A homolog of Bacillus subtilis trigger factor in Listeria monocytogenes is involved in stress tolerance and bacterial virulence

Molecular chaperones play an essential role in the folding of nascent chain polypeptides, as well as in the refolding and degradation of misfolded or aggregated proteins. They also assist in protein translocation and participate in stress functions. We identified a gene, designated tig, encoding a protein homologous to trigger factor (TF), a cytosolic ribosome-associated chaperone, in the genome of Listeria monocytogenes. We constructed a chromosomal Delta tig deletion and evaluated the impact of the mutation on bacterial growth in broth under various stress conditions and on pathogenesis. The Delta tig deletion did not affect cell viability but impaired survival in the presence of heat and ethanol stresses. We also identified the ffh gene, encoding a protein homologous to the SRP54 eukaryotic component of the signal recognition particle. However, a Delta ffh deletion was not tolerated, suggesting that Ffh is essential, as it is in Bacillus subtilis and Escherichia coli. Thus, although dispensable for growth, TF is involved in the stress response of L. monocytogenes. The Delta tig mutant showed no or very modest intracellular survival defects in eukaryotic cells. However, in vivo it showed a reduced capacity to persist in the spleens and livers of infected mice, revealing that TF has a role in the pathogenicity of L. monocytogenes.     

Role of the envelope genetic context in the development of enfuvirtide resistance in human immunodeficiency virus type 1-infected patients

Acquired human immunodeficiency virus type 1(HIV-1) resistance to the fusion inhibitor enfuvirtide (ENF) is primarily associated with mutations within the highly conserved first heptad repeat (HR1) region of gp41. Viral env sequences, however, are remarkably variable, and the envelope genetic background could have an important impact on optimal expression of HR1 mutations. We have examined the genetic evolution of env sequences, ENF susceptibility, and Env replicative capacity in patients failing ENF treatment. Sequential plasma-derived virus populations, obtained from six patients initiating ENF treatment as part of a salvage therapy, were studied using a recombinant phenotypic assay evaluating the entire gp120 and the gp41 ectodomains. Regardless of major differences in the baseline ENF susceptibilities, viral populations with similar phenotypic ENF resistance (50% inhibitory concentration, >3,000 ng/ml) were selected under treatment in four of six patients. As expected, in all patients ENF-resistant viruses harbored one or more HR1 mutations (positions 36, 38, and 43). Interestingly, in five patients the emergence of resistance mutations was not associated with reduced Env replicative capacity. Phylogenetic analysis of env sequences in sequential samples from two patients showed that the HR1 mutations had emerged in the context of env quasi-species that were different from those prevalent at baseline. Thus, the envelope genetic context appears to play a critical role in the selection of HR1 mutations and the expression of ENF resistance, thereby conditioning the evolution of HIV-1 under fusion inhibitor selective pressure.     

Choreoathetosis – an unusual adverse effect of dihydroartemisinin-piperaquine: a case report

Background

Dihydroartemisinin-piperaquine is a combination of dihydroartemisinin and piperaquine which is highly effective in the treatment of uncomplicated falciparum malaria. Its adverse effects are generally tolerable and temporary. Choreoathetosis, an involuntary movement disorder characterized by continuous irregular twisting of the body, is not a documented adverse effect of this medication.

Case presentation

A 41-year-old Cameroonian man of black African ethnicity was brought to our primary care hospital because over the previous 6 hours he had been experiencing involuntary twisting movements of his body and he no longer had control of his limbs. Earlier that day, he had been prescribed an appropriate dose of dihydroartemisinin-piperaquine in our hospital. The abnormal movements started approximately 3 hours after ingesting the first dose of the drug. The review of systems and his past history were unremarkable. On clinical examination, he was conscious and oriented but was unsteady and displayed continuous generalized irregular twisting movements combined with abrupt low amplitude flinging of his limbs. Dihydroartemisinin-piperaquine-induced generalized choreoathetosis was diagnosed. He was sedated with diazepam and dihydroartemisinin-piperaquine was discontinued. The antimalarial drug was substituted with artemether-lumefantrine combination. The clinical progress was good and he was discharged home after 72 hours. No further abnormalities were noted during 7 months of follow-up.

Conclusion

Although dihydroartemisinin-piperaquine is increasingly popular as a well-tolerated/efficacious antimalarial drug, clinicians must note the rare possibility of choreoathetosis as an adverse effect of this medication and educate patients accordingly.

     

Sequencing and expression of the CD3 gamma/delta mRNA in Pleurodeles waltl (urodele amphibian)

The CD3 complex is an essential component of the T-cell receptor (TCR) implicated in T-cell maturation and activation. This TCR has been identified in both cartilaginous and bony vertebrates. In different studies where the CD3 chains were cloned and sequenced, it appeared that the CD3 complex is composed of several chains, all susceptible to phosphorylation and able to transduce signals. Here, by an approach combining degenerative oligonucleotide primers and RACE-PCR, we report the cloning and sequencing of a CD3 cDNA from the salamander Pleurodeles waltl, highly homologous to the Xenopus and chicken CD3 gamma/delta cDNAs. Using semi-quantitative PCR and Northern blot analysis, we found the highest CD3 gamma/delta mRNA expression in the thymus; weaker expression was observed in the spleen and blood, followed by the intestine, therefore confirming the tissue and lymphoid specificities of this mRNA. The signals in the spleen, blood and intestine represented 55%, 33% and 16%, respectively, of the signal detected in the thymus. During the embryonic and larval stages of Pleurodeles waltl development, CD3 gamma/delta mRNA expression begins early at the neurula stage (stage 15, 69 h after laying), increases up to stage 33 (9 days after laying) and afterwards remains stable, at least until the larval stage 42 (28 days after laying). As the thymus primordium appears much later, the question of the formation and maturation of the first T-cell precursors outside this organ is posed.     

Linkage of one gene for familial glucocorticoid deficiency type 2 (FGD2) to chromosome 8q and further evidence of heterogeneity

In several cases of familial glucocorticoid deficiency (FGD), referred to as FGD type 1, mutations have been described in the coding exon of the adrenocorticotropin receptor (melanonocortin receptor type 2, MC2R) gene. However, for the majority of cases (FGD type 2), no mutations were found in this gene. In the more informative families, the involvement of the MC2R locus could be excluded by linkage or sequencing analysis and, as there was no obvious candidate gene, a genome linkage scan was performed. Fourteen families were studied in this report. Evidence of linkage was found with markers on chromosome 8q in three out of the 14 families (maximum heterogeneity LOD score of 2.81 at D8S1763). These three families were consanguineous and the gene could be located by homozygosity mapping between markers D8S285 and D8S1718 in a 8.8-cM region. No potential candidate genes were apparent in the region. Linkage to this region could be excluded in some families from our sample giving highly negative LOD scores with the markers of the region. This result suggests that at least one other gene, located on a different region, must be responsible for FGD in these families and provides new evidence of genetic heterogeneity of this disorder.     

Regulatory CD4+ T cells are crucial for preventing CD8+ T cell-mediated autoimmunity

In vivo studies have shown that regulatory CD4(+) T cells regulate conventional CD4(+) T cell responses to self- and environmental Ags. However, it remains unclear whether regulatory CD4(+) T cells control CD8(+) T cell responses to self, directly, or indirectly by decreasing available CD4(+) T cell help. We have developed an experimental mouse model in which suppressive and helper T cells cannot mediate their functions. The mouse chimeras generated were not viable and rapidly developed multiple organ autoimmunity. These features were correlated with strong CD8(+) T cell activation and accumulation in both lymphoid and nonlymphoid organs. In vivo Ab treatment and secondary transfer experiments demonstrated that regulatory CD4(+) T cells play an important direct role in the prevention of peripheral CD8(+) T cell-mediated autoimmunity.     

A novel bioactive peptide from yoghurts modulates expression of the gel-forming MUC2 mucin as well as population of goblet cells and Paneth cells along the small intestine

Several studies demonstrated that fermented milks may provide a large number of bioactive peptides into the gastrointestinal tract. We previously showed that beta-casomorphin-7, an opioid-like peptide produced from bovine β-casein, strongly stimulates intestinal mucin production in ex vivo and in vitro models, suggesting the potential benefit of milk bioactive peptides on intestinal protection. In the present study, we tested the hypothesis that the total peptide pool (TPP) from a fermented milk (yoghurt) may act on human intestinal mucus-producing cells (HT29-MTX) to induce mucin expression. Our aim was then to identify the peptide(s) carrying the biological activity and to study its impact in vivo on factors involved in gut protection after oral administration to rat pups (once a day, 9 consecutive days). TPP stimulated MUC2 and MUC4 gene expression as well as mucin secretion in HT29-MTX cells. Among the four peptide fractions that were separated by preparative reversed-phase high-performance liquid chromatography, only the C2 fraction was able to mimic the in vitro effect of TPP. Interestingly, the sequence [94-123] of β-casein, present only in C2 fraction, also regulated mucin production in HT29-MTX cells. Oral administration of this peptide to rat pups enhanced the number of goblet cells and Paneth cells along the small intestine. These effects were associated with a higher expression of intestinal mucins (Muc2 and Muc4) and of antibacterial factors (lysozyme, rdefa5). We conclude that the peptide β-CN(94-123) present in yoghurts may maintain or restore intestinal homeostasis and could play an important role in protection against damaging agents of the intestinal lumen.     

Medicinal plants and phytochemicals against multidrug-resistant tumor cells expressing ABCB1, ABCG2, or ABCB5: a synopsis of 2 decades

Phytochemistry Reviews - Multidrug resistance is a major factor causing the failure of cancer chemotherapy. Efflux pumps of the ATP-binding cassette (ABC) transporter family expel a large array of...