In the late 1980s, the University of Hawaii began developing a papaya cultivar resistant to Papaya Ringspot Virus. To do this, certain viral genes encoding capsid proteins were transferred to the papaya genome. These viral capsid proteins elicit something similar to an "immune response" from the papaya plant. These new, genetically modified papaya plants are no longer susceptible to infection, allowing farmers to cultivate the fruit even when the virus is widespread.