Malarone treatment failure and in vitro confirmation of resistance of Plasmodium falciparum isolate from Lagos, Nigeria

We report the first in vitro and genetic confirmation of Malarone(®) (GlaxoSmithKline; atovaquone and proguanil hydrochloride) resistance in Plasmodium falciparum acquired in Africa. On presenting with malaria two weeks after returning from a 4-week visit to Lagos, Nigeria without prophylaxis, a male patient was given a standard 3-day treatment course of Malarone(®). Twenty-eight days later the parasitaemia recrudesced. Parasites were cultured from the blood and the isolate (NGATV01) was shown to be resistant to atovaquone and the antifolate pyrimethamine. The cytochrome b gene of isolate NGATV01 showed a single mutation, Tyr268Asn which has not been seen previously

Two Different, Highly Exposed, Bulged Structures for an Unusually Long Peptide Bound to Rat MHC Class I RT1-Aa

AbstractThe rat MHC class Ia molecule RT1-Aa has the unusual capacity to bind long peptides ending in arginine, such as MTF-E, a thirteen-residue, maternally transmitted minor histocompatibility antigen. The antigenic structure of MTF-E was unpredictable due to its extraordinary length and two arginines that could serve as potential anchor residues. The crystal structure of RT1-Aa-MTF-E at 2.55 Å shows that both peptide termini are anchored, as in other class I molecules, but the central residues in two independent pMHC complexes adopt completely different bulged conformations based on local environment. The MTF-E epitope is fully exposed within the putative T cell receptor (TCR) footprint. The flexibility demonstrated by the MTF-E structures illustrates how different TCRs may be raised against chemically identical, but structurally dissimilar, pMHC complexes

Characterisation of RT1-E2, a multigenic family of highly conserved rat non-classical MHC class I molecules initially identified in cells from immunoprivileged sites

BACKGROUND: So-called "immunoprivileged sites" are tissues or organs where slow allograft rejection correlates with low levels of expression of MHC class I molecules. Whilst classical class I molecules are recognised by cytotoxic T lymphocytes (CTL), some MHC class I molecules are called "non-classical" because they exhibit low polymorphism and are not widely expressed. These last years, several studies have shown that these can play different, more specialised roles than their classical counterparts. In the course of efforts to characterise MHC class I expression in rat cells obtained from immunoprivileged sites such as the central nervous system or the placenta, a new family of non-classical MHC class I molecules, which we have named RT1-E2, has been uncovered. RESULTS: Members of the RT1-E2 family are all highly homologous to one another, and the number of RT1-E2 loci varies from one to four per MHC haplotype among the six rat strains studied so far, with some loci predicted to give rise to soluble molecules. The RT1(n )MHC haplotype (found in BN rats) carries a single RT1-E2 locus, which lies in the RT1-C/E region of the MHC and displays the typical exon-intron organisation and promoter features seen in other rat MHC class I genes. We present evidence that: i) RT1-E2 molecules can be detected at the surface of transfected mouse L cells and simian COS-7 cells, albeit at low levels; ii) their transport to the cell surface is dependent on a functional TAP transporter. In L cells, their transport is also hindered by protease inhibitors, brefeldin A and monensin. CONCLUSIONS: These findings suggest that RT1-E2 molecules probably associate with ligands of peptidic nature. The high homology between the RT1-E2 molecules isolated from divergent rat MHC haplotypes is particularly striking at the level of their extra-cellular portions. Compared to other class I molecules, this suggests that RT1-E2 molecules may associate with well defined sets of ligands. Several characteristics point to a certain similarity to the mouse H2-Qa2 and human HLA-G molecules

GIMAP6 is required for T cell maintenance and efficient autophagy in mice

The GTPases of the immunity-associated proteins (GIMAP) GTPases are a family of proteins expressed strongly in the adaptive immune system. We have previously reported that in human cells one member of this family, GIMAP6, interacts with the ATG8 family member GABARAPL2, and is recruited to autophagosomes upon starvation, suggesting a role for GIMAP6 in the autophagic process. To study this possibility and the function of GIMAP6 in the immune system, we have established a mouse line in which the Gimap6 gene can be inactivated by Cre-mediated recombination. In mice bred to carry the CD2Cre transgene such that the Gimap6 gene was deleted within the T and B cell lineages there was a 50-70% reduction in peripheral CD4(+) and CD8(+) T cells. Analysis of splenocyte-derived proteins from these mice indicated increased levels of MAP1LC3B, particularly the lipidated LC3-II form, and S405-phosphorylation of SQSTM1. Electron microscopic measurements of Gimap6(-/-) CD4(+) T cells indicated an increased mitochondrial/cytoplasmic volume ratio and increased numbers of autophagosomes. These results are consistent with autophagic disruption in the cells. However, Gimap6(-/-) T cells were largely normal in character, could be effectively activated in vitro and supported T cell-dependent antibody production. Treatment in vitro of CD4(+) splenocytes from GIMAP6(fl/fl) ERT2Cre mice with 4-hydroxytamoxifen resulted in the disappearance of GIMAP6 within five days. In parallel, increased phosphorylation of SQSTM1 and TBK1 was observed. These results indicate a requirement for GIMAP6 in the maintenance of a normal peripheral adaptive immune system and a significant role for the protein in normal autophagic processes. Moreover, as GIMAP6 is expressed in a cell-selective manner, this indicates the potential existence of a cell-restricted mode of autophagic regulation

Gametocytaemia after Drug Treatment of Asymptomatic Plasmodium falciparum

OBJECTIVES: Treatment of Plasmodium falciparum malaria with sulfadoxine-pyrimethamine (SP) is followed by a sharp rise in the prevalence and density of gametocytes. We did a randomized trial to determine the effect of treatment of asymptomatic infections with SP or SP plus one dose of artesunate (SP+AS) on gametocyte carriage. DESIGN: The study was a three-arm open-label randomized trial. We randomized asymptomatic carriers of P. falciparum to receive antimalarial treatment or placebo, and recorded the prevalence and density of gametocytes over the next 2 mo. SETTING: The trial was conducted during the dry (low malaria transmission) season in four rural villages in Gambia. PARTICIPANTS: Participants were adults and children aged over 6 mo with asexual P. falciparum infection and confirmed free of clinical symptoms of malaria over a 2-d screening period. INTERVENTIONS: Participants were randomized to receive a single dose of SP or SP+AS or placebo. OUTCOME MEASURES: The outcome measures were the presence of gametocytes 7 and 56 d after treatment, and the duration and density of gametocytaemia over 2 mo. RESULTS: In total, 372 asymptomatic carriers were randomized. Gametocyte prevalence on day 7 was 10.5% in the placebo group, 11.2% in the SP group (risk difference to placebo 0.7%, 95% confidence interval −7.4% to 8.7%, p = 0.87), and 7.1% in the SP+AS group (risk difference to placebo 4.1%, 95% confidence interval −3.3% to 12%, p = 0.28). By day 56, gametocyte prevalence was 13% in the placebo group and 2% in both drug-treated groups. Gametocyte carriage (the area under the curve of gametocyte density versus time), was reduced by 71% in the SP group, and by 74% in the SP+AS group, compared to placebo. Gametocyte carriage varied with age and was greater among children under 15 than among adults. CONCLUSIONS: Treatment of asymptomatic carriers of P. falciparum with SP does not increase gametocyte carriage or density. Effective treatment of asexual parasitaemia in the dry season reduces gametocyte carriage to very low levels after 4 wk

Glucose modifies the effect of endovascular thrombectomy in patients with acute stroke: a pooled-data meta-analysis

Background and Purpose: Hyperglycemia is a negative prognostic factor following acute ischemic stroke but is not known whether glucose is associated with the effects of endovascular thrombectomy in patients with large vessel stroke. In a pooled-data meta-analysis, we analyzed whether serum glucose is a treatment modifier of the efficacy of endovascular thrombectomy in acute stroke. Methods: Seven randomized trials compared endovascular thrombectomy with standard care between 2010 and 2017 (HERMES Collaboration). 1764 patients with large vessel stroke were allocated to endovascular thrombectomy (n=871) or standard care (n=893). Measurements included blood glucose on admission and functional outcome [modified Rankin Scale (mRS) range: 0-6; lower scores indicating less disability] at 3 months. The primary analysis evaluated whether glucose modified the effect of EVT over standard care on functional outcome, using ordinal logistic regression to test the interaction between treatment and glucose level. Results: Median (IQR) serum glucose on admission was 120 (104-140) mg/dl [6.6mmol/l (5.7-7.7) mmol/l]. Endovascular thrombectomy (EVT) was better than standard care in the overall pooled-data analysis [common odds ratio (acOR), 2.00 (95% CI 1.69–2.38); however, lower glucose levels were associated with greater effects of EVT over standard care. The interaction was nonlinear such that significant interactions were found in subgroups of patients split at glucose < or > 90mg/dl (5.0mmol/l) [(p=0.019 for interaction, acOR 3.81 (95% CI 1.73–8.41) for patients < 90 mg/dl vs 1.83 (95% CI 1.53–2.19) for patients > 90 mg/dl], and glucose < or > 100mg/dl (5.5mmol/l) [(p=0.004 for interaction, acOR 3.17 (95% CI 2.04–4.93) vs acOR 1.72 (95% CI 1.42–2.08)], but not between subgroups above these levels of glucose. Conclusions: Endovascular thrombectomy improved stroke outcomes compared to standard treatment regardless of glucose levels but the treatment effects were larger at lower glucose levels, with significant interaction effects persisting up to 90 to 100mg/dl (5.0-5.5mmol/l). Whether tight control of glucose improves the efficacy of endovascular thrombectomy following large vessel stroke warrants appropriate testing