RESUMEN
To reduce the embryonic pathogenicity of Newcastle disease virus (NDV), escape mutants of the La Sota strain were produced with selected monoclonal antibodies. Immunoselection resulted in the elimination of an epitope by single amino acid substitution (F and HN molecule) or in a conformational change (HN molecule). The embryonic pathogenicity of these escape mutants was reduced and their dose was optimised for in ovo vaccination. Because antibody responses and protection of in ovo vaccinated chicks were similar to controls vaccinated at hatch with the La Sota strain, immunoselection appears a valuable technique to produce attenuated NDV strains, which are candidate in ovo vaccines.
Asunto(s)
Anticuerpos Antivirales/sangre , Embrión de Pollo/inmunología , Pollos/inmunología , Mutación , Enfermedad de Newcastle/prevención & control , Virus de la Enfermedad de Newcastle/inmunología , Vacunas Virales/inmunología , Animales , Embrión de Pollo/virología , Epítopos/genética , Epítopos/inmunología , Genes Virales , Proteína HN/análisis , Proteína HN/genética , Proteína HN/inmunología , Pruebas de Inhibición de Hemaglutinación , Inmunoglobulina G/sangre , Inmunoglobulina M/sangre , Datos de Secuencia Molecular , Virus de la Enfermedad de Newcastle/genética , Virus de la Enfermedad de Newcastle/patogenicidad , Análisis de Secuencia de ADN , Organismos Libres de Patógenos Específicos , Vacunas Atenuadas/administración & dosificación , Vacunas Atenuadas/inmunología , Vacunas Atenuadas/aislamiento & purificación , Proteínas Virales de Fusión/genética , Proteínas Virales de Fusión/inmunología , Vacunas Virales/administración & dosificación , Vacunas Virales/aislamiento & purificaciónRESUMEN
The sequences of the L1 loop of the hexon protein from representative fowl adenovirus (FAdV) strains of the different European and American collections were determined and compared. This study highlighted the lack of consensus in the numbering of the individual serotypes between the American and the European classifications. An identification system is proposed based on restriction fragment length polymorphism of the hexonA/hexonB polymerase chain reaction product. In addition, new insights into the relationships among FAdV strains are presented and discussed on the basis of phylogenetic analysis of the L1 loops sequences. Six clusters of strains that are supported by high bootstrap values were identified. Three of them are clearly independent, forming groups A, B and C, whereas the three others are clustered in a single 'supergroup', denominated D. Interestingly, the Japanese strain TR22 that is presently classified as European type 5 (species B) could not be assigned to any of the aforementioned clusters and might therefore constitute the sole representative of a seventh cluster.