Herpesviruses and AIDS

It is well recognized clinically that herpesviruses can cause disease in AIDS patients once human immunodeficiency virus (HIV) has precipitated marked immunosuppression. However, in addition to this opportunistic relationship, there is evidence to suggest that herpesviruses could increase the pathogenicity of HIV by acting as cofactors. Experiments in vitro have shown that several herpesviruses can activate HIV gene expression or alter the cellular tropism of HIV through a variety of mechanisms (antigen presentation, cytokine release, pseudotype formation, CD4 cell surface upregulation, Fc receptor formation, transactivation). Studies of human autopsy material have shown that some herpesviruses (particularly cytomegalovirus, human herpes virus 6 and herpes simplex virus) are found frequently in AIDS patients. If such herpesviruses act as cofactors in vivo, then their inhibition by aciclovir could explain why a survival benefit has been reported from the use of this drug in two double-blind, placebo-controlled randomized trials.