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Background: Platelet Activating Factor (PAF) has been shown to be an important mediator
of vascular leak in acute dengue. Antibody dependent enhancement (ADE) and microbial
translocation has also shown to contribute to severe dengue. Since monocytes are one of the
primary targets of the dengue virus (DENV) we sought to investigate if monocytes were a
source of PAF, and die effect of ADE and microbial endotoxin (LPS) on; DENV infected
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monocytes.
Methods:! PAF and cytokine levels were evaluated in serial blood samples’ in patients with
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acute dengue infection. The effect of ADE and LPS in production of PAF and cytokines from
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DENV infected primary human monocytes derived macrophages (MDM0) was assessed.
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Gene expression analysis was undertaken to investigate* mechanisms by which LPS
potentiates PAF and cytokine production by DENV infected MDM0.
Results:; Serum PAF levels significantly correlated with both TNF-a (p<0.0001) and IL-l|i
(p<0.0001) in patients with acute DENV infection. Although primary human MDM0
produced inflammatory cytokines following infection with the DENV, they did not produce
PAF following in vitro DENV infection alone, or in the presence of dengue immune serum.
Levels of PAF produced by DENV infected MDM0 co-cultured with LPS was significantly
higher ithan uninfected MDM0S co-cultured with LPS. Although TLR-4 was upregulated in
uninfected MDM0S co-cultured with LPS, this upregulation was not significant in DENV
infected MDM0. Only expression of R1G-I was significantly up regulated (p<0.05) when
DENV infected MDM0 were co-cultured with LPS.
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Conclusion: LPS acts synergistically with the DENV to induce production of PAF and other
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inflammatory cytokines, which suggests that microbial translocation that has shown to occur
in acute dengue, could contribute to dengue disease severity.
