MS analysis of MIP-1α isoforms and their interaction with CCR5 coreceptor. (A) Extract ion LC-ESI-MS chromatograms of CCL3 and CCL3L1 from recombinant isoforms mixture and from supernatants of PBMCs of HTLV-2/HIV-1^MEU subjects. Retention peaks of the isoforms were extracted from chromatogram by processing data through known ions representative of MIP-1α isoforms and compared with those of rCCL3and rCCL3L1. In addition, MIP-1α cation exchange-positive fractions from HTLV-2/HIV-1^MEU persons were immunoprecipitated with anti–MIP-1α or anti-CCL4 polyclonal Ab before MS analysis. (B) Deconvolution spectra of CCL3 and CCL3L1 isoforms from recombinant isoform mixture and from HTLV-2/HIV-1^MEU subjects. Retention MIP-1α isoform peaks were subjected to MS analysis. The multiple-charged spectra represent the relative ion abundance of the various isoform charge states according to mass-charge ratio (m/z). (C) MS analysis of MIP-1α isolated from immunoreactive fractions of PBMCs of HTLV-2–infected persons eluted using physiologic conditions. (D) MS analysis of MIP-1α secreted by unstimulated PBMCs from HTLV-2/HIV-1–coinfected LTNPs. (E) Flow cytometric analysis of CCR5 expression on CCL3/CCL3L1 binding. The thin black line represents the background-negative control; thick black line, Hos-CCR5 cells (MFI = 19.97); gray line, Hos-CCR5 cells incubated with purified MIP-1α forms (MFI = 13.14).