Macrophages and lymphocyte responiveness to mitogen

Purified B-cells fail to proliferate in response to the strong thymus-independent (TI) antigen Lipopolysaccharide (LPS) in the absence of macrophages (Corbel and Melchers, 1983). The fact that macrophages, or factors derived from them are required is supported by the inability of marginal zone B-cells in infants to respond to highly virulent strains of bacteria such as Neisseria meningitidis and Streptococcus pneumoniae (Timens, 1989). This may be due to the lack of CD21 expression on B-cells in infants which could associate with its co-receptor (C3d) on adjacent macrophages. It is not clear whether cell surface contacts and/or soluble products are involved in lymphocyte-macrophage interactions in response to certain antigens. This thesis describes the importance of the macrophage in lymphocyte responses to T-dependent (TD) and TI antigens. The major findings of this thesis were as follows: (1). Macrophages were essential for a full proliferative response to a range of T - and B-cell mitogens and TI-1 and TI-2 antigens, including Concanavalin A, LPS, Pokeweed mitogen (PWM), Dextran sulphate, Phytohaemagglutinin-P (PHA-P) and Poly[I][C]. (2). A ratio of 1 macrophage to 1000 lymphocytes was sufficient for the mitogens to exert their effects. (3). The optimal conditions were established for the activation of an oxidative burst in cells of the monocyte/macrophage lineage as measured by luminometry. The order of ability was OpZ >PMA/lonomycin >f-MLP >Con A >DS >PHA >Poly[I][C] >LPS >PWM. Responses were only substantial and protracted with OpZ and PMA. Peritoneal macrophages were the most responsive cells, whereas splenic and alveolar macrophages were significantly less active and no response could be elicited with Kupffer cells, thus demonstrating heterogeneity between macrophages. (4). Activated macrophages that were then fixed with paraformaldehyde were unable to restore mitogenic responsiveness, even with a ratio of 1 macrophage to 5 lymphocytes. (5). Although highly purified T- and B-cells could respond to mitogen provided live macrophages were present, maximum activation was only observed when all 3 cell types were present. (6). Supernatants from purified macrophage cultures treated with a range of activators were able to partially restore lymphocyte responses to mitogen in macrophage-depleted splenocyte cultures, and purified T - and B-cell cultures. In fact supernatants from macrophages treated with LPS for only 30 minutes could restore responsiveness. Supernatants from OpZ treated macrophages were without effect. (7). Macrophage supernatants could not induce proliferation in the absence of mitogen. They therefore provide a co-mitogenic signal required by lymphocytes in order to respond to mitogen. (8). Macrophage product profiles revealed that LPS and Con A-treated macrophage supernatants showed elevated levels of IL-1β, TNF -α L TB4 and TXB2. These products were therefore good candidates as the co-mitogenic factor. The possible inhibitory factors secreted by OpZ-treated macrophages were PGE2, IL-10 and NO. (9). The removal of cytokines, eicosanoids and TNF-α from LPS-treated macrophage supernatants using Cycloheximide, Dexamethasone and an MMPI respectively, resulted in the inability of these supernatants to restore macrophage-depleted lymphocyte responses to mitogen. (10). rIL-1β and rTNF-α are co-mitogenic factors, as macrophage-depleted lymphocytes incubated with rIL-1β and rTNF-α can respond to mitogen.

Epidemias bacterianas emergentes do século XXI

As doenças infeciosas distantes de serem um problema do passado têm aumentado drasticamente nestes últimos anos, causando epidemias emergentes, quer de origem bacteriana ou vírica ou de outros tipos de microrganismos. Esta dissertação tem como objetivo uma pesquisa atual bibliográfica sobre o estudo de algumas epidemias bacterianas emergentes do século XXI, como a Tuberculose, Cólera, Staphylococcus aureus resistente à meticilina (MRSA) e Meningite Meningocócica, bem como os seus dados epidemiológicos. A Tuberculose é uma das doenças mais antigas, que apresenta uma elevada taxa de mortalidade e com o passar do tempo tem vindo a aumentar a nível mundial. A TB é causada por uma bactéria denominada Mycobacterium tuberculosis que normalmente afeta os pulmões e outros órgãos. O tratamento, a prevenção e o diagnóstico precoce são pontos essenciais, para ter um bom desfecho para o doente. A Cólera tem-se propagado pelo mundo desde o século XX. Esta doença caracteriza-se por uma diarreia aguda grave que é causada pela bactéria Vibrio cholerae. O seu tratamento se for realizado precocemente é tratado facilmente, com apenas hidratação com sais orais. A prevenção é uma medida essencial para ter um bom prognóstico, e evitar surtos emergentes desta infeção. Devido à sua virulência, Staphylococcus aureus é responsável por infeções graves adquiridas em hospital e na comunidade. Na maioria das vezes esta infeção é assintomática, mas pode causar infeções graves até mesmo fatais. Devido às resistências aos antibióticos β-lactâmicos e de outros tipos de antibióticos, e também devido ao aumento do número crescente de quadros infeciosos de MRSA, houve necessidade de novos antibióticos como o linezolide, as cefasloporinas de 5ª geração no combate a estas infeções. As medidas de prevenção são essenciais, visto que se não forem realizadas pode haver progressão da doença. Além de um estudo científico constante dos mecanismos de resistências desta bactéria, ser essencial. A meningite bacteriana é um grave problema de Saúde Pública devido à alta incidência em crianças. A meningite meningocócica é causada pela bactéria Neisseria meningitidis que origina um processo inflamatório das meninges. Há algum tempo atrás a mortalidade era elevada, mas com o advento da antibioterapia reduziu significativamente. As vacinas fizeram com que ocorresse uma mudança bastante significativa na epidemiologia desta patologia, e mais uma vez a prevenção é essencial.

Estudo do papel da proteína multifuncional APE1/Ref-1 sobre a resposta inflamatória na meningite bacteriana

Despite advances in antibiotic therapy, bacterial meningitis (BM) remains with high mortality and morbidity rates in worldwide. One important mechanism associated to sequels during disease is the intense inflammatory response which promotes an oxidative burst and release of reactive oxygen species, consequently leading to cell death. Activation of DNA repair enzymes during oxidative stress has been demonstrated in several neurological disorders. APE1/Ref-1 is a multifunctional protein involved in DNA repair and plays a redox function on transcription factors such as NFkB and AP-1.The aim of this study was assess the role of APE1/Ref-1 on inflammatory response and the possibility of its modulation to reduce the sequels of the disease. Firstly it was performed an assay to measure cytokine in cerebrospinal fluid of patients with BM due to Streptococcus pneumoniae and Neisseriae meningitides. Further, a cellular model of inflammation was used to observe the effect of the inhibition of the endonuclease and redox activity of APE1/Ref-1 on cytokine levels. Additionally, APE1/Ref-1 expression in cortex and hippocampus of rat with MB after vitamin B6 treatment was evaluated. Altogether, results showed a similar profile of cytokines in the cerebrospinal fluid of patients from both pathogens, although IFNy showed higher expression in patients with BM caused by S. pneumoniae. On the other hand, inhibitors of APE1/Ref-1 reduced cytokine levels, mainly TNF-α. Reduction of oxidative stress markers was also observed after introduction of inhibitors in the LPS-stimulated cell. In the animal model, BM increased the expression of the protein APE1/Ref-1, while vitamin B6 promoted reduction. Thereby, this data rise important factors to be considered in pathogenesis of BM, e.g., IFNy can be used as prognostic factor during corticosteroid therapy, APE1/Ref-1 can be an important target to modulate the level of inflammation and VIII oxidative stress, and vitamin B6 seems modulates several proteins related to cell death. So, this study highlights a new understanding on the role of APE1/Ref-1 on the inflammation and the oxidative stress during inflammation condition

Artrite meningocócica primária na criança

A artrite é uma complicação conhecida da doença meningocócica. Contudo, a artrite meningocócica primária (AMP), na ausência de meningite ou manifestações de meningococemia aguda, é rara. Descreve-se o caso de uma criança do sexo masculino, 17 meses, saudável, com quadro de febre, recusa da marcha e limitação dos movimentos da anca esquerda. Sem instabilidade hemodinâmica, exantema ou sinais meníngeos. Analiticamente tinha elevação dos parâmetros inflamatórios. Foi isolada Neisseria meningitidis serotipo B no líquido articular e foi medicado com ceftriaxone, seguido de amoxicilina oral, com boa evolução clínica e analítica. Apresentamos este caso raro, salientando a importância do diagnóstico etiológico de artrite séptica na criança.

Dissection of the protective response elicited by the DOMV component of the 4CMenB vaccine

Neisseria meningitidis serogroup B is the major etiological agent of meningitis and life-threatening sepsis, against which two vaccines are licensed. The 4CMenB vaccine is composed of three major protein antigens (fHbp, NHBA and NadA) and detergent-extracted outer membrane vesicles (DOMV) from the NZ98/254 strain. DOMV are safe, immunogenic and able to raise bactericidal antibodies, mainly attributed to the immunodominant PorA protein. Nevertheless, DOMV offer a complex reservoir of potentially immunogenic proteins, whose relative contribution in protection is still poorly characterized. By testing antisera from vaccinated infants in serum bactericidal assay, we observed that the addition of DOMV in the vaccine formulation enhanced breadth of coverage compared to recombinant proteins alone against a panel of 11 meningococcal strains mismatched for the vaccine antigens. To unravel the DOMV components involved in such protection, 30 DOMV antigens were cloned and expressed in Escherichia coli as recombinant proteins and/or in vesicles to maintain their native conformation. Samples obtained were both included in tailor-made protein-microarrays to immunoprofile the antibody repertoire raised by DOMV-containing formulations and were individually used for mouse immunization studies to assess their ability to induce bactericidal antibodies. The protein-array immunosignature of mouse DOMV/4CMenB antisera unveiled a subset of 8 DOMV-reactive proteins potentially responsible for the additional protective responses. The antisera derived from mouse immunizations showed high levels of antibodies and recognized the corresponding antigen across different meningococcal strains. Among the protein-array reactive antigens, OpcA, NspA and PorB induced antibodies able to kill 10 of the 11 genetically diverse meningococcal strains and the specificity of the protective role of OpcA and PorB was also confirmed in 4CMenB infant vaccinee sera. In conclusion, we identified additional PorA-independent antigens within DOMV involved in broadening the coverage of 4CMenB, thus supporting the key role played by vesicles in this multivalent formulation.

Interrogation of human monoclonal antibodies induced by 4C-MenB to identify protective antigens contained in the OMV component

Neisseria meningitidis is a gram negative human obligated pathogen, mostly found as a commensal in the oropharyngeal mucosa of healthy individuals. It can invade this epithelium determining rare but devastating and fast progressing outcomes, such as meningococcal meningitidis and septicemia, leading to death (about 135000 per year worldwide). Conjugated vaccines for serogroups A, C, W135, X and Y were developed, while for N. meningitidis serogroup B (MenB) the vaccines were based on Outern Membrane Vesicles (OMV). One of them is the 4C-MenB (Bexsero). The antigens included in this vaccine’s formulation are, in addition to the OMV from New Zeland epidemic strain 98/254, three recombinant proteins: NadA, NHBA and fHbp. While the role of these recombinant components was deeply characterized, the vesicular contribution in 4C-MenB elicited protection is mediated mainly by porin A and other unidentified antigens. To unravel the relative contribution of these different antigens in eliciting protective antibody responses, we isolated human monoclonal antibodies (mAbs) from single-cell sorted plasmablasts of 3 adult vaccinees peripheral blood. mAbs have been screened for binding to 4C-MenB components by Luminex bead-based assay. OMV-specific mAbs were purified and tested for functionality by serum bactericidal assay (SBA) on 18 different MenB strains and characterized in a protein microarray containing a panel of prioritized meningococcal proteins. The bactericidal mAbs identified to recognize the outer membrane proteins PorA and PorB, stating the importance of PorB in cross-strain protection. In addition, RmpM, BamE, Hyp1065 and ComL were found as immunogenic components of the 4C-MenB vaccine.