Priming of cytotoxic T lymphocytes by five heat‐aggregated antigens in vivo: Conditions, efficiency, and relation to antibody responses

Abstract

Mice were immunized i.p. with soluble or heat-denatured protein antigens [ovalbumin, beta-galactosidase, or recombinant E7 protein of human papilloma virus type 16 (HBV)]. Heat-denatured (100 degrees C) preparations of these proteins were able to induce cytotoxic T lymphocytes (CTL) that recognize cells expressing the respective genes, whereas native protein was either inefficient or required up to 30-fold higher doses. If the heat-treated proteins were separated into aggregated and soluble fractions by ultracentrifugation, only the aggregated fractions were able to induce specific CTL; this is probably because of the easier access to one of the major histocompatibility complex class I loading pathways for exogenous antigen. Addition of the adjuvant aluminium hydroxide (alum) to aggregated proteins abolished their ability to induce CTL; thus, a condition leading to a strong antibody response appeared to inhibit CTL induction. Interestingly, immunization with heat-denatured ovalbumin plus alum increased the IgM/IgG1 ratio compared to immunization with native ovalbumin and alum. Immunization of B6 mice transgenic for an HLA-A2/H-2K(b) hybrid gene with heat-denatured, recombinant HPV 16-E7 protein induced D(b)-restricted CTL specific for the peptide 49-57 of E7, indicating that this epitope is immunodominant over any A2-restricted E7 epitope in these mice. A whole influenza virus preparation heated to 100 degrees C or even autoclaved was still able to induce virus-specific CTL and BALB/c spleen cells heated to 100 degrees C could still cross-prime minor H-specific CTL in B6 mice, although with lower efficiency than fresh spleen cells. Thus, aggregated proteins can be considered as components for future vaccines.

A Decaepitope Polypeptide Primes for Multiple CD8+ IFN-γ and Th Lymphocyte Responses: Evaluation of Multiepitope Polypeptides as a Mode for Vaccine Delivery

“…Our results suggest that multiepitope polypeptides can be potent immunogens due to their capacity to aggregate and form particulates. Previous studies by other groups have provided similar evidence supporting this hypothesis (17)(18)(19)(20)(21). Finally, our results suggest that multiepitope polypeptides might offer significant advantages in terms of priming for memory CD8 ϩ IFN-␥ responses, compared with DNA vaccines.…”

“…In most cases, exogenous Ags that effectively induce class I-restricted responses are particulate, and may access a specialized uptake mechanism by professional APCs (17)(18)(19)(20)(21). Class I-restricted presentation can also occur via binding to surface MHC by short peptides generated or present extracellularly (22,23).…”

Anti-tumor immunostimulatory effect of heat-killed tumor cells

“…By this reason, rather than serving as target cells, tumor vaccines must be processed and presented to MHC I molecules by professional APCs to induced CTL responses. Although the experimental conditions were different, our results along with Speidel et al (1997) clearly indicated that tumor cell extracts can be processed and presented to not only CD4 + T cells but also CD8 + T cells through cross priming as were shown by target cell-specific CTL responses. For the cross priming of CD8 + T cells by the extracellular antigens, phagocytosed antigens need to be processed either in the cytosol or the antigens processed in the lysosomal compartment need to be transported to endoplasmic reticulum, where cross presentation to the MHC I occurs (Shen and Rock, 2006).…”

“…Thus, it remains possible that the denatured form of self-molecules, which were introduced during the preparation of the HK vaccine, might be detected by TLRs. Speidel et al (1997) also showed that heat-denatured protein antigens were able to enhance antigenspecific CTL responses. Interestingly in their paper, stronger minor antigen H-specific CTL response was induced when the recipients were immunized with fresh spleen cells compared to heat-killed spleen cell-immunization.…”

Dendritic cells loaded with apoptotic tumour cells induce a stronger T-cell response than dendritic cell–tumour hybrids in B-CLL

“…30 The higher proliferative response that we obtained using Apo-DC may be attributed to the fact that particulate antigens prime T-cell more effectively. 31 Furthermore, residual nonhybridised B-CLL cells may serve to anergise T-cells. 32 All these parameters may affect the proliferation response when using DC fusion hybrids to stimulate autologous antileukaemic T-cells.…”