Parvovirus B19 in the Context of Hematopoietic Stem Cell Transplantation: Evaluating Cell Donors and Recipients.

BACKGROUND: Parvovirus B19 (B19V) is a common human pathogen, member of the family Parvoviridae. Typically, B19V has been found to infect erythroid progenitors and cause hematological disorders, such as anemia and aplastic crisis. However, the persistence of genomic deoxyribonucleic acid (DNA) has been demonstrated in tonsils, liver, skin, brain, synovial, and testicular tissues as well as bone marrow, for both symptomatic and asymptomatic subjects. Although the molecular and cellular mechanisms of persistence remain undefined, it raises questions about potential virus transmissibility and its effects in the context of allogeneic hematopoietic stem cell transplantation (allo-HSCT) recipients. METHODS: With this aim, we retrospectively screened allogeneic stem cell donors from 173 patients admitted for allo-HSCT from January 2008 to May 2013 using a seminested polymerase chain reaction approach. RESULTS: We found 8 positive donor samples, yielding a 4.6% of parvovirus prevalence (95% confidence interval, 2.36-8.85). Pre- and post-HSCT samples (n = 51) from the 8 recipients of the positive donors were also investigated, and 1 case exhibited B19V DNA in the post-HSCT follow-up (D + 60). Direct DNA sequencing was performed to determine the genotype of isolates and classification, performed by phylogenetic reconstruction, showed a predominance of genotype 1a, whereas the rare genotype 3b was detected in 2 additional patients. By molecular cloning, different B19V 1a substrains polymorphisms were evidenced in the single case in which donor and its recipient were B19V+. CONCLUSIONS: Our results suggest that HSCT allografts are not a main source for B19V transmission, pointing to potential events of reinfection or endogenous viral reactivation.

Epigenetic alterations of p15(INK4B) and p16(INK4A) genes in pediatric primary myelodysplastic syndrome.

We studied the methylation status of the p15(INK4B) and p16(INK4A) genes in 47 pediatric patients with primary MDS, its correlation with subtype, and the role of p15(INK4B) and p16(INK4A) in the evolution of MDS toward AML. Aberrant methylation of the p15(INK4B) gene was detected in 15 of 47 patients (32%), whereas only four patients demonstrated methylation of the p16(INK4A) gene (8%). The frequency of p15(INK4B) methylation was significantly higher in RAEB and RAEB-t subtypes (p<0.003). Aberrant methylation of the p16(INK4A) gene was also more frequent in the subtypes that characterize advanced stages of the disease (p<0.05). Evolution of disease was verified in 17 (36%) of the 47 patients. The association of p15(INK4B) and p16(INK4A) methylation status with evolution of disease was clearly significant (p<0.008 and p<0.05, respectively). These results suggest that methylation of the p15(INK4B) and p16(INK4A) genes is an epigenetic biomarker of pediatric disease evolution.

Seleção de doador não aparentado / HLA antibodies and donor selection

Apesar da presença de anticorpos anti-HLA em transplantes de órgãos sólidos estar associada à rejeição, essa correlação não havia sido pesquisada em transplante alogênico de células progenitoras hematopoéticas (TCPH). Estudos mais recentes na literatura têm demonstrado que a falência da enxertia no TCPH pode ser mediada por aloanticorpos anti-HLA doador especifico (DSA). A especificidade desses anticorpos pode ser evidenciada pelas técnicas de fase sólida, onde os antígenos HLA únicos são aderidos a pérolas de poliestireno, que permite a realização da prova cruzada virtual. Na presença de DSA, é recomendável selecionar outro doador ou realizar as estratégias de remoção dos anticorpos.

In spite of Anti-HLA antibodies being associated to rejection in solid organs transplantation, this correlation has not been well established yet in allogenic bone marrow transplantation.Recent studies in the literature have demonstrated that engraftment failure in hematopoietic cell transplantation (HCT) can be mediated by donor specific anti-HLA antibodies (DSA). These antibodies specificity can be detected by solid-phase techniques, where single HLA antigens are adhered to microbeads, which allows the interpretation of host reactivity by "virtual crossmatch". In the presence of DSA, it is advisable to either search for another donor or remove the antibodies prior to transplantation.