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Invasion of human red blood cells by the malaria parasite Plasmodium falciparum is an essential step in the development of the disease. Consequently, the molecular players involved in host cell invasion represent important targets for inhibitor design and vaccine development. The process of merozoite invasion is a succession of steps underlined by the sequential secretion of the organelles of the apical complex. However, little is known with regard to how their contents are exocytosed. Here, we identify a phosphoinositide‐binding protein conserved in apicomplexan parasites and show that it is important for the attachment and subsequent invasion of the erythrocyte by the merozoite. Critically, removing the protein from its site of action by knock sideways preferentially prevents the secretion of certain types of micronemes. Our results therefore provide evidence for a role of phosphoinositide lipids in the malaria invasion process and provide further insight into the secretion of microneme organelle populations, which is potentially applicable to diverse apicomplexan parasites.

Dihydroartemisinin-piperaquine (DHA-PPQ), the current frontline artemisinin combination therapy used to treat Plasmodium falciparum malaria in multiple Southeast Asian countries, is now increasingly failing in Cambodia, where artemisinin resistance is nearly fixed, which suggests that PPQ resistance has emerged and is spreading rapidly in the Greater Mekong Subregion. Recent reports have shown that amplification of the genes encoding plasmepsins 2 and 3 is a molecular marker of PPQ resistance; however, whether these enzymes play a role in the mechanism of resistance is currently unknown. We show here that inactivating the genes encoding plasmepsin 2 or 3 individually in P. falciparum reference strain 3D7 results in hypersusceptibility to PPQ. Interestingly, no significant differences in the susceptibility to other antimalarials were observed, which suggests specific roles of plasmepsins 2 and 3 in PPQ susceptibility. The piperaquine hyper-sensitivity of the plasmepsin-2-and-3-inactivated lines provides direct evidence that these enzymes modulate parasite susceptibility to PPQ in the context of a single copy of PfMDR1 and independent of Kelch13 mutations conferring artemisinin resistance.

Aging is associated with hyporesponse to vaccination, whose mechanisms remain unclear. In this study hepatitis B virus (HBV)-naive older adults received three vaccines, including one against HBV. Here we show, using transcriptional and cytometric profiling of whole blood collected before vaccination, that heightened expression of genes that augment B-cell responses and higher memory B-cell frequencies correlate with stronger responses to HBV vaccine. In contrast, higher levels of inflammatory response transcripts and increased frequencies of pro-inflammatory innate cells correlate with weaker responses to this vaccine. Increased numbers of erythrocytes and the haem-induced response also correlate with poor response to the HBV vaccine. A transcriptomics-based pre-vaccination predictor of response to HBV vaccine is built and validated in distinct sets of older adults. This moderately accurate (area under the curve≈65%) but robust signature is supported by flow cytometry and cytokine profiling. This study is the first that identifies baseline predictors and mechanisms of response to the HBV vaccine., Ageing is associated with poor responses to vaccines but the underlying mechanism remains unclear. Here the authors use a systems-based approach to define molecular signatures present before vaccination that correlate with non-responsiveness to hepatitis B vaccination in healthy, elderly adults.

The molecular events involved in the establishment and maintenance of CD4+ central memory and effector memory T cells (TCM and TEM, respectively) are poorly understood. In this study, we demonstrate that ex vivo isolated TCM are more resistant to both spontaneous and Fas-induced apoptosis than TEM and have an increased capacity to proliferate and persist in vitro. Using global gene expression profiling, single cell proteomics, and functional assays, we show that the survival of CD4+ TCM depends, at least in part, on the activation and phosphorylation of signal transducer and activator of transcription 5a (STAT5a) and forkhead box O3a (FOXO3a). TCM showed a significant increase in the levels of phosphorylation of STAT5a compared with TEM in response to both IL-2 (P < 0.04) and IL-7 (P < 0.002); the latter is well known for its capacity to enhance T cell survival. Moreover, ex vivo TCM express higher levels of the transcriptionally inactive phosphorylated forms of FOXO3a and concomitantly lower levels of the proapoptotic FOXO3a target, Bim. Experiments aimed at blocking FOXO3a phosphorylation confirmed the role of this phosphoprotein in protecting TCM from apoptosis. Our results provide, for the first time in humans, an insight into molecular mechanisms that could be responsible for the longevity and persistence of CD4+ TCM.

Plasmodium falciparum, the causative agent of the deadliest form of malaria, and human immunodeficiency virus type-1 (HIV-1) are among the most important health problems worldwide, being responsible for a total of 4 million deaths annually 1 . Due to their extensive overlap in developing regions, especially Sub-Saharan Africa, co-infections with malaria and HIV-1 are common, but the interplay between the two diseases is poorly understood. Epidemiological reports have suggested that malarial infection transiently enhances HIV-1 replication and increases HIV-1 viral load in co-infected individuals 2,3 . Because this viremia stays high for several weeks after treatment with antimalarials, this phenomenon could have an impact on disease progression and transmission. The cellular immunological mechanisms behind these observations have been studied only scarcely. The few in vitro studies investigating the impact of malaria on HIV-1 have demonstrated that exposure to soluble malarial antigens can increase HIV-1 infection and reactivation in immune cells. However, these studies used whole cell extracts of P. falciparum schizont stage parasites and peripheral blood mononuclear cells (PBMC), making it hard to decipher which malarial component(s) was responsible for the observed effects and what the target host cells were 4,5 . Recent work has demonstrated that exposure of immature monocyte-derived dendritic cells to the malarial pigment hemozoin increased their ability to transfer HIV-1 to CD4+ T cells 6,7 , but that it decreased HIV-1 infection of macrophages 8 . To shed light on this complex process, a systematic analysis of the interactions between the malaria parasite and HIV-1 in different relevant human primary cell populations is critically needed. Several techniques for investigating the impact of HIV-1 on the phagocytosis of micro-organisms and the effect of such pathogens on HIV-1 replication have been described. We here present a method to investigate the effects of P. falciparum-infected erythrocytes on the replication of HIV-1 in human primary monocyte-derived macrophages. The impact of parasite exposure on HIV-1 transcriptional/translational events is monitored by using single cycle pseudotyped viruses in which a luciferase reporter gene has replaced the Env gene while the effect on the quantity of virus released by the infected macrophages is determined by measuring the HIV-1 capsid protein p24 by ELISA in cell supernatants.

Background The immunogenicity of an autologous dendritic cell (DC) anti-HIV therapy, AGS-004, was evaluated in a multicenter Phase 2 trial. The treatment regiment consisted of four intradermal doses, administered monthly in combination with anti-retroviral therapy (ART) followed by a well-controlled structured treatment interruption (STI). The immunotherapy consisted of monocyte-derived DC co-electroporated with CD40L in vitro transcribed (IVT) RNA along with amplified IVT RNA encoding for 4 HIV-1 antigens (GAG, NEF, REV and VPR).

Survivin is a member of the inhibitor of apoptosis protein family and its over-expression has been reported in many cancer types such as melanoma, colon, brain, breast, and ovarian cancers making it a promising target for immunotherapy. DPX-Survivac is a Survivin multi-epitope vaccine that covers a broad range of HLA haplotypes (HLA-A1, A2, A3, A24, B7). The adjuvanted water free depot vaccine is designed to specifically induce CD8+ T cells. In a Phase I study in ovarian cancer patients (n=18), we aimed to evaluate one dose level of the vaccine (0.5 mL) without cyclophosphamide (Cohort A) and two dose levels (0.1 mL and 0.5 mL) combined with oral low dose cyclophosphamide as an immune modulator (Cohorts B and C). Using multiparametric flow cytometry, we measured the ex-vivo frequency, phenotype and function of Regulatory T cells (CD25+FoxP3+Ki67+) and Survivin-specific CD4 and CD8 T cells. Our data shows that cohort C preferentially mounted survivin-specific CD8 T cells which significantly peaked at one month following the third vaccination (study day 70) and persisted until at least day 126 post-vaccination. This polyfunctional T cell response was endowed with cytotoxic and proliferative functions as measured by the expression of IL-2, IFNγ, TNFα, Granzyme B and CD107a. The immune responses identified in this cohort functionally diversified over time and were distributed within the Effector memory (CD45RA-CD27-), Central Memory (CD45RA-CD27+) and Late Differentiated CD8 T cell pool (CD45RA+CD27-). Of note, polyfunctional CD4 helper responses directed against tetanus toxoid and Survivin were induced by DPX-Survivac and possibly contributed to the maintenance of the CD8 T cell response. Taken together, the data presented herein shows that DPX-Survivac induced durable polyfunctional CD4 helper and CD8 T cells providing a strong rationale for combining the targeted immune therapy with immune modulation using metronomic cyclophosphamide. Citation Format: Yoav Peretz, Dominike Sauvé, Dominic Gagnon, Salim Ahmed Khan, Geneviève Lévesque, Nathalie Saha, Gilbert Croteau, Valérie Hébert, Karyne Savard, Bader Yassine Diab, Jean-Francois Poulin, Claire Landry, Mohan Karkada, Marc Mansour. Immune profiling of patients vaccinated with the survivin targeted therapeutic vaccine DPX-Survivac demonstrates durable polyfunctional CD4+ and CD8+ T cells in ovarian cancer patients. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr CT411. doi:10.1158/1538-7445.AM2014-CT411