Is Prime Boost Strategy a Promising Approach in HIV Vaccine Development?

HIV prevention strategies to reduce the spread of HIV remain a global public health priority. An effective HIV vaccine, if available, would have several advantages over behavioral and other biological prevention strategies as it would not need sustained behavior changes as well as strict adherence for the efficacy, in addition to probably providing long term protection. Although inactivated and live attenuated vaccines are being effectively used for other viral infections, they are not being considered favorably in case of HIV because of safety concerns. Hence most of the efforts towards HIV vaccine development have been focused on newer strategies such as synthetic envelope protein subunits or recombinant viral vectors carrying HIV-specific inserts or naked DNA [1]. Although most of these vaccine candidates have failed to elicit effective immune responses when used alone [2,3], their combined use has been shown to strengthen and broaden HIVspecific immune responses [4-6]. Such a combination strategy is known as prime-boost strategy where the immune system primed by one vaccine candidate is boosted with either the same (homologous) or a different (heterologous) vaccine candidate.