The Plasmodium vivax Duffy Binding Protein (DBP) is the ligand in the major pathway for P. vivax invasion of human reticulocytes, making it an appealing vaccine candidate. Region II of DBP (DBP-RII) is the minimal portion of the ligand that mediates recognition of the Duffy Antigen Receptor for Chemokines (DARC receptor) on the reticulocyte surface and constitutes the primary vaccine target. Analysis of natural variation in the coding sequences of DBP-RII revealed signature evidence for selective pressure driving variation in the residues of the putative receptor-binding site. We hypothesize that anti-DBP immunity in P. vivax infections is strain-specific and hindered by polymorphic residues altering sensitivity to immune antibody inhibition. To comprehend the human IgG response following P. vivax infections we investigated the specificity of IgG in Pursat Province, Western Cambodia. Using ELISAs, we quantified the antibody titer against five variant alleles of DBP-RII. We also sequenced the DBP-RII of the field isolates to determine their relationship to the variant alleles used in the ELISAs. When correlating the IgG titer between the DBP variants a strain-specific immune response was observed in patients with a high antibody titer to DBP-RII_AH as compared to the other variants. This was different from the correlation of high antibody titers between DBP-RII_P and DBP-RII_7.18 (ρ=0.88, p-value<0.0001) and DBP-RII_P and DBP-RII_O (ρ=0.87, p-value<0.0001). There appeared to be little correlation between specific polymorphic residues and IgG titer. Understanding the immune response to the polymorphisms within PvDBP will allow further identification of epitopes to enable the production of a more effective P. vivax vaccine

Les adultes conspécifiques (ou évolutivement proches) réduisent le recrutement des graines/plantules à leur proximité, à cause d’une forte pression de prédation par des ennemis spécialistes ou peu mobiles (Hypothèse de Janzen-Connell). Cependant, l’importance de l’effet Janzen-Connell reste controversé, suggérant que les interactions entre adultes et plantules ne se restreignent pas aux adultes conspécifiques proches, ni aux ennemis spécialistes : les adultes hétérospécifiques, la taille des adultes et la représentation de leur lignée dans la canopée pourraient aussi contrôler le recrutement des plantules. De plus, les effets des adultes sur les graines/plantules pourraient être médiés par des ennemis généralistes et très mobiles, par des champignons mutualistes et par certaines conditions micro-environnementales. Nous avons étudié les effets des arbres adultes sur le recrutement des graines/plantules de chêne, via les ennemis mobiles, les champignons mutualistes et enfin les conditions micro-environnementales. Nos résultats démontrent que : (i) un adulte conspécifique empêche le recrutement des plantules à proximité, via une accumulation des décomposeurs spécialistes qui augmentent la qualité nutritionnelle des plantules, attirant ainsi les ennemis. De plus, un adulte de grande taille attire des herbivores mollusques ; (ii) un adulte hétérospécifique favorise le recrutement des plantules à sa proximité, en réduisant l’herbivorie et en améliorant le microenvironnement ; (iii) une canopée évolutivement proche favorise le recrutement des graines et plantules, en rassasiant les prédateurs de graines et en augmentant le soutien par les mycorhizes, respectivement. Ainsi, nos résultats permettent d’identifier les structures forestières optimales pour le recrutement du chêne. De plus, nos résultats suggèrent que le recrutement maintient les chênes proches de leurs espèces apparentées et donc dans leur niche ancestrale. / Conspecific (or closely related) adults reduce seed/seedling recruitment in their proximity, due to high pressure from specialized or little mobile enemies (Janzen-Connell Hypothesis). However, the importance of the Janzen-Connell effect remains controversial, suggesting that interactions between adults and seedlings are not restricted to close conspecific adults, nor to specialized enemies: heterospecific adults, size of adults and dominance of their lineage in the canopy may also control seed/seedling recruitment. Moreover, effects of adults on seeds/seedlings may be mediated by generalist or mobile enemies, fungal mutualists, and microenvironmental conditions. We studied the effect of adult trees on recruitment of oak seeds/seedlings, via mobile enemies, fungal mutualists, and finally microenvironmental conditions. Our results demonstrated that (i) a conspecific adult impedes recruitment of proximate seedlings by accumulating specialist decomposers that favor nutritional quality of seedlings and thereby attract herbivores. Moreover, a large adult attracts mollusk herbivores; (ii) a heterospecific adult favors recruitment of proximate seedlings, by reducing herbivory and improving the micro-environment; (iii) a closely related canopy favors seeds and seedlings recruitment, by oversaturating seed predators and increasing mycorrhizal support, respectively. Hence, our results permit to identify forest structures that are optimal for oak recruitment. Moreover, our results suggest that recruitment maintain oaks close to related species, in their ancestral niche.