Michel Tibayrenc

Molecular Typing of Trypanosoma cruzi Isolates, United States

Studies have characterized Trypanosoma cruzi from parasite-endemic regions. With new human cases, increasing numbers of veterinary cases, and influx of potentially infected immigrants, understanding the ecology of this organism in the United States is imperative. We used a classic typing scheme to determine the lineage of 107 isolates from various hosts.

Genetic Characterization of Trypanosoma cruzi DTUs in Wild Triatoma infestans from Bolivia: Predominance of TcI

Background The current persistence of Triatoma infestans (one of the main vectors of Chagas disease) in some domestic areas could be related to re-colonization by wild populations which are increasingly reported. However, the infection rate and the genetic characterization of the Trypanosoma cruzi strains infecting these populations are very limited. Methodology/Principal Findings Of 333 wild Triatoma infestans specimens collected from north to south of a Chagas disease endemic area in Bolivia, we characterized 234 stocks of Trypanosoma cruzi using mini-exon multiplex PCR (MMPCR) and sequencing the glucose phosphate isomerase (Gpi) gene. Of the six genetic lineages (“discrete typing units”; DTU) (TcI-VI) presently recognized in T. cruzi, TcI (99.1%) was overdominant on TcIII (0.9%) in wild Andean T. infestans, which presented a 71.7% infection rate as evaluated by microscopy. In the lowlands (Bolivian Chaco), 17 “dark morph” T. infestans were analyzed. None of them were positive for parasites after microscopic examination, although one TcI stock and one TcII stock were identified using MMPCR and sequencing. Conclusions/Significance By exploring large-scale DTUs that infect the wild populations of T. infestans, this study opens the discussion on the origin of TcI and TcV DTUs that are predominant in domestic Bolivian cycles.

Trypanosoma cruzi: New insights on ecophylogeny and hybridization by multigene sequencing of three nuclear and one maxicircle genes

Natural populations of Trypanosoma cruzi are structured into five genetic lineages, T. cruzi I and T. cruzi II a to e, as the result of clonal evolution with rare genetic recombination events. To explore more in depth these phenomenons, a multigene sequencing approach was used, for the first time in the case of T. cruzi. Three nuclear loci and a maxicircle locus were sequenced on 18 T. cruzi stocks. Sequences were used to build phylogenetic trees from each locus and from concatenated sequences of all loci. The data confirmed the hybrid origin of DTUs IId and IIe, as the result of an ancient genetic recombination between strains pertaining to IIb and IIc. The data confirmed also a hybrid origin of DTUs IIa and IIc. Contrary to previous reports, we failed to detect mosaic genes. The phylogenetic relationship between DTUs and the respective roles of recombination and selection were tested.

Impact of number of isoenzyme loci on the robustness of intraspecific phylogenies using multilocus enzyme electrophoresis: consequences for typing of Trypanosoma cruzi.

Thirty-one stocks of Trypanosoma cruzi, the agent of Chagas disease, representative of the genetic variability of the 2 principal lineages, that subdivide T. cruzi, were selected on the basis of previous multilocus enzyme electrophoresis analysis using 21 loci. Analyses were performed with lower numbers of loci to explore the impact of the number of loci on the robustness of the phylogenies obtained, and to identify the loci that have more impact on the phylogeny. Analyses were performed with numerical (UPGMA) and cladistical (Wagner parsimony analysis) methods for all sets of loci. Robustness of the phylogenies obtained was estimated by bootstrap analysis. Low numbers of randomly selected loci (6) were sufficient to demonstrate genetic heterogeneity among the stocks studied. However, they were unable to give reliable phylogenetic information. A higher number of randomly selected loci (15 and more) were required to reach this goal. All loci did not convey equivalent information. The more variable loci detected a greater genetic heterogeneity among the stocks, whereas the least variable loci were better for robust clustering. Finally, analysis was performed with only 5 and 9 loci bearing synapomorphic allozyme characters previously identified among larger samples of stocks. A set of 9 such loci was able to uncover both genetic heterogeneity among the stocks and to build robust phylogenies. It can therefore be recommended as a minimum set of isoenzyme loci that bring maximal information for all studies aiming to explore the phylogenetic diversity of a new set of T. cruzi stocks and for any preliminary genetic typing. Moreover, our results show that bootstrap analysis, like any statistics, is highly dependent upon the information available and that absolute bootstrap figures should be cautiously interpreted.

Molecular epidemiology of Mycobacterium tuberculosis and its relevance to the surveillance and control of TB: an e-debate.

Loubna Tazi a, Barry Kreiswirth b, Christian Carriere c, Michel Tibayrenc a,∗ a Genetics of Infectious Diseases, Unite mixte de Recherche Centre National de la Recherch Scientifique/Institut de Recherche pour le Developpement no. 9926, IRD, BP 64501, 34394 Montpellier Cedex 5, France b Public Health Research Institute Tuberculosis Center, International Center for Public Health, 225 Warren Street, Newark, NJ 07103, USA c Laboratoire de Bacteriologie, Hopital Arnaud de Villeneuve, 371 Avenue du Doyen Giraud, 34295 Montpellier Cedex 5, France

Genetic characterization of Trypanosoma cruzi natural clones from the state of Paraíba, Brazil

Eighteen Trypanosoma cruzi stocks from the state of Paraíba, Brazil, isolated from man, wild mammals, and triatomine bugs were studied by multilocus enzyme electrophoresis and random primed amplified polymorphic DNA. Despite the low number of stocks, a notable genetic, genotypic, and phylogenetic diversity was recorded. The presence of the two main phylogenetic subdivisions, T. cruzi I and II, was recorded. The strong linkage disequilibrium observed in the population under survey suggests that T. cruzi undergoes predominant clonal evolution in this area too, although this result should be confirmed by a broader sample. The pattern of clonal variation does not suggests a recent origin by founder effect with a limited number of different genotypes.

A European centre to respond to threats of bioterrorism and major epidemics

The recent anthrax attacks in the USAhave increased everyone’s awarenessof the extreme difficulty of handlingmajor health dangers in a coordinatedmanner.Evenwithoutthislatestdrama,the need for improved coordination isobvious in the light of recent outbreakssuch as those of bovine spongiformencephalopathy and foot-and-mouthdisease, and the cacophony of theEuropean response to these problems.The Americans are fortunateenough to have a central agency fordealing with such matters: the Centersfor Disease Control and Prevention(CDC), of which the National Centerfor Infectious Diseases (NCID) is animportant part. This is a big federalorganization with more than 1500employees. It combines advancedresearch, surveillance, control, andtraining. Each US state has its ownhealth policy and disease surveillanceand control system, but the NCIDplays an important role in coordinatingactivities and collecting data. In termsof research, the NCID’s work iscomplemented by that of many otherresearch centres, including theNational Institutes of Health (NIH),theUSArmylaboratoriesandthousandsof university laboratories.Clearly an organization in Europeanalogous to the NCID — a EuropeanCentre for Infectious Diseases (ECID)— is sorely needed, and this idea hasbeguntotakeshape(1,2).Theprincipleis to set up a central structure with walls,which, like its American counterpart,would coordinate advanced research,surveillance and professional training.The ECID would not be limited to theEuropean Union, and would includecountries such as Switzerland, as wellas those of Eastern Europe. It wouldalso have strong links with developingcountries, because if we want tocontrol epidemics in Europe, we haveto do it in developing countries too:microorganisms are no respectersof national borders (2). And as far asbioterrorism is concerned uncoordi-nated health systems offer a strategicadvantage for causing havoc.It is important to underline thatthe ECID would be only one piece ofthe European system in this domain.It does not aim to replace nationalstructures such as the Pasteur Institutesin France or the Karolinska Institute inSweden. Nor would it aim to competewith national control structures such astheInstitut deVeille Sanitaire inFrance.On the contrary, its goal would be tocomplement and optimize the actionof existing structures.The harsh reality is that the taskbefore us is huge, and so far there is noEuropean system to tackle it. Europeneeds a centralized structure even morethan the USA, because of the politicalcompartmentalization of this continent.In spite of the excellence of theexisting institutions, European workon researching and controlling infec-tiousdiseasesisadistressingcacophony,like an orchestra with no conductor(3). It has been argued that a centralstructure would be useless, and that a‘‘virtual CDC’’ (surveillance networkselectronically operated) would be moreefficient (4, 5). Actually, the twoconcepts are complementary. TheEuropean Centre would be efficientlycompleted by electronic networks,outposts and cooperation centres.It is proposed that as part of theirongoing work the ECID programmeswould take advantage of the genomicandpost-genomicrevolutiontodevelopfar-reaching holistic research on theepidemiology of infectious diseases.In doing so it would find ways toreconcile new powerful technologiessuchasmassivesequencing,DNAchipsand bioinformatics with valuable butvanishing savoir-faires such as classicalmedical entomology, parasitology andbacteriology. The European dimensionof the enterprise would make itpossibletoworkonascalethatishardlypossible within national frameworks.By analogy, only the successful Eur-opean Space Agency made it possibleto develop the Ariane launchers.Much discussion has been alreadygenerated around the idea of thisproject (6, 7). It has enabled the ECIDscientific board and its steering com-mittee to develop the concept, andour goal now is to relaunch the debatethroughaseriesofmeetingsandarticles,to turn the idea into a reality. Prepared-ness for disease emergencies is sucha hot topic now (8) that there is no wayto avoid the question and its practicalimplications. In the end, of course, it isa matter that has to be taken up bypoliticians and decision-makers. In itspresent state, the ECID is a privateundertaking supported by a group ofscientists and health professionals,andnotanofficialprojectofanynationalinstitution.

Hybridization in Trypanosoma congolense does not challenge the predominant clonal evolution model. A comment on Tihon et al., 2017, Mol. Ecol.

Tihon et al. have just published in Mol. Ecol. a fine genomic study on Trypanosoma congolense, agent of Animal African Trypanosomiasis. They present very convincing evidence that T. congolense underwent several hybridization events between distinct genetic lines in Zambia. They claim that their data challenge our predominant clonal evolution model (PCE) of micropathogens. We point out the main tenets of our model and show that Tihon et al.s claim is based on a misinterpretation of the PCE model. Actually, their data strongly support PCE in T. congolense at a microevolutionary level.