High Frequency of Familial Hemophagocytic Lymphocytosis Associated Immune Gene Defects In Refractory Viral Infection of Unknown Origin

Abstract 2775

Refractory virus infection of unknown origin is a series of life-threatening disorders which include virus associated hemophagocytic lymphohistocytosis (HLH), chronic active EB virus infection (CAEBV) and virus associated lymphoma, etc. Familial HLH (FHL) is a kind of autosomal recessive hereditary disease that is caused by inherited immune gene defects. PRF1, UNC13D, STX11, STXBP2, SH2D1A and XIAP genes are most commonly reported as FHL associated genes. To investigate the incidence of six FHL associated gene defects as mentioned above and relevant clinical characteristics in the patients with refractory virus infection of unknown origin, a total of 25 patients were screened for six FHL associated genes. The median age was 9(1-22)years old. For FHL associated gene analysis, the genomic DNA from the patients' peripheral blood (PB) was amplified by PCR. Bi-directional sequencing was performed with AB3130XL, and then gene including full length of coding region and splicing donor and receptor site were analyzed with Variant Reporter V1.0 software. The cDNA and the amino acid number were defined based on the GeneBank. The structural domain and functional locus were defined basing on the data bank in UniProtKB. The PB or lymphoma tissue from the patients was screened for HHV1 to HHV8 DNA by multiplex PCR, the positive virus was then quantified by real-time PCR. The refractory virus infection is defined as the level of the virus DNA continuously or repeatedly positive for more than 3 months after antiviral therapy. HLH is diagnosed according to the criteria by International Society of Histocyte in 2009, and lymphoma is diagnosed according to the criteria by WHO in 2008. All cases were diagnosed or excluded hematological malignancy by morphology, tissue pathology, and immunol histochemistry, flowcytometry, gene rearrangement of IgH, TCR, and cytogenetic analysis. No family history of the same disease was identified in all patients. Thirteen patients carried 1 kind of gene defect (see Table1), among them, 3 cases had only 1 heterozygous gene mutation and their mothers or fathers are healthy carriers. The other patients have 2 mutated genes or the male patients have 1 XIAP or SH2D1A gene defect. One case with EBV associated peripheral T lymphoma gave up the therapy, the other 12 cases survived by Jul. 2010 after therapy. Two cases received allogeneic hematopoietic stem cell transplantation (allo-HSCT) and achieved disease-free survival by now. Twelve cases have no immune gene defects, and 4 of them were EBV associated HLH (developed into peripheral T lymphoma 3 years after diagnosis in one patient, CAEBV in 3 cases). Our results have shown for the first time that high frequency of FHL associated immune gene defects is in refractory virus infection in Chinese. Therefore, FHL associated immune gene defects may be responsible for refractory virus infection of unknown origin and result in HLH, CAEBV and virus associated lymphoma. One heterozygous immune gene mutation may combine with other factors to result in refractory viral infection. DNA sequence analysis of six common FHL associated genes is very helpful to make definite diagnosis and choose appropriate therapy for the patients.