Human natural killer cells control Plasmodium falciparum infection by eliminating infected red blood cells.

Immunodeficient mouse-human chimeras provide a powerful approach to study host-specific pathogens, such as Plasmodium falciparum that causes human malaria. Supplementation of immunodeficient mice with human RBCs supports infection by human Plasmodium parasites, but these mice lack the human immune system. By combining human RBC supplementation and humanized mice that are optimized for human immune cell reconstitution, we have developed RBC-supplemented, immune cell-optimized humanized (RICH) mice that support multiple cycles of P. falciparum infection. Depletion of human natural killer (NK) cells, but not macrophages, in RICH mice results in a significant increase in parasitemia. Further studies in vitro show that NK cells preferentially interact with infected RBCs (iRBCs), resulting in the activation of NK cells and the elimination of iRBCs in a contact-dependent manner. We show that the adhesion molecule lymphocyte-associated antigen 1 is required for NK cell interaction with and elimination of iRBCs. Development of RICH mice and validation of P. falciparum infection should facilitate the dissection of human immune responses to malaria parasite infection and the evaluation of therapeutics and vaccines.

Pulsatile ex vivo perfusion of human saphenous vein grafts under controlled pressure conditions increases MMP-2 expression.

BACKGROUND: The use of human saphenous vein grafts (HSVGs) as a bypass conduit is a standard procedure in the treatment of coronary artery disease while their early occlusion remains a major problem. METHODS: We have developed an ex vivo perfusion system, which uses standardized and strictly controlled hemodynamic parameters for the pulsatile and non-static perfusion of HSVGs to guarantee a reliable analysis of molecular parameters under different pressure conditions. Cell viability of HSVGs (n = 12) was determined by the metabolic conversion of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) into a purple formazan dye. RESULTS: Under physiological flow rates (10 mmHg) HSVGs remained viable for two weeks. Their exposure to arterial conditions (100 mmHg) was possible for one week without important reduction in viability. Baseline expression of matrix metalloproteinase-2 (MMP-2) after venous perfusion (2.2 ± 0.5, n = 5) was strongly up-regulated after exposure to arterial conditions for three days (19.8 ± 4.3) or five days (23.9 ± 6.1, p < 0.05). Zymographic analyses confirmed this increase on the protein level. Our results suggest that expression and activity of MMP-2 are strongly increased after exposure of HSVGs to arterial hemodynamic conditions compared to physiological conditions. CONCLUSION: Therefore, our system might be helpful to more precisely understand the molecular mechanisms leading to an early failure of HSVGs.

Basigin is a druggable target for host-oriented antimalarial interventions.

Plasmodium falciparum is the parasite responsible for the most lethal form of malaria, an infectious disease that causes a large proportion of childhood deaths and poses a significant barrier to socioeconomic development in many countries. Although antimalarial drugs exist, the repeated emergence and spread of drug-resistant parasites limit their useful lifespan. An alternative strategy that could limit the evolution of drug-resistant parasites is to target host factors that are essential and universally required for parasite growth. Host-targeted therapeutics have been successfully applied in other infectious diseases but have never been attempted for malaria. Here, we report the development of a recombinant chimeric antibody (Ab-1) against basigin, an erythrocyte receptor necessary for parasite invasion as a putative antimalarial therapeutic. Ab-1 inhibited the PfRH5-basigin interaction and potently blocked erythrocyte invasion by all parasite strains tested. Importantly, Ab-1 rapidly cleared an established P. falciparum blood-stage infection with no overt toxicity in an in vivo infection model. Collectively, our data demonstrate that antibodies or other therapeutics targeting host basigin could be an effective treatment for patients infected with multi-drug resistant P. falciparum.

De Novo Generated Human Red Blood Cells in Humanized Mice Support Plasmodium falciparum Infection.

Immunodeficient mouse-human chimeras provide a powerful approach to study host specific pathogens like Plasmodium (P.) falciparum that causes human malaria. Existing mouse models of P. falciparum infection require repeated injections of human red blood cells (RBCs). In addition, clodronate lipsomes and anti-neutrophil antibodies are injected to suppress the clearance of human RBCs by the residual immune system of the immunodeficient mice. Engraftment of NOD-scid Il2rg-/- mice with human hematopoietic stem cells leads to reconstitution of human immune cells. Although human B cell reconstitution is robust and T cell reconstitution is reasonable in the recipient mice, human RBC reconstitution is generally poor or undetectable. The poor reconstitution is mainly the result of a deficiency of appropriate human cytokines that are necessary for the development and maintenance of these cell lineages. Delivery of plasmid DNA encoding human erythropoietin and interleukin-3 into humanized mice by hydrodynamic tail-vein injection resulted in significantly enhanced reconstitution of erythrocytes. With this improved humanized mouse, here we show that P. falciparum infects de novo generated human RBCs, develops into schizonts and causes successive reinvasion. We also show that different parasite strains exhibit variation in their ability to infect these humanized mice. Parasites could be detected by nested PCR in the blood samples of humanized mice infected with P. falciparum K1 and HB3 strains for 3 cycles, whereas in other strains such as 3D7, DD2, 7G8, FCR3 and W2mef parasites could only be detected for 1 cycle. In vivo adaptation of K1 strain further improves the infection efficiency and parasites can be detected by microscopy for 3 cycles. The parasitemia ranges between 0.13 and 0.25% at the first cycle of infection, falls between 0.08 and 0.15% at the second cycle, and drops to barely detectable levels at the third cycle of infection. Compared to existing mouse models, our model generates human RBCs de novo and does not require the treatment of mice with immunomodulators.

Identification of an up-regulated anti-apoptotic network in the internal thoracic artery.

BACKGROUND: The radial artery (RA) is known as an atherosclerosis-prone vessel in contrast to the atherosclerosis-resistant internal thoracic artery (ITA). The purpose of the present study was to compare the gene expression profile of these arteries from the same patient in order to identify genes involved in atherogenesis or intimal hyperplasia. METHODS: Paired specimens of RA and ITA (n=6) were analyzed by histomorphometry and whole genome microarray. The microarray data underwent pathway analysis to identify biological networks. Laser microdissection (LMD) was used to identify the cellular expression of candidate genes in the intimal or medial layer of the ITA and RA. RESULTS: Histomorphometric analyses revealed a significantly higher degree of intimal hyperplasia in the RA compared to the ITA. 552 genes were differentially expressed in the ITA and RA. qRT-PCR confirmed a significant up-regulation of six anti-apoptotic genes. p21 (11.8-fold, p=0.011), CCL2 (5.4-fold, p=0.034), SOCS3 (7.2-fold, p=0.002), IER3 (4.1-fold, p=0.048), MCL-1 (2.6-fold, p=0.025) and IL-6 (17.8-fold, p=0.046) were up-regulated in the ITA. LMD confirmed that cells of the intimal layer of the ITA consistently expressed higher levels of all six candidate genes than those of the RA. CONCLUSIONS: Microarray analysis and qRT-PCR identified significantly up-regulated genes in the ITA involved in an anti-apoptotic network. LMD revealed a higher expression of all anti-apoptotic genes in the intimal area of the ITA. These genes may play an important role in protecting the intima of the ITA from developing hyperplasia and atherosclerosis.