196 research outputs found
Host genetics and parasitic infections
No full textParasites still impose a high death and disability burden on human populations, and are therefore likely to act as selective factors for genetic adaptations. Genetic epidemiological investigation of parasitic diseases is aimed at disentangling the mechanisms underlying immunity and pathogenesis by looking for associations or linkages between loci and susceptibility phenotypes. Until recently, most studies used a candidate gene approach and were relatively underpowered, with few attempts at replicating findings in different populations. However, in the last 5 years, genome-wide and/or multicentre studies have been conducted for severe malaria, visceral leishmaniasis, and cardiac Chagas disease, providing some novel important insights. Furthermore, studies of helminth infections have repeatedly shown the involvement of common loci in regulating susceptibility to distinct diseases such as schistosomiasis, ascariasis, trichuriasis, and onchocherciasis. As more studies are conducted, evidence is increasing that at least some of the identified susceptibility loci are shared not only among parasitic diseases but also with immunological disorders such as allergy or autoimmune disease, suggesting that parasites may have played a role in driving the evolution of the immune system
Genetics of susceptibility to Plasmodium falciparum: from classical malaria resistance genes towards genome-wide association studies.
No full textPlasmodium falciparum represents one of the strongest selective forces on the human genome. This stable and perennial pressure has contributed to the progressive accumulation in the exposed populations of genetic adaptations to malaria. Descriptive genetic epidemiology provides the initial step of a logical procedure of consequential phases spanning from the identification of genes involved in the resistance/susceptibility to diseases, to the determination of the underlying mechanisms and finally to the possible translation of the acquired knowledge in new control tools. In malaria, the rational development of this strategy is traditionally based on complementary interactions of heterogeneous disciplines going from epidemiology to vaccinology passing through genetics, pathogenesis and immunology. New tools including expression profile analysis and genome-wide association studies are recently available to explore the complex interactions of host-parasite co-evolution. Particularly, the combination of genome-wide association studies with large multi-centre initiatives can overcome the limits of previous results due to local population dynamics. Thus, we anticipate substantial advances in the interpretation and validation of the effects of genetic variation on malaria susceptibility, and thereby on molecular mechanisms of protective immune responses and pathogenesis
Virulence genes in Escherichia Coli isolated from diarrheic rabbits in intensive farms of Southern Italy
No full textRischio trasfusionale per Trypanosoma cruzi: screening dei donatori presso il laboratorio di Parassitologia dell'Azienda Ospedaliero Universitaria Pisana.
No full textIntroduzione
La legge 219 del 21/10/2015 e le relative linee guida (4.10/2015/66 e 4.10/2015/71) stabiliscono che soggetti nati in Paesi dove la malattia di Chagas è endemica, o che sono stati trasfusi o hanno soggiornato in condizioni di rischio in tali Paesi, possono essere ammessi alla donazione di sangue solo in presenza di un test per anticorpi anti-Trypanosoma cruzi negativo.
Materiali e metodi
Il laboratorio di Parassitologia dell'U. O. di Microbiologia dell' Azienda Ospedaliero Universitaria Pisana (AOUP) da Febbraio 2016 effettua il test di screening dei donatori che fanno capo ai centri trasfusionali dell’AOUP stessa e dell'Azienda USL Nord Ovest della Regione Toscana (Pisa, Livorno, Lucca, Massa Carrara, Pontedera e Viareggio), utilizzando la metodica dell'immunocromatografia (IC; Chagas Quick Test, Cypress Diagnostics) su campioni di siero. I campioni con risultato positivo sono stati ulteriormente testati tramite immunoblot (IB; Chagas IgG LineBlot, Novatec) e chemiluminescenza (CL; Architect Chagas, Abbott). Sono stati inoltre testati con le tre metodiche, in qualità di controlli, 10 sieri raccolti dal Centro Malattie Tropicali di Negrar (cortesia del Dott. Angheben).
Risultati
Nel periodo dal 15/02/2016 al 08/09/2016 sono stati testati 755 donatori. Quattro donatori (0.53%) sono risultati positivi al test ICT. Di questi, 3 sono risultati negativi al test IB e 4 al test CL. Tra i controlli, 8 sono risultati positivi a tutti i test, 1 è risultato negativo a tutti i test, e 1 è risultato negativo al test ICT, dubbio al test IB e debolmente positivo al test CL.
Conclusioni
Tra i 755 donatori di sangue afferenti all' Azienda USL Nord Ovest della Regione Toscana sottoposti a ricerca per anticorpi anti-Trypanosoma cruzi durante il periodo di studio sono risultati positivi al test ICT 4 soggetti, risultati però negativi al test CL, indicando una prevalenza di donatori sieropositivi dello 0%. I risultati del confronto tra i test ICT, IB e CL mostrano una buona concordanza, e suggeriscono di proseguire nell'utilizzo del test ICT come test di screening e del test CL come test di conferma, mentre l'IB potrà essere usato nel caso di discordanza dell'esito delle prime due metodiche, come suggerito dall'Organizzazione Mondiale della Sanita
Electrochemically controlled assembling/disassembling processes with a bis-imino bis-quinoline ligand and the CuII/CuI couple
No full textThe bis-iminoquinoline quadridentate ligand L is capable of forming air- and moisture-stable complexes both with Cu-II and Cu-I; thus the L/Cu-II/I set is a bistable system. Owing to its quite rigid preorganized structure, L forms the 1:1 complex [(CuL)-L-II](2+) when binding the d(9) cation Cu2+, while with the d(10) cation Cu+, dimeric complexes of the [(Cu2L2)-L-I](2+) type are formed in which each copper cation is coordinated by two iminoquinoline fragments belonging to two different ligands. Crystal and molecular structure determinations showed that, in [(CuL)-L-II](CF3SO3)(2), L binds to the metal center in a square-planar fashion, while in [(Cu2L2)-L-I](CF3SO3)(2) the Cu+ cations are coordinated with a tetrahedral geometry, with the two ligands L intertwined in a double helix. On the other hand, in the case of [(Cu2L2)-L-I](ClO4)(2) both a helical species and a dimeric nonhelical one were found to coexist in the same crystal cell. However, spectrophotometric and H-1 NMR studies demonstrated that, in acetonitrile solution, only two helical forms exist, one of which is more prevalent (87%, at 20 degrees C). The interconversion equilibrium between the two helical forms has been studied in acetonitrile by temperature variable H-1 NMR and the pertinent Delta H-circle minus and Delta S-circle minus values have been determined; these account for the small difference in energy between the two species. Finally, cyclic voltammetry and spectroelectrochemical experiments demonstrated that in acetonitrile solution it is possible to rapidly transform [(CuL)-L-II](2+) into the helical [(Cu2L2)-L-I](2+) dimer (or vice versa) by changing the potential applied to the working electrode, that is, it is possible to electrochemically control the self-assembly/disassembly process through the Cu-II/Cu-I redox couple. Moreover, it has been shown that self-assembly (reduction)/disassembly (oxidation) cycles can be repeated at will, without any degradation of the system
Differential antibody response to the Anopheles gambiae gSG6 and cE5 salivary proteins in individuals naturally exposed to bites of malaria vectors.
No full textBackgroundMosquito saliva plays crucial roles in blood feeding but also evokes in hosts an anti-saliva antibody response. The IgG response to the Anopheles gambiae salivary protein gSG6 was previously shown to be a reliable indicator of human exposure to Afrotropical malaria vectors. We analyzed here the humoral response to the salivary anti-thrombin cE5 in a group of individuals from a malaria hyperendemic area of Burkina Faso.MethodsELISA was used to measure the anti-cE5 IgG, IgG1 and IgG4 antibody levels in plasma samples collected in the village of Barkoumbilen (Burkina Faso) among individuals of the Rimaibé ethnic group. Anti-gSG6 IgG levels were also determined for comparison. Anopheles vector density in the study area was evaluated by indoor pyrethrum spray catches.ResultsThe cE5 protein was highly immunogenic and triggered in exposed individuals a relatively long-lasting antibody response, as shown by its unchanged persistence after a few months of absent or very low exposure (dry season). In addition cE5 did not induce immune tolerance, as previously suggested for the gSG6 antigen. Finally, IgG subclass analysis suggested that exposed individuals may mount a Th1-type immune response against the cE5 protein.ConclusionsThe anti-cE5 IgG response is shown here to be a sensitive indicator of human exposure to anopheline vectors and to represent an additional tool for malaria epidemiological studies. It may be especially useful in conditions of low vector density, to monitor transiently exposed individuals (i.e. travellers/workers/soldiers spending a few months in tropical Africa) and to evaluate the impact of insecticide treated nets on vector control. Moreover, the gSG6 and cE5 salivary proteins were shown to trigger in exposed individuals a strikingly different immune response with (i) gSG6 evoking a short-lived IgG response, characterized by high IgG4 levels and most likely induction of immune tolerance, and (ii) cE5 eliciting a longer-living IgG response, dominated by anti-cE5 IgG1 antibodies and not inducing tolerance mechanisms. We believe that these two antigens may represent useful reagents to further investigate the so far overlooked role of Anopheles saliva and salivary proteins in host early immune response to Plasmodium parasites
Investigating the evolutionary link between malaria and autoimmunity: a large scale immunogenetic study in two West African populations.
No full textAIM. Despite equivalent exposure to infection and comparable use of protective measures, the Fulani of West Africa have been shown to mount stronger immune responses to Plasmodium falciparum antigens and to be less susceptible to infection and mild disease than sympatric populations (Modiano et al. 1996, PNAS). The Fulani also show a higher response to other pathogens, and both their Th1 and Th2 responses are enhanced, suggesting that their resistance to malaria could result from a generally stronger immune activation. Key genes related to T regulatory cell function are indeed down-regulated in the Fulani (Torcia et al. 2008 PNAS). This disorder of immune homeostasis could be driven by genetic factors positively selected by P. falciparum and may underlie the higher susceptibility of the Fulani to diseases with autoimmune pathogenesis reported in the literature (Fish et al. 1987, Diabetologia; Mahe et al. 1996, Br J Dermatol; Brieger et al. 1997, Trop Med Int Health). The general aim of the proposed investigation is to explore the genetic basis of the lower susceptibility to malaria observed in the Fulani, and in particular to evaluate the role of autoimmunity loci. MATERIALS AND METHODS. To investigate this hypothesis, we conducted a large-scale epidemiological study in rural villages of Burkina Faso inhabited by Fulani, Mossi and Rimaibe communities. The field study lasted 2 years (2007-8) and consisted in a combination of cross sectional and longitudinal surveys. At each survey we collected parasitological (P. falciparum index and parasite density), clinical (fever, anemia, spleen size) and serological data (IgG levels against P. falciparum and self antigens). We genotyped 363 Single Nucleotide Polymorphisms (SNPs) on 2186 samples using the Sequenom System, based on allele-specific primer extension and MALDI-TOF Mass Spectrometry. SNPs included polymorphisms previously shown to be involved in resistance to severe malaria, in resistance to infection and/or in antibody production, as well as polymorphisms at autoimmunity loci. We conducted population genetic analyses and genetic association analysis with parasitological, clinical and serological phenotypes using the free software package R. RESULTS. Principal component analysis revealed that Mossi and Rimaibe (Non-Fulani) are not genetically distinct among themselves, whereas the Fulani are a clearly distinct group, in agreement with data obtained on HLA class I-II alleles (Modiano et al. 2001, Tissue Antigens; Lulli et al. 2009, Hum Immunol). We therefore compared allele frequencies and calculated Fst, a measure of population genetic differentiation, between Fulani and Non-Fulani. We observed that the proportion of autoimmunity SNPs with Fst>0.05 (indicating moderate/high differentiation and corresponding to at least a two-fold difference in allele frequency) is 20%, versus 10% shown by other loci (p=0.03). Genetic association analysis of susceptibility to infection and infection levels showed association signals among genes involved in resistance to severe malaria (TNF, DDC, ABO, IFNG-IL22, GNAS, MECP2, G6PD). Furthermore we observed strong signals of association, both in Fulani and Non-Fulani, in the 5q31 region of the genome, which has been previously linked to P. falciparum infection levels (Rihet et al. 1998, Am J Hum Genet; Mangano et al. 2008, Genes Immun). Finally, association signals were also observed among genes related to T regulatory cell function and/or involved in autoimmunity (TGFBR3, CD25, FCGR2A, CR1, IL1R1L-IL18RAP, IL1A-IL1B, IL21, BLK, ORMDL3, TGFB1). CONCLUSIONS. The results of our investigation support the hypothesis that malaria has exerted a selective pressure on the immune system and has affected is evolution, and provide evidence that common gene regulatory networks could underlie susceptibility to malaria and to immunological disorders such as autoimmune diseases
Genetic association of IFN-gamma loci with immuno-parasitological phenotypes in Mossi and Fulani of Burkina Faso
No full textHLA-DRB1 and -DQB1 loci in three west African ethnic groups: genetic relationship with sub-Saharan African and European populations
No full textThe Fulani of west Africa have been shown to be less susceptible to malaria and to mount a stronger immune response to malaria than sympatric ethnic groups. The analysis of HLA diversity is useful for the assessment of the genetic distance between the Fulani and sympatric populations, which represents the necessary theoretical background for the investigation of genetic determinants of susceptibility to malaria. We assessed the polymorphism of HLA-DRB1 and -DQB1 loci and analyzed the distribution of alleles/haplotypes in Fulani, Mossi, and Rimaibé from Burkina Faso. We then investigated the genetic relationship of these three ethnic groups with other sub-Saharan African populations as well as with Europeans. We confirmed that the Fulani from Burkina Faso are genetically distinct from sympatric Mossi and Rimaibé. Furthermore the Fulani from Burkina Faso are close to those from The Gambia and, intriguingly, share the distribution of specific alleles with east African populations (Amhara and Oromo). It is noteworthy that the HLA-DRB1*04 and -DQB1*02 alleles, which are implicated in the development of several autoimmune diseases, are present at high frequency in the Fulani, suggesting their potential involvement in the enhanced immune reactivity observed in this population
Novel qRT-PCR assay for the detection and quantification of male and female Plasmodium falciparum gametocytes in human populations
No full textThe presence of Plasmodium falciparum gametocytes in peripheral blood is essential for human to mosquito malaria transmission. The detection and quantification of gametocytes as well as the estimation of the sex-ratio are essential to assess the human host ability to infect mosquitoes, and comprehensively evaluate malaria transmission risk. The mature gametocytes, responsible for parasite transmission, often circulate at low densities, therefore sensitive molecular tools are necessary to improve detection of low densities of gametocytes and submicroscopic infections to identify potential transmission reservoir.
The aim of our work is to develop sensitive and cheap Real Time qPCR assays for large-scale epidemiological surveys, based on the detection and quantification of gametocyte-specific transcripts.
RT-qPCR methods based on SYBR Green were developed for target genes expressed by male and female gametocytes. We selected two genes Pfs25 and Pfs230p known to be expressed in females and males respectively, and two new target genes GK (female) and Pf13(male).
RNA was extracted from blood samples collected in a village of Burkina Faso. To overcome the inherent variability of RNA and different reverse transcription and PCR efficiencies, the quantification obtained for each target were normalized by human housekeeping gene (18S).
Preliminary results obtained for 50 samples showed that, as expected, the assays are more sensitive than microscopic examinations. Pf13 male target gene seems to be more sensitive than Pfs230p. The normalization by 18S quantity, improved the correlation between gametocytes density estimated by microscopy and qPCR (correlation coefficient 0.13 vs 0.42).
Ongoing work is aimed at the conversion of transcript copies/μl into gametocytes/μl and at sex-ratio determination
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