Project description:The chemokine receptor CCR5 is a major co-receptor for human immunodeficiency virus 1 (HIV-1) mediating infection of target cells1,2. Beyond its function as co-receptor, CCR5 also influences the course of HIV disease and progression to AIDS3. However, it is unclear how CCR5 affects HIV-associated damage to the central nervous system (CNS) and development of HIV-associated neurocognitive disorders (HAND) independently of its co-receptor function. Here we show in a transgenic model of brain damage induced by HIV envelope protein gp1204 that genetic ablation of CCR5 prevents neuronal injury and loss and limits microglial activation, but fails to abrogate astrocytosis. CCR5 deficiency also protected gp120-transgenic mice against impairment of spatial learning and memory. Thus, CCR5-deficiency revealed that astrocytosis, a prominent pathological feature of AIDS brains5, can occur independently from neuronal demise and behavioral impairment. Since the viral envelope protein expressed in the transgenic mouse model originated from HIV-1 LAV4, a CXCR4-preferring virus that can infect macrophages6, CCR5 appeared to exert its control of neuronal injury predominantly in an indirect fashion and independently from its function as a co-receptor. Using analysis of genome-wide CNS gene expression we identified a subset of 734 genes that were differentially regulated in association with neuronal injury in the presence of CCR5. This subset of genes indicated that neuronal injury was associated with activation of macrophages and microglia. A set of 1305 genes was only differentially regulated in association with gp120 in the absence of CCR5 and indicated changes to leukocyte function and the anti-viral immune response besides a down-regulation of components in the GABAergic neurotransmission system. Interestingly, the most significantly differentially expressed genes were observed in a separate subset of 461 genes that was regulated in association with gp120 but independently of the CCR5 genotype. The finding that differential regulation of the 461 and 1305 gene sets was not necessarily linked to neuronal damage and loss suggested that altered expression of at least some of these factors may represent a protective adaptive response of the brain to the presence of viral gp120. Additional experiments using quantitative RT-PCR, protein assays and flow cytometry further supported the notion that CCR5 deficiency blunted microglial activation, a hallmark of HIV-associated brain injury7-9 without significantly affecting the expression of viral gp120. These results provide in vivo evidence for a significant role of CCR5 in HIV-associated CNS injury and behavioral impairment that is independent of the molecules’ function as HIV co-receptor. To characterize the neuroprotective effect of CCR5 ablation in the presence of HIV gp120, we next performed a genome-wide gene expression analysis using whole brain RNA preparations of mice from lines 1 and 2. We decided to collect samples from two time points before and after the ages of when we analyzed histopathology (6 months) and behavior (8 to 9 months) in order to identify genes for which differential regulation may be affected by an interaction of HIVgp120 expression and age. Accordingly, we collected brain tissue of gp120tg, CCR5KO x gp120tg, WT and CCR5KO mice at five different ages: 1.5, 3, 6, 12, and 20 (line 1) or 16 (line 2) months.

Project description:The chemokine receptor CCR5 is a major co-receptor for human immunodeficiency virus 1 (HIV-1) mediating infection of target cells1,2. Beyond its function as co-receptor, CCR5 also influences the course of HIV disease and progression to AIDS3. However, it is unclear how CCR5 affects HIV-associated damage to the central nervous system (CNS) and development of HIV-associated neurocognitive disorders (HAND) independently of its co-receptor function. Here we show in a transgenic model of brain damage induced by HIV envelope protein gp1204 that genetic ablation of CCR5 prevents neuronal injury and loss and limits microglial activation, but fails to abrogate astrocytosis. CCR5 deficiency also protected gp120-transgenic mice against impairment of spatial learning and memory. Thus, CCR5-deficiency revealed that astrocytosis, a prominent pathological feature of AIDS brains5, can occur independently from neuronal demise and behavioral impairment. Since the viral envelope protein expressed in the transgenic mouse model originated from HIV-1 LAV4, a CXCR4-preferring virus that can infect macrophages6, CCR5 appeared to exert its control of neuronal injury predominantly in an indirect fashion and independently from its function as a co-receptor. Using analysis of genome-wide CNS gene expression we identified a subset of 734 genes that were differentially regulated in association with neuronal injury in the presence of CCR5. This subset of genes indicated that neuronal injury was associated with activation of macrophages and microglia. A set of 1305 genes was only differentially regulated in association with gp120 in the absence of CCR5 and indicated changes to leukocyte function and the anti-viral immune response besides a down-regulation of components in the GABAergic neurotransmission system. Interestingly, the most significantly differentially expressed genes were observed in a separate subset of 461 genes that was regulated in association with gp120 but independently of the CCR5 genotype. The finding that differential regulation of the 461 and 1305 gene sets was not necessarily linked to neuronal damage and loss suggested that altered expression of at least some of these factors may represent a protective adaptive response of the brain to the presence of viral gp120. Additional experiments using quantitative RT-PCR, protein assays and flow cytometry further supported the notion that CCR5 deficiency blunted microglial activation, a hallmark of HIV-associated brain injury7-9 without significantly affecting the expression of viral gp120. These results provide in vivo evidence for a significant role of CCR5 in HIV-associated CNS injury and behavioral impairment that is independent of the molecules’ function as HIV co-receptor.

Project description:ObjectiveCoreceptor switch from CCR5 to CXCR4 is associated with HIV disease progression. The molecular and evolutionary mechanisms underlying the CCR5 to CXCR4 switch are the focus of intense recent research. We studied the HIV-1 tropism dynamics in relation to coreceptor usage, the nature of quasispecies from ultra deep sequencing (UDPS) data and their phylogenetic relationships.MethodsHere, we characterized C2-V3-C3 sequences of HIV obtained from 19 patients followed up for 54 to 114 months using UDPS, with further genotyping and phylogenetic analysis for coreceptor usage. HIV quasispecies diversity and variability as well as HIV plasma viral load were measured longitudinally and their relationship with the HIV coreceptor usage was analyzed. The longitudinal UDPS data were submitted to phylogenetic analysis and sampling times and coreceptor usage were mapped onto the trees obtained.ResultsAlthough a temporal viral genetic structuring was evident, the persistence of several viral lineages evolving independently along the infection was statistically supported, indicating a complex scenario for the evolution of viral quasispecies. HIV X4-using variants were present in most of our patients, exhibiting a dissimilar inter- and intra-patient predominance as the component of quasispecies even on antiretroviral therapy. The viral populations from some of the patients studied displayed evidences of the evolution of X4 variants through fitness valleys, whereas for other patients the data favored a gradual mode of emergence.ConclusionsCXCR4 usage can emerge independently, in multiple lineages, along the course of HIV infection. The mode of emergence, i.e. gradual or through fitness valleys seems to depend on both virus and patient factors. Furthermore, our analyses suggest that, besides becoming dominant after population-level switches, minor proportions of X4 viruses might exist along the infection, perhaps even at early stages of it. The fate of these minor variants might depend on both viral and host factors.

Dataset Information

IFN-alpha-induced upregulation of CCR5 leads to expanded HIV tropism in vivo.

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IFN-alpha-induced upregulation of CCR5 leads to expanded HIV tropism in vivo.

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