The DEISA Consortium operates the Distributed European Infrastructure for Supercomputing Applications. DEISA aims at delivering a turnkey operational solution for a future persistent European HPC ecosystem, as suggested by the European Strategy Forum on Research Infrastructures (ESFRI). The ecosystem will integrate national supercomputer centres (Tier-1), and leadership-class European HPC centres (Tier-0), as planned by the Partnership for Advanced Computing in Europe (PRACE). By joining DEISA, CEA will become an integrated part of the European HPC infrastructure, and DEISA is enhancing the European HPC ecosystem by completing their members with a future Tier-0 HPC centre. This partnership is strengthening the efforts and synergies of DEISA and CEA in their engagements for the advancement of computational sciences in a European HPC infrastructure, and will tighten the integration of the HPC user communities at European level. Collaborations are envisaged at various levels. These will address both technical issues as well as the HPC support for scientific communities and potentially pilot industry projects. Benefits and synergies are expected through the usage of the DEISA service structures. The collaboration is especially valued since CEA is a PRACE Principal Partner and candidate to hosting one of the future leadership class Tier-0 supercomputer systems in a European HPC ecosystem.