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Biomedical subjects

Robert M Grant

Publications and source records attributed to Robert M Grant.

At least 19 recordsLinked to original sources
PubMed2006

Distinct patterns of cytokine regulation of APOBEC3G expression and activity in primary lymphocytes, macrophages, and dendritic cells.

Human APOBEC3G (A3G), a deoxycytidine deaminase, is a broadly acting antiretroviral factor expressed in a variety of cells. Mitogen activation of CD4 T cells enhances A3G expression and leads to recruitment of low molecular mass (LMM) A3G, which functions as a post-entry human immunodeficiency virus (HIV) restriction factor, into enzymatically inactive, high molecular mass (HMM) RNA-protein complexes that include Staufen RNA-transporting granules. We now report that interleukin-2 (IL-2), IL-15 and, to a lesser extent, IL-7 enhance the expression of A3G in peripheral blood lymphocytes and that this effect is blocked by inhibitors of the JAK and MAPK signaling pathways. In mixed cultures of CD4+ T cells containing either HMM or LMM A3G, HIV preferentially infected cells containing HMM A3G. A3G shifted into a HMM complex when IL-2, -7, or -15 was added to resting T cells, likely explaining how cytokine treatment renders resting CD4+ T cells permissive to HIV infection. Similarly, poly(I:C)/tumor necrosis factor-alpha-induced maturation of dendritic cells was associated with a sharp increase in A3G expression; however, this induction led to the accumulation of LMM A3G. Together, these results highlight the distinct inductive effects of select cytokines on A3G gene expression and A3G complex assembly that occur in natural cellular targets of HIV infection.

APOBEC-3G Deaminase↗
PubMed2006

Routine surveillance for the detection of acute and recent HIV infections and transmission of antiretroviral resistance.

OBJECTIVE: To estimate the rate of acute and recent HIV infections and the prevalence of primary antiretroviral resistance. DESIGN, SETTING, AND SUBJECTS: A consecutive sample of individuals presenting for HIV testing at the San Francisco municipal sexually transmitted diseased (STD) clinic in 2004 (n = 3789). MAIN OUTCOME MEASURES: HIV antibody-positive specimens were screened by BED IgG capture enzyme immunoassay to identify recent infections. HIV antibody-negative specimens were screened by nucleic acid amplification testing (NAAT) to detect acute infections. Newly detected infections were genotyped to detect primary antiretroviral resistance. RESULTS: There were 11 acute and 44 recent HIV infections among the total 136 newly detected cases. NAAT increased case identification by 8.08% over standard antibody testing. Acute HIV infections were associated with having a known HIV-positive partner, and a history of hepatitis B, syphilis, and chlamydia. The prevalence of primary antiretroviral resistance was 13.2%, with drug-resistant mutations detected in 17 of 129 cases genotyped. Mutations conferring resistance to non-nucleoside reverse transcriptase inhibitors (NNRTI) were present in 11 of 17 cases. CONCLUSION: The integration of HIV nucleic acid amplification, recent infection, and antiretroviral resistance testing enhanced HIV/STD surveillance. The high proportion of NNRTI mutations detected suggests they may be more common in source partners or more fit for transmission than other forms of drug-resistant HIV-1. Primary antiretroviral resistance monitoring in STD clinic patients may guide the selection of treatment and post-exposure prophylaxis regimens active against viruses being transmitted in the community, and provide health departments with surveillance data in a sentinel population at risk of HIV transmission.

Acute Disease↗
PubMed2006

Greater CD4 T-cell gains after one year of antiretroviral therapy are associated with lower HIV-1 pol replication capacity.

We sought to determine whether pretreatment low pol replication capacity (polRC) is associated with CD4 T-cell count gains during antiretroviral therapy (ART). Patients were recruited at north American and Australian sites. Viral polRC was measured before starting ART in all subjects. We examined 243 individuals for a median 260 days after initiating ART. Low baseline polRC was associated with greater CD4 T-cell gains independent of virological responses.

Anti-HIV Agents↗
PubMed2006

Human immunodeficiency virus type 1 Vpr induces DNA replication stress in vitro and in vivo.

The human immunodeficiency virus type 1 (HIV-1) viral protein R (Vpr) causes cell cycle arrest in G2. Vpr-expressing cells display the hallmarks of certain forms of DNA damage, specifically activation of the ataxia telangiectasia mutated and Rad3-related kinase, ATR. However, evidence that Vpr function is relevant in vivo or in the context of viral infection is still lacking. In the present study, we demonstrate that HIV-1 infection of primary, human CD4+ lymphocytes causes G2 arrest in a Vpr-dependent manner and that this response requires ATR, as shown by RNA interference. The event leading to ATR activation in CD4+ lymphocytes is the accumulation of replication protein A in nuclear foci, an indication that Vpr likely induces stalling of replication forks. Primary macrophages are refractory to ATR activation by Vpr, a finding that is consistent with the lack of detectable ATR, Rad17, and Chk1 protein expression in these nondividing cells. These observations begin to explain the remarkable resilience of macrophages to HIV-1-induced cytopathicity. To study the in vivo consequences of Vpr function, we isolated CD4+ lymphocytes from HIV-1-infected individuals and interrogated the cell cycle status of anti-p24Gag-immunoreactive cells. We report that infected cells in vivo display an aberrant cell cycle profile whereby a majority of cells have a 4N DNA content, consistent with the onset of G2 arrest.

Ataxia Telangiectasia Mutated Proteins↗
PubMed2006

Antiretroviral therapy for hepatitis B virus-HIV-coinfected patients: promises and pitfalls.

Coinfections with human immunodeficiency virus (HIV) and hepatitis B virus (HBV) are common globally. HIV infection modifies the course of HBV infection by increasing rates of chronicity, prolonging HBV viremia, and increasing liver-related morbidity. To minimize the emergence of HIV and/or HBV resistance, as well as the emergence of liver enzyme flares, the treatment of both infections should be coordinated. Lamivudine or emtricitabine monotherapy readily selects resistant strains in the YMDD motif of the polymerase gene. Adefovir and tenofovir are fully active in the presence of YMDD mutations [corrected] If HBV treatment can be deferred until combination antiretroviral therapy for HIV infection is needed, the combination of tenofovir plus lamivudine or emtricitabine provides potent HBV therapy and a solid backbone for HIV combination antiretroviral therapy, and it likely decreases the emergence of HBV resistance.

Adenine↗
PubMed2006

Linking HIV and antiretroviral drug resistance surveillance in Peru: a model for a third-generation HIV sentinel surveillance.

BACKGROUND: HIV drug resistance surveillance is limited by recruitment and selection bias and by limited information regarding HIV incidence rates, secondary resistance, and treatment prevalence. METHODS: A second-generation HIV sentinel surveillance among men who have sex with men (MSM), regardless of prior history of HIV screening, serostatus, or treatment, was conducted in Peru in 2002. Recent HIV infection was estimated using sensitive/less sensitive enzyme immunoassay testing. Genotypic resistance testing was performed. RESULTS: HIV prevalence was 13.9% (456 HIV positive of 3280 participants). HIV incidence was estimated to be 5.1 per 100 person-years (95% confidence interval: 3.1-8.3). Among 143 MSM who were aware of their HIV infection before testing, only 20 (14.0%) were receiving antiretrovirals (ARV). Mutations conferring ARV resistance were found in 12 (3.3%) of 359 treatment-naive and 5 (31.3%) of 16 treatment-experienced participants with successful genotyping. One recently infected man from Lima demonstrated 3-class multidrug resistance. The most frequently observed mutations in treatment-naive, chronically infected persons from Lima were M184V (1.7%), D30N (1.3%), L90M (1.3%), and L10I (1.3%). CONCLUSIONS: The prevalence of ARV resistance among treatment-naive MSM in Peru is low, reflecting limited access to treatment before 2004, and contrasts with the history of ARV treatment in developed countries, where high levels of nucleoside reverse transcriptase inhibitor resistance occurred before introduction of highly active antiretroviral therapy. Linking ARV resistance and HIV sentinel surveillance in developing settings is feasible and should be considered in third-generation HIV sentinel surveillance programs.

Adult↗
PubMed2006

Genotypic resistance and immunologic outcomes among HIV-1-infected women with viral failure.

OBJECTIVES: To describe the prevalence of specific protease inhibitor (PI) and nonnucleoside reverse transcriptase inhibitor (NNRTI) resistance mutations and the relationship between the presence of these mutations and immunologic outcomes following PI/NNRTI initiation among a cohort of HIV-1-infected women. METHODS: Viral genotypic resistance testing was done for 366 women enrolled in the Women's Interagency HIV Study at the visit immediately prior to 1st reported use of PI or NNRTI (baseline) and at the visit approximately 1 year after PI/NNRTI initiation. We modeled the changes in CD4+ T-cell counts and HIV RNA levels approximately 1 year after therapy initiation as a function of baseline and follow-up markers, type of antiretroviral therapy used, and resistance mutations. RESULTS: At baseline, 52% of women showed only nucleoside reverse transcriptase inhibitor (NRTI) mutations, 38% showed no mutations, and 10% showed PI or NNRTI mutations. Only 40% of women showed viral response (HIV-1 RNA < or = 80 copies/mL) 1 year after initiating a PI or NNRTI. Among those without a viral response, 54% developed PI or NNRTI mutations. NNRTI (among those with baseline NRTI mutations) and PI resistance mutations were associated with better CD4+ cell count changes (mean increase of 118 cells/mm3 and 64 cells/mm3, respectively, as compared with viral nonresponders with no PI or NNRTI mutations). CONCLUSIONS: In this population-based cohort, virologic failure with PI or NNRTI resistance was common. Viremia with these resistance mutations was associated with preserved CD4+ T-cell count responses, providing evidence of reduced virulence or viral fitness.

CD4 Lymphocyte Count↗
PubMed2006

HIV drug-resistant strains as epidemiologic sentinels.

Observed declines in drug resistance to nucleoside reverse transcriptase inhibitors among persons recently infected with HIV-1 in monitored subpopulations can be interpreted as a positive sign and lead public health officials to decrease efforts towards HIV prevention. By means of a mathematical model, we identified 3 processes that can account for the observed decline: increase in high-risk behavior, decrease in proportion of acutely infected persons whose conditions are treated, and change in treatment efficacy. These processes, singly or in combination, can lead to increases or decreases in disease and drug-resistance prevalence in the general population. We discuss the most appropriate public health response under each scenario and emphasize how further data collection and analyses are required to more reliably evaluate the observed time trends and the relative importance of forces shaping the epidemic. Our study highlights how drug resistance markers can be used as epidemiologic sentinels to devise public health solutions.

Anti-HIV Agents↗
PubMed2005

High-risk sexual behavior in adults with genotypically proven antiretroviral-resistant HIV infection.

BACKGROUND: The substantial frequency of drug resistance in persons recently infected with HIV implies exposure among HIV-uninfected individuals to HIV-infected persons with drug-resistant virus. Although there is an increasing emphasis on understanding high-risk behavior among HIV-infected patients, little work has focused on those with drug-resistant virus. METHODS: We examined antiretroviral-treated patients with drug resistance in the Study of the Consequences of the Protease Inhibitor Era, a clinic-based cohort of HIV-infected adults. Sexual behavior was ascertained by self-administered questionnaire. Genotypic antiretroviral resistance testing was performed on isolates from participants with a plasma HIV RNA level > or =100 copies/mL. RESULTS: Among 279 participants on antiretroviral therapy, 168 (60%) had genotypic resistance to at least 1 drug. In those with drug resistance, 27% of men who have sex with men (MSM) and 11% of heterosexual men and women reported at least 1 episode of unprotected penile-anal or penile-vaginal intercourse in the previous 4 months; 17% of MSM and 6% of heterosexual participants reported unprotected intercourse with an HIV-uninfected or status unknown partner. In a multivariable model of predictors of unprotected anal or vaginal intercourse with an HIV-uninfected or status unknown partner, there was strong evidence for an effect of younger age, depression, and sildenafil use and moderate evidence for frequent alcohol use. CONCLUSIONS: Among HIV-infected patients with drug-resistant viremia, there is a substantial prevalence of high-risk sex with HIV-uninfected partners. The presence of definable risk factors for unsafe sex suggests a role for targeted rather than broad intervention, particularly when resources are limited.

Adult↗
PubMed2005

Seroconversion following nonoccupational postexposure prophylaxis against HIV.

BACKGROUND: The efficacy of antiretroviral postexposure prophylaxis (PEP) against infection with human immunodeficiency virus (HIV) following occupational exposures has prompted the use of PEP after nonoccupational exposures. There are, however, important differences between occupational and nonoccupational exposures, and the effectiveness of PEP following nonoccupational exposure is unknown. We sought to describe the occurrence and circumstances of HIV seroconversion following nonoccupational PEP. METHODS: HIV uninfected individuals reporting potential sexual or injection drug use exposures to HIV in the preceding 72 h received a 28-day regimen of antiretroviral therapy and counseling in a nonrandomized trial. The level of HIV antibody was measured 12 weeks after PEP initiation. RESULTS: Of 877 exposed subjects, 702 were evaluable 12 weeks after exposure. Seroconversion was detected in 7 subjects (1%; 95% confidence interval, 0.4%-2%). Three seroconverters reported having no exposures after PEP initiation and, thus, probably represent evidence of chemoprophylactic failure. In the other 4 subjects, additional exposures to HIV after PEP initiation or detection of HIV RNA in plasma specimens obtained at baseline precluded determination of the source of seroconversion. No exposure source was available to assess genetic concordance with the seroconverter's virus. CONCLUSIONS: As for occupational exposure, PEP is not completely effective in preventing HIV infection following nonoccupational exposure. Therefore, primary prevention remains essential. In contrast to the occupational setting, the potential source of exposure is rarely available for testing in the nonoccupational setting, and exposures are often not isolated. Thus, it is often impossible to determine whether seroconversion resulted from failure of PEP or from other exposures, posing difficulties for future comparative studies seeking to evaluate the effectiveness of PEP.

Anti-HIV Agents↗
PubMed2005

Interruption of treatment with individual therapeutic drug classes in adults with multidrug-resistant HIV-1 infection.

BACKGROUND: Many antiretroviral-treated human immunodeficiency virus (HIV)-infected patients experience sustained immunologic and virologic benefit despite the presence of multidrug-resistant HIV. We hypothesized that the use of simplified regimens could maintain treatment benefit while preventing viral evolution and reducing drug-related toxicity and costs. METHODS: We conducted a 48-week nonrandomized study of adults with multidrug-resistant HIV type 1 infection. Subjects interrupted protease inhibitor (PI) (n=18), reverse-transcriptase inhibitor (RTI) (n=6), or nonnucleoside RTI (NNRTI) (n=6) treatment. RESULTS: At study entry, subjects had a median reduction in HIV RNA levels of 1.2 log10 copies/mL relative to pretreatment levels. Interruption of PI treatment was associated with stable HIV RNA levels (mean change per week, +0.005 log10 copies/mL; P=.36). PI mutations waned and replicative capacity and HIV RNA levels increased after long-term observation. HIV RNA levels also remained stable in subjects interrupting NNRTI treatment. In contrast, all subjects who interrupted RTI treatment exhibited immediate increases in HIV RNA levels, and most exhibited a subsequent loss of the M184V mutation. CONCLUSIONS: These data indicate that nucleoside analogues often exert continued antiviral activity in the setting of drug-resistance mutations and that both nucleoside analogues and PIs can select for drug-resistance mutations that reduce viral fitness. These observations support the evaluation of treatment strategies aimed at maintaining the treatment benefit of therapy while reducing drug exposure.

Anti-Retroviral Agents↗
PubMed2005

Enrichment of activated monocytes in cerebrospinal fluid during antiretroviral therapy.

OBJECTIVES: In HIV infection, activated monocytes are enriched in blood and in the perivascular area of the brain, especially in patients with HIV-associated dementia. Although clinical brain disease is uncommon during combination antiretroviral therapy (ART), autopsy series indicate that HIV-infected brain tissue can contain high numbers of monocytes/macrophages despite ART. DESIGN: We assessed activated monocytes in blood and cerebrospinal fluid (CSF) in 76 living patients on and off ART. Plasma lipids were measured because they have been associated with monocyte activation and ART. METHODS: A novel quantitative six-color flow cytometric approach was used to identify monocytes in blood and CSF and to evaluate monocyte activation status. RESULTS: The mean percentage and number of activated CD16 monocytes in CSF was highest in individuals on combination ART, especially in those receiving protease inhibitors (PI). CSF viral load was also associated with higher monocyte activation in CSF. The mean calculated low density lipoprotein (LDL)-, oxidized LDL- and total cholesterol in plasma were highest in patients receiving PI. CONCLUSIONS: Activated monocytes are enriched in the CSF of persons living with HIV-1 and receiving ART. This finding is consistent with previously reported autopsy series. The mechanisms and long-term clinical consequences of persistent monocyte activation require further study.

Adult↗
PubMed2005

T-cell activation and memory phenotypes in cerebrospinal fluid during HIV infection.

We characterized T cell phenotypes in 74 paired blood and cerebrospinal fluid (CSF) samples of HIV-infected and uninfected persons using four-color flow cytometry. CD4+ and CD8+ T cells subsets were further characterized by identifying activated/resting and memory/naive subsets in CSF and blood using the markers CD38/HLA-DR and CD45RA/CD62L, respectively. With and without HIV-infection, the proportion of CD4+ T cells and memory T cells among T cells in CSF was higher compared to blood. In HIV-infection, activated CD4+ and CD8+ T cells in CSF were more abundant than in uninfected controls. As expected, combination antiretroviral therapy (ART) reduced T cell activation in CSF and blood.

Adult↗