made into the amnion with either ILK or nonimmune ILK (NILK) or were not injected (untreated). On the day of hatch, whole blood was collected from 20 of the chicks per treatment group for heterophil isolation. All remaining chicks were orally challenged with 5 x 10(4) cfu SE. Twenty-four hours after SE challenge, organs (liver and spleen) from the chicks were cultured for SE. Hatchability of ILK- and NILK-treated chicks was not different from that of untreated chicks. Hatch weights of ILK-treated chicks were approximately 1 g less (P < .05) than that of NILK-treated or untreated chicks. In vitro bactericidal activity of peripheral blood heterophils derived from ILK-treated chicks was increased (P < .05) above activity from heterophils derived from NILK-treated or untreated chicks. Organ invasion with SE was markedly and significantly decreased in the ILK-treated chicks as compared with chicks treated with NILK or untreated chicks. These results suggest that in ovo administration of ILK confers protection to neonatal chicks against SE organ infectivity at hatch.

Characterization of the pattern of inflammatory cell influx in chicks following the intraperitoneal administration of live Salmonella enteritidis and Salmonella enteritidis-immune lymphokines

We characterized the inflammatory cell influx in day-old chicks induced by the i.p. administration of live Salmonella enteritidis (SE) and lymphokines from concanavalin A-stimulated SE-immune T lymphocytes (ILK). An i.p. injection of ILK along with 5 x 10(3) cfu SE increased the survival rate of chicks 48 h later from 70% (ILK-treated controls) compared with 25% (saline-treated). The injection of both the ILK and live SE (but not formalin-killed SE) resulted in an increased influx of inflammatory heterophils into the peritoneum that peaked at 4 h after the injections with no increase in peritoneal macrophages. The heterophil accumulation was not influenced by polymyxin B, but was sensitive to heat treatment (100 C for 1 h) of the ILK, suggesting that lipopolysaccharide (LPS) did not contribute to the induced accumulation of heterophils. Treatment of the chicks with nordihydroguaiaretic acid or indomethacin did not abrogate the induced heterophil accumulation, suggesting that arachidonic acid metabolites were not involved in the SE/ILK-induced accumulation of peritoneal heterophils. The results from the current studies indicate that 1) ILK-mediated resistance to SE-induced mortality is mediated by a rapid influx of inflammatory heterophils to the site of infection; 2) live SE, during invasion, are vital for the site-directed migration of the heterophils; and 3) the mechanisms of induced heterophil accumulation are unknown but involve neither LPS nor arachidonic acid metabolites.

Dynamics of avian inflammatory response to Salmonella-immune lymphokines. Changes in avian blood leukocyte populations

Investigations in our laboratories have indicated that an increased resistance to SE organ infectivity in chicks was conferred by the immunoprophylactic administration of SE-immune lymphokines (SE-ILK). This resistance was associated with an increase in the lamina propria thickness due to a marked infiltration of inflammatory polymorphonuclear cells (PMNs). In the present study, we determined whether the hematological profile of SE-ILK-treated chicks might reflect changes that are associated with the protection against organ invasion by SE. As protection has been observed in previous studies within 24 h of SE-ILK administration, we evaluated alterations in the circulating leukocyte profile in 1-day-old Leghorn chicks during this time period. We also determined whether the alterations in the peripheral blood leukocytes correlated with the increased protection against SE organ invasion induced by the SE-ILK. Within 4 h after an intraperitoneal injection of SE-ILK and challenge with SE, the number of circulating leukocytes increased significantly (P < 0.05) from all of the other treatment groups. The number of circulating PMNs was found to account for more than 80% of the increase in the number of circulating leukocytes. Using correlation analysis, we found a strong association between the number of circulating PMNs and the protection induced by SE-ILK against SE organ invasion. These studies associate the expansion of the available pool of circulating PMNs and the expression of innate resistance to organ invasion by SE.