Use of recombinant poxviruses to stimulate anti-melanoma T cell reactivity

Abstract

Human DC are receptive to infection by recombinant poxviruses encoding MAA genes and are capable of efficiently processing and presenting these MAA to cytotoxic T cells. The potential advantage of this approach is the ability to present specific antigen independent of the identification of the epitope or the MHC restriction element. This strategy may be useful for the identification of relevant epitopes for a diverse number of HLA alleles and for active immunization in patients.

Biased epitope selection by recombinant vaccinia-virus (rVV)-infected mature or immature dendritic cells

“…7,8,27 In particular, we observed that this strategy was more efficient than the exogenous pulsing of iDC with saturating levels of relevant epitope. 7,8 The reason for the enhanced efficiency remained unclear, and we postulated that the longer persistence of Ag on the surface of DC due to the prolonged production of antigenic molecules driven by the viral promoters might have been responsible. 8 Surprisingly, however, in the conduct of these studies we noted that rVV-infected DC had very little ability to stimulate generation of IFN-g production by several Agspecific T-cell clones studied (unpublished observation).…”

“…In average 36.473.9% of iDC and 34.073.2% of mDC demonstrated expression of gp100 (Figure 1c), a figure similar to our previous experience using this infection protocol. 8 Cells demonstrating evidence of gp100 expression were separately gated and assessed for intensity of expression of the melanoma Ag. No significant differences were noted in intensity of gp100 expression between iDC and mDC (Figure 1d), nor with the constitutive level of expression of gp100 by the SK23 melanoma cell line (data not shown).…”

“…34 Indeed, we have utilized in the past rVV for the in vitro induction of antimelanoma differentiation antigen-specific CTL. 7,8 We, however, noted that MART-1/MelanA-specific immune reactivity was more easily elicited than that of the larger melanoma differentiation antigen gp100. In addition, we observed that the reactivity elicited against MART-1 was almost exclusively limited to the HLA-A*0201-associated MART-1:27-35 epitope, suggesting that the immunogenicity of a protein may not be necessarily expandable to multiple HLA alleles as desired by the whole Ag vaccination approach.…”

“…7,8 The reason for the enhanced efficiency remained unclear, and we postulated that the longer persistence of Ag on the surface of DC due to the prolonged production of antigenic molecules driven by the viral promoters might have been responsible. 8 Surprisingly, however, in the conduct of these studies we noted that rVV-infected DC had very little ability to stimulate generation of IFN-g production by several Agspecific T-cell clones studied (unpublished observation). Since these studies yielded indirect information about TCR engagement as they measured the cumulative production of IFN-g by T-cells over a 24-h period, we tested the efficiency of Ag presentation by iDC and mDC using new technologies that address more directly TCR/ epitope engagement.…”

“…1,2 In natural conditions, DC most likely present exogenous Ag up-take from dead cells. 3,4 However, for therapeutic purposes, endogenous presentation of Ag encoded by viral vectors infecting DC has been proposed in murine 5 and human [6][7][8][9] models. This strategy of Ag delivery can induce human leukocyte antigen (HLA) class I-and class II-associated immune responses and may represent a potent immunization tool inducing prolonged Ag-specific stimulation within cells capable of powerful costimulation.…”