The standard treatment of human visceral leishmaniasis involves the use of pentavalent antimony (Sb V ). Its mechanism of action is unknown because of the limited information available about intracellular antimony metabolism and about the genes that regulate these processes. Herein, flow injection-inductively coupled plasma mass spectrometry (ICP-MS), flow injection hydride generation ICP-MS, and ion chromatography ICP-MS were used to measure antimony accumulation and intracellular metabolism in the human protozoan parasite Leishmania donovani. V reduction has yet to be identified, and it may or may not be enzymatic. This is the first description of intracellular Sb V reducing activity in Leishmania as well as in any prokaryotic or eukaryotic cell.Leishmania donovani is the major causative agent of visceral leishmaniasis. In nature, the parasite exists either as an extracellular promastigote found in the alimentary tract of sandflies or as an obligatory intracellular amastigote found in phagolysosomes of mammalian macrophages(1-3). During the last several years, a number of laboratories have utilized axenic culture of L. donovani amastigotes for the direct evaluation of cell biological and biochemical processes in the amastigote, devoid of the host macrophage (4 -7,8,9,10). This technique has also been used to investigate the mechanism of drug action and resistance as well as for screening of potential new drugs(11-13). The treatment of choice of human visceral leishmaniasis is the administration of pentavalent antimony (Sb V )-containing drugs such as sodium stibogluconate (Pentostam, Wellcome, Beckenham, UK) or meglumine antimoniate (Glucantime, Rhone-Poulenc, Paris, France). Despite extensive use of these compounds over the last decades, the mechanism of action remains unclear.It has been hypothesized that Sb V is not toxic to Leishmania, but rather that it is enzymatically reduced, probably by the host macrophage, to Sb III , the form of antimony that is highly Leishmania-toxic (14 -18). In contrast, it has been shown that Sb V is directly toxic to axenic amastigotes (12,13,19), thus negating the necessity of the macrophage for Sb V reduction. Furthermore, these data imply that either the parasite reduces Sb V to Sb III intracellularly, and thus Sb III is directly toxic to amastigotes, or that both oxidation states of antimony are active against Leishmania amastigotes. The modes of action of the two oxidation states of antimony (Sb III and Sb V ) on Leishmania are, as yet, not fully understood.Several groups have shown obligatory cross-resistance between Sb V , Sb III , and arsenite (As III ) in Leishmania tarentolae, Leishmania major, Leishmania mexicana, L. donovani and Leishmania infantum (11,[20][21][22]. In contrast, it has been suggested that, at least in L. donovani, such cross-resistance does not necessarily occur (12). Furthermore, it has been demonstrated that, when bound to organic compounds, structural similarities exist between Sb III and Sb V (23). For example, the trivalent antimony comp...

SummaryWe describe the first functional and molecular characterization of an amino acid permease (LdAAP3) from the human parasitic protozoan Leishmania donovani , the causative agent of visceral leishmaniasis in humans. This permease contains 480 amino acids with 11 predicted trans-membrane domains. Expressing LdAAP3 in Saccharomyces cerevisiae mutants revealed that LdAAP3 codes for a highaffinity arginine transporter ( K m 1.9 m M). LdAAP3 is highly specific for arginine as its transport was not inhibited by other amino acids or arginine-related compounds. Using green fluorescence protein (GFP) fused to the N-terminus of LdAAP3, this transporter was localized to the surface membrane of promastigotes. The GFP-LdAAP3 chimera mediated a threefold increase in arginine transport in promastigotes, indicating that it is active and confirmed that LdAAP3 codes for an arginine transporter in parasite cells as well. LdAAP3 is novel as it shares a high level of homology with amino acid permeases from other trypanosomatidae but almost none with permeases from other phyla. The results of this work suggest that LdAAP3 might play a role in host-parasite interaction.

Xenotransplantation of pig tissues has great potential to overcome the shortage of organ donors. One approach to address the vigorous immune rejection associated with xenotransplants is the use of embryonic precursor tissue, which induces and utilizes host vasculature upon its growth and development. Recently, we showed in mice that embryonic pig pancreatic tissue from embryonic day 42 (E42) exhibits optimal properties as a ␤ cell replacement therapy. We now demonstrate the proof of concept in 2 diabetic Cynomolgus monkeys, followed for 393 and 280 days, respectively. A marked reduction of exogenous insulin requirement was noted by the fourth month after transplantation, reaching complete independence from exogenous insulin during the fifth month after transplantation, with full physiological control of blood glucose levels. The porcine origin of insulin was documented by a radioimmunoassay specific for porcine C-peptide. Furthermore, the growing tissue was found to be predominantly vascularized with host blood vessels, thereby evading hyperacute or acute rejection, which could potentially be mediated by preexisting anti-pig antibodies. Durable graft protection was achieved, and most of the late complications could be attributed to the immunosuppressive protocol. While fine tuning of immune suppression, tissue dose, and implantation techniques are still required, our results demonstrate that porcine E-42 embryonic pancreatic tissue can normalize blood glucose levels in primates. Its long-term proliferative capacity, its revascularization by host endothelium, and its reduced immunogenicity, strongly suggest that this approach could offer an attractive replacement therapy for diabetes.immune-suppression ͉ rejection ͉ xeno-transplantation

IMPORTANCE BNT162b2 messenger RNA (mRNA) COVID-19 vaccination in the third trimester was found to be associated with a strong maternal humoral IgG response that crossed the placenta and approached maternal titers in the newborn.OBJECTIVE To evaluate maternal and neonatal SARS-CoV-2 immunoglobulin G (IgG) antibody levels at birth after mRNA COVID-19 vaccination during the second trimester of pregnancy. DESIGN, SETTING, AND PARTICIPANTSThis prospective cohort study, conducted at a single medical center in Haifa, Israel, from May to July 2021, included women with a singleton pregnancy over 24 weeks of gestation at least 7 days after receipt of their second COVID-19 vaccine dose who were not known to be previously infected with COVID-19.EXPOSURES BNT162b2 (Pfizer/BioNTech) vaccination. MAIN OUTCOMES AND MEASURESThe primary outcomes were SARS-CoV-2 IgG antibody titers measured in the parturient at admission and in the umbilical cord blood within 30 minutes after delivery. Secondary outcomes were the correlation between antibody titers, feto-maternal characteristics, maternal adverse effects after vaccination, and time interval from vaccination to delivery. RESULTS Antibody levels were measured for 129 women (mean [SD] age, 31.9 [4.9] years) and 114 neonates, with 100% of the tests having positive results. The mean (SD) gestational age at administration of the second vaccine dose was 24.9 (3.3) weeks. Neonatal IgG titers were 2.6 times higher than maternal titers (median [range], 3315.7 [350.1-17 643.5] AU/mL vs 1185.2 [146.6-32 415.1] AU/mL). A positive correlation was demonstrated between maternal and neonatal antibodies (r = 0.92; 95% CI, 0.89-0.94). Multivariable analysis revealed that for each week that passed since receipt of the second vaccine dose, maternal and neonatal antibody levels changed by −10.9% (95% CI, −17.2% to −4.2%; P = .002) and −11.7% (95% CI, −19.0 to −3.8%; P = .005), respectively. For each 1-year increase in the mother's age, maternal and neonatal antibody levels changed by −3.1% (95% CI, −5.3% to −0.9%; P = .007) and −2.7% (95% CI, −5.2% to −0.1%; P = .04), respectively. CONCLUSIONS AND RELEVANCEIn this cohort study, receipt of the BNT162b2 mRNA COVID-19 vaccine during the second trimester of pregnancy was associated with maternal and neonatal humoral responses, as reflected in maternal and neonatal SARS-CoV-2 IgG antibody levels measured after delivery. These findings support COVID-19 vaccination of pregnant individuals during the second trimester to achieve maternal protection and newborn safety during the pandemic.