Effect of promoter strength on protein expression and immunogenicity of an HSV-1 amplicon vector encoding HIV-1 Gag

Abstract

Helper-free herpes simplex virus type-1 (HSV-1) amplicon vectors elicit robust immune responses to encoded proteins, including human immunodeficiency virus type-1 (HIV-1) antigens. To improve this vaccine delivery system, seven amplicon vectors were constructed, each encoding HIV-1 Gag under the control of a different promoter. Gag expression levels were analyzed in murine and human cell lines, as well as in biopsied tissue samples from injected mice; these data were then compared with Gag-specific T cell responses in BALB/c mice. The magnitude of the amplicon-induced immune response was found to correlate strongly with the level of Gag production both in vitro and in vivo. Interestingly, the best correlation of the strength of the amplicon-induced immune response was with antigen expression in cultured DC rather than expression at the tissue site of injection or in cultured cell lines. These findings may have implications for the generation of improved HSV-1 amplicon vectors for HIV-1 vaccine delivery.

HSV-1 amplicon vectors elicit polyfunctional T cell responses to HIV-1 Env, and strongly boost responses to an adenovirus prime

“…This was unexpected, since all of the promoters used are considered to be broadly and constitutively active. Amplicon vectors containing these promoters exhibit a relative hierarchy of antigen expression, as follows: cmvr > cmv > hsv [20]. However, the differences in antigen expression levels between the three promoters are generally modest in most cell types, except for primary dendritic cells [20]; thus, the relationship between antigen expression levels and immune response quality remains to be determined.…”

“…The construction of pHSV(hsv)gp120 has been described [19], as has the process of vector packaging [19,20] …”

“…HSV-1 amplicon vectors elicit potent immune responses to encoded HIV-1 antigens [19,20]. However, there is little available information on the overall quality of the amplicon-induced cellular immune response, and on the ability of amplicon vectors to effectively synergize with another viral immunization modality.…”

“…These advantages include (i) their ability to elicit strong cellular immune responses to encoded antigens [19][20][21], (ii) their broad host cell tropism and ability to directly transduce antigen presenting cells, including dendritic cells (DC), both in vivo and in vitro [21,22]; (iii) their favorable safety profile and lack of expression of virally-encoded immunomodulatory genes; and (iv) their very large transgene capacity (up to 150 kb) [23,24].…”

“…Our laboratory has previously shown that a single injection of a helper-free HSV-1 amplicon vector can elicit potent [19,20] and durable [19] immune responses to an encoded HIV antigen even in the face of preexisting immunity to HSV [19]. While the magnitude of the cellular immune response elicited by amplicon vectors has been extensively studied, little is known about the quality of that response, or the effectiveness of heterologous prime-boost immunization regimens that combine amplicon vectors with another viral vaccine modality.…”