To provide a method to secure the safty against simia B virus for breeding business workers, laboratory workers, researchers and others who are engaged in breeding of monkeys.

To provided a gene vaccine against simia B virus, containing the gene coding glycoprotein D gene, which is consists of recombinant plasmid manifesting glycoprotein D gene in the body of mammals. Further provided method for preparing monkeys having capability for inhibiting proliferation of the B virus, the method including to produce the above-mentioned polypeptide in the body of Macca fuscata by administered the gene vaccine to Macca fuscata before infected with the B virus, or other monkeys who are already infected with the B virus. Also, to provided simia B virus-free Macca fuscata being inoculated with the gene vacine.