Determination of tumor necrosis factor-alpha levels in dengue virus infected patients by sensitive biotin-streptavidin enzyme-linked immunosorbent assay

A modified sandwich enzyme-linked immunosorbent assay using biotin-streptavidin system (BS-ELISA) was developed to determine levels of tumor necrosis factor-alpha (TNF-alpha) in serum samples of children infected with dengue virus (n = 99) and healthy controls (n = 41). The minimum detectable concentration of TNF-alpha by the BS-ELISA was 3.3 pg/ml. The mean TNF-alpha level was highest in those patients with dengue shock syndrome (DSS) or dengue hemorrhagic fever (DHF) grade III (37.44 +/- 42.0 pg/ml). Lower levels were found in DHF grade I (28.44 +/- 42.7 pg/ml), DHF grade II (24.21 +/- 25.4 pg/ml) and dengue fever (DF) (14.10 +/- 24.0 pg/ml). TNF-alpha in the sera of DF and DHF patients could be detected on days 2-6 after the onset of fever, the high level occuring on day 5. TNF-alpha was detected in 41.4% (24.01 +/- 35.2 pg/ml) of dengue virus infected patients and 7.3% (4.2 +/- 15.6 pg/ml) of control subjects. The sera of patients contained significantly higher levels of TNF-alpha than the sera of controls, P-value < 0.001. DHF patients had significantly higher levels of TNF-alpha than DF patients (P-value = 0.020) but no difference in the TNF-alpha levels from sera of DHF grades I-III patients was observed (P-value = 0.295). The results indicate that the BS-ELISA is a very sensitive method for determining TNF-alpha in serum samples of DF and DHF patients. The TNF-alpha levels might be associated with dengue virus infection and related to disease severity of DHF. (C) 2000 Published by Elsevier Science B.V.