title: Diatoms and diatomaceous earth as novel poultry vaccine adjuvants.
abstract: Diatoms are single cell eukaryotic microalgae; their surface possesses a porous nanostructured silica cell wall or frustule. Diatomaceous earth (DE) or diatomite is a natural siliceous sediment of diatoms. Since silica has been proved to have adjuvant capabilities, we propose that diatoms and DE may provide an inexpensive and abundant source of adjuvant readily available to use in livestock vaccines.In a first experiment, the safety of diatoms used as an adjuvant for in-ovo vaccination was investigated. In a second experiment, we assessed the humoral immune response after one in-ovo vaccination with inactivated Newcastle Disease Virus (NDV) and DE as adjuvant followed by 2 subcutaneous boosters on d 21 and 29 of age. In both experiments, results were compared to Freund's incomplete adjuvant and aluminum hydroxide.No detrimental effects on hatchability and chick quality were detected after in-ovo inoculation of diatoms and DE in experiments 1 and 2 respectively. In experiment 2 no humoral responses were detected after the in-ovo vaccination until 29 d of age. Seven d after the second subcutaneous booster an antibody response against NDV was detected in chickens that had received vaccines adjuvanted with Freund's incomplete adjuvant, aluminum hydroxide, and DE. These responses became significantly higher 10 d after the second booster. Finally, 15 d after the second booster, the humoral responses induced by the vaccine with Freund's incomplete adjuvant were statistically higher, followed by comparable responses induced by vaccines containing DE or aluminum hydroxide that were significantly higher than DE+PBS, PBS+INDV and PBS alone. From an applied perspective, we can propose that DE can serve as a potential adjuvant for vaccines against poultry diseases.
authors.affiliation: Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Dr. VM3B, Davis, CA 95616.
authors.forename: A
authors.initials: A
authors.lastname: Nazmi
authors.affiliation: Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Dr. VM3B, Davis, CA 95616.
authors.forename: R
authors.initials: R
authors.lastname: Hauck
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093.
authors.forename: A
authors.initials: A
authors.lastname: Davis
authors.affiliation: Scripps Institution of Oceanography, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093.
authors.forename: M
authors.initials: M
authors.lastname: Hildebrand
authors.affiliation: Department of Pathology, School of Medicine, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093.
authors.forename: L B
authors.initials: LB
authors.lastname: Corbeil
authors.affiliation: Department of Population Health and Reproduction, School of Veterinary Medicine, University of California, Davis, 1089 Veterinary Medicine Dr. VM3B, Davis, CA 95616 ragallardo@ucdavis.edu.
authors.forename: R A
authors.initials: RA
authors.lastname: Gallardo
mesh_terms: D000276:Adjuvants, Immunologic / Q000494:pharmacology; D000818:Animals; D002642:Chick Embryo / Q000187:drug effects; D002645:Chickens; D007692:Diatomaceous Earth / Q000494:pharmacology*; D017377:Diatoms / Q000737:chemistry*; D056724:Immunity, Humoral / Q000187:drug effects; D007117:Immunization, Secondary / Q000662:veterinary; D007279:Injections, Subcutaneous; D009521:Newcastle Disease / Q000276:immunology*; D009522:Newcastle disease virus / Q000276:immunology*; D011201:Poultry Diseases / Q000276:immunology*; D015164:Vaccines, Inactivated / Q000276:immunology; D014765:Viral Vaccines / Q000276:immunology*
chemical_list: D000276:Adjuvants, Immunologic; D015164:Vaccines, Inactivated; D014765:Viral Vaccines; D007692:Diatomaceous Earth
keywords: Diatoms; adjuvants; diatomaceous earth; immune responses; in-ovo; vaccines