THE DIFFERENTIATION STATE OF MONOCYTIC CELLS AFFECTS THEIR SUSCEPTIBILITY TO INFECTION AND THE EFFECTS OF INFECTION BY DENGUE VIRUS

This study describes the susceptibility to dengue virus infection of a monocytic cell line at different states of differentiation. Infectiou s virus titres increased in undifferentiated U937 cells following infe ction with clinical isolates but only when the cells were infected via their Fc receptors. No c.p.e. was observed and virus was not secreted into supernatant fluid. Once differentiated, cells were susceptible t o infection either with virus alone or with virus-antibody complexes. Infection was cytolytic and virus was released into the supernatant fl uid. Similar results were obtained with freshly isolated peripheral bl ood monocytes. Increased blood vessel permeability, which occurs in de ngue haemorrhagic fever and dengue shock syndrome patients, has been c orrelated with secondary heterotypic infections and has been postulate d to arise from antibody-enhanced infection of monocytes. The data pre sented suggest a possible mechanism whereby infected monocytes undergo ing diapedesis through blood vessel walls might differentiate sufficie ntly during the process to release virus and cytokines at localized si tes on blood vessels.