The present invention concerns a method for functional inactivation of endogenous erythropoietin (EPO) in a subject comprising the step of (a) co-administrating to said subject at least one agent and at least one erythropoietin protein or derivative, or at least one nucleic acid sequence encoding said erythropoietin protein or derivative, said agent being administrated simultaneously, sequentially or separately with said erythropoietin protein or derivative, or nucleic acid sequence encoding said erythropoietin protein or derivative, wherein said at least one agent and at least one erythropoietin protein or derivative, or at least one nucleic acid sequence encoding said erythropoietin protein or derivative are administrated in an effective amount for triggering the production of neutralizing antibodies against the endogenous erythropoietin (EPO) in said subject; a non human vertebrate which can be obtained by said method and a neutralizing antibody directed against erythropoietin isolated from said subject.