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Macrophages express the chemokine receptor CCR-5, a coreceptor for human immunodeficiency virus (HIV) entry. This receptor is ligated by beta chemokines, which influence HIV type 1 (HIV-1) replication in CCR-5-bearing cells in vitro and could influence the course of infection in the central nervous system. Cerebrospinal fluid (CSF) samples from 73 HIV-infected men were assayed for macrophage inflammatory protein-1 alpha (MIP-1alpha), MIP-1beta, and regulated upon activation, normal T cell expressed and secreted (RANTES). Distributions of all three were positively skewed. CSF chemokine concentrations were correlated with each other and were higher in demented patients. In a multivariate analysis, demented subjects were more likely to have detectable CSF MIP-1alpha, elevated CSF HIV RNA levels, and lower CD4+ cell counts. However, among those with detectable CSF MIP-1alpha, levels were lower in demented patients. CSF beta chemokine elevation is consistent with the macrophage activation known to occur in dementia and with studies of beta chemokine mRNA expression in the brain. Low, but detectable, levels of CSF MIP-1alpha were strongly associated with dementia, suggesting that higher levels may have neuroprotective effects.

Thymidine-sparing triple-nucleoside regimens have exhibited poor virologic response despite apparent phenotypic susceptibility to 2 of 3 regimen components at early time points. Phenotypic resistance masking by wild-type virus may explain this discrepancy.Consistent with this notion were (1) the presence of low level nucleoside reverse-transcriptase inhibitor-resistant human immunodeficiency virus in subjects receiving failing first-line regimens consisting of tenofovir (TDF), abacavir (ABC), and lamivudine (3TC); (2) lower fold resistance associated with mixtures versus mutants in a clinical-isolate database; and (3) dose dependent changes in susceptibility to ABC, 3TC, TDF, and didanosine on titration of K65R and/or M184V with wild-type virus. These findings underscore the limitations of stand-alone phenotypic susceptibility measures and emphasize the importance of complementary and/or more sensitive techniques.