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Polysaccharides (PS) have historically been viewed as T cell-independent antigens. However, in this paper I propose a new concept, based on substantial data from my laboratory over the previous 10 years, that during infections with PS-encapsulated extracellular bacteria, PS-specific IgG responses are largely CD4+ T cell dependent. Thus, capsular PS is typically encountered by the immune system covalently attached to the underlying subcapsular bacterial domain. I speculate that noncovalent association of PS with immunogenic proteins within the bacterial particle leads to recruitment of protein-specific CD4+ T cell help for the anti-PS response. However, differences in the composition and/or structure of the subcapsular domain of different extracellular bacteria may result in distinct anti-PS responses as well as differential effects on the immune response to coimmunizing soluble antigens. CD4+ T cell help for IgG anti-PS responses during infections with extracellular bacteria is likely to promote opsonic clearance of these rapidly growing pathogens. However, the expression of immunosuppressive components by certain bacteria may also serve to dampen such responses. [ABSTRACT FROM AUTHOR]

The goal of cancer vaccines is to induce antitumor immunity that ultimately will reduce tumor burden in tumor environment. Several strategies involving dendritic cells- (DCs)- based vaccine incorporating different tumor-associated antigens to induce antitumor immune responses against tumors have been tested in clinical trials worldwide. Although DCs-based vaccine such as fusions of whole tumor cells and DCs has been proven to be clinically safe and is efficient to enhance antitumor immune responses for inducing effective immune response and for breaking T-cell tolerance to tumor-associated antigens (TAAs), only a limited success has occurred in clinical trials. This paper reviews tumor immune escape and current strategies employed in the field of tumor/DC fusions vaccine aimed at enhancing activation of TAAs-specific cytotoxic T cells in tumor microenvironment. [ABSTRACT FROM AUTHOR]

A major challenge for immunologists has been the development of vaccines designed to emphasize cellular immune responses. One particularly promising approach is the prime–boost strategy, which has been shown to generate high levels of T-cell memory in animal models. Recently, several papers have highlighted the power of prime–boost strategies in eliciting protective cellular immunity to a variety of pathogens and have demonstrated efficacy in humans. Coupled with recent advances in our understanding of the mechanisms underlying the generation, maintenance and recall of T-cell memory, the field is poised to make tremendous progress. This Review discusses the impact of these recent developments on the future of prime–boost vaccine strategies. [Copyright &y& Elsevier]