Induction of humoral immune response and protective immunity in chickens against Salmonella enteritidis after a single dose of killed bacterium-loaded microspheres.
Formalin-inactivated Salmonella enteritidis phage type 4 strain 119/95 (SE) was encapsulated in biodegradable poly (DL-lactide co-glycolic acid) PLGA; (65:35) microspheres by a modified water-in-oil-in-water (w/o/w) double-emulsion solvent extraction/evaporation technique. These SE-loaded microspheres (SE-MS) were porous and spherical in shape with diameters of 0.4-10 microm and 20-80 microm in two preparations. SE-MS were subsequently used to vaccinate specific-pathogen-free chickens in a single dose in order to investigate the potency of a single-dose vaccination in inducing immune responses and protective immunity. In Experiment 1, 4-wk-old chickens that were vaccinated intramuscularly with 20-80-microm SE-MS generated long lasting (over 6 mo) and persistently high serum anti-SE immunoglobulin (Ig)G antibody response. In Experiment 2, 2-wk-old chickens were vaccinated orally with 0.4-10-microm or intramuscularly with 20-80-microm SE-MS and challenged with 10(9) colony-forming units of homologous SE strain at 6 wk postvaccination. When challenged intramuscularly, one each of the orally vaccinated (n = 10) and the intramuscularly vaccinated birds (n = 10) showed clinical signs and death, whereas all of the nonvaccinated control birds (n = 12) were sick and 11 of them were killed. When challenge was via oral route, 26.1% of cloacal swabs and 24.0% of organs (liver, spleen, and cecum) collected from orally vaccinated birds (n = 35) were positive for SE, comparable to 27.9% of feces and 18.7% of organs from the intramuscularly vaccinated birds (n = 35). These figures were significantly lower than those for nonvaccinated birds (n = 30) from which 59.3% of feces and 44.0% of organs tested SE positive (P < 0.05). The humoral immune response was also determined after vaccination with a single dose. The intramuscular vaccination elicited higher serum IgG response than oral administration, but the latter elicited a significant intestinal mucosal IgA antibody response. This is the first evidence that chickens vaccinated with killed SE-loaded PLGA microspheres, intramuscularly and orally in a single dose, developed systematic and local immune responses, thereby conferring protective immunity.
Liu
W
W
Institute of Molecular Agrobiology, The National University of Singapore, Singapore.
Yang
Y
Y
Chung
N
N
Kwang
J
J
D000284:Administration, Oral; D000818:Animals; D000907:Antibodies, Bacterial / Q000032:analysis / Q000096:biosynthesis*; D002645:Chickens; D005243:Feces / Q000382:microbiology; D007071:Immunoglobulin A, Secretory / Q000032:analysis / Q000096:biosynthesis; D007074:Immunoglobulin G / Q000096:biosynthesis / Q000097:blood; D007273:Injections, Intramuscular / Q000662:veterinary; D008855:Microscopy, Electron, Scanning / Q000662:veterinary; D008863:Microspheres; D009928:Organ Specificity; D011201:Poultry Diseases / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D012481:Salmonella Infections, Animal / Q000276:immunology / Q000382:microbiology / Q000517:prevention & control*; D012483:Salmonella Phages; D022562:Salmonella Vaccines / Q000008:administration & dosage* / Q000276:immunology; D012477:Salmonella enteritidis / Q000276:immunology* / Q000648:ultrastructure; D013047:Specific Pathogen-Free Organisms; D016019:Survival Analysis; D013997:Time Factors
D000907:Antibodies, Bacterial; D007071:Immunoglobulin A, Secretory; D007074:Immunoglobulin G; D022562:Salmonella Vaccines