Similarly, in the fat body, genetic activation of viral protein U (Vpu), an accessory protein in human immunodeficiency virus (HIV), inhibits Toll-dependent immune responses and impairs the ability of flies to combat fungal infection; this phenotype is similar to the fungal infection susceptibility phenotype observed in acquired immunodeficiency syndrome (AIDS) patients (131, 283). Here, TLR4 is linked to fungal infectious disease.