Two cases of self-limiting nephropathies secondary to dengue haemorrhagic fever.

We report two cases of dengue haemorrhagic fever which developed self-limiting gross nephrotic-range proteinuria. One patient was a 32-year-old Bangladeshi and the other a 42-year-old Chinese national. Both patients did not have manifestations of renal damage, such as increase in serum creatinine, haematuria or urinary casts. Gross nephrotic-range proteinuria, which was self-limiting due to dengue haemorrhagic fever, has not been previously reported in Singapore. We postulate that this nephrotic-range proteinuria is a manifestation of increased glomerular leakage of protein, due to glomerulonephritis associated with dengue haemorrhagic fever.

Heat-inducible vectors for use in gene therapy.

The objectives of this study were to quantity and compare the activities of a minimal heat shock (HS) promoter and other promoters used in gene therapy applications, and to identify strategies to amplify the heat inducibility of therapeutic genes. Human tumour cells were transiently or stably transfected with the HS promoter driving expression of reporter genes. HS promoter activity was induced transiently, with maximum activity 16-24 h after HS, and was dependent on temperature. The activity of the minimal HS promoter was similar, after 42 degrees C HS for 1 h, to that of the cytomegalovirus (CMV) promoter. To determine if the HS promoter could be used to activate a second conditional promoter, cells were transiently transfected with vectors containing both the HS and human immunodeficiency virus type 1 (HIV1) promoters. When the IL-2 gene was placed downstream of the HIV1 promoter. IL-2 production was temperature-independent. The addition of the HIV tat gene downstream of the HS promoter caused IL-2 to be induced more than 3 fold after a single 42 degrees C HS. These data indicate that the minimal HS promoter, following activation by clinically attainable temperatures (< or = 42 degrees C), can drive expression of therapeutic genes at levels comparable to the CMV promoter and be used in conjunction with a second conditional promoter to drive temperature-dependent, gene expression.

Construction of new amplifier expression vectors for high levels of IL-2 gene expression.

The success of IL-2 gene therapy in cancer is in part dependent on the development of high level IL-2 gene expression vectors. Currently, expression vectors based on the human cytomegalovirus (CMV) promoter give the highest levels of expression. We have attempted to construct new IL-2 expression vectors to test whether gene expression can be further increased. The first approach was to use the new SR-alpha promoter to control IL-2 gene expression. The second approach was to combine the Tat transcription activator gene and the HIV 1 and 2 promoters in the same construct so that the levels of gene expression can be amplified. Transient transfection results using the human colon cancer cell line SW480 showed that the SR-alpha promoter yields similar levels of activity as the CMV promoter. However, the HIV 1 and 2 promoter-based amplifier constructs produced 11 and 28 times more secreted IL-2 than the CMV promoter control. The augmented activity of the amplifier constructs was dependent on the presence of the Tat gene and the transcriptional units must be placed in the same orientation. Reducing the size of the vectors by elimination of the neomycin selectable marker did not increase the activity of the constructs.