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Biomedical subjects

N L Michael

Publications and source records attributed to N L Michael.

At least 19 recordsLinked to original sources
PubMed2001

Effects of CCR5-Delta32, CCR2-64I, and SDF-1 3'A alleles on HIV-1 disease progression: An international meta-analysis of individual-patient data.

BACKGROUND: Studies relating certain chemokine and chemokine receptor gene alleles with the outcome of HIV-1 infection have yielded inconsistent results. OBJECTIVE: To examine postulated associations of genetic alleles with HIV-1 disease progression. DESIGN: Meta-analysis of individual-patient data. SETTING: 19 prospective cohort studies and case-control studies from the United States, Europe, and Australia. PATIENTS: Patients with HIV-1 infection who were of European or African descent. MEASUREMENTS: Time to AIDS, death, and death after AIDS and HIV-1 RNA level at study entry or soon after seroconversion. Data were combined with fixed-effects and random-effects models. RESULTS: Both the CCR5-Delta32 and CCR2-64I alleles were associated with a decreased risk for progression to AIDS (relative hazard among seroconverters, 0.74 and 0.76, respectively; P = 0.01 for both), a decreased risk for death (relative hazard among seroconverters, 0.64 and 0.74; P < 0.05 for both), and lower HIV-1 RNA levels after seroconversion (difference, -0.18 log(10) copies/mL and -0.14 log(10) copies/mL; P < 0.05 for both). Having the CCR5-Delta32 or CCR2-64I allele had no clear protective effect on the risk for death after development of AIDS. The results were consistent between seroconverters and seroprevalent patients. In contrast, SDF-1 3'A homozygotes showed no decreased risk for AIDS (relative hazard for seroconverters and seroprevalent patients, 0.99 and 1.03, respectively), death (relative hazard, 0.97 and 1.00), or death after development of AIDS (relative hazard, 0.81 and 0.97; P > 0.5 for all). CONCLUSIONS: The CCR5-Delta32 and CCR2-64I alleles had a strong protective effect on progression of HIV-1 infection, but SDF-1 3'A homozygosity carried no such protection.

Acquired Immunodeficiency Syndrome↗
PubMed2001

Selective increases in HIV-specific neutralizing antibody and partial reconstitution of cellular immune responses during prolonged, successful drug therapy of HIV infection.

Because the immune response to HIV depends on viral gene expression, we examined the HIV-specific immune responses in persons whose viral load after highly active antiretroviral therapy (HAART) was <400 on at least 3 occasions over a 12-month interval. Eleven patients were identified. While there was little change in mean HIV-binding antibody (Ab) titers in this group, two persons mounted increases in HIV envelope-specific binding antibody. Neutralizing antibody (NAb) titers against a panel of HIV-1 primary isolates (BZ167, US1, and CM237) increased post-HAART (80% neutralization titer against US1, p = 0.06; against CM237, p = 0.04). The two persons with large increases in binding antibody also had increases in primary isolate NAb. Roughly half of HAART recipients had significant increases in neutralizing antibody to the primary isolates US1 and CM237. Compared with CD4-matched, non-HAART controls, there were significant increases in NAb against the subtype B primary isolate US1 (p < 0.0009); no increases were seen against more easily neutralized primary isolate BZ167. There were no differences after HAART in antibody-directed cellular cytotoxicity (ADCC). HAART resulted in a partial restoration of lymphoproliferative responses to recall antigens (tetanus and diphtheria). New responses developed to HIV Gag p24. No patient responded to HIV Env gp160 or gp120 either before or after HAART. The data underscore the lack of functional reconstitution of HIV-specific, CD4-mediated responses despite durable suppression of viral replication. In the setting of stable anti-HIV Ab levels, the development of increased NAb in certain individuals suggests that control of the virus by HAART may assist in immune control of HIV.

Anti-HIV Agents↗
PubMed2001

Clinical prognosis of patients with early-stage human immunodeficiency virus (HIV) disease: contribution of HIV-1 RNA and T lymphocyte subset quantitation.

Systems for the staging of individuals with human immunodeficiency virus type 1 (HIV-1) infection were developed 15 years ago. Subsequently, assays for quantitating HIV-1 RNA and immunophenotyping of lymphocyte subsets have been developed and validated. The utility of these assays for improved staging in early disease was evaluated in 256 HIV-infected adults (52% minority) with CD4 counts > or = 400 cells/microL followed in U.S. military medical centers before the highly active anti-retroviral therapy era. HIV viral load (RNA) was quantitated; the frequencies of select CD4+ immunophenotypes were determined in 112 subjects. The results were analyzed in relation to three outcome measures: death, first acquired immunodeficiency syndrome-defining opportunistic infection, and CD4 count < or = 200 cells/microL. Serum RNA level and CD4 count were each found to be predictive of all three outcomes. In addition, increases in the T-cell subsets CD28-CD4+ and CD29+CD26-CD4+ were found to be independently predictive of more rapid progression. The classification of early-stage HIV patients is improved by the quantitation of both viral RNA and T-lymphocyte subsets.

Adult↗
PubMed2000

Construction and biological characterization of infectious molecular clones of HIV-1 subtypes B and E (CRF01_AE) generated by the polymerase chain reaction.

We previously described the use of extended polymerase chain reaction (PCR) to amplify contiguous 9.2-kilobase (kb) single-long terminal repeat (LTR) proviral sequences from HIV-1 genetic subtypes A through G. We now extend these findings by describing a novel vector system to recover infectious molecular clones from long PCR amplicons. Directional ligation of 9.2-kb proviral amplicons into a recovery vector reconstitutes missing LTR sequences, providing candidate molecular clones for infectivity screening. We show that a previously characterized infectious molecular clone of HIV-1 retains its biological properties upon recovery with this strategy. Three additional infectious molecular clones generated, from primary isolates of subtype B (HIV-1(WR27)) and circulating recombinant form 01_AE (subtype E) (HIV-1(CM235)) by subtype-specific LTR reconstitution, displayed biological properties reflecting their cognate parental isolates. This represents the first report of infectious molecular clones from circulating recombinant form 01_AE (subtype E).

Cells, Cultured↗
PubMed2000

Clinical implications of identifying non-B subtypes of human immunodeficiency virus type 1 infection.

Although human immunodeficiency virus type 1 (HIV-1) infection in the United States has predominantly involved subtype B, increasing global travel is leading to wider dissemination of genetically heterogeneous subtypes. While physicians depend on HIV-1 viral load measurements to guide antiretroviral therapy, commonly used molecular assays may underestimate the viral load of patients with non-B subtypes. Nine patients with non-B subtypes of HIV-1 were identified by physicians who suspected a non-B subtype on the basis of a low or undetectable HIV-1 viral load, by the Amplicor HIV-1 Monitor test, version 1.0, in conjunction with either a declining CD4 cell count or history of travel outside the United States. Use of version 1.5 of the Amplicor HIV-1 Monitor test detected a median HIV-1 viral load that was 2.0 log(10) RNA copies/mL higher than was determined with version 1.0. Clinical management was altered in all cases after diagnosis of a non-B-subtype infection. These cases demonstrate that it is critical for physicians to suspect and diagnose non-B subtypes of HIV-1 so that an assay with reliable subtype performance can be used to guide antiretroviral therapy.

Adult↗
PubMed2000

Shorter survival of SDF1-3'A/3'A homozygotes linked to CD4+ T cell decrease in advanced human immunodeficiency virus type 1 infection.

The SDF-1 3'A allelic polymorphism has been reported to influence either positively or negatively the progression of human immunodeficiency virus type 1 (HIV-1) disease. Therefore, the SDF-1 genotype of 729 HIV-1-infected individuals pooled from 3 distinct cohorts was determined. A statistically nonsignificant association between the SDF1-3'A/3'A genotype and accelerated disease progression was evident among seroconverters (n=319), but a striking correlation of decreased survival after either diagnosis of AIDS according to the 1993 definition or loss of CD4(+) T cell counts <200 was observed. The relative hazards for SDF1-3'A/3'A homozygotes, compared with heterozygotes and wild-type homozygotes were 2.16 (P=.0047), for time from diagnosis according to the 1993 Centers for Disease Control and Prevention AIDS case definition (AIDS-'93) to death, and 3.43 (P=.0001), for time from CD4(+) T cells <200 to death. Because no difference in survival was observed after diagnosis according to AIDS-'87, the association of the SDF1-3'A/3'A genotype with the accelerated progression of late-stage HIV-1 disease appears to be explained for the most part by the loss of CD4(+) T lymphocytes.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Impact of pulmonary tuberculosis on survival of HIV-infected adults: a prospective epidemiologic study in Uganda.

BACKGROUND: Retrospective cohort studies of tuberculosis suggest that active tuberculosis accelerates the progression of HIV infection. The validity of these findings has been questioned because of their retrospective design, diverse study populations, variable compliance with anti-tuberculous therapy and use of anti-retroviral medication. To assess the impact of tuberculosis on survival in HIV infection we performed a prospective study among HIV-infected Ugandan adults with and without tuberculosis. METHODS: In a prospective cohort study, 230 patients with HIV-associated tuberculosis and 442 HIV-infected subjects without tuberculosis were followed for a mean duration of 19 months for survival. To assess changes in viral load over 1 year, 20 pairs of tuberculosis cases and controls were selected and matched according to baseline CD4 lymphocyte count, age, sex and tuberculin skin test status. RESULTS: During the follow-up period, 63 out of of 230 tuberculosis cases (28%) died compared with 85 out of 442 controls (19%), with a crude risk ratio of 1.4 [95% confidence interval (CI), 1.07-1.87]. Most deaths occurred in patients with CD4 lymphocyte counts < 200 x 10(6) cells/l at baseline (n = 99) and occurred with similar frequency in the tuberculosis cases (46%) and the controls (44%). When the CD4 lymphocyte count was > 200 x 10(6)/l, however, the relative risk of death in HIV-associated tuberculosis was 2.1 (95% CI, 1.27-3.62) compared with subjects without tuberculosis. For subjects with a CD4 lymphocyte count > 200 x 10(6)/l, the 1-year survival proportion was slightly lower in the cases than in the controls (0.91 versus 0.96), but by 2 years the survival proportion was significantly lower in the cases than in the controls (0.84 versus 0.91; P < 0.02; log-rank test). For subjects with a CD4 lymphocyte count of 200 x 10(6) cells/l or fewer, the survival proportion at 1 year for the controls was lower than cases (0.59 versus 0.64), but this difference was not statistically significant (P = 0.53; logrank test). After adjusting for age, sex, tuberculin skin test status, CD4 lymphocyte count, and history of HIV-related infections, the overall relative hazard for death associated with tuberculosis was 1.81 (95% CI, 1.24-2.65). In a nested Cox regression model, the relative hazard for death was 3.0 (95% CI, 1.62-5.63) for subjects with CD4 lymphocyte counts > 200 x 10(6)/l and 1.5 (95% CI, 0.99-2.40) for subjects with a CD4 lymphocyte count of 200 x 10(6)/l or fewer. CONCLUSION: The findings from this prospective study indicate that active tuberculosis exerts its greatest effect on survival in the early stages of HIV infection, when there is a reserve capacity of the host immune response. These observations provide a theoretical basis for the treatment of latent tuberculous infection in HIV-infected persons.

AIDS-Related Opportunistic Infections↗
PubMed2000

Use of calibrated viral load standards for group M subtypes of human immunodeficiency virus type 1 to assess the performance of viral RNA quantitation tests.

Optimal management of human immunodeficiency virus type 1 (HIV-1) disease requires accurate quantitation of viral RNA concentrations in plasma. Evidence for increasing geographic intermixing of HIV-1 subtypes makes equivalent quantitation of all subtypes essential. The performances of six quantitative viral RNA tests are described, for the first time, with calibrated viral isolates of diverse subtypes.

Acquired Immunodeficiency Syndrome↗
PubMed2000

Evaluation of performance of the Gen-Probe human immunodeficiency virus type 1 viral load assay using primary subtype A, C, and D isolates from Kenya.

Accurate and sensitive quantification of human immunodeficiency virus type 1 (HIV-1) RNA has been invaluable as a marker for disease prognosis and for clinical monitoring of HIV-1 disease. The first generation of commercially available HIV-1 RNA tests were optimized to detect the predominant HIV-1 subtype found in North America and Europe, subtype B. However, these tests are frequently suboptimal in detecting HIV-1 genetic forms or subtypes found in other parts of the world. The goal of the present study was to evaluate the performance of a new viral load assay with non-subtype B viruses. A transcription-mediated amplification method for detection and quantitation of diverse HIV-1 subtypes, called the Gen-Probe HIV-1 viral load assay, is under development. In this study we examined the performance of the Gen-Probe HIV-1 viral load assay relative to that of the commonly used commercial HIV-1 RNA assays using a panel of primary isolates from Kenya. For comparison, we included several subtype B cloned viruses, and we quantified each virus using an in-house quantitative-competitive reverse transcriptase PCR (QC-RT-PCR) method and gag(p24) antigen capture. The Gen-Probe HIV-1 viral load assay and a version of the Roche AMPLICOR HIV-1 MONITOR test (version 1.5) that was designed to detect a broader range of subtypes were both sensitive for the quantification of Kenyan primary isolates, which represented subtype A, C, and D viruses. The Gen-Probe HIV-1 viral load assay was more sensitive for the majority of viruses than the Roche AMPLICOR HIV-1 MONITOR test version 1.0, the Bayer Quantiplex HIV RNA 3.0 assay, or a QC-RT-PCR method in use in our laboratory, suggesting that it provides a useful method for quantifying HIV-1 RNAs from diverse parts of the world, including Africa.

Adult↗
PubMed1999

Host genetic influences on HIV-1 pathogenesis.

Cellular entry of HIV-1 is mediated by interaction with CD4 and chemokine receptors that serve as entry coreceptors. The immune response against HIV-1 is regulated by genes of the HLA locus. Genetic polymorphisms in these genes have recently been associated with effects on HIV-1 pathogenesis. The history and implications of these discoveries are described in this review.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Performance of the Affymetrix GeneChip HIV PRT 440 platform for antiretroviral drug resistance genotyping of human immunodeficiency virus type 1 clades and viral isolates with length polymorphisms.

The performance of a silica chip-based resequencing method, the Affymetrix HIV PRT 440 assay (hereafter referred to as the Affymetrix assay), was evaluated on a panel of well-characterized nonclade B viral isolates and on isolates exhibiting length polymorphisms. Sequencing of human immunodeficiency virus type 1 (HIV-1) pol cDNAs from clades A, C, D, E, and F resulted in clade-specific regions of base-calling ambiguities in regions not known to be associated with resistance polymorphisms, as well as a small number of spurious resistance polymorphisms. The Affymetrix assay failed to detect the presence of additional serine codons distal to reverse transcriptase (RT) codon 68 that are associated with multinucleoside RT inhibitor resistance. The increasing prevalence of non-clade B HIV-1 strains in the United States and Europe and the identification of clinically relevant pol gene length polymorphisms will impact the generalizability of the Affymetrix assay, emphasizing the need to accommodate this expanding pool of pol genotypes in future assay versions.

Acquired Immunodeficiency Syndrome↗
PubMed1999

Development of calibrated viral load standards for group M subtypes of human immunodeficiency virus type 1 and performance of an improved AMPLICOR HIV-1 MONITOR test with isolates of diverse subtypes.

Accurate determination of plasma human immunodeficiency virus type 1 (HIV-1) RNA levels is critical for the effective management of HIV-1 disease. The AMPLICOR HIV-1 MONITOR Test, a reverse transcription-PCR-based test for quantification of HIV-1 RNA in plasma, was developed when little sequence information on HIV-1 isolates from outside North America was available. It has since become apparent that many non-subtype B isolates, particularly subtypes A and E, are detected inefficiently by the test. We describe here the AMPLICOR HIV-1 MONITOR Test, version 1.5, an upgraded test developed to minimize subtype-related variation. We also developed a panel of HIV-1 standards containing 30 HIV-1 isolates of subtypes A through G. The virus particle concentration of each cultured viral stock was standardized by electron microscopic virus particle counting. We used this panel to determine the performance of the original AMPLICOR HIV-1 MONITOR Test and version 1.5 of the test with HIV-1 subtypes A through G. The original test underestimated the concentration of HIV-1 subtype A, E, F, and G RNA by 10-fold or more, whereas version of the 1.5 test yielded equivalent quantification of HIV-1 RNA regardless of the subtype. In light of the increasing intermixing of HIV-1 subtypes worldwide, standardization of PCR-based tests against well-characterized viral isolates representing the full range of HIV-1 diversity will be essential for the continued utility of these important clinical management tools.

Acquired Immunodeficiency Syndrome↗
PubMed1999

CCR2-64I polymorphism is not associated with altered CCR5 expression or coreceptor function.

A polymorphism in the gene encoding CCR2 is associated with a delay in progression to AIDS in human immunodeficiency virus (HIV)-infected individuals. The polymorphism, CCR2-64I, changes valine 64 of CCR2 to isoleucine. However, it is not clear whether the effect on AIDS progression results from the amino acid change or whether the polymorphism marks a genetically linked, yet unidentified mutation that mediates the effect. Because the gene encoding CCR5, the major coreceptor for HIV type 1 primary isolates, lies 15 kb 3' to CCR2, linked mutations in the CCR5 promoter or other regulatory sequences could explain the association of CCR2-64I with slowed AIDS pathogenesis. Here, we show that CCR2-64I is efficiently expressed on the cell surface but does not have dominant negative activity on CCR5 coreceptor function. A panel of peripheral blood mononuclear cells (PBMC) from uninfected donors representing the various CCR5/CCR2 genotypes was assembled. Activated primary CD4(+) T cells of CCR2 64I/64I donors expressed cell surface CCR5 at levels comparable to those of CCR2 +/+ donors. A slight reduction in CCR5 expression was noted, although this was not statistically significant. CCR5 and CCR2 mRNA levels were nearly identical for each of the donor PBMC, regardless of genotype. Cell surface CCR5 and CCR2 levels were more variable than mRNA transcript levels, suggesting that an alternative mechanism may influence CCR5 cell surface levels. CCR2-64I is linked to the CCR5 promoter polymorphisms 208G, 303A, 627C, and 676A; however, in transfected promoter reporter constructs, these did not affect transcriptional activity. Taken together, these findings suggest that CCR2-64I does not act by influencing CCR5 transcription or mRNA levels.

Blood Donors↗
PubMed1998

Genetic acceleration of AIDS progression by a promoter variant of CCR5.

The CCR5 gene encodes a cell surface chemokine receptor molecule that serves as the principal coreceptor, with CD4, for macrophage-tropic (R5) strains of human immunodeficiency virus-type 1 (HIV-1). Genetic association analysis of five cohorts of people with acquired immunodeficiency syndrome (AIDS) revealed that infected individuals homozygous for a multisite haplotype of the CCR5 regulatory region containing the promoter allele, CCR5P1, progress to AIDS more rapidly than those with other CCR5 promoter genotypes, particularly in the early years after infection. Composite genetic epidemiologic analyses of genotypes bearing CCR5P1, CCR5-Delta32, CCR2-64I, and SDF1-3'A affirmed distinct regulatory influences for each gene on AIDS progression. An estimated 10 to 17 percent of patients who develop AIDS within 3.5 years of HIV-1 infection do so because they are homozygous for CCR5P1/P1, and 7 to 13 percent of all people carry this susceptible genotype. The cumulative and interactive influence of these AIDS restriction genes illustrates the multigenic nature of host factors limiting AIDS disease progression.

Acquired Immunodeficiency Syndrome↗