A method for obtaining an immunogenic and non-hemolytic Actinobacillus pleuropneumoniae strain, from a virulent App strain, characterized in that it comprises the step of modifying at least one segment encoding a transmembrane domain of the apxIA gene and possibly a segment encoding a domain transmembrane of the apxIIA gene, in which the segment encoding a transmembrane domain of the apxIA gene corresponds to nucleotides 697 to 759, or nucleotides 886 to 945, or nucleotides 1105 to 1215, in which the segment encoding a transmembrane domain of the gene apxIIA corresponds to nucleotides 697 to 759, or nucleotides 886 to 945, or nucleotides 1105 to 1215, in which the segment of the gene's transmembrane domain is modified by substitution or by insertion of one or more nucleotides, or by partial or total deletion of a segment of the gene, either by chemically induced or radiation-induced mutagenesis disruption, and in which the modification does not exceed the transmembrane domains of the apxIA and apxIIA genes.Un método para obtener una cepa de Actinobacillus pleuropneumoniae inmunógena y no hemolítica, a partir de una cepa virulenta de App, caracterizado porque comprende la etapa de modificar al menos un segmento que codifica un dominio transmembrana del gen apxIA y eventualmente un segmento que codifica un dominio transmembrana del gen apxIIA, en el que el segmento que codifica un dominio transmembrana del gen apxIA corresponde a los nucleótidos 697 a 759, o nucleótidos 886 a 945, o nucleótidos 1105 a 1215, en el que el segmento que codifica un dominio transmembrana del gen apxIIA corresponde a los nucleótidos 697 a 759, o nucleótidos 886 a 945, o nucleótidos 1105 a 1215, en el que el segmento del dominio transmembrana del gen se modifica por sustitución o por inserción de uno o varios nucleótidos, o por deleción parcial o total de un segmento del gen, o bien mediante la disrupción por mutagénesis inducida químicamente o inducida por radiación, y en el que la modifica
