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IMMUNOLOGY, HEALTH, AND DISEASE: Research Note |

* Animal Parasitic Diseases Laboratory, Animal and Natural Resources Institute, USDA-ARS, Beltsville, MD 20705; and
Imagilin Technology LLC, Frederick, MD 21701
1 Corresponding author: hlilleho{at}anri.barc.usda.gov
| ABSTRACT |
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Key Words: Pediococcus probiotic coccidiosis broiler antibody
| INTRODUCTION |
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Recent evidence that various dietary and microbial supplements can influence host immunity against enteric diseases prompted us to investigate the role of a commercial probiotic (MitoGrow, Imagilin Technology LLC) on coccidiosis. This probiotic consists of live Pediococcus acidilactici, which belongs to the homofermentative gram-positive bacteria, able to grow in a wide range of pH, temperatures, and osmotic pressures, and thus able to colonize and inhabit the digestive tract (Klaenhammer, 1993). Some commercial bacteria have been found to enhance development of both the intestinal epithelia and the gastrointestinal lymphoid system (Falk et al., 1998; Umesaki and Setoyama, 2000). A balanced microbial population would support the inherent defense mechanisms of a healthy intestinal tract, resulting in better control of intestinal pathogens (Pollmann et al., 2005). Pediococci exert antagonism against other microorganisms, including enteric pathogens, primarily through the production of lactic acid and secretion of bacteriocins known as pediocins (Daeschel and Klaenhammer, 1985). Guerra et al. (2006) suggested that the nonpathogenic and nontoxic bacterium Pediococcus acidilactici induces healthy intestinal conditions in pigs. We hypothesized that Mito-Grow, containing P. acidilactici, may interfere with the pathogen infection sites, produce antimicrobial peptides, or induce host immune responses, thus enhancing its resistance to enteric pathogens like Eimeria. In the present work, 2 trials were conducted to investigate the potential protective effects of the probiotic MitoGrow in broiler chickens experimentally infected with Eimeria acervulina or Eimeria tenella.
| MATERIALS AND METHODS |
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Experiment 2.
In the second trial, 120 day-old broilers were randomly assigned to 12 pens (n = 10/pen) of an electrically heated battery and were equally assigned to 1 of 3 experimental diets (4 pens/diet group): REG, MG 0.1, or MG 0.2, as above. At 12 d of age, half of the birds from each diet group (n = 20) were then orally inoculated with 5,000 E. tenella-sporulated oocysts, and 10 birds from each treatment were placed at 2 birds/cage (5 cages/treatment) as above. In addition to measuring weight gains and oocyst shedding (6 to 10 dpi), serum samples were collected 10 dpi, and Eimeria-specific antibody (Ab) titers were determined by ELISA.
All diets were formulated to meet or exceed the nutrient requirements for broilers as recommended by the NRC (1994). Feed was provided ad libitum, and the animal trials were performed according to the guidelines established by the Beltsville Area Institutional Animal Care and Use Committee.
Oocyst Shedding
Oocyst shedding was assessed as described by Dalloul et al. (2002). Briefly, droppings from 10 birds in 5 cages (2 birds/cage) were collected for 4 to 5 d starting on 6 dpi, fecal material was ground and homogenized, and two 35-mL samples were taken, diluted, and the oocysts were counted microscopically using a McMaster counting chamber. The total number of oocysts was calculated using the following formula: total oocysts/bird = oocyst count x dilution factor x (fecal sample volume/counting chamber volume)/number of birds per cage.
ELISA for Serum Ab Levels
Blood samples were obtained 10 dpi from individual birds (n = 3/group), allowed to clot for 4 to 5 h at 4°C, and the sera were collected. Serum samples were tested for Eimeria-specific Ab levels using ELISA, as described (Dalloul et al., 2003). Briefly, a microtiter plate was coated overnight with 10 µg/well of the recombinant coccidial antigen, EtMIC2. The plate was washed with PBS-0.05% Tween and blocked with PBS-1% BSA. Serum dilutions (1:16; 100 µL/well) were added, incubated with continuous gentle shaking, washed with PBS-0.05% Tween, and bound Ab detected with peroxidase-conjugated rabbit anti-chicken IgG (Sigma-Aldrich, St. Louis, MO) and peroxidase-specific substrates. Optical density was determined with a microplate reader (BioRad, Richmond, CA) at 450 nm.
Statistical Analyses
Mean values for BW gains, fecal oocyst shedding, and Ab titers were compared by the Tukey-Kramer multiple comparisons test following ANOVA, using InStat software (GraphPad, San Diego, CA). Differences between means were considered significant at P < 0.05.
| RESULTS |
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| DISCUSSION |
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In earlier work, Dalloul et al. (2003) reported that administration of a Lactobacillus-based probiotic induced protective immunity against E. acervulina infection. Some strains of Pediococcus species produce antimicrobial peptides (bacteriocins) that inhibit closely related lactic acid bacteria and other gram-positive spoilage and pathogenic bacteria (Klaenhammer, 1993; Ennahar and Deschamps, 2000). These bacteriocins are designated pediocins, and they have been shown to exert high antimicrobial activity against Listeria species (Ennahar et al., 2000). Pediococcus acidilactici is reported as a nonpathogenic and nontoxic bacterium inducing healthy intestinal conditions in pigs (Guerra et al., 2006). In the current study, we showed for the first time that MitoGrow consisting of live P. acidilactici bacteria provided some degree of defense against E. acervulina and E. tenella infections in broiler chickens.
The microneme protein EtMIC2 was cloned from E. tenella (Tomley et al., 1996; Lillehoj and Lillehoj, 2000; Dalloul et al., 2005). Additionally, EtMIC2 represents 1 of nearly 30 Eimeria genes that have been cloned and characterized at the molecular level (Allen and Fetterer, 2002). Eimeria-specific antibodies to EtMIC2 antigen were significantly (P < 0.05) higher in chickens fed the MitoGrow diets in E. tenella-infected birds. The role of parasite-specific antibodies has been extensively studied in coccidiosis (Lillehoj and Ruff, 1987; Fayer and Jenkins, 1992; Dalloul et al., 2005). Although humoral immunity to coccidiosis seems to play a minor function (Dalloul and Lillehoj, 2005, 2006), Eimeria infections trigger a significant specific Ab immune response in serum (Dalloul et al., 2005), and immunoglobulins could have a contributory function in the defense of the host against Eimeria (Wakelin and Rose, 1990; Lillehoj and Trout, 1996). Eimeria tenella-infected birds fed Mito-Grow produced more parasite-specific antibodies in the circulation, and these Ab-mediated responses may play a more protective role against a secondary E. tenella infection than a single inoculation, as was the case in the present work.
In conclusion, these results demonstrate that a P. acidilactici-based probiotic (MitoGrow) enhances the resistance of birds and partially protects against coccidiosis. However, the mechanistic details mediating such protection are not fully understood and remain to be clarified, especially in light of the wide array of immune cells activated by probiotic bacteria. In particular, analysis of the different cytokines and chemokines induced by feeding MitoGrow will provide valuable new information on its protective immunity to coccidiosis. Also, the exact modes of action of this probiotic and its activity against different species of Eimeria such as Eimeria maxima need to be explored in future work.
| ACKNOWLEDGMENTS |
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Received for publication May 16, 2006. Accepted for publication August 26, 2006.
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