Objective: Newcastle disease (ND) is the major viral infection of poultry inducing high morbidity, mortality, and significant economic impacts on the poultry industry. ND is caused by virulent strains of avian paramyxovirus serotype 1 (aPMV-1) which have the capacity to spread over long distances by animal and human movements. All strains of aPMV-1 belong to a single serotype and current vaccines have been used worldwide for a long time and demonstrated their efficacy in terms of clinical protection. Up to date vaccines have been made of old genotypes that emerged several decades ago. However, recent studies have shown that the virus has undergone significant evolution which has led to the progressive emergence of new genotypes with potential antigenic drifts. The recently described genotype XI in Madagascar contains original amino acid substitutions on F and HN proteins, some of them clustered in the head of the proteins, presumably exposed to the host immune system, suggesting that these substitutions may account for antigenic drifts. Indeed, we showed in vivo, under controlled conditions, that current vaccines conferred clinical protection against both the homologous genotype and genotype XI, but were unable to prevent virus shedding of heterologous genotype. Our objective was to produce genotype adapted vaccines, using reverse genetics to replace the F and HN of a live attenuated old-genotype virus (the genotype II Lasota strain) by the corresponding proteins of the more recent Madagascar genotype XI. This chimeric genotype XI-II will be characterized in vivo and evaluated in immunization/challenge trials. Methods: NDV minigenomes expressing eGFP under two promoters (pT7 polymerase and pCMV) have been constructed and compared in vitro. Subsequently, segments of the full genome of the genotype XI MG-725 strain and LaSota strain have been generated by reverse transcription, cloned and assembled under the control of CMV promoter. Rescue of the virus is done by co-t