Protective effect of an SDF-1 variant in HIV disease: abstract and commentary.
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Anti-HIV Agents↗
Biomedical subjects
N L Michael
Publications and source records attributed to N L Michael.
Genomic organization and functional characterization of the chemokine receptor CXCR4, a major entry co-receptor for human immunodeficiency virus type 1.
CXCR4 is both a chemokine receptor and entry co-receptor for T-cell line-adapted human immunodeficiency virus type 1. The genomic organization and promoter function for the entire transcription unit of CXCR4 were determined. The gene contains 2 exons of 103 and 1563 base pairs (bp) interrupted by a 2132-bp intron precisely between codons 5 and 6 of the coding sequences. A transcription start site was identified 88 bp upstream of the initiation codon, and a polyadenylate addition site was identified 22 bp 3' to a polyadenylation signal. Transient expression assays defined a minimal promoter at positions -114 to +43 relative to the transcription start site. This region contains a TATA box, a nuclear respiratory factor-1 (NRF-1) site, and two GC boxes. Specific factor binding to the NRF-1 site and GC boxes were demonstrated by gel mobility shifts and DNase I footprinting. Site-directed mutagenesis showed that the NRF-1 site is crucial for promoter activity providing the first evidence for the regulation of a signal transduction gene by NRF-1. Sequences between -691 and -191 repress CXCR4 promoter activity. Further study of these regulatory elements will be important to understanding how CXCR4 functions as both a chemokine receptor and human immunodeficiency virus type 1 entry co-receptor.
Amino Acid Sequence↗
Correlation between humoral responses to human immunodeficiency virus type 1 envelope and disease progression in early-stage infection.
Human immunodeficiency virus (HIV)-1-infected rapid and slow progressors showed differential humoral responses against HIV envelope peptides and proteins early in infection. Sera from slow progressors reacted more strongly with short envelope peptides modeling gp160NL4-3, predominantly in gp41. Reactivity to six peptides (in constant regions C3, C4, and C5 of gp120 and in gp41) correlated with slower progression. In a novel association, reactivity to three peptides (in constant regions C1 and C3 and variable region V3 of gp120) correlated with faster progression. Envelope peptide reactivity correlated with subsequent course of disease progression as strongly as did reactivity to gag p24. Patients heterozygous for 32-bp deletions in the CCR5 coreceptor reacted more frequently to an epitope in gp41. Rapid progressors had greater gp120 native-to-denatured binding ratios than did slow progressors. While antibody-dependent cellular cytotoxicity against gp120 did not strongly differentiate the groups, slow progressors showed a broader neutralization pattern against 5 primary virus isolates.
Biosensing Techniques↗
Major histocompatibility complex genotype is associated with disease progression and virus load levels in a cohort of human immunodeficiency virus type 1-infected Caucasians and African Americans.
To assess the influence of HLA on AIDS-free survival, human immunodeficiency virus load, and CD4 cell counts, 91 Caucasian and 48 African-American seroprevalent men were typed for HLA classes I and II and TAP alleles. HLA associations with these markers were assessed by assigning sum integer scores based on 7 class I allele-TAP variants (+1) and 13 class I-class II-TAP combinations (-1) with different AIDS-free survival times found in a prior study. Subjects in both racial groups and combined with positive sum scores were less likely to have CD4 cell decline (P=.0004), to have increased virus burden (P=.014), and to develop AIDS (P=.034) in the follow-up period than were Caucasians and African Americans with scores of 0 or -1. These results confirm the reported associations of specific major histocompatibility complex genes with AIDS-free survival time in Caucasians and specifically extend them to African Americans and to two established markers of disease progression.
ATP Binding Cassette Transporter, Subfamily B, Mem↗
Neutralizing monoclonal antibodies block human immunodeficiency virus type 1 infection of dendritic cells and transmission to T cells.
Prevention of the initial infection of mucosal dendritic cells (DC) and interruption of the subsequent transmission of HIV-1 from DC to T cells are likely to be important attributes of an effective human immunodeficiency virus type 1 (HIV-1) vaccine. While anti-HIV-1 neutralizing antibodies have been difficult to elicit by immunization, there are several human monoclonal antibodies (MAbs) that effectively neutralize virus infection of activated T cells. We investigated the ability of three well-characterized neutralizing MAbs (IgG1b12, 2F5, and 2G12) to block HIV-1 infection of human DC. DC were generated from CD14(+) blood cells or obtained from cadaveric human skin. The MAbs prevented viral entry into purified DC and the ensuing productive infection in DC/T-cell cultures. When DC were first pulsed with HIV-1, MAbs blocked the subsequent transmission to unstimulated CD3(+) T cells. Thus, neutralizing antibodies can block HIV-1 infection of DC and the cell-to-cell transmission of virus from infected DC to T cells. These data suggest that neutralizing antibodies could interrupt the initial events associated with mucosal transmission and regional spread of HIV-1.
Antibodies, Monoclonal↗
Exclusive and persistent use of the entry coreceptor CXCR4 by human immunodeficiency virus type 1 from a subject homozygous for CCR5 delta32.
Individuals who are homozygous for the 32-bp deletion in the gene coding for the chemokine receptor and major human immunodeficiency virus type 1 (HIV-1) coreceptor CCR5 (CCR5 -/-) lack functional cell surface CCR5 molecules and are relatively resistant to HIV-1 infection. HIV-1 infection in CCR5 -/- individuals, although rare, has been increasingly documented. We now report that the viral quasispecies from one such individual throughout disease is homogenous, T cell line tropic, and phenotypically syncytium inducing (SI); exclusively uses CXCR4; and replicates well in CCR5 -/- primary T cells. The recently discovered coreceptors BOB and Bonzo are not used. Although early and persistent SI variants have been described in longitudinal studies, this is the first demonstration of exclusive and persistent CXCR4 usage. With the caveat that the earliest viruses available from this subject were from approximately 4 years following primary infection, these data suggest that HIV-1 infection can be mediated and persistently maintained by viruses which exclusively utilize CXCR4. The lack of evolution toward the available minor coreceptors in this subject underscores the dominant biological roles of the major coreceptors CCR5 and CXCR4. This and two similar subjects (R. Biti, R. Ffrench, J. Young, B. Bennetts, G. Stewart, and T. Liang, Nat. Med. 3:252-253, 1997; I. Theodoreu, L. Meyer, M. Magierowska, C. Katlama, and C. Rouzioux, Lancet 349:1219-1220, 1997) showed relatively rapid CD4+ T-cell declines despite average or low initial viral RNA load. Since viruses which use CXCR4 exclusively cannot infect macrophages, these data have implications for the relative infection of the T-cell compartment versus the macrophage compartment in vivo and for the development of CCR5-based therapeutics.
Acquired Immunodeficiency Syndrome↗
Human monoclonal antibodies to the V3 loop of HIV-1 with intra- and interclade cross-reactivity.
Five human anti-V3 mAbs were generated from Ab-producing cells derived from the blood of HIV-1-infected individuals from North America and selected using the V3 peptide of a divergent clade B isolate, HIV(RF). The anti-V3(RF) mAbs were mapped to a cluster of three overlapping epitopes present in the KSITKGP sequence located in the hypervariable region on the N-terminal side of the V3 loop. Broad immunochemical cross-reactivity was noted when the mAbs were tested for binding to V3 peptides derived from four clade A viruses, nine clade B viruses, and two clade C viruses. These results demonstrate antigenic relatedness in the V3 regions of these three HIV-1 clades. Affinities determined by surface plasmon resonance were higher for recombinant gp120 than for V3 peptides, suggesting that these mAbs recognize both linear and conformationally dependent epitopes of the V3 loop. Two of the mAbs neutralized four clade B T cell line-adapted and primary isolates with varying degrees of potency. The two neutralizing mAbs were the most cross-reactive with V3 peptides from several clades, had the highest affinity for V3(RF) and V3(MN), and stained HIV-infected cells. The data suggest that cross-reactivity, affinity, cell surface staining, and neutralizing activity are characteristics that describe an optimal fit between Ag and Ab. The results also demonstrate that the V3 peptides representing the sequence of several clade A, B, and C viruses share antigenic features that are recognized by the human immune response, a finding that suggests that cross-clade immunity to HIV-1 may be inducible by HIV-1 vaccines.
Antibodies, Monoclonal↗
CCR5-delta 32 gene deletion in HIV-1 infected patients.
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Acquired Immunodeficiency Syndrome↗
Comparison of serum and plasma viral RNA measurements in primary and chronic human immunodeficiency virus type 1 infection.
We sought to define the relation between serum and plasma HIV-1 viral RNA load in patients with primary and chronic HIV-1 disease. HIV-1 viral load was determined from 116 serum and plasma samples, including 33 matched pairs, from five patients with primary and three patients with chronic HIV disease using the Roche HIV Monitor assay. The mean +/- standard deviations of the serum and plasma viral RNA levels from the 33 matched pairs were 4.372 +/- 0.885 and 4.478 +/- 0.950 log10 (copies/ml), respectively. This -0.106 log difference between serum and plasma viral RNA levels, which equates to 21% of non-log-transformed values, was not statistically significant by the Wilcoxon sign rank test (p = 0.09). The distributions of serum and plasma viral load slopes, calculated from all available viral RNA load data for each patient, were also not statistically different (p = 0.07). The levels of HIV-1 RNA measured in the serum or plasma of HIV-seropositive patients yield equivalent biologic information.
Acquired Immunodeficiency Syndrome↗
HIV-1 infection in a man homozygous for CCR5 delta 32.
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Adolescent↗
Dynamics of cell-free viral burden in HIV-1-infected patients.
Whereas previous cross-sectional studies have shown a 1-2 log increase in cell-free HIV-1 RNA viral burden associated with disease progression, recent longitudinal studies reveal a less dynamic association. We addressed this conundrum in a cohort of 17 rapid and 20 slow progressors. Initial levels of serum viral RNA from the rapid progressors were 1 log unit higher than those from the slow progressors. Serum RNA increased by >0.5 log in 10 of the rapid progressors (increase group), but the remaining seven showed a <0.5 log increase (static group). Patients whose serum RNA increased had lower amounts of serum RNA at study entry but not at follow-up compared with the static group. There was a trend toward lower CD4 counts in the static group at follow-up. These data suggest that the timing of specimen evaluation can influence interpretation of viral RNA dynamics in HIV disease.
Artifacts↗
The role of viral phenotype and CCR-5 gene defects in HIV-1 transmission and disease progression.
Cellular entry of human immunodeficiency virus type 1 (HIV-1) requires binding to both CD4 (ref, 1, 2) and to one of the chemokine receptors recently discovered to act as coreceptors. Viruses that infect T-cell lines to form syncytia (syncytium-inducing, SI) are frequently found in late-stage HIV disease and utilize the chemokine receptor CXCR-4; macrophage-tropic viruses are non-syncytium-inducing (NSI), found throughout disease and utilize CCR-5 (ref. 3-11). We postulated that CCR-5 gene defects might reduce infection risk in seronegative subjects and prolong AIDS-free survival in seropositive subjects with NSI but not SI virus. Homozygous (delta ccr5/delta ccr5) and heterozygous (CCR5/delta ccr5) CCR-5 deletions (delta ccr5) were found in 7 (2.7%) and 51 (19.5%), respectively, of 261 seronegative subjects from the San Francisco Men's Health Study. CCR-5/delta ccr5 genotype was identified in 33 of 172 (19.2%) nonprogressors and 25 of 234 (10.7%) progressors from the seropositive arm of this cohort. The delta ccr5 allele conferred a significant protective effect against HIV-1 infection (P = 0.001) and a survival advantage against disease progression (P = 0.02). Although both progressing and nonprogressing CCR5/delta ccr5 subjects were identified, a distinct survival advantage was shown for those with NSI virus (P < 0.0001). Thus, the protective effect of delta ccr5 against disease progression is lost when the infecting virus uses CXCR-4 as a coreceptor.
CD4-Positive T-Lymphocytes↗
The role of CCR5 and CCR2 polymorphisms in HIV-1 transmission and disease progression.
Entry of human immunodeficiency virus type 1 (HIV-1) into target cells requires both CD4 (ref. 1, 2) and one of a growing number of G-protein-coupled seven-transmembrane receptors. Viruses predominantly use one, or occasionally both, of the major co-receptors CCR5 or CXCR4, although other receptors, including CCR2B and CCR3, function as minor co-receptors. CCR3 appears critical in central nervous system infection. A 32-base pair inactivating deletion in CCR5 (delta 32) common to Northern European populations has been associated with reduced, but not absolute, HIV-1 transmission risk and delayed disease progression. A more commonly distributed transition causing a valine to isoleucine switch in transmembrane domain I of CCR2B (64I) with unknown functional consequences was recently shown to delay disease progression but not reduce infection risk. Although we confirm the lack of association of CCR2B 64I with transmission, we cannot confirm the association with delayed progression. Although subjects with CCR5 delta 32 defects had significantly reduced median viral load at study entry, providing a plausible explanation for the association with delayed progression, this association was not seen with CCR2B 64I. Further studies are needed to define the role of CCR2B64I in HIV pathogenesis.
Acquired Immunodeficiency Syndrome↗
Rapid disease progression without seroconversion following primary human immunodeficiency virus type 1 infection--evidence for highly susceptible human hosts.
A patient is described who rapidly progressed from primary human immunodeficiency virus (HIV) type 1 infection to death without seroconversion but with consistently high plasma viremia. His asymptomatic sex partner had been HIV-1 seropositive for >8 years prior to transmission. Analysis of viral sequences from these subjects and controls confirmed the transmission event. Although the biologic properties of the patient's virus were unremarkable, he had poor functional immune responses to HIV and an HLA haplotype associated with rapid disease progression. The disparity between immune responses and clinical course in this transmission pair, coupled with infection with an unremarkable HIV-1 isolate, underscores the crucial importance of host factors in HIV-1 pathogenesis.
Adult↗
Evolution of human immunodeficiency virus type 1 env sequence variation in patients with diverse rates of disease progression and T-cell function.
We examined the relationship between env sequence variation and disease progression in 10 human immunodeficiency virus type 1 (HIV-1)-seropositive subjects selected from a longitudinal cohort receiving zidovudine therapy. Five subjects were chosen for stable clinical status and CD4 counts (slow progressors), and five were selected for rapid clinical deterioration and CD4 count decline (rapid progressors). The slow progressors had significantly lower plasma viral RNA loads and greater lymphoproliferative responses to mitogens than the rapid progressors. DNA sequences representing the C1 through C3 regions of env were amplified from two peripheral blood mononuclear cell DNA samples from each subject separated by an average of 2.5 years. Molecular clones of these amplicons were then sequenced, and DNA sequence and deduced amino acid sequence distances were compared. Inter-time point sequence comparison showed a higher rate of sequence evolution for the rapid progressors in three of five matched pairs of rapid progressors and slow progressors and for the slow progressors in the remaining two subject pairs. However, intra-time point sequence comparisons showed that four of five slow progressors developed a more diverse quasispecies over time and one showed no change. In contrast, four of five rapid progressors showed no change in quasispecies diversity over time and one showed a significant decrease in diversity. The overall C1 through C3 region quasispecies diversity in the slow progressors at baseline was lower than that for the rapid progressors, but this difference was not significant at the follow-up time points. These diversity relationships were obscured if sequence analyses were limited to the 300-bp C2 to V3 region. Thus, HIV-1 quasispecies diversity increased over time in subjects with more functional immune systems.
Base Sequence↗
Sequences and phylogenetic analysis of the nef gene from Thai subjects harboring subtype E HIV-1.
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Amino Acid Sequence↗
V3 seroreactivity and sequence variation: tracking the emergence of V3 genotypic variation in HIV-1-infected patients.
OBJECTIVE: To investigate the relationship between V3-specific immune responses and viral quasispecies evolution in 10 HIV-1-seropositive patients enrolled in a phase I trial of recombinant gp160. METHODS: Serologic responses to the HIVLAI V3 loop and autologous V3 loop DNA sequences were sequentially determined over a 3-4-year interval. RESULTS: Six patients either seroconverted or had a > or = 42-fold boost in titer to the V3 reagent associated with an average of 3.2 amino-acid changes in their autologous V3 loops. Four patients with < or = 11-fold change in titer to the V3 loop showed an average of 0.75 amino-acid changes. Attempts to measure autologous V3 loop responses in four patients using a peptide enzyme-linked immunosorbent assay technique did not show a distinct binding preference for autologous versus heterologous V3 loop peptides. Thus, we interpret seroreactivity to the heterologous HIVLAI V3 loop to reflect the broadness of the V3 immune response rather than a direct measure of epitope-specific immune pressure. CONCLUSIONS: These data suggest that the broadness of serologic responses to viral epitopes are reflected in the rate of evolution of their cognate coding sequences and support the view that the immune response to HIV-1 results in the continuous selection of new viral variants during the course of disease.
AIDS Vaccines↗
Recovery of virtually full-length HIV-1 provirus of diverse subtypes from primary virus cultures using the polymerase chain reaction.
In the course of the global pandemic, the human immunodeficiency virus type-1 (HIV-1) has established at least eight distinct genotypes in the main (M), or prevalent, group of isolates, a variety of rare outlier forms, and intergenotypic recombinants of group M viruses. This genotypic diversity has been documented, for the most part, by sequencing of subgenomic segments of the provirus. Using DNA from virus cultures on peripheral blood mononuclear cells (PBMC) and recent improvements of the PCR technique, we have amplified virtually full-length HIV-1 genomes from genetic subtypes A through G of group M viruses and molecularly cloned several of them. Resequencing of the complete genome of a prototype strain after long PCR amplification and cloning has established a PCR error rate of 0.14%. We also report the first complete PCR-derived sequence of a U.S. clinical isolate of genotype B expanded only in primary PBMC; this provirus harbors a uniquely truncated V3 loop.
Amino Acid Sequence↗