Molecular profile of human cytomegalovirus in bone marrow transplant recipients with active infection / Aspectos moleculares do citomegalovirus humano durante infecção ativa em pacientes submetidos ao transplante de medula ossea

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Human Cytomegalovirus (HCMV) remains a significant cause of morbidity in immunocompromised patients, especially in bone marrow transplant recipients. It may manifest severe complications including hepatitis, gastrointestinal disease, and interstitial pneumonitis or as so-called ?HCMV viral syndrome? with fever, leukopenia, and thrombocytopenia. The HCMV may also has an immunomodulatory effect, potentially making HCMV infection an important risk factor for the development of an acute and chronic allograft rejection and for coinfection with other herpesviruses. The detection of the HCMV genome by PCR (Polymerase Chain Reaction) is specific and sensitive. Besides this, it can be used as a powerful tool for the early diagnoses of the infection caused by this virus. Variations in functionally relevant areas of the HCMV genome have been used as genetic markers in numerous clinical studies to differentiate the HCMV strains and to associate them with the viral pathogenesis further with the patients? clinical manifestations. The glycoprotein B (gB) is the major glycoprotein of HCMV?s envelope and it has been implicated in host cell entry, cell-to-cell virus transmission, consequently in the fusion of infected cells. The gB amplification by PCR combined with the restriction analysis by RFLP in polymorphic areas are effective for the identification of the HCMV genotypes, becoming possible the distinction of at least 4 electrophoretic patterns. On the other hand, the determination of the viral load in the immunologically affected patients has been associated as marker or predictor for the development of the organ specific disease by the HCMV. Hence, the determination of the viral load in these specific patients is fundamental for the management of the antiviral therapy. In addition, the viral load values are related to levels of the immune-suppression, the pathogenesis of the HCMV and the group of patients and/or the type of transplant. Furthermore, the viral load values can indicate the beginning of the antiviral therapy administration. A real-time PCR (RT-PCR) assay was applied for quantifying the HCMV genome load in clinical samples and the detection and quantification of HCMV DNA in blood serum through RT-PCR are able to distinguish patients with symptomatic infections among those with latent or inactive infections. Advances have been made in the prevention of HCMV disease after bone marrow transplantation, including prophylactic administration of antivirals such as Acyclovir and Ganciclovir. The HCMV prophylaxis with antiviral in this patients? group is administered for prolonged periods of therapy, consequently it can originate resistant viruses related mainly to two genes: the viral phosphotransferase (UL97) and the viral DNA polymerase (UL54). Ahead the importance of the identification of HCMV strains in bone marrow transplant patients, the HCMV strains performance in the patients? infection and clinical presentation, the relevance of determinating the viral load as a disease predictor, and finally, the detection of the resistant strains to the available antivirals, this study prospectively evaluated bone marrow transplant recipients followed at Hemocentro/UNICAMP. Moreover, it had as main goals: to determine the prevalence of the HCMV gB genotypes, to evaluate a possible gB genotype association with the patients? clinical presentation; to determinate the viral load for monitoring the antiviral therapy, and to correlate Ganciclovir resistant mutations in UL97 and UL54 gene with the viral load and patients? clinical presentation. From 22 bone marrow transplant recipients, DNA samples of peripheral blood (169) and DNA samples of blood serum (187) were included in this casuistic. Among 47 HCMV positive samples, 42 were genotyped. We observed the prevalence of gB1 genotype (47%), as described in the specific literature, however without statistical analysis, the raw data exhibited that gB1 genotype can be related to patients? better prognostics. From 12 followed bone marrow transplant recipients, we applied the RT-PCR in 96 DNA blood serum samples and we observed that the method was accurate for the viral load evaluation in this patients? group. However, it is necessary to establish a crucial cutoff to consider whether a specific value of viral load is a predictive value to cause HCMV disease and to monitor the patients? treatment. This method was more precise than the nested-PCR for blood serum samples. Additionally, we identified 8 new mutations in UL97 gene, one of them can be related to Ganciclovir HCMV resistance. Among all of identified polymorphisms, 3 of them can be related to gB1 genotype and may be used as genetic marker to HCMV genotyping. In the region IV of the UL54 gene, 5 new mutations were identified, and can possibly be related to Ganciclovir HCMV resistance. We concluded that the determination of the patients? viral load is crucial, even so it is not the only way to evaluate the antiviral treatment efficacy. Then, the evaluation of other molecular parameters as genotyping and mutations related to the HCMV antiviral resistance, are complementary information and must be considered to monitor the clinical evolution of bone marrow transplant recipients

ASSUNTO(S)

infecção infection bone marrow transplantation genotyping genotipagem molecular biology medula ossea - transplante citomegalovirus biologia molecular cytomegaloviruses

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