7th Conference on Retroviruses and Opportunistic Infections San Francisco, CA - January 30 -February 4, 2000

Conf Retroviruses Opportunistic Infect 2000 Jan 30-Feb 2; 7:157 (abstract no. 432)

Gardner J, Frolov I, Ji Y, Perri S, Belli B, Driver D, Sherrill S, Liu M, Dubensky T, Polo J; Chiron Corp., Emeryville, CA.

Dendritic cells (DCs) are the most potent antigen presenting cell population and play a pivotal role in eliciting the humoral and cellular immune responses central to successful vaccination. We have developed alphavirus-based replicon particles for efficient gene delivery to human DCs, using the prototype alphavirus, Sindbis virus (SIN). This system provides an exciting platform for genetic immunization with high-level transient expression of antigens. In addition, the availability of stable packaging cell lines makes these vector particles amenable to production in sufficient quantities for clinical testing. SIN variants that efficiently transduced immature human DCs derived from peripheral blood monocytes in vitro were isolated and the specific mutations responsible for DC tropism were mapped to the E2 envelope glycoprotein gene. Generation of SIN-GFP reporter vector particles packaged with the variant E2 glycoproteins permitted detailed characterization of the cell population susceptible to infection. In the hematopoietic lineage, only immature DCs could be infected, with up to 30-50% of cells transduced routinely at relatively low multiplicities of infection. Mature DC, as well as T cells, B cells, monocytes and NK-cells, were refractory to infection, even at high multiplicities of infection (>100). Costimulatory (CD80, CD86) and MHC molecules were upregulated on transduced immature DCs, emphasizing the natural adjuvant activity of the SIN vector particles. To confirm the DC-tropic phenotype in vivo, SIN-GFP vector particles were inoculated intradermally into mice. Laser scanning cytometric analysis of the draining lymph node at 24 hours post-injection demonstrated the presence of GFP expressing cells that exhibited dendritic morphology. This novel system represents a highly efficient modality for targeted gene delivery to DCs and should facilitate the development of potent vaccines for a variety of human diseases, including HCV and HIV.

2000-01-30
432

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