RESUMO
Candida auris is an emerging multidrug resistant fungal pathogen, which represents a major challenge for newborns systemic infections worldwide. Management of C. auris infections is complicated due to its intrinsic antifungal resistance and the limited information available on its pathogenesis, particularly during neonatal period. In this study, we developed a murine model of C. auris neonatal invasive infection. C. auris dissemination was evaluated by fungal burden and histopathological analysis of lung, brain, liver, kidney, and spleen at different time intervals. We found fungal cells in all the analyzed tissues, neonatal liver and brain were the most susceptible tissues to fungal invasion. This model will help to better understand pathogenesis mechanisms and facilitate strategies for control and prevention of C. auris infections in newborns.
Assuntos
Candida , Candidíase Invasiva , Animais , Antifúngicos/farmacologia , Antifúngicos/uso terapêutico , Candida auris , Candidíase Invasiva/tratamento farmacológico , Farmacorresistência Fúngica , Camundongos , Testes de Sensibilidade MicrobianaRESUMO
Lymph nodes (LNs) have evolved to maximize antigen (Ag) collection and presentation as well as lymphocyte proliferation and differentiation-processes that are spatially regulated by stromal cell subsets, including fibroblastic reticular cells (FRCs) and follicular dendritic cells (FDCs). Here, we showed that naïve neonatal mice have poorly organized LNs with few B and T cells and undetectable FDCs, whereas adult LNs have numerous B cells and large FDC networks. Interestingly, immunization on the day of birth accelerated B cell accumulation and T cell recruitment into follicles as well as FDC maturation and FRC organization in neonatal LNs. However, compared to adults, the formation of germinal centers was both delayed and reduced following immunization of neonatal mice. Although immunized neonates poorly expressed activation-induced cytidine deaminase (AID), they were able to produce Ag-specific IgGs, but with lower titers than adults. Interestingly, the Ag-specific IgM response in neonates was similar to that in adults. These results suggest that despite an accelerated structural maturation of LNs in neonates following vaccination, the B cell response is still delayed and reduced in its ability to isotype switch most likely due to poor AID expression. Of note, naïve pups born to Ag-immunized mothers had high titers of Ag-specific IgGs from day 0 (at birth). These transferred antibodies confirm a mother-derived coverage to neonates for Ags to which mothers (and most likely neonates) are exposed, thus protecting the neonates while they produce their own antibodies. Finally, the type of Ag used in this study and the results obtained also indicate that T cell help would be operating at this stage of life. Thus, neonatal immune system might not be intrinsically immature but rather evolutionary adapted to cope with Ags at birth.
RESUMO
Airways infection with Mycobacterium tuberculosis (Mtb) is contained mostly by T cell responses, however, Mtb has developed evasion mechanisms which affect antigen presenting cell (APC) maturation/recruitment delaying the onset of Ag-specific T cell responses. Hypothetically, bypassing the natural infection routes by delivering antigens directly to APCs may overcome the pathogen's naturally evolved evasion mechanisms, thus facilitating the induction of protective immune responses. We generated a murine monoclonal fusion antibody (α-DEC-ESAT) to deliver Early Secretory Antigen Target (ESAT)-6 directly to DEC205+ APCs and to assess its in vivo effects on protection associated responses (IFN-γ production, in vivo CTL killing, and pulmonary mycobacterial load). Treatment with α-DEC-ESAT alone induced ESAT-6-specific IFN-γ producing CD4+ T cells and prime-boost immunization prior to Mtb infection resulted in early influx (d14 post-infection) and increased IFN-γ+ production by specific T cells in the lungs, compared to scarce IFN-γ production in control mice. In vivo CTL killing was quantified in relevant tissues upon transferring target cells loaded with mycobacterial antigens. During infection, α-DEC-ESAT-treated mice showed increased target cell killing in the lungs, where histology revealed cellular infiltrate and considerably reduced bacterial burden. Targeting the mycobacterial antigen ESAT-6 to DEC205+ APCs before infection expands specific T cell clones responsible for early T cell responses (IFN-γ production and CTL activity) and substantially reduces lung bacterial burden. Delivering mycobacterial antigens directly to APCs provides a unique approach to study in vivo the role of APCs and specific T cell responses to assess their potential anti-mycobacterial functions.
Assuntos
Células Apresentadoras de Antígenos/imunologia , Antígenos de Bactérias/imunologia , Proteínas de Bactérias/imunologia , Mycobacterium tuberculosis/imunologia , Linfócitos T/imunologia , Tuberculose Pulmonar/imunologia , Tuberculose Pulmonar/microbiologia , Animais , Anticorpos Monoclonais/administração & dosagem , Anticorpos Monoclonais/imunologia , Antígenos de Bactérias/química , Antígenos de Bactérias/genética , Antígenos CD/genética , Antígenos CD/metabolismo , Carga Bacteriana , Proteínas de Bactérias/química , Proteínas de Bactérias/genética , Linhagem Celular , Citotoxicidade Imunológica , Modelos Animais de Doenças , Citometria de Fluxo , Imunização , Interferon gama/biossíntese , Lectinas Tipo C/genética , Lectinas Tipo C/metabolismo , Masculino , Camundongos , Antígenos de Histocompatibilidade Menor , Mycobacterium tuberculosis/patogenicidade , Peptídeos/imunologia , Receptores de Superfície Celular/genética , Receptores de Superfície Celular/metabolismo , Proteínas Recombinantes de Fusão/genética , Proteínas Recombinantes de Fusão/imunologia , Subpopulações de Linfócitos T/imunologia , Subpopulações de Linfócitos T/metabolismo , Linfócitos T/metabolismo , Tuberculose Pulmonar/metabolismo , Tuberculose Pulmonar/patologiaRESUMO
Armadillos are apparently important reservoirs of Mycobacterium leprae and an animal model for human leprosy, whose immune system has been poorly studied. We aimed at characterizing the armadillo's langerhans cells (LC) using epidermal sheets instead of tissue sections, since the latter restrict analysis only to cut-traversed cells. Epidermal sheets by providing an en face view, are particularly convenient to evaluate dendritic morphology (cells are complete), spatial distribution (regular vs. clustered), and frequency (cell number/tissue area). Lack of anti-armadillo antibodies was overcome using LC-restricted ATPase staining, allowing assessment of cell frequency, cell size, and dendrites extension. Average LC frequency in four animals was 528 LC/mm(2), showing a rather uniform non-clustered distribution, which increased towards the animal's head, while cell size increased towards the tail; without overt differences between sexes. The screening of antibodies to human DC (MHC-II, CD 1a, langerin, CD86) in armadillo epidermal sheets, revealed positive cells with prominent dendritic morphology only with MHC-II and CD86. This allowed us to test DC mobilization from epidermis into dermis under topical oxazolone stimulation, a finding that was corroborated using whole skin conventional sections. We hope that the characterization of armadillo's LC will incite studies of leprosy and immunity in this animal model.