Immunological aspects of infections part 42

Another example of viral bystander damage is dengue fever in which immune enhancement plays an important part. Here, the dengue virus can infect macrophages via Fc receptors, and its capacity to enter the target cell is enhanced if it is bound to IgG antibodies. Thus, the first infection with a specific dengue virus  type elicits antibodies to that specific virus. However, cross immunity to the other dengue serotypes is fleeting and lasts only a few weeks. When the individual is exposed to a second dengue virus serotype, the pre-existing  antibody to the first type binds to it but does not neutralize the virus. The antibody-enhanced second virus enters the macrophage, setting of a veritable explosion  of proteases, lymphokines complement activation, coagulation cascade, and vascular permeability factors. The result is a much more severe disease called dengue hemorrhagic fever, whose mortality rate in areas with poor medical fascilities and treatment may be as high as 50%.