Infection In Experimental Animals Research Articles

Evaluation of Transcript Labeling Techniques and Development of a Membrane-based Parallel Gene Expression Assay

An inexpensive alternative to micro arrays was developed to examine the expression of small sets of genes in parallel and used to compare direct and indirect transcript labeling methods. Psoralen-biotin direct labeling was ~10-fold less sensitive than reverse transcriptase-biotin-dUTP labeling, but the enzymatic method generated higher levels of background noise in miniarray hybridizations. The reproducibility of hybridization intensities was the same for the two labeling methods, although differences in signal intensities for several genes were observed. The miniarray hybridization assay was validated using the known responses of mycobacteria to heat shock, exposure to isoniazid and growth phase. Expression profiles were generated for 14 Mycobacterium smegmatis and 26 M. tuberculosis genes. The transcriptional response to isoniazid and peculiar regulation of acr in different growth phases were confirmed and a potential role of oxidative stress enzymes in the heat shock response was revealed. The miniarray system was also used to demonstrate that an RNA stabilizing reagent, RNALaterTM , was effective in inhibiting both RNA degradation and transcription in mycobacteria, which may prove useful when significant manipulation of the bacteria are required prior to RNA extraction such as in experimental infections of cell cultures or animals.

The improved survival of experimental animals fed with fish oil is suppressed by a leukotriene inhibitor.

Fish oil is believed to alter the immune response and improve survival after infections in experimental animals. This effect may be due to altered production of the leukotrienes (LT). We, therefore, performed a study in order to evaluate whether the effect of fish oil on the immune response of experimental animals is mediated through altered production of the LT. Female NMRI mice in four groups were fed with fish oil, fish oil with 5-lipoxygenase (5-LO) inhibitor (Zileuton, Abbott Laboratories, Chicago, IL, USA), corn oil or corn oil with 5-LO inhibitor. After 6 weeks, the mice were infected with Klebsiella pneumoniae and the survival was monitored. The experiment was performed twice. Analysis was performed mainly on data pooled from both experiments. The survival of the groups fed with fish oil was increased, compared to that of all the other groups and when compared to the groups fed with fish oil with 5-LO inhibitor (log-rank test) the difference was significant (P = 0.007). It has been postulated that the effect of fish oil on the immune system is mediated through altered production of LT. In our study, blocking of the production of the LT eliminated the beneficial effects of fish oil. Our results are in concord with the hypothesis that the effect of fish oil is, at least partly, mediated through altered production of LT.

Varicella zoster virus latency, neurological disease and experimental models: an update.

Varicella zoster virus (VZV), a ubiquitous neurotropic human herpesvirus, causes chickenpox (varicella) and then remains latent for decades in cranial nerve, dorsal root and autonomic nervous system ganglia along the entire neuraxis. Virus reactivation, most often after age 60, produces shingles (zoster), characterized by pain and rash usually restricted to 1-3 dermatomes. In elderly individuals, zoster is frequently complicated by postherpetic neuralgia (PHN), pain that persists for months to years after the resolution of rash. Virus may also spread beyond ganglia to the spinal cord to cause myelitis, as well as to blood vessels of the brain, producing a unifocal or multifocal vasculopathy. The increased incidence of zoster in the elderly and immunocompromised individuals appears to be due to a VZV-specific host immunodeficiency. Recent studies indicate that PHN may be due to a chronic active VZV ganglionitis, and that VZV vasculopathy is caused by a productive virus infection in cerebral arteries. Since neurological disease produced by VZV is due to reactivation from ganglia, the physical state of viral nucleic acid and expression during latency as well as the possible mechanisms by which VZV latency is maintained and reactivates are discussed. Finally, VZV is an exclusively human herpesvirus, and experimental infection of animals with VZV does not produce disease nor does VZV reactivate from ganglia. Two varicella models in primates have proven useful: one that mimics varicella latency in humans, and one that can be used to study the efficacy of antiviral agent in driving varicella virus back to a latent state.

The Pasteurella multocida toxin interacts with signalling pathways to perturb cell growth and differentiation

AbstractSome years ago we showed that the Pasteurella multocida toxin (PMT) is a potent mitogen for cells in culture. It is an intracellularly acting toxin that stimulates several signal transduction pathways. The heterotrimeric G-protein, Gq, is stimulated, which in turn causes activation of protein kinase C and an increase in inositol trisphosphates. The Rho GTPase is also activated, leading via the Rho kinase, to activation of the focal adhesion kinase and to cytoskeletal rearrangements.Analysis of the PMT sequence suggested the presence of three domains that encode receptor binding, translocation and catalytic domains. The location of all three domains has been confirmed directly. Competitive binding assays confirmed that the N-terminus of PMT encoded the receptor-binding domain, while cytoplasmic microinjection of expressed PMT fragments identified the location of the C-terminal catalytic domain. Recently, we have demonstrated the presence of key amino acids that affect membrane insertion within the putative transmembrane domain.Several lines of evidence suggest that PMT activates Gαq, and that this is one potential molecular target for the toxin. Gαq is known to be tyrosine phosphorylated when activated normally via a G-protein-coupled receptor (GPCR), and it has been suggested that this is an essential part of the activation process. We have shown that PMT induces Gαq tyrosine phosphorylation, but that this is not essential for activation of the G-protein. Furthermore, a totally inactive mutant of PMT stimulates Gαq phosphorylation without leading to its activation. Phosphorylation of Gαq triggered by the inactive mutant potentiates activation of Gq via a GPCR, demonstrating that phosphorylation of Gq cannot lead to receptor uncoupling.Natural or experimental infection of animals with toxigenic P. multocida, or injection with purified recombinant PMT causes loss of nasal turbinate bone. The effects on bone have been analysed in vitro using cultures of osteoblasts – cells that lay down bone. PMT blocks the formation of mature calcified bone nodules and the expression of differentiation markers such as CBFA-1, alkaline phosphatase and osteocalcin. These effects can be partially prevented by inhibitors of Rho or Rho kinase function, implicating this pathway in osteoblast differentiation. Indeed, inhibitors of Rho stimulate the formation of bone nodules in vitro.In summary, PMT is a novel toxin that acts via signalling pathways to promote proliferation in many cells, while specifically inhibiting differentiation in osteoblast cells.

Nouveaux antifongiques : voriconazole et caspofungine

Among new available antifungal agents voriconazole is a new triazole with an intravenous (IV) and oral formulation, and caspofungin is an echinocandin, new family with a new mode of action on the cell wall. It is available as an IV preparation. Both drugs have a broad spectrum targeting most of the usual pathogens : Candida and Aspergillus, even with low suceptibility or resistance to other antifungals. Voriconazole is also active on Scedosporium and Fusarium. The efficacy of these molecules was established in vitro and in experimental infections in animals either normal or immunosuppressed. Voriconazole is active in oropharyngeal and esophageal candidiasis, in refractory invasive candidiasis and as a first line treatment of invasive aspergillosis with better results than amphotericine B. It was also effective in scedosporiosis and in fusariosis. Caspofungin is active in oropharyngeal and esophageal candidiasis, in invasive candidiasis ranking among the best drugs in non neutropenic patients. It was shown effective in refractory aspergillosis. As empirical treatment of febrile neutropenic patients, these molecules should probably be restricted to the highest risk-population. Safety is good, side effects are a rare cause of discontinuation of treatment, class specific drug-drug interactions occur with voriconazole. These molecules open an important field of investigations with combination of antifungal agents.

West Nile viruses: Clinical and diagnostic considerations

32. Mathieson, M.J. et al. 1998. The dominant epitope of Borrelia garinii outer surface protein C recognized by sera from patients with neuroborreliosis has a surface-exposed conserved structural motif. Infect. Immun. 66:4073-4079. 33. Bacon, R.M. et al. 2003. Serodiagnosis of Lyme disease by kinetic enzymelinked immunosorbent assay using recombinant VlsEl or peptide antigens of Borrelia burgdorferi compared with 2 tiered testing using whole cell lysates. J. Infect. Dis. 187:1187-1199. burgdorferi infection in experimental animals and in humans. J. Infect. Dis. 184:870-878.

Leishmaniasis--current chemotherapy and recent advances in the search for novel drugs.

Abstract The chemotherapy currently available for leishmaniasis is far from satisfactory. Resistance to the pentavalent antimonials, which have been the recommended drugs for the treatment of both visceral (VL) and cutaneous leishmaniasis (CL) for >50 years, is now widespread in India. Although new drugs have become available in recent years for the treatment of VL, including AmBisome ® , the excellent but highly expensive liposomal formulation of amphotericin B, and the oral drug miltefosine, which has now been registered in India, treatment problems remain. Parenteral and topical formulations of the aminoglycoside paromomycin offer potential treatments for VL and CL, respectively. The search for new drugs continues, with bisphosphonates, for example, risedronate and pamidronate, and plant derivatives such as licochalcone A and quinoline alkaloids being reported to have activity against experimental animal infections. The immunomodulator imiquimod has proved to be an adjunct for CL therapy. Many potential drug targets have been identified in biochemical and molecular studies, and some have been validated. Attempts to exploit these targets are in progress.

In vitro and in vivo assessment of 99mTc-UBI specificity for bacteria

Technetium-99m labeled ubiquicidin peptide 29-41 ( 99mTc-UBI) is a cationic human antimicrobial peptide fragment that has been shown to bind bacteria in vitro and accumulates at sites of infection in experimental animals. To help determine if 99mTc-UBI is bound to the bacterial cell envelope by a simple nonspecific electrostatic interaction, a comparative study of the in vitro binding of 99mTc-UBI and two different 99mTc labeled cationic peptides ( 99mTc-Tat-1-Scr and 99mTc-Tat-2-Scr) to bacteria and to two tumor cell line (LS174T and ACHN) was performed. The in vivo specificity of 99mTc-UBI for infection in mice was also evaluated using dual labels in the same animal and comparing the target/non-target ratio for 67Ga-citrate and 99mTc-UBI at sites of induced infection and sterile inflammation. Under conditions of this study, the in vitro binding of 99mTc-UBI, 99mTc-Tat-1-Scr and 99mTc-Tat-2-Scr to S. aureus was 35, 78 and 87% respectively. While the binding of 99mTc-Tat-1-Scr and 99mTc-Tat-2-Scr was 37 and 33% to colon tumor cells (LS174T) and 39 and 41% to renal tumor cells (ACHN) respectively, the binding of 99mTc-UBI to both cell types was much lower at less than 4%. In vivo studies revealed that there is a significant difference (p < 0.05) in the radioactive accumulation of 99mTc-UBI between the sites of infection and inflammation compared to 67Ga-citrate. Thus, 99mTc-UBI showed an average infection/inflammation ratio of 2.08 ± 0.49 compared to 1.14 ± 0.45 for 67Ga-citrate. In conclusion, the in vitro and in vivo results provide evidence that a specific mechanism is responsible of the 99mTc-UBI bacterial intracellular accumulation.

Intracellular expression of the Salmonella plasmid virulence protein, SpvB, causes apoptotic cell death in eukaryotic cells

The spv genes carried on the Salmonella virulence plasmid are commonly associated with severe systemic infection in experimental animals. The SpvB virulence-associated protein has been shown to ADP-ribosylate actin, and this enzymatic activity is essential for virulence in mice. Here, we present evidence that intracellular expression of SpvB protein induces not only disruption of actin filaments but also apoptotic cell death in eukaryotic cells.

Extracellular secretion of the virulence plasmid-encoded ADP-ribosyltransferase SpvB in Salmonella

Nontyphoid Salmonella enterica requires the plasmid-encoded spv genes to establish successful systemic infection in experimental animals. The SpvB virulence-associated protein has recently been shown to contain the ADP-ribosyltransferase domain. SpvB ADP-ribosilates actin and depolymerizes actin filaments when expressed in cultured epithelial cells. However, spontaneous secretion or release of SpvB has not been observed under in vitro growth conditions. In the present study we investigated the secretion of SpvB from Salmonella using in vitro and in vivo assay systems. We showed that SpvB is secreted into supernatant from Salmonella strains that contain the cloned spvB gene on a plasmid when they grew in intracellular salts medium (ISM), a minimal medium mimicing the intracellular iron concentrations of eukaryotic cells. A series of mutant SpvB proteins revealed that an N-terminal region of SpvB located at amino acids 1–229 was sufficient to promote secretion into extracellular milieu. Confocal immunofluorescence microscopy also demonstrated efficient localization of the N-terminal domain of SpvB 1-360 tagged with biotinylated peptide within infected host cell cytosol but not truncated SpvB 1-179 fusion protein. In addition, mutations that inactivate genes within Salmonella pathogenicity island 1 or Salmonella pathogenicity island 2 that encode type III secretion systems (TTSS) could secrete the SpvB protein into the culture medium. These results indicate that SpvB protein is transported from the bacteria and into the host cytoplasm independent of TTSS.

Virulence of water-induced coccoidHelicobacter pyloriand its experimental infection in mice

To explore the virulence and the infectivity of coccoid Helicobacter pylori (H. pylori) transformed from spiral form by exposure to sterile tap water. Three strains of H. pylori, isolated from gastric biopsy specimens of confirmed peptic ulcer, were converted from spiral into coccoid form by exposure to sterile tap water. Both spiral and coccoid forms of H. pylori were tested for the urease activity, and the adherence to Hep-2 cells. The presence of flagella was examined under electron microscopy. In the experimental animal infection, the spiral and coccoid forms of H. pylori originated from the same strain F49 were inoculated intragastrically into BALB/c mice respectively four times at a 3-day interval. Half of the mice from each group were sacrificed at Day 21 and Day 28 after the last inoculation. Histology and H. pylori colonization were detected by urease test of gastric mucosa, cultures of H. pylori, and electron microscopy and so on. The urease activity and the ability of adherence to Hep-2 cells were found to be lower in coccoid H. pylori than that in its spiral form. For example, the transformation in strain F(44) led to a significant decrease of the adherence rate and adherence index from 70.0+/-5.3 % to 30.2+/-3.5 % (P<0.01), and from 2.6+/-0.4 to 0.86+/-0.3 (P<0.01), respectively. The flagella of coccoid H. pylori were observed under electron microscope. In the experimental infection in mice, the positive rate of gastric mucosa urease test was 93.8 % (15/16) in the group infected by spiral H. pylori and 50 % (8/16) in the group infected by coccoid H. pylori, and the estimated coccoid H. pylori colony number was 1.75 vs 0.56. The positive rates of H. pylori culture were 87.5 % (14/16) in spiral H. pylori group and 68.8 % (11/16) in coccoid H. pylori group. There was no significant difference in either urease test or bacterial culture rate between the groups examined at Day 21 and Day 28 after inoculation. Electron microscopic examination of the samples taken from both groups showed the adherence of H. pylori in spiral, bacillary and coccoid shapes to the epithelial cells of gastric wall. Histological examination showed the occurrence of gastric mucosal injury as indicated by various degrees of erosion, ulcer, and inflammatory cell infiltration. Mucosal injury was slighter in the mice infected by coccoid H. pylori. No positive result was obtained in the control group that received intragastrical administration of sterile tap water. Although the virulence of coccoid H. pylori induced by water decrease, coccoid H. pylori still remains a considerable urease activity and the adhering ability to epithelial cells. Furthermore, the flagella, an important component responsible for bacterial movement and infection, were still observed as a cellular structure of coccoid H. pylori under electron microscope. The coccoid H. pylori induced by water is capable of colonizing in gastric mucosa and causing gastrititis in mice.

Pharmacological properties and expected clinical role of an injectable new quinolone antibiotic, pazufloxacin mesilate

Pazufloxacin mesilate (PZFX: Pasil INJECTION, Pazucross INJECTION) is a novel injectable quinolone antibiotic that was discovered by Toyama Chemical Co., Ltd. and codeveloped by Toyama Chemical Co. Ltd. and Mitsubishi Pharma Corporation. Laboratory studies indicated that PZFX reached high plasma levels quickly after intravenous administration, and it exhibited weak convulsion inducing activity, low local irritant effect, and less hypotensive activity, all of which are generally recognized as side effects associated with other injectable quinolones. PZFX has potent antibacterial and bactericidal activities against cephalosporin-, carbapenem-, and aminoglycoside-resistant strains. These favorable antibacterial and bactericidal activities gave PZFX superior therapeutic effects, compared to injectable cephalosporin antibiotics, on experimental animal infection models caused by those resistant strains. Clinical studies also revealed PZFX was as safe and effective as the injectable cephalosporin, ceftazidime, against various moderate to severe infections. Furthermore, PZFX showed good clinical effects on the infections resistant to chemotherapy by the other antimicrobial agents. These results indicate that PZFX is a viable choice for various bacterial infections. In this review, results of laboratory and clinical studies are summarized and the clinical role of PZFX among the injectable antimicrobials is discussed.

Virus y desmielinización: ¿por qué sospechar la implicación de virus en la etiología de la esclerosis múltiple?

Epidemiological data indicate that environmental factors, possibly infections, are associated with the development of multiple sclerosis. Different viruses are known to produce demyelination in natural and experimental animal infections. In humans some virus cause acute or chronic diseases that course with central nervous system demyelination. A series of virus have been claimed to be etiological agents of multiple sclerosis, although a causal role for any of them has so far been demonstrated.The mechanisms of viral demyelination are diverse,ranging from direct destruction of infected oligodendrocytes to triggering autoimmune responses without virus multiplication in target cells. The potential indirect mechanisms of viral demyelination and the heterogeneous histopathology shown in multiple sclerosis patients, suggesting an heterogeneus etiology, might explain why not a single virus has been as yet identified as the cause of this disease.Viral infections that cause demyelination in animals and humans are briefly reviewed, focusing on the potential myelin destruction mechanisms and obstacles to the identifying viruses that might cause multiple sclerosis.

In vivo transmission and dynamics of deleted genomes after experimental infection of woodchuck hepatitis B virus in adult animals.

The presence of Deleted Genomes has been shown in a number of viral models including Hepadnaviridae. The analysis of woodchuck hepatitis B virus (WHV) population after experimental infection of woodchuck 197 (W197) with WHV7-PI inoculum revealed the presence of two Deleted Genomes: DG600 lacking a 1330 bp region (Core/Polymerase/PreS1) and DG900 showing a deletion of 869 nts (Pol/PreS/S). These mutants were also present in WHV7-PI. The successive WHV experimental infections in adult animals were performed using W197-w7 inoculum containing DG600 and DG900. Infections were divided into three groups presenting different patterns of viral replication, different presence of markers, occurrence of variants and persistence of infection. The first group displayed 2-3 weeks viremic phase and WHV-DNA titres of 10-30 ng/ml; the second a longer viremic phase (8-9 weeks) and higher WHV-DNA titres (up to 78 ng/ml). In contrast, the third group exhibited lifetime presence of WHV-DNA and WHVeAg in serum and viral replication in liver. The Deleted Genomes were transmitted in the newly infected animals with the same genomic organization. DG600 was persistently found only in chronically infected woodchuck, whereas a different pattern of presence was described for DG900. The characterization of these classes of deleted mutants in woodchuck-WHV model raises new questions on the link between DGs and persistent infections.

CYTOKINES IN EXPERIMENTAL HERPES SIMPLEX VIRUS INFECTION

Herpes simplex virus (HSV) causes productive and latent forms of infection in humans and experimental animals. The primary infection and reactivation of the latent infection evoke an immune response in the host organism, involving activities of macrophages, CD4+ and CD8+ lymphocytes, and B lymphocytes. Strong cytokine responses are associated with the acute and recurrent phases of HSV infection. Also, during the latent phase of HSV infection in the senory ganglia, expression of certain cytokines can be detected. The cytokine response to HSV infection is dominated by proinflammatory and Th1 type cytokines; however, Th2 type cytokines such as interleukin-4 also are expressed in the infected tissue. The use of novel HSV-derived, cytokine-expressing gene therapy vectors necessitates studies on the possible modulation of the host responses by the virus-encoded cytokine transgenes. This review focuses on the roles of certain Th1 and Th2 type cytokines in different phases of the experimental HSV infections.

Interleukin-4 Receptor–Stat6 Signaling in Murine Infections with a Tissue-Dwelling Nematode Parasite

Interleukin-4 (IL-4) has been shown to be crucial in parasite expulsion in several gastrointestinal nematode infection models. Data from both epidemiological studies with humans and experimental infections in animals imply a critical role for the type II helper response, dominated by IL-4, in host protection. Here we utilized inbred mice on two distinct backgrounds to document the involvement of IL-4 in the clearance of a primary infection of Brugia from the murine host. Our data from infections of IL-4 receptor(-/-) and Stat6(-/-) mice further indicate that IL-4 exerts its effects by activating the Stat6 molecule in host target cells, a finding which links clearance requirements of a gastrointestinal tract-dwelling nematode with those of a tissue-dwelling nematode. Additionally, we show that the requirements for IL-4 receptor binding and Stat6 activation extend to accelerated clearance of a secondary infection as well. The data shown here, including analysis of cell populations at the site of infection and infection of immunoglobulin E (IgE)(-/-) mice, lead us to suggest that deficiencies in eosinophil recruitment and isotype switching to IgE production may be at least partially responsible for slower parasite clearance in the absence of IL-4.

Synthesis of the retro-inverso peptide analogues of N-acetylmuramyl-L-alanyl-D-isoglutamine (MDP)

Two novel retro-inverso analogues of a conformationally restricted carbocyclic muramyl dipeptide (MDP) derivative N-(2-methyl-3-oxo-3,4-dihydro-2H-1,4-benzoxazine-2carbonyl)-L-alanyl-D-isoglutamine were prepared and tested in a immunorestoration test in mice. Both retro-inverso MDP analogues did not enhance non-specific resistance to experimental fungal infection in immunosuppressed animals, suggesting that the intact amide bond is essential for the immunorestorating activity in this type of rigidified carbocyclic MDP analogues.

Modulatory effects of dietary lipids on immune system functions.

Dietary lipid manipulation may affect a great number of immune parameters, such as lymphocyte proliferation, cytokine synthesis, natural killer (NK) cell activity, phagocytosis and so on. The immunomodulation induced by dietary fatty acids may be applied in the amelioration of inflammatory disorders, such as autoimmune diseases. However, the mechanisms that participate in these processes are still poorly understood. It is probable that modulation of immune system by fatty acids of the diet may occur by alteration of membrane fluidity, lipid peroxide formation, eicosanoid production or regulation of gene expression. However, recent studies have reported the effects of several free fatty acids on apoptosis induction of in vitro cultures. In fact, a possible explanation of the effects that fatty acids promote on the immune system cells could be associated with an apoptotic process performed in an irreversible way. In vivo studies have demonstrated the ability of fatty acids to alter the survival of animals fed diets containing oils and infected with a pathogenic bacterium. Experimental infection in animals fed dietary lipids produces a modification of resistance to micro-organisms. The present review analyses all of these parameters that dietary fatty acids are capable of altering in order to modify the immune response. Further studies will be needed to establish the mechanisms involved in immune system regulation, reduction of symptoms derived from autoimmune pathologies and so on.

Vaccination against helminth parasites--the ultimate challenge for vaccinologists?

Helminths are multicellular pathogens which infect vast numbers of human and animal hosts, causing widespread chronic disease and morbidity. Vaccination against these parasites requires more than identification of effective target antigens, because without understanding the immunology of the host-parasite relationship, ineffective immune mechanisms may be invoked, and there is a danger of amplifying immunopathogenic responses. The fundamental features of the immune response to helminths are therefore summarised in the context of vaccines to helminth parasites. The contention between type-1 and type-2 responses is a central issue in helminth infections, which bias the immune system strongly to the type-2 pathway. Evidence from both human and experimental animal infections indicates that both lineages contribute to immunity in differing circumstances, and that a balanced response leads to the most favourable outcome. A diversity of immune mechanisms can be brought to bear on various helminth species, ranging from antibody-independent macrophages, antibody-dependent granulocyte killing, and nonlymphoid actions, particularly in the gut. This diversity is highlighted by analysis of rodent infections, particularly in comparisons of cytokine-depleted and gene-targeted animals. This knowledge of protective mechanisms needs to be combined with a careful choice of parasite antigens for vaccines. Many existing candidates have been selected with host antibodies, rather than T-cell responses, and include a preponderance of highly conserved proteins with similarities to mammalian or invertebrate antigens. Advantage has yet to be taken of parasite genome projects, or of directed searches for novel, parasite-specific antigens and targets expressed only by infective stages and not mature forms which may generate immunopathology. With advances under way in parasite genomics and new vaccine delivery systems offering more rapid assessment and development, there are now excellent opportunities for new antihelminth vaccines.

Parasitological cure of Chagas disease: is it possible? Is it relevant?

Nearly 90 million people (about a quarter ofthe Latin American population) live in zones whereChagas disease is endemic while 18-20 million arealready infected with is causative agent, Trypano-soma (Schizotrypanum) cruzi. It is estimated thatthere are currently >550,000 new cases and 50,000deaths associated to this condition every year(Docampo & Schmunis 1997). This disease leadsto an annual loss of 2.7 millions of disability ad-justed years, being the largest parasitic diseaseburden in the continent and only third on a globalscale after malaria and schistosomiasis (WorldBank 1993). Chemotherapy of this disease is stillvery unsatisfactory, being based in nitrofurans(nifurtimox, Bayer; recently discontinued) andnitroimidazoles (benznidazole, Roche) developedempirically three decades ago. These compoundshave activity in the acute and short-term (up to afew years) chronic phase (Andrade et al.1996), butis efficacy varies according to the geographicalarea, probably due to differences in drug suscepti-bility of different T. cruzi strains (Filardi & Brener1987); however, they have little or no activity inprevalent, long term chronic form of the disease,which is widely considered an incurable disease(Rassi & Luquetti 1992, de Castro 1993, Quintaset al.1996, Andrade et al.1996, Croft et al.1997).Furthermore, both drugs have frequent side effects(generally less severe in pediatric patients) includ-ing anorexia, vomiting, peripheral neuropathy andallergic dermopathy (Rassi & Luquetti 1992, deCastro 1993, Quintas et al.1996, Croft et al.1997).Although great advances have been made in re-cent years in the control of the vectorial and trans-fusional transmission of the disease, particularlythrough the Southern Cone Initiative involvingBrazil, Argentina, Paraguay and Uruguay, progressis uneven in other parts of the continent and theproblem of the persons already infected remainsunsolved.In this brief review I would like to discuss re-cent work, involving the joint effort of biochem-ists, chemists, parasitologists, molecular and cellbiologists and immunologists, that have raised thepossibility of radical parasitological cure in chroni-cally infected experimental animals and humansthorough rational chemotherapeutic approaches. Iwould also like to discuss the role of parasites inthe pathogenesis of chronic Chagas disease andthus the relevance of parasitological cure in theclinical outcome of this disease. A more extendedversion of this discussion has been presented else-where (Urbina 1999).