Gene therapy: advances, challenges and perspectives / Terapia gênica: avanços, desafios e perspectivas

ABSTRACT The ability to make site-specific modifications to the human genome has been an objective in medicine since the recognition of the gene as the basic unit of heredity. Thus, gene therapy is understood as the ability of genetic improvement through the correction of altered (mutated) genes or site-specific modifications that target therapeutic treatment. This therapy became possible through the advances of genetics and bioengineering that enabled manipulating vectors for delivery of extrachromosomal material to target cells. One of the main focuses of this technique is the optimization of delivery vehicles (vectors) that are mostly plasmids, nanostructured or viruses. The viruses are more often investigated due to their excellence of invading cells and inserting their genetic material. However, there is great concern regarding exacerbated immune responses and genome manipulation, especially in germ line cells. In vivo studies in in somatic cell showed satisfactory results with approved protocols in clinical trials. These trials have been conducted in the United States, Europe, Australia and China. Recent biotechnological advances, such as induced pluripotent stem cells in patients with liver diseases, chimeric antigen receptor T-cell immunotherapy, and genomic editing by CRISPR/Cas9, are addressed in this review.

RESUMO A habilidade de fazer modificações pontuais no genoma humano tem sido o objetivo da medicina desde o conhecimento do DNA como unidade básica da hereditariedade. Entende-se terapia gênica como a capacidade do melhoramento genético por meio da correção de genes alterados (mutados) ou modificações sítio-específicas, que tenham como alvo o tratamento terapêutico. Este tipo de procedimento tornou-se possível por conta dos avanços da genética e da bioengenharia, que permitiram a manipulação de vetores para a entrega do material extracromossomal em células-alvo. Um dos principais focos desta técnica é a otimização dos veículos de entrega (vetores) que, em sua maioria, são plasmídeos, nanoestruturados ou vírus − sendo estes últimos os mais estudados, devido à sua excelência em invadir as células e inserir seu material genético. No entanto, existe grande preocupação referente às respostas imunes exacerbadas e à manipulação do genoma, principalmente em linhagens germinativas. Estudos em células somáticas in vivo apresentaram resultados satisfatórios, e já existem protocolos aprovados para uso clínico. Os principais trials têm sido conduzidos nos Estados Unidos, Europa, Austrália e China. Recentes avanços biotecnológicos empregados para o aprimoramento da terapia gênica, como células-tronco pluripotentes induzidas em pacientes portadores de doenças hepáticas, imunoterapia com células T do receptor do antígeno quimera e edição genômica pelos sistema CRISPR/Cas9, são abordados nesta revisão.

Shwachman-Diamond syndrome: first molecular diagnosis in a Brazilian child

Herein the first molecular diagnosis of a Brazilian child with Shwachman-Diamond Syndrome is reported. A 6-year-old boy was diagnosed with cystic fibrosis at the age of 15 months due to recurrent respiratory infections, diarrhea and therapeutic response to pancreatic enzymes. Three sweat tests were negative. At the age of 5 years, he began to experience pain in the lower limbs, laxity of joints, lameness and frequent falls. A radiological study revealed metaphyseal chondrodysplasia. A complete blood cell count showed leukopenia (leukocytes: 3.1-3.5 x 103/µL), neutropenia (segmented neutrophils: 15-22%), but normal hemoglobin, hematocrit and platelet count. A molecular study revealed biallelic mutations in the Shwachman-Bodian-Diamond Syndrome gene (183-184TA-CT K62X in exon 2 and a 258+2T-C transition) confirming the diagnosis of Shwachman-Diamond Syndrome. A non-pathologic, silent nucleotide A to G transition at position 201 was also found in heterozygosis in the Shwachman-Bodian-Diamond Syndrome gene. This is the first report to describe a Brazilian child with molecular diagnosis of Shwachman-Diamond Syndrome, a rare autosomal recessive disorder characterized by exocrine pancreatic insufficiency, intermittent or persistent neutropenia and skeletal changes. Other characteristics include immune system, hepatic and cardiac changes and predisposition to leukemia. Recurrent bacterial, viral and fungal infections are common. The possibility of Shwachman-Diamond Syndrome should be kept in mind when investigating children with a diagnosis of cystic fibrosis and normal sweat tests.