Baculovirus structure, illustration. Baculoviruses are rod-shaped, enveloped (yellow lipid bilayer) viruses, with a large double-stranded DNA (deoxyribonucleic acid, red) genome packed inside nucleocapsids (protein coats, green). They are a natural pathogen of invertebrates, particularly butterflies at the caterpillar stage. They were originally studied for curing viral attack in economically important insects. Subsequently, it was found that baculoviruses can be easily manipulated through genetic engineering for molecular biologists to synthesise specific peptides and proteins. Other applications may include production of insecticides, proteins for diagnostic screening in medicine, and possibly the production of a vaccine against HIV.