Muramyl dipeptide inhibits replication of human immunodeficiency virus in vitro

In the search for compounds capable of inducing endogenous production of colony-stimulating factor (CSF) and possessing activity against human immunodeficiency virus (HIV), an immunomodulator, muramyl dipeptide (MDP), was investigated. MDP can enhance monocyte-macrophage CSF in serum and promote nonspecific resistance against a variety of microbial pathogens. MDP exhibited an inhibitory activity against HIV infection of CD4+ H9 lymphocytes and U937 monocytoid cells. An inhibitor of viral reverse transcriptase, 2', 3'-dideoxyadenosine, produced potent inhibition in cultures which were similarly infected with HIV. MDP could partially reduce antigen production in persistently HIV-infected KE37/1 lymphocyte cultures.