Associação entre o polimorfismo VKORC1: C. 174-136G>A (rs9934438) e a dose semanal de varfarina em pacientes idosos ­ estudo piloto / Association between VKORC1: C.174-136G> A (rs9934438) polymorphism and weekly warfarin dose in elderly patients - pilot study

A varfarina é um anticoagulante utilizado na prevenção e no tratamento de doenças tromboembólicas, com janela terapêutica estreita e, elevado risco de hemorragias. Nos idosos, a principal indicação para tratamento anticoagulante oral é fibrilação atrial, cuja prevalência aumenta com a idade, atingindo 8% após os 80 anos. O exame utilizado para controle da anticoagulação oral é o tempo de protrombina, através do cálculo da razão normalizada internacional (RNI), visando o ajuste de dose e manutenção da faixa terapêutica (RNI= 2 a 3). Os idosos requerem um monitoramento efetivo devido a fatores inerentes da idade. Embora seja conhecido que os fatores genéticos influenciam na resposta terapêutica à varfarina, na rotina da maioria dos hospitais a farmacogenética ainda não é considerada no ajuste de dose. Visando estabelecer uma conduta terapêutica personalizada, o presente estudo tem como objetivo avaliar a associação entre o polimorfismo rs9934438 do gene VKORC1, que codifica a enzima vitamina K epóxido redutase, e a dose semanal de varfarina necessária para atingir o RNI adequado. Até o momento, foram incluídos 52 pacientes com idade superior a 70 anos, de ambos os sexos e em uso de varfarina. A análise do polimorfismofoi realizada através da PCR em tempo real utilizando os reagentes TaqMan™ Sample-to-SNP™ e o sistema de detecção TaqMan® SNP Genotyping Assay. As análises estatísticas foram realizadas utilizando o pacote SPSS v. 16.0 e nível de significância adotado foi de 5%. Dos 52 pacientes incluídos até o momento, 37 (71%) permaneceram na faixa terapêutica (Time in Therapeutic Range, TTR) em pelo menos 50% do tempo de anticoagulação e, para eles a dose semanal de varfarina variou de 15mg a 62,5mg. Apesar de ser um estudo piloto, a distribuição dos genótipos está em equilíbrio gênico, segundo Hardy-Weinberg (AA=19,2%, AG=34,6%, GG= 46,2%, χ2= 3,34 e p=0,067). Para os idosos com TTR ≥50%, a frequência do alelo A foi significantemente maior entre os pacientes que utilizaram doses menores de varfarina (Exato de Fisher, p=0,005). Adicionalmente, os portadores do genótipo AA necessitaram, em média, de aproximadamente metade da dose para atingir a faixa terapêutica quando comparados aos portadores do genótipo GG, 20,5 versus 36,5 mg/semana, respectivamente (ANOVA, p=0,006/ Pós-teste Bonferroni, p=0,039). Os resultados permitem concluir que portadores de alelo A são mais responsivos ao tratamento com varfarina, sugerindo que o perfil genotípico pode ser de grande valor para o direcionamento da dose terapêutica em idosos. (AU)

CD4+CD25+Foxp3+ indirect alloreactive T cells from renal transplant patients suppress both the direct and indirect pathways of allorecognition.

Alloreactive T cells recognize donor antigens by two routes: direct and indirect pathways of allorecognition. Although the direct pathway is reported to be dominant in allograft rejection, indirect allorecognition also plays an important role. Indirect alloreactivity is also observed in renal transplant patients irrespective of rejection. Previously we showed a predominance of interleukin (IL)-10 induced by indirect allorecognition of donor human leucocyte antigen (HLA)-DR peptides, suggesting the existence of indirect alloreactive T cells displaying regulatory activity. In the present work, our objective was to characterize these regulatory T cells. We detected indirect alloproliferation of peripheral blood mononuclear cells (PBMC) from renal transplant patients, induced by donor HLA-DR peptides, dependent on IL-4 or IL-10, suggesting regulatory activity as part of the alloreactive T-cell repertoire. PBMC-derived indirect alloreactive T-cell lines were established and produced both inflammatory and regulatory cytokines. We showed that two of these T-cell lines which were able to inhibit both direct and indirect alloproliferation of another T-cell line from the same patient presented a CD4(+)CD25(+)Foxp3(+) T-cell population. These data support the idea that indirect alloreactive T cells may also have regulatory activity and may contribute to the maintenance of the human renal allograft.

CD4+CD25+Foxp3+ indirect alloreactive T cells from renal transplant patients suppress both the direct and indirect pathways of allorecognition

Alloreactive T cells recognize donor antigens by two routes: direct and indirect pathways of allorecognition. Although the direct pathway is reported to be dominant in allograft rejection, indirect allorecognition also plays an important role. Indirect alloreactivity is also observed in renal transplant patients irrespective of rejection. Previously we showed a predominance of interleukin (IL)-10 induced by indirect allorecognition of donor human leucocyte antigen (HLA)-DR peptides, suggesting the existence of indirect alloreactive T cells displaying regulatory activity. In the present work, our objective was to characterize these regulatory T cells. We detected indirect alloproliferation of peripheral blood mononuclear cells (PBMC) from renal transplant patients, induced by donor HLA-DR peptides, dependent on IL-4 or IL-10, suggesting regulatory activity as part of the alloreactive T-cell repertoire. PBMC-derived indirect alloreactive T-cell lines were established and produced both inflammatory and regulatory cytokines. We showed that two of these T-cell lines which were able to inhibit both direct and indirect alloproliferation of another T-cell line from the same patient presented a CD4+CD25 +Foxp3+ T-cell population. These data support the idea that indirect alloreactive T cells may also have regulatory activity and may contribute to the maintenance of the human renal allograft.