| Summary: | 碩士 === 國立成功大學 === 微生物及免疫學研究所 === 92 === Dengue virus (DEN) can cause either self-limited mild disease of dengue fever (DF), or severe dengue hemorrhagic fever (DHF) and dengue shock syndrome (DSS). It is well known that children with secondary infection of a different serotype of dengue virus will cause more severe DHF/DSS that might be fatal. Antibody-dependent enhancement of infection (ADE) is widely accepted to be central to the development of these clinical entites. When the virus is bonded by sub-neutralizing or non-neutralizing antibodies from previous infection, the complex can be captured by Fc gamma receptor-bearing cells via the Fc portion of the immunoglobulins, and then enhances the viral entrance and replication. However, the mechanism responsible for this ADE phenomenon has not been clearly defined. In order to characterize it, we have set up an in vitro infectious model to study the role of enhancing antibodies on DEN infection. Because autoantibodies were found in DHF/DSS patients and B cell could support the DEN replication, we first chose a human B lymphoma, BJAB, as a model. The DEN serotype 2 (DEN2)-infected BJAB expressed dengue viral non-structural protein 1 (NS1), envelope protein（E） and core protein post infection that could be detected by flow cytometer. Infectious viral particles were detected by plaque assay in the culture supernatant. DEN2 not only replicated in BJAB cells but also activated them to up-regulate activation markers, including CD70 and CD86. A sub-neutralizing titer (1:6000) of heterologous DEN3-immune serum was able to enhance DEN2 infection in BJAB cells. Furthermore, a panel of hybridomas secreting antibodies recognizing different DEN2 antigens was infected by DEN2. Surprisingly, only those hybridomas secreting anti-DEN precursor membrane protein (anti-preM) antibodies could be infected. This implicates that anti-preM antibody may mediate the ADE. Indeed, the infection of DEN2 on Fc receptor-bearing cells, such as DC2.4 cell line and other non-permissible hybridoma, was enhanced at least 10 fold in the presence of anti-preM antibody. Anti-preM antibodies mediated enhancement could also be demonstrated on non-Fc receptor-bearing cells, such as BHK and A549. This enhancement was not found for anti-E antibodies. These studies can help us understand the characteristics of enhancing antibody, although its mechanism and biological significance need further investigation.
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