Ensaio do linfonodo local murino (LLNA) na diferenciação entre a dermatite de contato alérgica e de contato irritante: um estudo da expressão de marcadores de superfície de linfócitos T / Local Lymph node assay in the differentiation between an allergic contact dermatitis and irritation: study of the expression of T lymphocyte surface markers

Introdução: O ensaio do linfonodo local murino (LLNA) foi desenvolvido como uma alternativa aos testes de Buhler e Maximização. O teste é utilizado com o objetivo de identificar substâncias capazes de induzir dermatite de contato e tem como desfecho a quantificação celular nos linfonodos auriculares. Embora recomendado por agências internacionais envolvidas no desenvolvimento de metodologias alternativas, o LLNA ainda necessita de aprimoramento. Objetivo: O objetivo do trabalho foi estudar possíveis diferenças nos padrões de subpopulações linfocitárias entre camundongos tratados com substâncias irritantes e dermosensibilizantes. Método: Os animais foram tratados com os sensibilizantes dinitroclorobenzeno (DNCB) e parafenilenidiamina (PPD), os irritantes lauril sulfato de sódio (LSS) e tritonX-100 (TX-100), por três dias consecutivos no dorso de ambas as orelhas. As subpopulações foram analisadas por citometria de fluxo e possíveis alterações histopatológicas nas orelhas dos animais foram também analisadas. Resultados: Foram observadas diferenças nas células CD4+CD25+ e CD4+CD69+, assim como na proliferação dessas subpopulações. Nenhuma diferença foi vista nos estudos histopatológicos das orelhas dos animais quando tratados com dermosensibilizantes ou irritantes. Conclusões: A fenotipagem de linfócitos T pode ser considerada útil no desenvolvimento de possíveis protocolos de ensaios que visem a diferenciação entre substâncias dermosensibilizantes e irritantes. Além disso, os resultados obtidos podem vir a contribuir com o aumento do conhecimento nesta área e auxiliar na busca por um ensaio in vitro correlato.

Introduction: The Local Lymph Node Assay (LLNA) was developed as an alternative to Buhler and Maximization assays. It is applied to discriminate substances that are able to induce contact dermatitis and the endpoint is cell quantification in mice auricular lymph nodes. Although recommended by international agencies involved in the development of alternative methodologies, LLNA still needs to be improved. Objective: In this context, the goal of this study was to investigate possible differences in lymphocyte subpopulation patterns among mice treated with irritants and dermosensitizers. Method: Animals were treated with sensitizers dinitrochlorobenzene (DNCB) and paraphenylenediamine (PPD) and irritants sodium lauryl sulfate (SLS) and tritonX-100 (TX-100) for 3 days, using dorsum area of both ears. The percentage of different lymphocyte subpopulations were analyzed by flow cytometry. Ears of animals were also evaluated for possible pathological alterations. Results: Differences were observed in CD4+ CD25+ and CD4+ CD69+ cells, as well as in the proliferation of these subpopulations. The histopathological analysis of the ears showed no difference between the treatment with either dermosensitizers or irritants. Conclusions: T lymphocyte phenotyping might still be a useful tool in the development of an assay to differentiate between dermosensitizers and irritants. Moreover, these results may contribute to improving knowledge on this field and helping in the search of a correlate in vitro assay.

Flow Cytometry as a Tool for Quality Control of Fluorescent Conjugates Used in Immunoassays.

The use of antibodies in immunodiagnostic kits generally implies the conjugation of these proteins with other molecules such as chromophores or fluorochromes. The development of more sensitive quality control procedures than spectrophotometry is essential to assure the use of better fluorescent conjugates since the fluorescent conjugates are critical reagents for a variety of immunodiagnostic kits. In this article, we demonstrate a new flow cytometric protocol to evaluate conjugates by molecules of equivalent soluble fluorochromes (MESF) and by traditional flow cytometric analysis. We have coupled microspheres with anti-IgG-PE and anti-HBSAg-PE conjugates from distinct manufactures and/or different lots and evaluated by flow cytometry. Their fluorescence intensities were followed for a period of 18 months. Our results showed that there was a great difference in the fluorescence intensities between the conjugates studied. The differences were observed between manufactures and lots from both anti-IgG-PE and anti-HBSAg-PE conjugates. Coefficients of variation (CVs) showed that this parameter can be used to determine better coupling conditions, such as homogenous coupling. The MESF analysis, as well as geometric mean evaluation by traditional flow cytometry, showed a decrease in the values for all conjugates during the study and were indispensable tools to validate the results of stability tests. Our data demonstrated the feasibility of the flow cytometric method as a standard quality control of immunoassay kits.

Phenotypic profiles and detection of target genes by PCR in isolates from different sources and reference strains, identified as Cronobacter spp. (Enterobacter sakazakii)

Cronobacter, formerly known as Enterobacter sakazakii, is a novel genus of the Enterobacteriaceae family recognized as a cause of high number of fatal cases in neonates, after consuming infant formula. The conventional methods for detecting these organisms are time-consuming and lack sensitivity. The ISO/TS 22964:2006 is the most recently standardized methodology for detecting Cronobacter in powderedinfant formula. This study aimed at confirming the Brazilian isolates previously identified as E. sakazakiias Cronobacter spp. by biochemical assays, and also to compare characteristics of 37 Cronobacter andnon-Cronobacter isolates; and the miniaturized kits and the ISO/TS methodology were evaluated. A conventional PCR protocol targeting dna G was also developed and a previously described gluA targeting protocol was used. The majority of the Brazilian isolates were not confirmed as Cronobacter spp., and the selective enrichment step of ISO/TS methodology was inhibitory to some Cronobacter strains. The ID 32 Ewas the most reliable kit. The PCR protocol targeting gluA showed consistent results with ID 32E and the developed dnaG PCR protocol was 100% sensitive and specific. Thus, the PCR protocols targeting gluA and dnaG might be used to complement the Cronobacter spp. detection or identification after performing the conventional isolation and identification methods.

RNA interference-mediated knockdown of CD49e (α5 integrin chain) in human thymic epithelial cells modulates the expression of multiple genes and decreases thymocyte adhesion.

BACKGROUND: The thymus is a central lymphoid organ, in which bone marrow-derived T cell precursors undergo a complex process of maturation. Developing thymocytes interact with thymic microenvironment in a defined spatial order. A component of thymic microenvironment, the thymic epithelial cells, is crucial for the maturation of T-lymphocytes through cell-cell contact, cell matrix interactions and secretory of cytokines/chemokines. There is evidence that extracellular matrix molecules play a fundamental role in guiding differentiating thymocytes in both cortical and medullary regions of the thymic lobules. The interaction between the integrin α5ß1 (CD49e/CD29; VLA-5) and fibronectin is relevant for thymocyte adhesion and migration within the thymic tissue. Our previous results have shown that adhesion of thymocytes to cultured TEC line is enhanced in the presence of fibronectin, and can be blocked with anti-VLA-5 antibody. RESULTS: Herein, we studied the role of CD49e expressed by the human thymic epithelium. For this purpose we knocked down the CD49e by means of RNA interference. This procedure resulted in the modulation of more than 100 genes, some of them coding for other proteins also involved in adhesion of thymocytes; others related to signaling pathways triggered after integrin activation, or even involved in the control of F-actin stress fiber formation. Functionally, we demonstrated that disruption of VLA-5 in human TEC by CD49e-siRNA-induced gene knockdown decreased the ability of TEC to promote thymocyte adhesion. Such a decrease comprised all CD4/CD8-defined thymocyte subsets. CONCLUSION: Conceptually, our findings unravel the complexity of gene regulation, as regards key genes involved in the heterocellular cell adhesion between developing thymocytes and the major component of the thymic microenvironment, an interaction that is a mandatory event for proper intrathymic T cell differentiation.

Hepatic damage associated with dengue-2 virus replication in liver cells of BALB/c mice.

One difficulty in studying dengue virus (DENV) is the lack of an experimental model that reproduces the human disease. In a previous work, we have shown that BALB/c mice intraperitoneally inoculated with a DENV-2 isolate presented viremia and mild focal areas of liver injuries. In this study, mice were inoculated by the intravenous route and presented extensive damage areas in the liver tissue, which were evaluated by histopathological and ultrastructural analysis. Hepatic injury was noted mainly around the central vein and portal tracts. Damages consist of hepatocyte injury, including steatosis, swelling and necrosis. Further, erythrophagocytosis, intercellular edema and vascular damages were evident, including hemorrhage, which is characteristic of the dengue-induced hepatitis in human liver. Hepatic lesions were already noted 2 days post infection (p.i.), although effects were more extensive after the seventh day p.i. An increase in alanine aminotransferase and aspartate aminotransferase serum levels was detected 7 and 14 days p.i., respectively, and had correlation to hepatic lesions. Alterations caused by the DENV infection were self-limiting, with a remarkable reduction of all liver damages 49 days p.i. Virus antigens were detected in hepatocytes, Kupffer cells and vascular endothelium, suggesting virus replication in these cells. In situ hybridization, using a probe that anneals in the virus negative RNA strand, showed positive reaction in hepatocytes and vascular endothelium cells of infected mice, thus confirming virus replication in such cells. In general, results revealed that this mouse model reproduces some histopathological effects observed in humans and supports previous findings indicating virus replication in the hepatic tissue.