A higher production of platelet activating factor in ex vivo heterologously secondary dengue-2 virus infections.

Patients with a dengue-1 virus (DV-1) infection followed by another DV-2 infection were reported to have a higher incidence of dengue haemorrhagic fever (DHF). Mononuclear leukocytes (MNLs) are principal cells for DV replication so that we challenge MNLs obtained from non-immune and previously DV-1-infected donors with DV-2 to mimic primary and heterologously secondary DV-2 infections. Production of platelet activating factor (PAF), thromboxane B2 (TxB2), and prostaglandin D2 (PGD2) by MNLs in the DV-2 infections was measured by radioimmunoassay. We found that MNLs, no matter primary or heterologously secondary exposure to DV-2, could release significant amount of PAF, TxB2, and PGD2. PAF but not TxB2 or PGD2 levels released by MNLs were significantly higher in those obtained from previously DV-1-infected donors (75.8 +/- 28.5 vs 21.2 +/- 13.4 pg/ml; p < 0.05). These results suggest that PAF, which is known to enhance inflammatory reactions and to augment platelet aggregation, may in part participate in the pathogenesis of DHF.