Analyses using antibodies directed against α-synuclein play a key role in the understanding of the pathologies associated with neurodegenerative disorders such as Parkinson's disease (PD), dementia with Lewy bodies (DLB) and multiple system atrophy (MSA). However, the generation of antibodies against immunogens with significant sequence similarity to host proteins such as α-synuclein is often hindered by host immunotolerance. In contrast to wild-type C57BL/6J and BALB/c mice immunized with recombinant human α-synuclein, C57BL/6S Δsnca mice presenting a natural deletion of the α-synuclein locus, bypassed the immunotolerance process which resulted in a much higher polyclonal antibody response. The native or fibrillized conformation of α-synuclein used as the immunogen did not have an impact on the amounts of specific antibodies in sera of the host. The immunization protocols resulted in the generation of the IgG AS11, raised against fibrillized recombinant human α-synuclein in C57BL/6S Δsnca mice. This monoclonal antibody, recognizing an N-terminal α-synuclein epitope, was selected for its specificity and significant reactivity in Western-blot, immunofluorescence and immunohistochemistry assays. The ability of AS11 to detect both soluble and aggregated forms of α-synuclein present in pathological cytoplasmic inclusions was further assessed using analysis of human brains with PD or MSA, transgenic mouse lines expressing A53T human α-synuclein, and cellular models expressing human α-synuclein. Taken together, our study indicates that novel antibodies helpful to characterize alterations of α-synuclein leading to neurodegeneration in PD and related disorders could be efficiently developed using this original immunization strategy.