Study On The Immunoprotective Effect And Mechanism Of Aspergillus Fumigatus Thioredoxin Reductase GliT Against Invasive Aspergillosis

The Aspergillus fumigates,a human opportunistic funal pathogen,is responsible for most fatal cases of invasive aspergillosis(IA)that occur in patients undergoing chemotherapy,glucocorticoid,solid organ transplantation and hematopoietic stem cell transplantation.Timely and effective antifungal therapy has been shown to improve the prognosis of IA patient.However,antifungal agents are challenged by their hepatorenal toxicity and drug resistance.Therefor,vaccination is a novel approach against IA,and a vaccine that effectively protects immunocompromised patients from IA is the key of successful therapy.In previous study,our research group found that thioredoxin reductase GliT(TR),a novel immunodominant antigen of Aspergillus fumigatus,strongly reacted with the IA patient's sera,which may be used as a candidate antigen for protection vaccine to cure IA.ObjectiveTo evaluate the immunoprotection in mice immunized with thioredoxin reductase GliT of Aspergillus fumigatus and its potential as vaccine candidate,investigate recombinant TR's protective mechanism.MethodsC57BL/6 mice were randomly assigned into two groups:immunization group intramuscularly immunized with recombinant TR for two times,immunosuppressed by giving cyclophosphamide and dexamethasone before challenged with conidial suspension;control group intramuscularly immunized with PBS instead of TR,and the other procedure is the same as immunization group.Survival rate,A.fumigatus lung burdens,pathologic examination and cell count of alveolar lavage were evaluated the immunoprotection of recombinant TR.Levels for IFN-?,IL-4,IL-10,IL-17A in lung homogenates from vaccinated mice and nonimmunized mice were analyzed to investigate recombinant TR's protective mechanism.ResultsThe survival rate of immunization group was 64.7%within 7 days after infection while that of control group was 0.The medians of CFUs from the lung tissues of the suvivors and the nonsuvivors were 0 and 44(P25,P75 were 21,70)respectively(P<0.01).Pulmonary pathology indicated that the lungs of the dead immunized mice and control mice showed alveolar hemorrhage,inflammatory cells recruitment,focal tissue necrosis and hyphal elements throughout the entire lung.In contrast,the lung tissues of the survivors were damaged slightly and free of hyphal elements.Alveolar lavage fluid smear showed that the counting of the survival is given priority to with mononuclear cells,accounting for about 84.2%,neutrophils accounted 15.8%.The counting of the nonsurvival is given priority to with neutrophils,accounting for about 66.4%,while 33.6%mononuclear cells.ELISA assay showed that the level of IFN-?in the lung tissue was significantly increased in the survivors of immunization group when compared with the control group(P<0.01).The levels of IL-4,IL-10 and IL-17A in the lung tissue were significantly decreased in the survivors of immunization group when compared with the control group(P<0.01 or 0.05).ConclusionWe concluded that recombinant TR of Aspergillus fumigatus can induce a modest protection in a murine model of invasive aspergillosis and has potential as a protective antigen.Recombinant TR's protective possible mechanism is that recombinant TR can induce the CD4+Th1 cell-mediated immune response,clearing the fungal.