Biology subjects

Greif, G.

Publications and source records attributed to Greif, G..

8 recordsLinked to original sources

bioRxiv2026

Extended tissue tropism and vertical transmission in a murine model of Mayaro virus infection

Mayaro virus (MAYV) is an emerging mosquito-borne alphavirus associated with acute febrile illness and persistent arthralgia, with increasing reports in Latin America and potential for geographic expansion. However, its dissemination dynamics, tissue tropism and transmission routes remain incompletely defined. Here, we developed a murine model to characterize systemic viral dissemination, tissue tropism and the impact of gestational stage on maternal-fetal outcomes. A nanoluciferase-expressing MAYV reporter enabled non-invasive in vivo imaging, revealing rapid and widespread systemic dissemination under controlled conditions. Complementary infection with wild-type (WT) virus confirmed broad tropism across lymphoid, musculoskeletal and reproductive tissues. At 24 hours post-infection (hpi), viral distribution was relatively homogeneous across tissues, whereas at 48 hpi, tissue-specific differences emerged, with increased viral loads in selected organs, including the spleen and male reproductive tissues. Transient sex-dependent differences were observed at 24 hpi but were not sustained at later time points. Hematological and biochemical analyses revealed early systemic alterations consistent with changes in leukocyte distribution during acute infection. Infectious viral particles were detected in reproductive tissues of both sexes, including in sperm, supporting the biological plausibility of non-vector transmission, although detection in exposed animals was limited. Gestational stage influenced infection outcomes: early gestation (infected at 7.5-8.5 dpc; analyzed at 9.5-10.5 dpc) was associated with detection of infectious virus in fetal tissues, whereas mid-gestation (infected at 13.5-14.5 dpc; analyzed at 15.5-16.5 dpc) showed no detectable infectious virus in fetuses despite evidence of viral antigen persistence and sustained infectious viral presence in maternal and placental compartments. Together, these findings provide a preclinical framework for investigating MAYV pathogenesis and underscore the role of tissue tropism and gestational context in shaping infection dynamics and maternal-fetal involvement. Author summaryMayaro virus (MAYV) is an emerging mosquito-borne virus that causes fever and long-lasting joint pain, with increasing reports in Latin America and potential for wider geographic spread. Despite its growing relevance, key aspects of MAYV pathogenesis remain to be fully defined, including the mechanisms underlying systemic dissemination and tissue tropism, as well as its potential to affect pregnancy or be transmitted through non-vector routes. Here, we used a mouse model with a luminescent reporter virus to track MAYV dissemination in vivo, revealing rapid and widespread distribution across multiple tissues. In studies using wild-type virus, infectious virus was detected not only in muscle and immune-related organs but also in reproductive tissues of both females and males. Importantly, gestational stage influenced viral distribution. When infection occurred early in gestation, infectious viral particles were detected in fetal tissues. In contrast, at later stages of pregnancy, infectious virus was no longer detectable in fetuses, despite evidence of viral antigen persistence and sustained infectious viral presence in maternal and placental tissues. Together, these findings advance our understanding of MAYV infection, highlight gestational timing as a factor associated with fetal exposure and suggest the possibility of transmission through routes other than mosquitoes, providing a framework for future studies on this emerging virus.

microbiology↗

bioRxiv2025

Trypanosoma cruzi Has 32 Chromosomes: A Telomere-to-Telomere Assembly Defines Its Karyotype.

Trypanosoma cruzi, the causative agent of Chagas disease, exhibits remarkable genomic variability and possesses an expanded genome rich in multigene families. However, its precise chromosomal composition has remained elusive due to the challenges posed by extensive repetitive regions. Using PacBio HiFi long-read sequencing, we assembled the complete nuclear genome of the Dm28c strain into 32 telomere-to-telomere chromosomes. This assembly revealed conserved chromosomal structures and synteny patterns when compared to the independently sequenced Dm25 strain, indicating that the 32-chromosome karyotype is a stable and conserved feature of T. cruzi. The species is diploid for all chromosomes, except for chromosome 16, which is consistently tetraploid in all strains analyzed, and homologous to chromosome 31 of Leishmania, also tetraploid. Through a comprehensive annotation pipeline, we refined gene content and resolved haplotypes, resulting in an approximately 25% reduction in core gene redundancy. All chromosomes display a conserved, compartmentalized architecture comprising core, disruptive, and newly defined subtelomeric regions. Subtelomeres, enriched in RHS, TS, and DGF-1 genes and depleted in MASP and mucins, constitute a distinct third genomic compartment, that is transcriptionally active, and represents the main source of genome variability among strains. Altogether, this work defines the complete chromosomal complement of T. cruzi, establishing a robust framework for comparative genomics and enabling detailed studies into genome organization, antigenic variability, and evolutionary dynamics across strains and clades. This assembly redefines the genomic reference landscape and opens new avenues for exploring T. cruzi biology, pathogenic diversity, and adaptive mechanisms.

genomics↗

bioRxiv2024

Improved Serodiagnosis of Trypanosoma vivax Infections in Cattle Reveals Higher Infection Rates in the Livestock Regions of Argentina

Bovine trypanosomiasis, caused by Trypanosoma vivax, currently affects cattle, resulting in significant economic consequences in sub-Saharan Africa and South America. The development of new diagnostic antigens is crucial for improving and refining existing methods. Our study assessed the effectiveness of two recombinant antigens in detecting specific antibodies in cattle. These antigens are derivatives of an invariant surface glycoprotein (ISG) from T. vivax. We evaluated a fraction of an antigen previously described (TvY486_0045500), referred to as TvISGAf, from an African strain, and identified a new ISG antigen from an American isolate, TvISGAm. ELISA evaluation using these antigens was conducted on 212 samples from cattle. The diagnostic performance was enhanced when utilizing a combination of both antigens (denominated TvISG-based ELISA), achieving a sensitivity of 89.6% and specificity of 93.8%. Following validation of the TvISG-based ELISA, we determined the seroprevalence of T. vivax infection in 892 field samples from cattle in the central region of Argentina. The average seroprevalence of T. vivax was 53%, with variation across the six surveyed departments ranging from 21% to 69%. These results support the use of the TvISG ELISA as a valuable serological tool for detecting and monitoring T. vivax infection in cattle. They also reported for the first time T. vivax seroprevalence in Argentina, highlighting the widespread endemic nature of the disease in the region. To effectively manage the increasing spread of T. vivax in the vast livestock production areas of South America, we support the need for consistent surveillance programs and implementation of preventive strategies.

ecology↗

bioRxiv2022

Trypanosoma cruzi isolates naturally adapted to congenital transmission display a unique strategy of transplacental passage

Chagas disease is mainly transmitted by vertical transmission (VT) in non-endemic areas and in endemic areas where vector control programs have been successful. For the present study, we isolated natural strains vertically transmitted through three generations and proceeded to study their molecular mechanism of VT. No parasitemia was detected in immunocompetent mice, but they were able to induce an immune response and colonize different organs. VT experiments revealed that infection with the different strains did not affect mating, pregnancy or resorptions, but despiting low parasitemia, VT strains reached the placenta and resulted in higher vertical transmission rates than strains of either moderate or high virulence. While the virulent strain modulated more than 2500 placental genes, VT strains modulated 150, and none of the modulated genes is shared between them. VT strains downregulate genes associated with cell division and replication and upregulate immunomodulatory genes leading to anti-inflammatory responses and tolerance. The virulent strain stimulates a strong pro-inflammatory immune response, and this molecular footprint correlated with histopathological analyses. We herein describe a unique placental response regarding the passage of T cruzi VT isolates across the maternal-fetal interphase, challenging the current knowledge derived mainly from studies of laboratory-adapted or highly virulent strains.

microbiology↗

bioRxiv2021

Indigenous ancestry and admixture in the Uruguayan population

The Amerindian group known as the Charruas inhabited Uruguay at the timing of European colonial contact. Even though they were extinguished as an ethnic group as a result of a genocide, Charruan heritage is part of the Uruguayan identity both culturally and genetically. While mitochondrial DNA studies have shown evidence of Amerindian ancestry in living Uruguayans, here we undertake whole-genome sequencing of 10 Uruguayan individuals with Charruan heritage. We detect chromosomal segments of Amerindian ancestry supporting the presence of indigenous genetic ancestry in living descendants. Specific haplotypes were found to be enriched in Charruas and rare in the rest of the Amerindian groups studied. Some of these we interpret as the result of positive selection, as we identified selection signatures and they were located mostly within genes related to the infectivity of specific viruses. Historical records describe contacts of the Charruas with other Amerindians, such as Guarani, and patterns of genomic similarity observed here concur with genomic similarity between these groups. Less expected, we found a high genomic similarity of the Charruas to Diaguita from Argentinian and Chile, which could be explained by geographically proximity. Finally, by fitting admixture models of Amerindian and European ancestry for the Uruguayan population, we were able to estimate the timing of the first pulse of admixture between European and Uruguayan indigenous peoples in 1658 and the second migration pulse in 1683. Both dates roughly concurring with the Franciscan missions in 1662 and the foundation of the city of Colonia in 1680 by the Spanish.

genomics↗

bioRxiv2021

Maxicircle architecture and evolutionary insights into Trypanosoma cruzi complex

We sequenced maxicircles from T. cruzi strains representative of the species evolutionary diversity by using long-read sequencing, which allowed us to uncollapse their repetitive regions, finding that their real lengths range from 35 to 50 kb. T. cruzi maxicircles have a common architecture composed of four regions: coding region (CR), AT-rich region, short (SR) and long repeats (LR). Distribution of genes, both in order and in strand orientation are conserved, being the main differences the presence of deletions affecting genes coding for NADH dehydrogenase subunits, reinforcing biochemical findings that indicate that complex I is not functional in T. cruzi. Moreover, the presence of complete minicircles into maxicircles of some strains lead us to think about the origin of minicircles. Finally, a careful phylogenetic analysis was conducted using coding regions of maxicircles from up to 29 strains, and 1023 single copy nuclear genes from all of the DTUs, clearly establishing that taxonomically T. cruzi is a complex of species composed by group 1 that contains clades A, B and D, and group 2 containing clade C. No significant differences were found in hybrid strains that justify the existence of TcV and Tc VI as separate clades: our results indicate that a unique event of hybridization between TcII and TcIII occurred. Three variants of maxicircles exist in T. cruzi: a, b and c, in correspondence with clades A, B, and C from mitochondrial phylogenies. While A and C carry maxicircles a and c respectively, both clades B and D carry b maxicircle variant; hybrid strains also carry the b- variant. We then propose a new nomenclature that is self-descriptive and makes use of both the phylogenetic relationships and the maxicircle variants present in T. cruzi.

genomics↗

bioRxiv2020

Reevaluation of the Toxoplasma gondii and Neospora caninum genomes reveals misassembly, karyotype differences and chromosomal rearrangements

Neospora caninum primarily infects cattle causing abortions with an estimated impact of a billion dollars on worldwide economy, annually. However, the study of its biology has been unheeded by the established paradigm that it is virtually identical to its close relative, the widely studied human pathogen, Toxoplasma gondii. By revisiting the genome sequence, assembly and annotation using third generation sequencing technologies, here we show that the N. caninum genome was originally incorrectly assembled under the presumption of synteny with T. gondii. We show that major chromosomal rearrangements have occurred between these species. Importantly, we show that chromosomes originally annotated as ChrVIIb and VIII are indeed fused, reducing the karyotype of both N. caninum and T. gondii to 13 chromosomes. We reannotate the N. caninum genome, revealing over 500 new genes. We sequence and annotate the non-photosynthetic plastid and mitochondrial genomes, and show that while apicoplast genomes are virtually identical, high levels of gene fragmentation and reshuffling exists between species and strains. Our results correct assembly artifacts that are currently widely distributed in the genome database of N. caninum and T. gondii, but more importantly, highlight the mitochondria as a previously oversighted source of variability and pave the way for a change in the paradigm of synteny, encouraging rethinking the genome as basis of the comparative unique biology of these pathogens.

genomics↗

bioRxiv2018

Nanopore sequencing significantly improves genome assembly of the eukaryotic protozoan parasite Trypanosoma cruzi

Chagas disease was described by Carlos Chagas, who first identified the parasite Trypanosoma cruzi from a two-year-old girl called Berenice. Many T. cruzi sequencing projects based on short reads have demonstrated that genome assembly and downstream comparative analyses are extremely challenging in this species, given that half of its genome is composed of repetitive sequences. Here, we report de novo assemblies, annotation and comparative analyses of the Berenice strain using a combination of Illumina short reads and MinION long reads. Our work demonstrates that Nanopore sequencing improves T. cruzi assembly contiguity and increases the assembly size in ~16 Mb. Specifically, we found that assembly improvement also refines the completeness of coding regions for both single copy genes and repetitive transposable elements. Beyond its historical and epidemiological importance, Berenice constitutes a fundamental resource since it now represents the best-quality assembly available for TcII, a highly prevalent lineage causing human infections in South America. The availability of Berenice genome expands the known genetic diversity of T. cruzi and facilitates more comprehensive evolutionary inferences. Our work represents the first report of Nanopore technology used to resolve complex protozoan genomes, supporting its subsequent application for improving trypanosomatid and other highly repetitive genomes.

genomics↗