Heat stress response in plants: a complex game with chaperones and more than twenty heat stress transcription factors.

Compared to the overall multiplicity of more than 20 plant Hsfs, detailed analyses are mainly restricted to tomato and Arabidopsis and to three important representatives of the family (Hsfs A1, A2 and B1). The three Hsfs represent examples of striking functional diversification specialized for the three phases of the heat stress (hs) response (triggering, maintenance and recovery). This is best illustrated for the tomato Hsf system: (i) HsfA1a is the master regulator responsible for hs-induced gene expression including synthesis of HsfA2 and HsfB1. It is indispensible for the development of thermotolerance. (ii) Although functionally equivalent to HsfA1a, HsfA2 is exclusively found after hs induction and represents the dominant Hsf, the "working horse" of the hs response in plants subjected to repeated cycles of hs and recovery in a hot summer period. Tomato HsfA2 is tightly integrated into a network of interacting proteins (HsfA1a, Hsp17-CII, Hsp17-CI) influencing its activity and intracellular distribution. (iii) Because of structural peculiarities, HsfB1 acts as coregulator enhancing the activity of HsfA1a and/or HsfA2. But in addition, it cooperates with yet to be identified other transcription factors in maintaining and/or restoring housekeeping gene expression.

Evaluation of immune responses elicited in mice against a recombinant malaria vaccine based on Plasmodium vivax Duffy binding protein.

Plasmodium vivax Duffy binding protein (PvDBP) binds the Duffy blood group antigen as the obligate receptor for erythrocyte invasion. We have tested in mice the immunogenicity of recombinant P. vivax region II (PvRII), the receptor-binding domain of PvDBP, formulated with five adjuvants, namely, Montanide ISA720, AS02A, alum, QS21 and MF59. All the formulations elicited high titer antibodies, with Montanide ISA720 and AS02A yielding the highest titers followed by MF59, QS21 and alum. Sera raised against PvRII formulated with AS02A and Montanide ISA720 followed by alum were most effective at blocking PvRII binding to erythrocytes in a functional assay. Analysis of cellular immune responses indicated that all adjuvant groups induced significant interferon-gamma, with alum being the highest interferon-gamma inducer. These results suggest that recombinant PvRII formulated with human compatible adjuvants is immunogenic in small animal models and that Montanide ISA720, AS02A and alum perform better than MF59 and QS21 in terms of their ability to elicit high titer binding inhibitory antibodies.