Avaliação das histonas de L. infantum como candidatos à vacinas na infecção por l.infantum em hamsters / Evaluation of histones from L. infantum as candidate vaccines in infection in hamsters l.infantum

A leishmaniose visceral é uma doença infecciosa grave, causada por protozoários intracelulares obrigatórios do gênero Leishmania. Vários antígenos de Leishmania têm sido avaliados como candidatos vacinais, destacando-se as proteínas de histonas (HIS), antígenos altamente conservados. A exposição de HIS pela Leishmania induz uma resposta imune potente no hospedeiro vertebrado. Desse modo, neste estudo, avaliamos, em hamsters, a capacidade imunoprotetora dos antígenos de histonas contra a infecção por Leishmania infantum. Os animais foram vacinados com estratégia homóloga, utilizando-se plasmídeos de DNA que codificam para HIS (pcDNA3LiH2A-H3, pcDNA3LiH2B-H4) ou heteróloga (DNA/proteínas HIS) mais 1nM de CpG. Quinze dias após a última imunização, os animais foram desafiados pela via intradérmica com 105 Leishmania infantum metacíclicas mais 0,5 par de glândula salivar de Lutzomya longipalpis. Após a última imunização e durante a infecção, realizaram-se dosagens de citocinas por PCR em tempo real (linfonodo e baço), sorologia por ELISA (soro), carga parasitária por diluição limitante e análise histopatológica de tecidos (linfonodo, baço e fígado). Detectou-se produção de anticorpos IgG anti HIS nos grupos imunizados com a estratégia homóloga e heteróloga, quando comparados aos hamsters não imunizados. As imunizações homóloga e heteróloga diferiram na razão IFN-γ/IL-10 no linfonodo em relação ao grupo controle. Não houve diferença significativa na expressão dessas citocinas no baço após a imunização, entretanto, cinco meses após o desafio o grupo homólogo apresentou um aumento na produção de IL-10 nesse órgão. Na análise histopatológica do baço, verificou-se formação de mais folículos com centro germinativo, evidentes nos animais imunizados independentemente do grupo analisado. Observou-se, também, leucocitose intrasinusoidal e periportal no fígado, e folículos reativos no linfonodo. Nenhuma das estratégias de imunizações com antígenos de histonas acarretou em diminuição da carga parasitária no linfonodo, baço e fígado. As estratégias de imunização homóloga e heteróloga, com antígenos de histonas nucleossomais, não foram capazes de proteger contra infecção por L. infantum no modelo do hamster.

Low levels of anti-histone antibodies in north Indian children with juvenile rheumatoid arthritis.

BACKGROUND & OBJECTIVES: Early onset pauciarticular disease with uveitis is distinctly uncommon in Indian children with juvenile rheumatoid arthritis (JRA). The occurrence of anti-histone antibodies (AHA) in serum is strongly associated with presence of uveitis. There is a paucity of information from India on the levels of AHA in patients of JRA. In this study, an attempt was made to evaluate the levels of IgG and IgM antibodies to histones in children with JRA in north India. METHODS: Serum samples of 148 children with JRA (84 boys, 64 girls) were collected. Clinical details including onset, symptoms and course of the disease in each patient were recorded. Detailed eye examination including slit lamp examination was done in all patients at presentation and yearly thereafter to rule out uveitis. The presence of antihistone IgG and IgM antibodies was studied by ELISA. Antinuclear antibodies (ANA) were measured by indirect immunofluorescence using HEP-2 cells as substrate at a screening dilution of 1:40. RESULTS: Of the 148 children, 54 had pauciarticular (12 early onset and 42 late onset), 64 polyarticular and 30 systemic onset disease respectively. ANA were present in two children. AHA were raised in 15 (10%) children, of whom 10 had IgM antibodies, 3 had IgG and 2 had both isotypes. None of the children with early onset pauciarticular disease had uveitis, ANA or AHA. INTERPRETATION & CONCLUSION: The low occurrence of AHA and uveitis in our subset of patients with JRA is in contrast to that reported from Western countries. The low occurrence is unlikely due to technical reasons as the antigen that has been used consistently showed significant binding to serum from patients with systemic lupus erythematosus (SLE). This is in accordance with the rarity of early onset pauciarticular disease and chronic uveitis in these patients. More studies from other parts of the country are required to validate this observation.

An IgM monoclonal antibody to Japanese encephalitis virus recognizing a cross-reactive epitope on nuclear histones.

An IgM class of monoclonal antibody (MAb) raised against 'envelope' (E) glycoprotein of Japanese encephalitis (JE) virus, cross reacted with nuclear histones, in addition to recognizing the viral antigen present in the cytoplasm of infected cells by indirect fluorescent antibody (FA) technique. The experiments on histone depletion by the acid treatment of uninfected PS (porcine kidney) cells, revealed the loss of nuclear immunofluorescence (IF) which was regained after the reconstitution of acid treated cells with histones, prior-to reacting with MAb NHA-2. The IgM MAb recognized specifically the viral antigens expressed on the surface of JE virus infected PS cells by a modified indirect FA. The adsorption of MAb NHA-2 with calf thymus histones (type II-AS) showed a comparative higher drop in the reactivity to JE virus (54.2% reduction) as compared to that against uncomplexed histones (33.3%) by ELISA, thus indicating a higher MAb affinity to the former. In contrast, the adsorption of MAb with chicken RBC nuclei resulted in comparatively more reduction in the reactivity to the uncomplexed histones (52.4% reduction) as against JE virus (37.5%), suggesting that DNA plays some role in modifying and presenting these epitopes. The cross-linkage of epitopes by glutaraldehyde treatment of JE virus antigen and histones showed a 2-fold and higher rise in the MAb reactivity as against those with unfixed or methanol fixed antigens (no cross-linkage), suggesting that the epitope is conformation dependent. Thus, histones seem to share a partial conformational homology with 'E' glycoprotein of JE virus and immune reaction with histones might lead to an autoimmune disorder.

Cellular immune response to retinal S-antigen & interphotoreceptor retinoid binding protein fragments in idiopathic human uveitis.

The role of retinal antigens in idiopathic human uveitis has been studied in 38 patients of uveitis, and 30 patients of systemic connective tissue disease (CTD) and 30 healthy volunteers. Lymphocyte proliferative responses were tested in vitro against native S-antigen, its uveitopathogenic peptides (peptide M, peptide G), yeast histone H3 peptide and uveitopathogenic fragment of interphotoreceptor retinoid binding protein (IRBP: R16) to establish their role in pathogenesis of human uveitis. Seven patients with uveitis, and none among CTD patients and healthy volunteers, responded (stimulation index > 3) to at least one retinal antigen used. One uveitis patient showed response to native S-antigen, peptide M and yeast histone H3. One responded to both S-antigen and peptide M and another responded to both peptide G and R16 peptide. Two responded to S-antigen only, one to peptide M and one to peptide G. In addition, one uveitis patient responded to yeast histone H3 only. These results suggest that retinal antigens may play a role in the etiopathogenesis of a subset of idiopathic human uveitis.

Caracterizaçäo clínico-laboratorial de auto-anticorpos induzidos por isoniazida / Clinical and laboratorial characterization of autoantibodies induced by isoniazid

A INH é uma das drogas capazes de induzir a formaçäo de auto-anticorpos e, em alguns casos, uma síndrome semelhante ao LE. Os autores avaliaram longitudinalmente, no soro de 24 pacientes com tuberculose tratados com INH, a presença de A-AH e fraçöes às quais säo dirigidos. O fator antinuclear foi positivo em dois pacientes tratados e anticorpos IgM anti-histona foram detectados em 4/24 (6%); estes também foram observados em um paciente pré-tratamento. Soros com IgM-AH que apresentavam reatividade forte por Elisa reconheciam todas as fraçös de histona no western blotting e os com reatividade menor ligavam-se somente à fraçäo H1. Näo se verificou correlaçä com manifestaçöes clínicas de LE

Anticorpos anti-histona: observaçöes num grupo de doentes com lúpus eritematoso sistêmico e artrite reumatóide / On anti-histona antibodies: observations on patients with systemic lupus erythematosus and rheumatoid arthrits

Os autores relatam experiência com anticorpo anti-histona que encontraram positivo em doentes com lúpus eritematoso sistêmico e artrite reumatóide, presente na fase ativa da doença