Viral damage to leaves. Virus-infected leaves (at left) and a healthy leaf of the cowpea plant Vigna unguiculata. The mottled leaves are infected with cowpea mosaic virus (CPMV), a natural pathogen of this plant which produces black-eye beans. Research is being conducted at the John Innes Institute in Norwich, England, to use this virus to make a plant vaccine for AIDS. The CPMV virus is harmless to humans and ideal for genetic engineering. A gene from the HIV virus (the virus causing AIDS) can be inserted into the CPMV virus. By then infecting cowpea leaves with this altered CPMV virus, an AIDS vaccine of virus particles can be produced by the plant.