Quantifying Gp96/Grp94 complexes preparations for vaccines: a key step often inaccurate

Glycoprotein 96 (Gp96)-peptide complexes are highly investigated for vaccines preparation, particularly in cancer therapy. Gp96, formerly called tumor rejection antigen (TRA)-1, is able to elicit an immune response that can protect mice against tumors, when the mice share the same haplotype than those bearing the tumors from which Gp96 was purified. Secreted Gp96-peptide complexes act as danger signals thereby stimulating the innate immunity regardless of the chaperoned peptides. In contrast, the tumor rejection antigen role of Gp96-peptide complexes is held by the chaperoned peptides in a dose-dependent manner. The purification step is crucial both for insuring the quality and the quantity of Gp96-peptide complexes. To this aim, different methods have been described but they are often suboptimal for the quantification of these complexes. In this review, we discuss a hot topic: the use of the chaperone Gp96 for vaccination purposes in cancer, and also detail the current methods for quantifying Gp96-peptide preparations.