SIVmac, or Simian Immunodeficiency Virus from macaques, is a type of virus that primarily infects macaque monkeys. It is similar to the human immunodeficiency virus (HIV) and is used in research to understand how HIV affects humans. SIVmac helps scientists study the immune response and the progression of viral infections. Researchers often use SIVmac in laboratory settings to develop vaccines and treatments for HIV. By studying how SIVmac interacts with the immune system of macaques, scientists can gain insights that may lead to better strategies for combating HIV in humans.