Plasmodium 6-cysteine proteins determine the commitment of sporozoites to liver-infection.

Plasmodium sporozoites travel a long way from the site where they are released by a mosquito bite to the liver, where they infect hepatocytes and develop into erythrocyte-invasive forms. The success of this infection depends on the ability of the sporozoites to correctly recognize the hepatocyte as a target and change their behavior from migration to infection. However, how this change is accomplished remains incompletely understood. In this paper, we report that 6-cysteine protein family members expressed in sporozoites including B9 are responsible for this ability. Experiments on parasites using double knockouts of B9 and SPECT2, which is essential for sporozoite to migrate through the hepatocyte, showed that the parasites lacked the capacity to stop migration. This finding suggests that interactions between these parasite proteins and hepatocyte-specific cell surface ligands mediate correct recognition of hepatocytes by sporozoites, which is an essential step in malaria transmission to humans.

A potent malaria vaccine based on adenovirus with dual modifications at Hexon and pVII.

Adenovirus (Ad) is thought to be one of the most promising platforms for a malaria vaccine targeted against its liver stages, because of its ability to induce a strong T-cell response against a transgene. However, a further improvement of this platform is needed in order to elicit another arm of the immunity, i.e. humoral response, against malaria. In order to augment immunogenicity and protective efficacy of Ad-based malaria vaccine, we inserted B-cell, as well as CD4+ T-cell, epitopes of Plasmodium falciparum circumsporozoite protein (PfCSP) into the capsid protein, Hexon, and the core protein, VII (pVII), of Ad, respectively, in addition to the PfCSP transgene. Insertion of PfCSP-derived B cell epitope to Hexon significantly enhanced the epitope-specific antibody response compared to AdPfCSP, an Ad vaccine expressing only PfCSP transgene. PfCSP-derived CD4+ T-cell epitope insertion into pVII augmented not only PfCSP-specific CD4+ T-cell response but also anti-PfCSP antibody response. Finally, mice immunized with AdPfCSP having both Hexon and pVII modifications were more protected than AdPfCSP or Hexon-modified AdPfCSP against challenge with transgenic rodent malaria parasites expressing the PfCSP. Overall, this study has demonstrated that Hexon and pVII-modified AdPfCSP vaccine is a promising malaria vaccine which induces strong PfCSP-specific humoral, CD4+ T-cell, and CD8+ T-cell responses and protects against infection with transgenic malaria parasites expressing the PfCSP.

A potent adjuvant effect of a CD1d-binding NKT cell ligand in human immune system mice.

OBJECTIVES: A CD1d-binding invariant natural killer T (iNKT)-cell stimulatory glycolipid, namely 7DW8-5, is shown to enhance the efficacy of radiation-attenuated sporozoites (RAS)-based malaria vaccine in mice. In the current study, we aim to determine whether 7DW8-5 can display a potent adjuvant effect in human immune system (HIS) mice. METHODS: HIS-A2/hCD1d mice, which possess both functional human iNKT cells and CD8+ T cells, were generated by the transduction of NSG mice with adeno-associated virus serotype 9 expressing genes that encode human CD1d molecules and HLA-A*0201, followed by the engraftment of human hematopoietic stem cells. The magnitudes of human iNKT-cell response against 7DW8-5 and HLA-A*0201-restricted human CD8+ T-cell response against a human malaria antigen in HIS-A2/hCD1d mice were determined by using human CD1d tetramer and human HLA-A*0201 tetramer, respectively. RESULTS: We found that 7DW8-5 stimulates human iNKT cells in HIS-A2/hCD1d mice, as well as those derived from HIS-A2/hCD1d mice in vitro. We also found that 7DW8-5 significantly increases the level of a human malarial antigen-specific HLA-A*0201-restricted human CD8+ T-cell response in HIS-A2/hCD1d mice. CONCLUSIONS: Our study indicates that 7DW8-5 can display a potent adjuvant effect on RAS vaccine-induced anti-malarial immunity by augmenting malaria-specific human CD8+ T-cell response.

Identification of an AP2-family protein that is critical for malaria liver stage development.

Liver-stage malaria parasites are a promising target for drugs and vaccines against malaria infection. However, little is currently known about gene regulation in this stage. In this study, we used the rodent malaria parasite Plasmodium berghei and showed that an AP2-family transcription factor, designated AP2-L, plays a critical role in the liver-stage development of the parasite. AP2-L-depleted parasites proliferated normally in blood and in mosquitoes. However, the ability of these parasites to infect the liver was approximately 10,000 times lower than that of wild-type parasites. In vitro assays showed that the sporozoites of these parasites invaded hepatocytes normally but that their development stopped in the middle of the liver schizont stage. Expression profiling using transgenic P. berghei showed that fluorescent protein-tagged AP2-L increased rapidly during the liver schizont stage but suddenly disappeared with the formation of the mature liver schizont. DNA microarray analysis showed that the expression of several genes, including those of parasitophorous vacuole membrane proteins, was significantly decreased in the early liver stage of AP2-L-depleted parasites. Investigation of the targets of this transcription factor should greatly promote the exploration of liver-stage antigens and the elucidation of the mechanisms of hepatocyte infection by malaria parasites.

Cysteinyl leukotrienes enhance the degranulation of bone marrow-derived mast cells through the autocrine mechanism.

The cysteinyl leukotrienes (LTs), LTC(4), LTD(4), and LTE(4), are potent inflammatory mediators and are involved in allergic reactions, such as bronchoconstriction, eosinophilic inflammation, and allergic cell proliferation. The present study aimed to elucidate the role of constitutively produced cysteinyl LTs in mast cell activation. We used a newly developed quantification method based on mass spectrometry to detect cysteinyl LTs in the cultured medium of mouse bone marrow-derived mast cells (BMMCs), which were obtained by interleukin (IL)-3-conditioned culture of mouse bone marrow. BMMCs were stimulated with immunoglobulin (Ig) E and antigen (IgE/Ag) or lipopolysaccharide for 1 or 24 h. This new quantification method revealed that unstimulated BMMCs produced and secreted LTB4 and LTE4 after 24 h of incubation. The treatment of unstimulated BMMCs for 2 h with montelukast, an antagonist of a cysteinyl LT receptor, CysLT1, resulted in the suppression of a downstream signaling event of this receptor, i.e., the decrease in phosphorylation of extracellular responsive kinases. Thus, cysteinyl LTs constitutively simulate BMMCs through the CysLT1 receptor in an autocrine manner. Treatment of BMMCs for 3 weeks with montelukast, which caused long-term inhibition of the autocrine cyteinyl LT-derived signal, significantly attenuated the IgE/Ag-dependent degranulation, as judged by the decrease in the release of beta-hexosaminidase, an enzyme contained in the granules, whereas the production of cytokines, such as IL-6 and tumor necrosis factor-alpha, were largely unaffected. In conclusion, an autocrine signal derived from constitutively produced cysteinyl LTs predisposes mast cells to the degranulation upon allergic stimulation.

Role of 2B4-mediated signals in the pathogenesis of a murine hepatitis model independent of Fas and Valpha14 NKT cells.

Concanavalin A (Con A)-induced hepatitis is a T-cell-mediated murine experimental model of autoimmune hepatitis. Mice lacking Valpha14 NKT cells were found to be less sensitive to this hepatitis and the MRL/Mp-Fas(lpr/lpr) (MRL/lpr; i.e. Fas deficient) mice were also less sensitive. We report herein that MRL/Mp-Fas(lpr/lpr)-Sap(rpl/-) (MRL/lpr/rpl) mice lack Valpha14 NKT cells and are deficient in the Fas antigen but sensitive to Con A-induced hepatitis. The signaling lymphocytic activation molecule (SLAM)-associated protein (SAP) is an adaptor molecule containing a Src homology 2 (SH2) domain. We previously reported new mutant mice found among MRL/lpr mice and revealed that SAP deficiency led to the regression of autoimmune phenotypes in mutant MRL/lpr/rpl mice. It was also revealed that CD4(+) and CD8(+) T cells were effector cells and that blockade of 2B4, one of the SLAM family receptors, inhibited the induction of hepatitis in MRL/lpr/rpl mice. These data suggest that signals mediated by molecules other than SAP from 2B4 in T cells played important roles in the induction of hepatitis in MRL/lpr/rpl mice.

Fatty acid-binding protein regulates LPS-induced TNF-alpha production in mast cells.

There has been increasing evidence for the involvement of fatty acid-binding proteins (FABPs) in the cytokine production of macrophages and dendritic cells probably through the control of cellular lipid metabolism and signal transduction. Since mast cells (MCs) are recently shown to be involved in immune response through modification of cytokine production, it is possible that some FABPs could also be involved in the immune response of MCs. In this study, we found that epidermal-type FABP (E-FABP) was expressed in murine bone marrow-derived MCs (BMMCs). Using BMMCs from genetically E-FABP-null mutated mice, we demonstrated that E-FABP in BMMCs plays a key role in the production of TNF-alpha following lipopolysaccharide (LPS) stimulation. In the in vivo septic peritonitis model (cecal ligation and puncture model), E-FABP-null mice showed a significantly increased mortality compared to wild-type mice. However, no significant difference in antigen-induced cytokine production was observed between wild-type and E-FABP-null BMMCs, and systemic anaphylaxis was equally induced in vivo in both wild-type and E-FABP-null mice. These results suggest that E-FABP is specifically involved in the LPS-induced cytokine production of MCs, and could play a role in the host-defense against bacterial infection, possibly through regulation of TNF-alpha production.

Simultaneous quantification of seven prostanoids using liquid chromatography/tandem mass spectrometry: the effects of arachidonic acid on prostanoid production in mouse bone marrow-derived mast cells.

We have developed a method for the simultaneous estimation of the levels of the prostanoids 6-keto prostaglandin (PG) Flalpha, PGB2, PGD2, PGE2, PGF2(alpha), PGJ2, and thromboxane (TX) B2 in blood- or serum-containing medium using liquid chromatography-tandem mass spectrometry. These prostanoids and their deuterium derivatives, which were used as internal standards, were subjected to solid-phase extraction using Empore C18 HD disk cartridges and analyzed in the selected reaction-monitoring mode. A linear response curve starting at 10 pg of prostanoid/tube was observed for each prostanoid. The accuracy of the method was demonstrated with samples containing known amounts of the prostanoids. Furthermore, we used this method to analyze the prostanoids produced in mouse bone marrow-derived mast cells stimulated with arachidonic acid, which resulted in the production of PGD2, PGE2, PGF2alpha, and TXB2. The results suggest that this simultaneous quantification method is useful for the analysis of the production of biomedically important prostanoids.

Changes in urinary excretion of six biochemical parameters in normotensive pregnancy and preeclampsia.

We evaluated renal functions by urinary biochemical parameters in normotensive pregnancy and preeclampsia. The parameters are expected to be altered resulting from different abnormalities of renal glomeruli and tubules. We chose N-acetyl-beta-d-glucosaminidase (NAG), beta2-microglobulin (beta2MG), total protein (TP), albumin (Alb), urea nitrogen (UN), uric acid (UA), and creatinine (Cr). Urinary excretion of these biochemical parameter concentrations (relative to Cr) was measured simultaneously in first morning fasting urine samples from 27 healthy nonpregnant women (group 1), 32 women with normotensive pregnancies (group 2), and 26 women with preeclampsia (group 3). The average gestational age at entry was 36 weeks. Serum UN and serum UA also were measured. All the ratios were significantly higher in group 2 than in group 1. The NAG-to-Cr, TP-to-Cr, and Alb-to-Cr ratios were significantly higher in group 3 than in group 2. In contrast, the UN-to-Cr and UA-to-Cr ratios were significantly lower in group 3 than in group 2. The percent increase in the beta2MG-to-Cr ratio in group 2 relative to that in group 1 was the highest, followed by percent increases in the NAG-to-Cr, TP-to-Cr, Alb-to-Cr, UA-to-Cr, and UN-to-Cr ratios. In contrast, the percent increase in the Alb-to-Cr ratio in group 3 relative to that in group 2 was the highest, followed by percent increases in the TP-to-Cr, NAG-to-Cr, beta2MG-to-Cr, UA-to-Cr, and UN-to-Cr ratios. The percent increases in the NAG-to-Cr and beta2MG-to-Cr ratios rose markedly in normotensive pregnancy, whereas percent increases of the Alb-to-Cr and TP-to-Cr ratios were far greater in preeclampsia than in normotensive pregnancy. Renal tubular damage and reabsorption dysfunction may be impaired markedly even in normotensive pregnancy, and further deterioration in reabsorption dysfunction may be slight in preeclampsia. Renal glomerular permeability of TP and Alb may be enhanced in normotensive pregnancy and markedly enhanced in preeclampsia.