Fundacion Instituto Leloir

Buenos Aires, Argentina

Fundacion Instituto Leloir

Buenos Aires, Argentina
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News Article | April 6, 2016

Researchers in Argentina say they have genetically modified an adenovirus - which can cause colds, conjunctivitis and bronchitis - to home in on cancer, killing tumor cells in patients without harming healthy tissue. Scientists have long been intrigued by the idea of using viruses to alert the immune system to seek and destroy cancerous cells. That interest has taken off in recent years as advances in genetic engineering allow them to customize viruses that target tumors. Dr. Osvaldo Podhjacer, Chief of the Laboratory of Molecular and Cellular Therapy at the Fundacion Instituto Leloir in Buenos Aires, and his team developed an 'oncolytic' virus designed to target both malignant cells and tumor-associated stromal cells. In February, Unleash Immuno Oncolytics announced it had entered a license agreement with Leloir Institute to develop immuno-oncology products for cancer treatment in Saint Louis. Unleash's leading product, developed thanks to work by Podhjacer, is called UIO-512. Dr. Podhjacer explained how the virus helps to attack cancer. "This is a virus, which, by genetic modification, we have restricted their infectivity exclusively to malignant cells, in spite of the fact, originally, the virus can infect normal cells and cause colds, conjunctivitis and bronchitis. Why immunotherapy? Because in addition to the changes we have made to restrict the infection only to malignant cells, it also has a gene that exacerbates the immune response. Then there is a direct attack on the tumor initial and an additional immunological response which in principle eliminates the residual tumor, which was not eliminated by the virus and disseminated metastases," Dr. Podhjacer said. Scientific journal Nature reported in October last year that cancer-fighting viruses had started to win approval. Researchers hope that ongoing clinical trials of similar oncolytic viruses and their approval will generate the enthusiasm and cash needed to spur further development of the approach. "These viruses are very effective in pre-clinical models of cancer, we have tested and in particular, ovarian cancer and melanoma but we also have other viruses for pancreatic and colon rectal cancer. These are non-toxic and they are as important as their therapeutic efficacy, where we have managed to reverse the levels of liver enzymes to a normal level with animals that have a tumor. These levels become very high due to the toxicity. In general terms, it allows us to qualify this virus as an ideal candidate to be taken to a clinical trial in humans beings," Dr. Podhjacer, said. Professor Lawrence Young, a cancer specialist from the University of Warwick, said that while similar research has been ongoing for many years, Podhjacer's team had added a mechanism to influence the cells surrounding the cancer tumor. "To be honest, it's not particularly novel. What they have done, however, which is a bit interesting is introduce a new bell or a new whistle, if you like, in terms of the virus, which is to also have an effect on some of the supporting cells. So one of the things that's very exciting about current cancer biology is an increased understanding of the fact that while you've got cancer cells and tumor cells, which are important targets; actually there's a lot of supporting cells around the cancer that also get modified in that environment and start to mis-behave," Young told Reuters. Podhajcer said that the virus attacks the entire tumor mass, not only the malignant cells themselves but also the stromal cells that support cancer dissemination. "We have prepared a virus with the ability to study everything that is characteristic of the tumor and to attack all the cells of the tumor. In other words, we have an approach different to what has been done to this day today, even within what is being used in the oncolytic therapy using these viruses which also generate secondary immune responses. In other words, it is a disruptive technology and we also add something that is unique to our research," Podhajcer said. Professor Young cautioned that there are a number of hurdles for the therapy to overcome. In addition to the cost implications for eventually making it widely available, he said that the body's own immune system could make subsequent doses of a treatment increasingly less effective. "Some of those immune responses will target the tumor, some won't. And so the degree to which you can re-use these viruses is a problem because as you get an immune response to them, as soon as you then expose a patient to a second or third dose their immune system starts to think "wait a minute, we've seen that before, we're going to wipe it out". So these are very challenging therapies," he said. According to the journal Nature, the strategy builds on a phenomenon which has been recognized for more than a century. Physicians in the 1800s first noted their cancer patients sometimes unexpectedly went into remission after experiencing a viral infection. Based on these reports, doctors in the 1950s and 1960s were then inspired to start injecting cancer patients with a menagerie of viruses. Sometimes the therapy destroyed the tumor, and on occasion it killed the person instead. According to Professor Young, however, the field of immunotherapy has advanced rapidly in the past ten years and there is a great deal of positivity for what the future holds in the fight against cancer. "I think that there's so much excitement about this now, and so much excitement about being able to use non-viral approaches to delivering drugs and genes, that it's quite clear that over the next ten years or so, we're going to see more of these therapies, especially in the more difficult to manage tumors," he said.

Beckwith E.J.,Fundacion Instituto Leloir | Beckwith E.J.,CONICET | Ceriani M.F.,Fundacion Instituto Leloir
Journal of Comparative Neurology | Year: 2015

Circadian rhythms are conserved across kingdoms and coordinate physiology and behavior for appropriate time-keeping. The neuronal populations that govern circadian rhythms are described in many animal models, and the current challenge is to understand how they interact to control overt rhythms, remaining plastic enough to respond and adapt to a changing environment. In Drosophila melanogaster, the circadian network comprises about 150 neurons, and the main synchronizer is the neuropeptide pigment-dispersing factor (PDF), released by the well-characterized central pacemaker neurons, the small ventral lateral neurons (sLNvs). However, the rules and properties governing the communication and coupling between this central pacemaker and downstream clusters are not fully elucidated. Here we genetically manipulate the speed of the molecular clock specifically in the central pacemaker neurons of Drosophila and provide experimental evidence of their restricted ability to synchronize downstream clusters. We also demonstrate that the sLNv-controlled clusters have an asymmetric entrainment range and were able to experimentally assess it. Our data imply that different clusters are subjected to different coupling strengths, and display independent endogenous periods. Finally, the manipulation employed here establishes a suitable paradigm to test other network properties as well as the cell-autonomous mechanisms running in different circadian-relevant clusters. © 2014 Wiley Periodicals, Inc.

Identification of catalytic residues (CR) is essential for the characterization of enzyme function. CR are, in general, conserved and located in the functional site of a protein in order to attain their function. However, many non-catalytic residues are highly conserved and not all CR are conserved throughout a given protein family making identification of CR a challenging task. Here, we put forward the hypothesis that CR carry a particular signature defined by networks of close proximity residues with high mutual information (MI), and that this signature can be applied to distinguish functional from other non-functional conserved residues. Using a data set of 434 Pfam families included in the catalytic site atlas (CSA) database, we tested this hypothesis and demonstrated that MI can complement amino acid conservation scores to detect CR. The Kullback-Leibler (KL) conservation measurement was shown to significantly outperform both the Shannon entropy and maximal frequency measurements. Residues in the proximity of catalytic sites were shown to be rich in shared MI. A structural proximity MI average score (termed pMI) was demonstrated to be a strong predictor for CR, thus confirming the proposed hypothesis. A structural proximity conservation average score (termed pC) was also calculated and demonstrated to carry distinct information from pMI. A catalytic likeliness score (Cls), combining the KL, pC and pMI measures, was shown to lead to significantly improved prediction accuracy. At a specificity of 0.90, the Cls method was found to have a sensitivity of 0.816. In summary, we demonstrate that networks of residues with high MI provide a distinct signature on CR and propose that such a signature should be present in other classes of functional residues where the requirement to maintain a particular function places limitations on the diversification of the structural environment along the course of evolution.

Biochemical studies have shown that Trypanosoma cruzi and Toxoplasma gondii are the only eukaryotic organisms so far described which are auxotrophic for polyamines. Both parasites are unable to carry out the de novo biosynthesis of putrescine, and therefore they need the addition of exogenous polyamines to the culture medium for their normal proliferation. Further investigations at the molecular level have demonstrated that the wild-type T. cruzi genome does not contain ornithine or arginine decarboxylase-like nucleic acid sequences, and that the corresponding genes have been presumably lost during evolution. Since T. cruzi behaves as a deletion mutant for ornithine decarboxylase (ODC) and arginine decarboxylase (ADC) genes, this parasite has been selected to study the regulation of the expression of heterologous genes involved in polyamine biosynthesis in other organisms. The resulting transgenic parasites have been useful tools to analyze the different stages of gene expression after transformation, as well as the mechanisms of drug resistance induction and the post-translational processing of enzyme precursors. © Springer-Verlag 2009.

Simonetti F.L.,Fundacion Instituto Leloir
Nucleic acids research | Year: 2013

MISTIC (mutual information server to infer coevolution) is a web server for graphical representation of the information contained within a MSA (multiple sequence alignment) and a complete analysis tool for Mutual Information networks in protein families. The server outputs a graphical visualization of several information-related quantities using a circos representation. This provides an integrated view of the MSA in terms of (i) the mutual information (MI) between residue pairs, (ii) sequence conservation and (iii) the residue cumulative and proximity MI scores. Further, an interactive interface to explore and characterize the MI network is provided. Several tools are offered for selecting subsets of nodes from the network for visualization. Node coloring can be set to match different attributes, such as conservation, cumulative MI, proximity MI and secondary structure. Finally, a zip file containing all results can be downloaded. The server is available at In summary, MISTIC allows for a comprehensive, compact, visually rich view of the information contained within an MSA in a manner unique to any other publicly available web server. In particular, the use of circos representation of MI networks and the visualization of the cumulative MI and proximity MI concepts is novel.

Dyck J.,University of Alberta | Lanuza G.M.,Fundacion Instituto Leloir | Gosgnach S.,University of Alberta
Journal of Neurophysiology | Year: 2012

Our understanding of the neural control of locomotion has been greatly enhanced by the ability to identify and manipulate genetically defined populations of interneurons that comprise the locomotor central pattern generator (CPG). To date, the dI6 interneurons are one of the few populations that settle in the ventral region of the postnatal spinal cord that have not been investigated. In the present study, we utilized a novel transgenic mouse line to electro physiologically characterize dI6 interneurons located close to the central canal and study their function during fictive locomotion. The majority of dI6 cells investigated were found to be rhythmically active during fictive locomotion and could be divided into two electro physiologically distinct populations of interneurons. The first population fired rhythmic trains of action potentials that were loosely coupled to ventral root output and contained several intrinsic membrane properties of rhythm-generating neurons, raising the possibility that these cells may be involved in the generation of rhythmic activity in the locomotor CPG. The second population fired rhythmic trains of action potentials that were tightly coupled to ventral root output and lacked intrinsic oscillatory mechanisms, indicating that these neurons may be driven by a rhythm-generating network. Together these results indicate that dI6 neurons comprise an important component of the locomotor CPG that participate in multiple facets of motor behavior. © 2012 the American Physiological Society.

Fernandez M.M.,University of Buenos Aires | Malchiodi E.L.,University of Buenos Aires | Algranati I.D.,Fundacion Instituto Leloir
Antimicrobial Agents and Chemotherapy | Year: 2011

Paromomycin, an aminoglycoside antibiotic having low mammalian cell toxicity, is one of the drugs currently used in the chemotherapy of cutaneous and visceral leishmaniasis. In order to understand the mode of action of this antibiotic at the molecular level, we have investigated the effects of paromomycin on protein synthesis in Leishmania and its mammalian hosts. We were able to demonstrate that in vivo protein synthesis in the promastigote stage of the parasite and its proliferation rate are markedly inhibited by paromomycin while being only slightly affected by other aminoglycoside antibiotics, such as streptomycin and neomycin B. Furthermore, both in vitro polypeptide synthesis induced by poly(U) as mRNA and accuracy of translation are significantly decreased by paromomycin in cell-free systems containing ribosomal particles of Leishmania promastigotes. Conversely, when ribosomes from mammalian cells are used instead of the protozoan particles, polyphenylalanine synthesis is only barely reduced by the antibiotic and the translation misreading remains almost unaltered. Surface plasmon resonance analysis of the interaction between paromomycin and protozoan or mammalian cell ribosomal RNAs shows a strong binding of antibiotic to the parasite ribosomal decoding site and practically no interaction with the mammalian cell counterpart. Our results indicating differential effects of paromomycin on the translation processes of the Leishmania parasite and its mammalian hosts can explain the therapeutic efficiency of this antibiotic as an antileishmaniasis agent. Copyright © 2011, American Society for Microbiology. All Rights Reserved.

Ferrari C.C.,Fundacion Instituto Leloir | Tarelli R.,Fundacion Instituto Leloir
Parkinson's Disease | Year: 2011

Peripheral inflammation triggers exacerbation in the central brain's ongoing damage in several neurodegenerative diseases. Systemic inflammatory stimulus induce a general response known as sickness behaviour, indicating that a peripheral stimulus can induce the synthesis of cytokines in the brain. In Parkinson's disease (PD), inflammation was mainly associated with microglia activation that can underlie the neurodegeneration of neurons in the substantia nigra (SN). Peripheral inflammation can transform the primed microglia into an active state, which can trigger stronger responses dealing with neurodegenerative processes. Numerous evidences show that systemic inflammatory processes exacerbate ongoing neurodegeneration in PD patient and animal models. Anti-inflammatory treatment in PD patients exerts a neuroprotective effect. In the present paper, we analyse the effect of peripheral infections in the etiology and progression in PD patients and animal models, suggesting that these peripheral immune challenges can exacerbate the symptoms in the disease. Copyright © 2011 Carina C. Ferrari and Rodolfo Tarelli.

Inis Biotech LLC and Fundacion Instituto Leloir | Date: 2013-07-17

The invention provides promoters inducible by reactive oxygen species (ROS), capable of driving the expression of a gene of interest, particularly in a tumor cell. More particularly, it refers to promoters inducible by reactive oxygen species, that may be used to drive the expression of a gene of interest, such as a therapeutic gene, or a reporter gene for use in image diagnosis. The promoter consists of a chimeric promoter containing an E6 element and a VE element. It also provides vectors carrying a human therapeutic or non therapeutic gene of interest, operably linked to said promoter sequence and compositions comprising the same.

Villordo S.M.,Fundacion Instituto Leloir | Alvarez D.E.,Fundacion Instituto Leloir | Gamarnik A.V.,Fundacion Instituto Leloir
RNA | Year: 2010

The plasticity of viral plus strand RNA genomes is fundamental for the multiple functions of these molecules. Local and long-range RNA - RNA interactions provide the scaffold for interacting proteins of the translation, replication, and encapsidation machinery. Using dengue virus as a model, we investigated the relevance of the interplay between two alternative conformations of the viral genome during replication. Flaviviruses require long-range RNA - RNA interactions and genome cyclization for RNA synthesis. Here, we define a sequence present in the viral 3′UTR that overlaps two mutually exclusive structures. This sequence can form an extended duplex by long-range 5′-3′ interactions in the circular conformation of the RNA or fold locally into a small hairpin (sHP) in the linear form of the genome. A mutational analysis of the sHP structure revealed an absolute requirement of this element for viral viability, suggesting the need of a linear conformation of the genome. Viral RNA replication showed high vulnerability to changes that alter the balance between circular and linear forms of the RNA. Mutations that shift the equilibrium toward the circular or the linear conformation of the genome spontaneously revert to sequences with different mutations that tend to restore the relative stability of the two competing structures. We propose a model in which the viral genome exists in at least two alternative conformations and the balance between these two states is critical for infectivity. Published by Cold Spring Harbor Laboratory Press. Copyright © 2010 RNA Society.

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