In vivo passage of a chimeric simian-human immunodeficiency virus (SHIV-89.6) expressing the human immunodeficiency virus type 1 (HIV-1) tat, rev, vpu, and env genes generated pathogenic viruses (SHIV-89.6P) inducing rapid CD4+ lymphocyte depletion and AIDS-like illness in rhesus monkeys (K. Reimann, J. T. Li, R. Veazey, M. Halloran, I.-W. Park, G. B. Karlsson, J. Sodroski, and N. L. Letvin, J. Virol. 70:6922-6928, 1996). To characterize the molecular changes responsible for this increase in virulence, infectious proviral clones of SHIV-89.6P isolates were derived. Viruses generated from some of these clones caused a rapid and profound decline of CD4+ lymphocytes in a high percentage of inoculated monkeys. Nucleotide changes potentially responsible for the increased virulence of SHIV-89.6P were limited to the env, tat, or long terminal repeat sequences, with most of the observed changes in env. Nucleotide changes in env altered 12 amino acids in the gp120 and gp41 exterior domains, and a 140-bp deletion in env resulted in the substitution of the carboxyl terminus of the SIVmac gp41 glycoprotein for that of the HIV-1 gp41 glycoprotein. The availability of pathogenic proviral clones should facilitate dissection of the molecular determinants of SHIV-89.6P virulence.

Pharmacologic antagonism of CCR5, a chemokine receptor expressed on macrophages and activated T cells, is an effective antiviral therapy in patients with macrophage-tropic HIV infection, but its efficacy in modulating inflammation and immunity is only just beginning to be investigated. In this regard, the recruitment of CCR5-bearing cells into clinical allografts is a hallmark of acute rejection and may anticipate chronic rejection, whereas conventionally immunosuppressed renal transplant patients homozygous for a nonfunctional Δ32 CCR5 receptor rarely exhibit late graft loss. Therefore, we explored the effects of a potent, highly selective CCR5 antagonist, Merck’s compound 167 (CMPD 167), in an established cynomolgus monkey cardiac allograft model. Although perioperative stress responses (fever, diminished activity) and the recruitment of CCR5-bearing leukocytes into the graft were markedly attenuated, anti-CCR5 monotherapy only marginally prolonged allograft survival. In contrast, relative to cyclosporine A monotherapy, CMPD 167 with cyclosporine A delayed alloantibody production, suppressed cardiac allograft vasculopathy, and tended to further prolong graft survival. CCR5 therefore represents an attractive therapeutic target for attenuating postsurgical stress responses and favorably modulating pathogenic alloimmunity in primates, including man.

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Eosinophils are major effector cells implicated in a number of chronic inflammatory diseases in humans, particularly bronchial asthma and allergic rhinitis. The ␤-chemokine receptor C-C chemokine receptor 3 (CCR3) provides a mechanism for the selective recruitment of eosinophils into tissue and thus has recently become an attractive biological target for therapeutic intervention. In order to develop in vivo models of inflammatory diseases, it is essential to identify and characterize the homologues of human eotaxin (C-C chemokine ligand 11) and CCR3 from other species, such as non-human primates. Accordingly, we cloned the macaque eotaxin and CCR3 genes and revealed that they were 91 and 92% identical at the amino acid level to their human homologues, respectively. Macaque CCR3 expressed in the murine pre-B L1-2 cell line bound macaque eotaxin with high affinity (K d ‫؍‬ 0.1 nM) and exhibited a robust eotaxin-induced Ca 2؉ flux and chemotaxis. Characterization of ␤-chemokines on native macaque CCR3 on eosinophils was performed by means of eotaxin-induced shape change in whole blood using a novel signaling assay known as gated autofluorescence forward scatter. Additionally, mAbs were raised against macaque CCR3 using two different immunogens: a 30-amino acid synthetic peptide derived from the predicted NH 2 terminus of macaque CCR3 and intact macaque CCR3-transfected cells. These anti-macaque CCR3 monoclonal antibodies exhibited potent antagonist activity in receptor binding and functional assays. The characterization of the macaque eotaxin/CCR3 axis and development of antagonistic anti-macaque CCR3 monoclonal antibodies will facilitate the development of CCR3 small molecule antagonists with the hope of ameliorating chronic inflammatory diseases in humans.