RESUMEN
Mycoplasma gallisepticum (MG) has become a common cause of conjunctivitis in free-living house finches (Carpodacus mexicanus) since its emergence in the early 1990s. To date, temporal and spatial genotypic variation in MG has been documented, but phenotypic variation in pathogenicity and immunogenicity has not been examined. House finches were inoculated with MG isolates Virginia (VA)1994, California (CA)2006, or North Carolina (NC)2006, which were cultured from free-living house finches with conjunctivitis in 1994, 2006, and 2006, respectively. Infection with NC2006 resulted in the most severe eye lesions, highest pathogen loads, and highest levels of pathogen-specific lachrymal and serum antibodies. Infection with CA2006 caused the least severe eye lesions, lowest pathogen load, and lowest levels of antibodies. A small number of birds in each group developed protracted, severe disease in spite of robust antibody responses, suggesting that immunopathology may contribute to the lesions. Immunoblot analyses indicated that isolates are antigenically similar; thus, there may be partial cross-protection if a house finch encounters two or more strains of MG throughout the course of its lifetime. This study provides evidence that MG strains or strain variants circulating in house finch populations vary in their ability to cause disease, induce antibody responses, and persist in the host.
Asunto(s)
Enfermedades de las Aves/inmunología , Enfermedades de las Aves/microbiología , Conjuntivitis Bacteriana/veterinaria , Pinzones/microbiología , Infecciones por Mycoplasma/veterinaria , Mycoplasma gallisepticum/inmunología , Mycoplasma gallisepticum/patogenicidad , Animales , Anticuerpos Antibacterianos/análisis , Anticuerpos Antibacterianos/sangre , Carga Bacteriana , Enfermedades de las Aves/patología , Conjuntivitis Bacteriana/inmunología , Conjuntivitis Bacteriana/microbiología , Conjuntivitis Bacteriana/patología , Genotipo , Infecciones por Mycoplasma/inmunología , Infecciones por Mycoplasma/microbiología , Infecciones por Mycoplasma/patología , Factores de TiempoRESUMEN
The IgA antibody response plays a vital role in mucosal immunity because it functions to neutralize pathogens at the mucosal surface and thus impedes attachment to underlying tissues. Although the importance of IgA in the mucosal immunity of galliform birds has been established, studies examining IgA-based immunity in passerine birds are lacking, perhaps due in part to the absence of reagents that can detect passerine IgA. A 469 base pair region of the house finch (Carpodacus mexicanus) IgA heavy chain was PCR-amplified from spleen cDNA and sequenced. The predicted amino acid sequence was found to share 55% and 46% identity with the IgA heavy chain of mallard (Anas platyrhynchos) and chicken (Gallus gallus), respectively. The heavy chain fragment was produced using a bacterial expression system and purified. Rabbit anti-sera were generated against the recombinant protein. The anti-sera reacted with a single house finch serum protein ( approximately 50-55kDa) in Western blot. The anti-sera were used to identify plasma cells in the Harderian gland and conjunctiva of house finches with conjunctivitis associated with Mycoplasma gallisepticum infection. The anti-sera were also utilized in an ELISA to detect M. gallisepticum-specific IgA antibodies in lachrymal samples of infected finches.
Asunto(s)
Anticuerpos Antiidiotipos/biosíntesis , Anticuerpos Antibacterianos/análisis , Pinzones/inmunología , Inmunoglobulina A Secretora/inmunología , Mycoplasma gallisepticum/inmunología , Secuencia de Aminoácidos , Animales , Especificidad de Anticuerpos , Secuencia de Bases , Enfermedades de las Aves/inmunología , Enfermedades de las Aves/microbiología , Pollos , Cartilla de ADN/genética , ADN Complementario/genética , Patos , Ensayo de Inmunoadsorción Enzimática , Pinzones/genética , Glándula de Harder/inmunología , Glándula de Harder/microbiología , Inmunidad Mucosa , Inmunoglobulina A Secretora/análisis , Inmunoglobulina A Secretora/genética , Inmunohistoquímica , Indicadores y Reactivos , Datos de Secuencia Molecular , Infecciones por Mycoplasma/inmunología , Infecciones por Mycoplasma/microbiología , Infecciones por Mycoplasma/veterinaria , Conejos , Homología de Secuencia de AminoácidoRESUMEN
A TaqMan-based real-time, quantitative polymerase chain reaction (qPCR) assay utilizing the mgc2 gene was developed to detect Mycoplasma gallisepticum in conjunctival swabs of experimentally infected house finches. The assay was demonstrated to be quantitative by the standard curve method with reproducible results within runs and between runs. The detection limit of the mgc2 assay was examined using two standards. The test had a detection limit of less than 14 copies per reaction when tested with a plasmid standard and less than 10 copies per reaction when tested with M. gallisepticum genomic DNA. All M. gallisepticum-negative birds (10 specific pathogen free chickens and 10 house finches) were negative by mgc2 qPCR assay. Existing evidence suggests that an important part of M. gallisepticum pathogenesis includes both its attachment to and invasion of host cells. Thus, our test also made use of rag-1 as an internal control gene. The rag-1 qPCR results showed that host cell quantity varied greatly between conjunctival samples. After inoculation, M. gallisepticum levels in the house finch conjunctiva increased over the 7-day period post infection. The bird with the most pronounced clinical conjunctivitis harboured the highest level of M. gallisepticum and the bird that did not develop conjunctivitis had very low numbers of M. gallisepticum. Thus, it appears that development of conjunctivitis may correlate with M. gallisepticum load.