Attempts by various research groups to elicit effective Th1 CD4+ and CD8+ T cell anti-brucellosis immune responses have resulted in the development of subunit (recombinant protein) vaccines [6-14] and DNA vaccines [15-20], however in terms of protective efficacy, subunit and DNA vaccines are still inferior to commercial live attenuated vaccines. The gene discussed is CD4; the disease is brucellosis.