Altered parasite life-cycle processes characterize Babesia divergens infection in human sickle cell anemia

Babesia divergens is an intra-erythrocytic parasite that causes malaria-like symptoms in infected people. As the erythrocyte provides the parasite with the infra-structure to grow and multiply, any perturbation to the cell should impact parasite viability. Support for this comes from the multitude of studies that have shown that the sickle trait has in fact been selected because of the protection it provides against a related Apicomplexan parasite, Plasmodium, that causes malaria. In this paper, we examine the impact of both the sickle cell anemia and sickle trait red blood cell (RBC) environment on different aspects of the B. divergens life-cycle, and reveal that multiple aspects of parasite biological processes are altered in the mutant sickle anemia RBC. Such processes include parasite population progression, caused potentially by defective merozoite infectivity and/or defective egress from the sickle cell, resulting in severely lowered parasitemia in these cells with sickle cell anemia. In contrast, the sickle trait RBC provide a supportive environment permitting in vitro infection rates comparable to those of wild-type RBC. The elucidation of these naturally occurring RBC resistance mechanisms is needed to shed light on host-parasite interaction, lend evolutionary insights into these related blood-borne parasites, and to provide new insights into the development of therapies against this disease

Robust adaptive immune response against Babesia microti infection marked by low parasitemia in a murine model of sickle cell disease.

The intraerythrocytic parasite Babesia microti is the number 1 cause of transfusion-transmitted infection and can induce serious, often life-threatening complications in immunocompromised individuals including transfusion-dependent patients with sickle cell disease (SCD). Despite the existence of strong long-lasting immunological protection against a second infection in mouse models, little is known about the cell types or the kinetics of protective adaptive immunity mounted following Babesia infection, especially in infection-prone SCD that are thought to have an impaired immune system. Here, we show, using a mouse B microti infection model, that infected wild-type (WT) mice mount a very strong adaptive immune response, characterized by (1) coordinated induction of a robust germinal center (GC) reaction; (2) development of follicular helper T (TFH) cells that comprise ∼30% of splenic CD4+ T cells at peak expansion by 10 days postinfection; and (3) high levels of effector T-cell cytokines, including interleukin 21 and interferon γ, with an increase in the secretion of antigen (Ag)-specific antibodies (Abs). Strikingly, the Townes SCD mouse model had significantly lower levels of parasitemia. Despite a highly disorganized splenic architecture before infection, these mice elicited a surprisingly robust adaptive immune response (including comparable levels of GC B cells, TFH cells, and effector cytokines as control and sickle trait mice), but higher immunoglobulin G responses against 2 Babesia-specific proteins, which may contain potential immunogenic epitopes. Together, these studies establish the robust emergence of adaptive immunity to Babesia even in immunologically compromised SCD mice. Identification of potentially immunogenic epitopes has implications to identify long-term carriers, and aid Ag-specific vaccine development. © 2018 by The American Society of Hematology

Transcriptional profiling reveals the expression of novel genes in response to various stimuli in the human dermatophyte Trichophyton rubrum

<p>Abstract</p> <p>Background</p> <p>Cutaneous mycoses are common human infections among healthy and immunocompromised hosts, and the anthropophilic fungus <it>Trichophyton rubrum </it>is the most prevalent microorganism isolated from such clinical cases worldwide. The aim of this study was to determine the transcriptional profile of <it>T. rubrum </it>exposed to various stimuli in order to obtain insights into the responses of this pathogen to different environmental challenges. Therefore, we generated an expressed sequence tag (EST) collection by constructing one cDNA library and nine suppression subtractive hybridization libraries.</p> <p>Results</p> <p>The 1388 unigenes identified in this study were functionally classified based on the Munich Information Center for Protein Sequences (MIPS) categories. The identified proteins were involved in transcriptional regulation, cellular defense and stress, protein degradation, signaling, transport, and secretion, among other functions. Analysis of these unigenes revealed 575 <it>T. rubrum </it>sequences that had not been previously deposited in public databases.</p> <p>Conclusion</p> <p>In this study, we identified novel <it>T. rubrum </it>genes that will be useful for ORF prediction in genome sequencing and facilitating functional genome analysis. Annotation of these expressed genes revealed metabolic adaptations of <it>T. rubrum </it>to carbon sources, ambient pH shifts, and various antifungal drugs used in medical practice. Furthermore, challenging <it>T. rubrum </it>with cytotoxic drugs and ambient pH shifts extended our understanding of the molecular events possibly involved in the infectious process and resistance to antifungal drugs.</p

Different forms of <i>Babesia divergens</i> in human RBCs as seen on a Giemsa-stained smear from <i>in vitro</i> cultured parasites (ring, dividing figure eights, Maltese cross parasites, and multiply infected RBCs).

<p>Different forms of <i>Babesia divergens</i> in human RBCs as seen on a Giemsa-stained smear from <i>in vitro</i> cultured parasites (ring, dividing figure eights, Maltese cross parasites, and multiply infected RBCs).</p

Identification and characterization of the RouenBd1987 Babesia divergens Rhopty-Associated Protein 1.

Human babesiosis is caused by one of several babesial species transmitted by ixodid ticks that have distinct geographical distributions based on the presence of competent animal hosts. The pathology of babesiosis, like malaria, is a consequence of the parasitaemia which develops through the cyclical replication of Babesia parasites in a patient's red blood cells, though symptoms typically are nonspecific. We have identified the gene encoding Rhoptry-Associated Protein -1 (RAP-1) from a human isolate of B. divergens, Rouen1987 and characterized its protein product at the molecular and cellular level. Consistent with other Babesia RAP-1 homologues, BdRAP-1 is expressed as a 46 kDa protein in the parasite rhoptries, suggesting a possible role in red cell invasion. Native BdRAP-1 binds to an unidentified red cell receptor(s) that appears to be non-sialylated and non-proteinacious in nature, but we do not find significant reduction in growth with anti-rRAP1 antibodies in vitro, highlighting the possibility the B. divergens is able to use alternative pathways for invasion, or there is an alternative, complementary, role for BdRAP-1 during the invasion process. As it is the parasite's ability to recognize and then invade host cells which is central to clinical disease, characterising and understanding the role of Babesia-derived proteins involved in these steps are of great interest for the development of an effective prophylaxis

A single amino acid substitution in one of the lipases of Aspergillus nidulans confers resistance to the antimycotic drug undecanoic acid

A plausible approach to evaluate the inhibitory action of antifungals is through the investigation of the fungal resistance to these drugs. We describe here the molecular cloning and initial characterization of the A. nidulans lipA gene, where mutation (lipA1) conferred resistance to undecanoic acid, the most fungitoxic fatty acid in the C(7:0)-C(18:0) series. The lipA gene codes for a putative lipase with the sequence consensus GVSIS and WIFGGG as the catalytic signature. Comparison of the wild-type and LIP1 mutant strain nucleotide sequences showed a G -> A change in lipA1 allele, which results in a Glu(214) -> Lys substitution in LipA protein. This ionic charge change in a conserved LipA region, next to its catalytic site, may have altered the catalytic properties of this enzyme resulting in resistance to undecanoic acid.FAPESPCNPqCAPESFAEP

Native BdRAP-1 localised to apical complex.

<p>A, Immunofluorescence staining with anti-rBdRAP-1 antibodies (FITC) on fixed cells infected with <i>B. divergens</i> parasites (DAPI) clearly shows that BdRAP-1 is localised to the apical ends of all 4 parasites in this Maltese Cross form of the intracellular parasite (see Merged panel). B, Electron microscopy of a singly-infected RBC (direct magnification of 30,000×, print magnification of ∼50,000×) shows the location of the rhoptry organelles and the presence of BdRAP-1. C, An enlarged section (direct magnification 49,000×, print magnification of ∼140,000×) clearly shows localisation of native BdRAP-1 is within the bulb of the rhoptry organelle.</p

Antigenicity of recombinant BdRAP-1 against sera from <i>B. divergens</i> –infected cows and hamsters.

<p>A, The reactivity of rBdRAP-1 in ELISA with pre-immune (PI) sera and experimentally <i>B. divergens</i>-infected sera from cows (n = 6). All infected bovine sera showed higher OD values than non-infected sera in a dilution-dependant manner at all dilutions. B, The reactivity of rBdRAP-1 in ELISA with pre-immune (PI) sera and experimentally <i>B. divergens</i>-infected sera from gerbils (n = 5). Four of the five gerbil sera showed s higher OD values than non-infected sera in a dilution-dependant manner at dilutions 1∶200 to 1∶6,400. One gerbil serum (G5) showed no reactivity. At dilutions 1∶12,800 and 1∶26,600, there is no difference in the reactivity of the gerbil sera and the pre-immune sera. C, Specificity for the animal serum against recombinant BdRAP-1 was confirmed independently by immunoblotting. Four of the six bovine sera and two of the three gerbil sera reacted strongly against rBdRAP-1. One gerbil sera (G3) reacted weakly. Sera which showed the greatest reactivity in ELISA (C3, G1 and G4) also showed greatest reactivity on the blots. Sera G2 and G3 showed moderate reactivity in ELISA but surprisingly very low reactivity in the Western analysis. Sera which did not show any significant reactivity in the ELISA (C5,C6 and G5) also did not react against rBdRAP-1 by immune-blotting.</p