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Human immunodeficiency virus type 1 (HIV-1) infected patients treated with combination antiretroviral therapy frequently have the level of HIV-1 RNA detectable in plasma driven below the lower limit of detection of current assays, 50... more
Human immunodeficiency virus type 1 (HIV-1) infected patients treated with combination antiretroviral therapy frequently have the level of HIV-1 RNA detectable in plasma driven below the lower limit of detection of current assays, 50 copies ml(-1). Patients may continue to exhibit viral loads (VLs) below the assay limit for years, yet on some occasions the VL may be above the limit of detection. Whether these 'blips' in VL are simply assay errors or are indicative of intermittent episodes of increased viral replication is of great clinical concern. By analyzing the occurrence of viral blips in 123 treated HIV-infected patients, we show that patients do not share a common probability distribution of blip amplitude and thus reject the hypothesis that blips are solely due to assay variation.
Research Interests: Biology, Virology, Medicine, HIV, Biological Sciences, and 13 moreAntiretroviral Therapy, Humans, Mathematical Sciences, Hiv Infection, Human immunodeficiency virus, Highly Active Antiretroviral Therapy, Statistical models, Viral Replication, Statistical Distributions, Viral Load, Probability Distribution, HIV infections, and limit of detection
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Research Interests: Biology, Medicine, Growth Kinetics, HIV, Biological Sciences, and 15 moreCell line, Humans, HIV protease, Multidrug Resistance, Female, Drug Resistance, Male, Human immunodeficiency virus, Reverse Transcriptase, Viral Replication, Infectivity, Molecular Sequence Data, Medical and Health Sciences, reverse transcriptase inhibitors, and HIV infections
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Research Interests: Biology, Medicine, HIV, Biological Sciences, Antiretroviral Therapy, and 15 moreHumans, Regression Analysis, Statistical Significance, Developing World, Lentivirus, Human immunodeficiency virus, Highly Active Antiretroviral Therapy, Liter, Reverse Transcriptase, Viral Replication, Acquired immunodeficiency syndrome, Viral Load, reverse transcriptase polymerase chain reaction, Medical and Health Sciences, and Peripheral blood
Background Historically lymphocyte (Lc) recovery following hematopoietic transplantation, immunosuppressive therapies, and infectious diseases has relied quite heavily on peripheral blood (PB) analysis. The PB, however, comprises less... more
Background Historically lymphocyte (Lc) recovery following hematopoietic transplantation, immunosuppressive therapies, and infectious diseases has relied quite heavily on peripheral blood (PB) analysis. The PB, however, comprises less than 2% of total Lcs in the body, hence small changes in trafficking rates (e.g., lymphoid tissue (LT) homing) could have profound effects on PB Lc count. In this study we explored the use of a radiotracer rhesus IgG1 anti-CD4R1 Tc99mFab'2 and single photon emission computed tomography (SPECT/CT) to sequentially image CD4+ Lc recovery in the whole-body following total body irradiation (TBI) and autologous CD34+ cell transplant. Methods Three specific pathogen free rhesus macaques were used in this study. Each received 4Gy TBI on two sequential days (8Gy total). CD34+ cells were immunoselected from a leukapheresis product following cytokine mobilization over 5 days using G-CSF and Stem Cell Factor. 4-9x106/kg CD34+ cells were reinfused on the last day of irradiation after being transduced in culture once with a SIV/HIV chimeric lentiviral vector expressing EGFP at a multiplicity of infection of 50. SPECT/CT images were taken prior to transplant as a baseline; following mobilization with AMD3100 at least two months prior to transplant; and at approximately 6, 30, 90, 150 and 260 days post-TBI/transplant. Development of immunogenicity to the radiotracer was monitored using size exclusion high performance liquid chromatography (HPLC) and an in vitro cell binding assay. Results Dynamic SPECT acquisition for two hours following mobilization with 1mg/kg AMD3100 SQ did not reveal measurable changes in the whole-body CD4 pool, despite an ∼ 2-fold maximum increase in CD4+ PB cell counts. This is consistent with a small percentage of CD4+ cells being released from tissues to PB without significantly affecting total Lc counts in the whole-body. Following 4Gyx2 TBI, all 3 animals experienced dramatic depletion of PB CD4 counts (a 90-98% decrease from baseline) (Table 1). Variability in tissue CD4 depletion was observed between and within hosts, with more dramatic decreases observed in axillary lymph nodes (73-92%) and only mild decreases in the spleen (36-40%). Similarly, recovery of the CD4 pools in LTs following transplant varied between and within hosts and appeared overall slower than the dynamics of repopulation in the PB, suggesting changes in trafficking rates between LTs and PB has a role in transplant recovery. By month 9 post-TBI, one animal (ZG41) had full recovery of the PB CD4+ Lc count and the CD4 pool in axillary LNs quantified by the SPECT/CT, but minimal recovery of CD4 pools were observed in the spleen. In another animal (ZG21), full recovery of the PB CD4+ cell count was observed by month 5 concomitant with full recovery of the spleen CD4 pool, despite still greater than 70% depletion of CD4 pool in axillary LNs. In the last animal (ZH32), by month 3 the CD4+ Lc count in PB was fully recovered, however, minimal CD4 pool recoveries were observed in LT through month 9 post-TBI (Figure 1). EGFP expressing Lcs first appeared in the circulation on average(SD) 69(48) days following transplant and were CD8+ and CD20+. In all animals, CD4+ EGFP+ Lcs were not observed until after month 5, suggesting that endogenous recovery preceded graft recovery in the PB. Of importance is that no immunogenicity to the radiotracer was detected despite sequential imaging up to month 5 in one animal and up to month 9 in the other two animals. This is in contrast to animals that were imaged several years post-transplant. In these animals immune complex formation to the radiotracer was observed by HPLC after a single exposure to the rhesus IgG1 anti-CD4R1 Tc99mFab'2. This suggests either tolerance was induced in animals exposed to the radiotracer shortly following transplant or that immune recovery remains incomplete after 150 days in these animals. Conclusions These results demonstrate for the first time that immune reconstitution of lymphoid tissues can be effectively monitored following transplant of autologous CD34+ cells and TBI, that the reconstitution appears to be discordant between PB and LT, as well as identifying a potential approach to decreasing immunogenicity to complex antigens through lymphocyte mobilization during antigen exposure. Disclosures: No relevant conflicts of interest to declare.
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This study aimed to assess immune activation in tissues by measuring glucose metabolism with 18F-fluorodeoxyglucose (FDG) and investigate the associations of various peripheral markers of disease progression with initiation and... more
This study aimed to assess immune activation in tissues by measuring glucose metabolism with 18F-fluorodeoxyglucose (FDG) and investigate the associations of various peripheral markers of disease progression with initiation and interruption of combination antiretroviral therapy in SIV-infected rhesus macaques (Macaca mulatta). Mixed-effect linear models revealed a significant inverse association of peripheral blood CD4+ T cell counts (p < 0.01) and a direct association of plasma viral load (p < 0.01) with the FDG uptake in the spleen, bone marrow, and most clusters of lymph nodes. In contrast, no significant associations were found for the liver and the bowel FDG uptake. We also found no association of the fraction of proliferating peripheral blood T and B lymphocytes with FDG uptake in any analyzed tissues. The bowel FDG uptake of uninfected animals was heterogeneous and reached levels as high as those seen in the bowel or the clusters of lymph nodes or the spleen of high vir...
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PurposePrevious SPECT and PET semi-quantitative in vivo imaging studies in monkeys have demonstrated specific uptake of radiolabeled rhesus recombinant anti-CD4 monoclonal antibody fragment CD4R1-F(ab΄)2in the spleen and clusters of lymph... more
PurposePrevious SPECT and PET semi-quantitative in vivo imaging studies in monkeys have demonstrated specific uptake of radiolabeled rhesus recombinant anti-CD4 monoclonal antibody fragment CD4R1-F(ab΄)2in the spleen and clusters of lymph nodes (LNs) but yielded conflicting results of imaging the gut CD4 + T-cell pool. Here, using PET dynamic imaging with kinetic analysis, we performed a fully quantitative CD4 imaging in rhesus macaques.MethodsThe biodistributions of [89Zr]Zr-CD4R1-F(ab΄)2and/or of [89Zr]Zr-ibalizumab were performed with static PET scans up to 144 h (6 days) post-injection in 18 rhesus macaques with peripheral blood CD4 + T cells/μl ranging from ~ 20 to 2400. Fully quantitative analysis with a 4-h dynamic scan, arterial sampling, metabolite evaluation, and model fitting was performed in three immunocompetent monkeys to estimate the binding potential of CD4 receptors in the LNs, spleen, and gut.ResultsThe biodistributions of [89Zr]Zr-CD4R1-F(ab΄)2and [89Zr]Zr-ibalizu...
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Background Historically lymphocyte (Lc) recovery following hematopoietic transplantation, immunosuppressive therapies, and infectious diseases has relied quite heavily on peripheral blood (PB) analysis. The PB, however, comprises less... more
Background Historically lymphocyte (Lc) recovery following hematopoietic transplantation, immunosuppressive therapies, and infectious diseases has relied quite heavily on peripheral blood (PB) analysis. The PB, however, comprises less than 2% of total Lcs in the body, hence small changes in trafficking rates (e.g., lymphoid tissue (LT) homing) could have profound effects on PB Lc count. In this study we explored the use of a radiotracer rhesus IgG1 anti-CD4R1 Tc99mFab'2 and single photon emission computed tomography (SPECT/CT) to sequentially image CD4+ Lc recovery in the whole-body following total body irradiation (TBI) and autologous CD34+ cell transplant. Methods Three specific pathogen free rhesus macaques were used in this study. Each received 4Gy TBI on two sequential days (8Gy total). CD34+ cells were immunoselected from a leukapheresis product following cytokine mobilization over 5 days using G-CSF and Stem Cell Factor. 4-9x106/kg CD34+ cells were reinfused on the last d...
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It has not been possible to evaluate immune recovery in tissues without invasive biopsy. Investigators have had to rely on peripheral blood lymphocytes (PBLs) for analysis. PBLs, however, represent only a very small percentage of cells in... more
It has not been possible to evaluate immune recovery in tissues without invasive biopsy. Investigators have had to rely on peripheral blood lymphocytes (PBLs) for analysis. PBLs, however, represent only a very small percentage of cells in lymphoid tissues (LTs). Using a combination of SPECTanda radiotracer, rhesus IgG1 anti-CD4R1 Tc-99m(Fab')2,we sequentially imaged CD4+ cell recovery in rhesus macaques following varying doses of total body irradiation (TBI) and reinfusion of vector transduced, autologous CD34+ cells. Seven rhesus were used in this study. Two received a dose of 3Gy on two sequential days (3Gyx2days) of TBI (6Gy total), three received 4Gyx2days TBI, and two 5Gyx2days TBI. CD34+ cells were immunoselected from a leukapheresis product following G-CSF and SCF mobilization over 5 days. On the last day of TBI a mean (SD) of 5.9(1.7)x106/kg autologous CD34+ cells were reinfused after being transduced once (moi=50) with a SIV/HIV chimeric lentiviral vector expressing EGF...
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An antibody is not the antidote An HIV therapeutic that would give long-term remission without sustained antiretroviral therapy (ART) is a long-term goal. Byrareddy et al. [ Science 354 , 197 (2016)] reported that treating simian... more
An antibody is not the antidote An HIV therapeutic that would give long-term remission without sustained antiretroviral therapy (ART) is a long-term goal. Byrareddy et al. [ Science 354 , 197 (2016)] reported that treating simian immunodeficiency virus (SIV)–positive macaques with an antibody against integrin α 4 β 7 during and after ART results in sustained virologic control after stopping all treatment. Three studies in this issue question the reproducibility of that result. Di Mascio et al. sequenced the virus used in the 2016 study and found that it was a variant with a stop codon in the nef gene rather than a wild-type virus. Abbink et al. used the same antibody for α 4 β 7 as before but tested control of a more commonly used pathogenic virus. Iwamato et al. used the same nef -stop virus as in the earlier paper but combined the antibody against the integrin with an antibody against the SIV envelope glycoprotein, which also blocks viral binding of the integrin. None of these thr...
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Neurological and cognitive problems are a common complication of HIV infection and are prevalent even in treated individuals. Although the molecular processes underlying brain involvement with HIV are not completely understood,... more
Neurological and cognitive problems are a common complication of HIV infection and are prevalent even in treated individuals. Although the molecular processes underlying brain involvement with HIV are not completely understood, inflammation is suspected to play a significant role. Our work presents an in vivo assessment of neuroinflammation in an animal model of HIV, the simian immunodeficiency virus (SIV)-infected rhesus macaque. Using positron emission tomography (PET) imaging, we identified changes in brain inflammation after inoculation with SIV over time. Interestingly, we found decreased binding of the PET ligand in the presence of very high cerebrospinal fluid (CSF) viral loads. These findings were supported by immunostaining which showed marked glial loss instead of inflammation. This study provides insight into glial and neuronal changes associated with very high CSF viral load and could reflect similar changes occurring in HIV-infected patients.
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The peripheral blood represents only a small fraction of the total number of lymphocytes in the body. To develop a more thorough understanding of T cell dynamics, including the effects of SIV/SHIV/HIV infection on immune cell depletion... more
The peripheral blood represents only a small fraction of the total number of lymphocytes in the body. To develop a more thorough understanding of T cell dynamics, including the effects of SIV/SHIV/HIV infection on immune cell depletion and immune reconstitution following combination antiretroviral therapy (cART), one needs to utilize approaches that allow direct visualization of lymphoid tissues. In the present study, noninvasive in vivo imaging of the CD4+ T cell pool has revealed that the timing of the CD4+ T cell pool reconstitution following initiation of ART in SIV-infected nonhuman primates (NHPs) appears seemingly stochastic among clusters of lymph nodes within the same host. At 4 weeks following initiation or interruption of cART, the changes observed in peripheral blood (PB) are primarily related to changes in the whole-body CD4 pool rather than changes in lymphocyte trafficking. Lymph node CD4 pools in long-term antiretroviral-treated and plasma viral load-suppressed hosts...
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Although rates of severe HIV-associated neurocognitive disorders have declined in the post-antiretroviral treatment (ART) era, subtle deficits persist, possibly exacerbated by treatment non-adherence. The actual effects of ART... more
Although rates of severe HIV-associated neurocognitive disorders have declined in the post-antiretroviral treatment (ART) era, subtle deficits persist, possibly exacerbated by treatment non-adherence. The actual effects of ART interruption/initiation on brain glucose metabolism as a reflection of viral replication and neuroinflammation remain unclear. Our study investigates how treatment initiation and interruption alter brain glucose metabolism in SIV-infected macaques, using F-FDG PET in correlation with plasma and CSF viral loads (VL) and cytokine levels. SIV-infected macaques (n = 7) underwent ART initiation only, ART interruption only, or both. Five uninfected animals served as controls. F-FDG PET imaging was performed at baseline and 1, 3, and 6 months after treatment modification. Mean and maximum standardized uptake values (SUV) for the whole-brain and subregions were calculated. Plasma and CSF VL and cytokine levels were measured. Paired t tests evaluated acute changes in w...
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Rapidly increasing number of therapeutic antibodies are being repurposed to imaging probes for noninvasive diagnosis, as well as monitoring during treatment or disease recurrence. Though antibody-based imaging involves tracer doses (~3... more
Rapidly increasing number of therapeutic antibodies are being repurposed to imaging probes for noninvasive diagnosis, as well as monitoring during treatment or disease recurrence. Though antibody-based imaging involves tracer doses (~3 log lower than therapeutic doses), and immune responses are severely reduced in patients with impaired immunity, formation of anti-tracer antibodies (ATA) has been observed hampering further diagnostic monitoring. Here, we explored the potential to develop humoral responses to intravenously administered tracer dose of a monoclonal antibody F(ab΄)2 fragment, and associated with host related immune measures in 49 rhesus macaques categorized into healthy (uninfected controls), SIV-progressors, SIV non-progressors, or total body irradiated (TBI). Antibody fragment administered in tracer amount (~100μg) induced immune responses with significantly lower odds in SIV-progressors or TBI macaques (P<0.005) as compared to healthy animals. Peripheral blood (PB...
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Ionizing irradiation is used routinely to induce myeloablation and immunosuppression. However, it has not been possible to evaluate the extent of ablation without invasive biopsy. For lymphoid recovery, peripheral blood lymphocytes (PBLs)... more
Ionizing irradiation is used routinely to induce myeloablation and immunosuppression. However, it has not been possible to evaluate the extent of ablation without invasive biopsy. For lymphoid recovery, peripheral blood lymphocytes (PBLs) have been used for analysis, but they represent< 2% of cells in lymphoid tissues (LTs). Using a combination of single-photon emission computed tomography(SPECT) and a radiotracer ((99m)Tc-labeled rhesus IgG1anti-CD4R1(Fab')2), we sequentially imaged CD4+ cell recovery in rhesus macaques following total body irradiation(TBI) and reinfusion of vector transduced, autologous CD34+ cells. Our results present for the first time a sequential, real time, non-invasive method to evaluate CD4+ cell recovery. Importantly, despite myeloablation of circulating leukocytes following TBI, total depletion of CD4+ lymphocytes in LTs such as the spleen is not achieved. The impact of TBI on LTs and PBLs is discordant, in which as few as 32.4% of CD4+ cells were ...
Research Interests: Pathology, Biology, Medicine, Computer Systems, Animals, and 15 moreBlood, Lentivirus, Bone marrow, Multimodal imaging, Clinical Sciences, In Vivo, Macaca Mulatta, Lymphoid Tissue, Lymphatic System, immunoglobulin G, Lymph nodes, Hematopoietic Stem Cell Transplantation, Cardiovascular medicine and haematology, Paediatrics and reproductive medicine, and ex vivo
Research Interests: Medicine, HIV, Transplantation, Humans, Female, and 14 moreMale, Clinical Sciences, Aged, Middle Aged, Adult, Protease Inhibitors, Highly Active Antiretroviral Therapy, Retrospective Studies, CART, Acquired immunodeficiency syndrome, Viral Load, Hematopoietic Stem Cell Transplantation, real time polymerase chain reaction, and reverse transcriptase inhibitors
A single-cycle simian immunodeficiency virus (scSIV) that undergoes only one round of infection and replication was constructed to calculate the total number of virons produced by an SIV-infected cell in vivo . Four Mamu-A*01 rhesus... more
A single-cycle simian immunodeficiency virus (scSIV) that undergoes only one round of infection and replication was constructed to calculate the total number of virons produced by an SIV-infected cell in vivo . Four Mamu-A*01 rhesus macaques were inoculated on two occasions 11 weeks apart with the scSIV by ex vivo infection and i.v. reinfusion of autologous cells. After each inoculation, plasma viral loads peaked between 1 and 2.5 days and then declined exponentially in one or two phases to below detection limits within 2 weeks. Although higher levels of SIV-specific cytotoxic T lymphocytes and modest increases in antibody responses were observed for each animal after the second inoculation, decay rates of the infected cells were only minimally affected. Analyzing the viral load data with a mathematical model, the in vivo viral burst size averaged 4.0 × 10 4 and 5.5 × 10 4 virions per cell for the first and second inoculations, respectively, with no significant difference between th...
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HIV infection is characterized by a brisk immune activation that plays an important role in the CD4 depletion and immune dysfunction of patients with AIDS. The mechanism underlying this activation is poorly understood. In the current... more
HIV infection is characterized by a brisk immune activation that plays an important role in the CD4 depletion and immune dysfunction of patients with AIDS. The mechanism underlying this activation is poorly understood. In the current study, we tested the hypothesis that this activation is the net product of two distinct pathways: the inflammatory response to HIV infection and the homeostatic response to CD4 T cell depletion. Usingex vivoBrdU incorporation of PBMCs from 284 patients with different stages of HIV infection, we found that CD4 proliferation was better predicted by the combination of CD4 depletion and HIV viral load (R2= 0.375,P< 0.001) than by either parameter alone (CD4 T cell counts,R2= 0.202,P< 0.001; HIV viremia,R2= 0.302,P< 0.001). Interestingly, CD8 T cell proliferation could be predicted by HIV RNA levels alone (R2= 0.334,P< 0.001) and this predictive value increased only slightly (R2= 0.346,P< 0.001) when CD4 T cell depletion was taken into account...
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ABSTRACTBoth naïve CD4+and naïve CD8+T cells are depleted in individuals with human immunodeficiency virus type 1 (HIV-1) infection by unknown mechanisms. Analysis of their dynamics prior to and after highly active antiretroviral... more
ABSTRACTBoth naïve CD4+and naïve CD8+T cells are depleted in individuals with human immunodeficiency virus type 1 (HIV-1) infection by unknown mechanisms. Analysis of their dynamics prior to and after highly active antiretroviral therapy (HAART) could reveal possible mechanisms of depletion. Twenty patients were evaluated with immunophenotyping, intracellular Ki67 staining, T-cell receptor excision circle (TREC) quantitation in sorted CD4 and CD8 cells, and thymic computed tomography scans prior to and ∼6 and ∼18 months after initiation of HAART. Naïve T-cell proliferation decreased significantly during the first 6 months of therapy (P< 0.01) followed by a slower decline. Thymic indices did not change significantly over time. At baseline, naïve CD4+T-cell numbers were lower than naive CD8+T-cell numbers; after HAART, a greater increase in naïve CD4+T cells than naïve CD8+T cells was observed. A greater relative change (n-fold) in the number of TREC+T cells/μl than in naïve...
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The meaning of viral blips in human immunodeficiency virus type 1 (HIV-1)-infected patients treated with seemingly effective highly active antiretroviral therapy (HAART) is still controversial and under investigation. Blips might... more
The meaning of viral blips in human immunodeficiency virus type 1 (HIV-1)-infected patients treated with seemingly effective highly active antiretroviral therapy (HAART) is still controversial and under investigation. Blips might represent low-level ongoing viral replication in the presence of drug or simply release of virions from the latent reservoir. Patients treated early during HIV-1 infection are more likely to have a lower total body viral burden, a homogenous viral population, and preserved HIV-1-specific immune responses. Consequently, viral blips may be less frequent in them than in patients treated during chronic infection. To test this hypothesis, we compared the occurrence of viral blips in 76 acutely infected patients (primary HIV infection [PHI] group) who started therapy within 6 months of the onset of symptoms with that in 47 patients who started HAART therapy during chronic infection (chronic HIV infection [CHI] group). Viral blip frequency was approximately twofol...
Research Interests: Immunology, Immune response, Biology, Virology, Treatment Outcome, and 15 moreMedicine, HIV, Biological Sciences, Humans, Standard Deviation, Hiv Infection, Human immunodeficiency virus, Time Factors, Highly Active Antiretroviral Therapy, Viral Replication, Viral Load, Chronic Infection, Medical and Health Sciences, HIV infections, and Viral Disease
It is believed that replication capacity is an important determinant of human immunodeficiency virus type 1 (HIV-1) pathogenicity and transmissibility. To explore this, we conducted a comprehensive analysis of the replication properties... more
It is believed that replication capacity is an important determinant of human immunodeficiency virus type 1 (HIV-1) pathogenicity and transmissibility. To explore this, we conducted a comprehensive analysis of the replication properties of nine drug-resistant and nine drug-susceptible viral isolates derived from patients with primary HIV-1 infection. Viral isolates were tested for single-cycle infectivity in the GHOST cell line. The infectivity of isolates carrying resistance-associated mutations was significantly higher than that of drug-susceptible isolates. Additionally, the growth kinetics of these isolates were determined in CD4 + T lymphocytes. Drug-resistant isolates replicated as well as drug-susceptible viruses. Insertion of the resistance-conferring regions into an NL4-3-based molecular background resulted in chimeras that displayed a modest but significant reduction in replication capacity compared to the drug-susceptible chimeric viruses. Of note, two multidrug-resistant...
Research Interests: Biology, Medicine, Growth Kinetics, HIV, Biological Sciences, and 15 moreCell line, Humans, HIV protease, Multidrug Resistance, Female, Drug Resistance, Male, Human immunodeficiency virus, Reverse Transcriptase, Viral Replication, Infectivity, Molecular Sequence Data, Medical and Health Sciences, reverse transcriptase inhibitors, and HIV infections
Mathematical models provide an understanding of in vivo replication kinetics of human immunodeficiency virus type 1 (HIV-1). With a novel intervention designed for increased potency, we have more accurately deduced the half-lives of... more
Mathematical models provide an understanding of in vivo replication kinetics of human immunodeficiency virus type 1 (HIV-1). With a novel intervention designed for increased potency, we have more accurately deduced the half-lives of virus-producing CD4 + T cells, 0.7 day, and the generation time of HIV-1 in vivo, approximately 2 days, confirming the dynamic nature of HIV-1 replication.
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Increased lymphocyte turnover is a hallmark of pathogenic lentiviral infection. To investigate perturbations in lymphocyte dynamics in natural hosts with nonpathogenic simian immunodeficiency virus (SIV) infection, the nucleoside analog... more
Increased lymphocyte turnover is a hallmark of pathogenic lentiviral infection. To investigate perturbations in lymphocyte dynamics in natural hosts with nonpathogenic simian immunodeficiency virus (SIV) infection, the nucleoside analog bromodeoxyuridine (BrdU) was administered to six naturally SIV-infected and five SIV-negative sooty mangabeys. As a measure of lymphocyte turnover, we estimated the mean death rate by fitting a mathematical model to the fraction of BrdU-labeled cells during a 2-week labeling and a median 10-week delabeling period. Despite significantly lower total T- and B-lymphocyte counts in SIV-infected sooty mangabeys than in SIV-negative mangabeys, the turnover rate of B lymphocytes and CD4 + and CD8 + T lymphocytes was not increased in the SIV-infected animals. A small, rapidly proliferating CD45RA + memory subset and a large, slower-proliferating CD45RA − central memory subset of CD4 + T lymphocytes identified in the peripheral blood of sooty mangabeys also di...
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Three of five virally suppressed human immunodeficiency virus type I (HIV-1)-infected patients treated with highly active antiretroviral therapy and followed intensively with a supersensitive reverse transcriptase PCR assay with a lower... more
Three of five virally suppressed human immunodeficiency virus type I (HIV-1)-infected patients treated with highly active antiretroviral therapy and followed intensively with a supersensitive reverse transcriptase PCR assay with a lower limit of quantitation of 5 copies/ml showed statistically significant viral load decays below 50 copies/ml, with half-lives of 5 to 8 months and a mean of 6 months. This range of half-lives is consistent with the estimated half-life of the latent HIV-1 reservoir in the peripheral blood. Those patients without decay of viral load in plasma may have significant cryptic HIV-1 residual replication.
Research Interests: Biology, Medicine, HIV, Biological Sciences, Antiretroviral Therapy, and 15 moreHumans, Regression Analysis, Statistical Significance, Developing World, Lentivirus, Human immunodeficiency virus, Highly Active Antiretroviral Therapy, Liter, Reverse Transcriptase, Viral Replication, Acquired immunodeficiency syndrome, Viral Load, reverse transcriptase polymerase chain reaction, Medical and Health Sciences, and Peripheral blood
Although intermittent episodes of low-level viremia are often observed in well-suppressed highly active antiretroviral therapy (HAART)-treated patients, the timing and amplitude of viral blips have never been examined in detail. We... more
Although intermittent episodes of low-level viremia are often observed in well-suppressed highly active antiretroviral therapy (HAART)-treated patients, the timing and amplitude of viral blips have never been examined in detail. We analyze here the dynamics of viral blips, i.e., plasma VL measurements of >50 copies/ml, in 123 HAART-treated patients monitored for a mean of 2.6 years (range, 5 months to 5.3 years). The mean (± the standard deviation) blip frequency was 0.09 ± 0.11/sample, with about one-third of patients showing no viral blips. The mean viral blip amplitude was 158 ± 132 human immunodeficiency virus type 1 (HIV-1) RNA copies/ml. Analysis of the blip frequency and amplitude distributions suggest that two blips less than 22 days apart have a significant chance of being part of the same episode of viremia. The data are consistent with a hypothetical model in which each episode of viremia consists of a phase of VL rise, followed by two-phase exponential decay. Thus, th...
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Therapy for human immunodeficiency virus (HIV)‐infected patients requires chronic multidrug administration. The eventual failure of therapy in some patients has brought into question the tissue concentration of the drugs. With an... more
Therapy for human immunodeficiency virus (HIV)‐infected patients requires chronic multidrug administration. The eventual failure of therapy in some patients has brought into question the tissue concentration of the drugs. With an appropriately radiolabeled compound, we could utilize positron emission tomography to provide quantitative time–activity curves for various tissues. We have developed a fluorine‐18 labeled analog of Tenofovir, the active metabolite of Tenofovir DF, a commonly prescribed component of multidrug therapy. Because (1‐(6‐amino‐9H‐purin‐9‐yl)‐3‐fluoropropan‐2‐yloxy)methylphosphonic acid (FPMPA) has a chiral center, we prepared both enantiomers and confirmed that the S‐isomer exhibited significantly higher antiviral activity than the R‐isomer. In viral replication inhibition assays in human MT4 cells infected with SHIVDH12R, S‐FPMPA had an IC50 of 1.85 µM (95% CI; 0.8–5.53), while the R‐isomer was inactive. An appropriate chiral precursor was prepared to allow the ...
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Research Interests: Infectious Diseases, Medicine, HIV, Biological Sciences, Humans, and 15 moreOrganophosphorus Compounds, Infectious, Highly Active Antiretroviral Therapy, Lamivudine, Adenine, Efavirenz, Potency, Cohort Studies, Combination Therapy, ritonavir, Lopinavir, Medical and Health Sciences, Oxazines, reverse transcriptase inhibitors, and HIV infections
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The role of CD8+ T lymphocytes in controlling replication of live, attenuated simian immunodeficiency virus (SIV) was investigated as part of a vaccine study to examine the correlates of protection in the SIV/rhesus macaque model. Rhesus... more
The role of CD8+ T lymphocytes in controlling replication of live, attenuated simian immunodeficiency virus (SIV) was investigated as part of a vaccine study to examine the correlates of protection in the SIV/rhesus macaque model. Rhesus macaques immunized for >2 yr with nef-deleted SIV (SIVmac239Δnef) and protected from challenge with pathogenic SIVmac251 were treated with anti-CD8 antibody (OKT8F) to deplete CD8+ T cells in vivo. The effects of CD8 depletion on viral load were measured using a novel quantitative assay based on real-time polymerase chain reaction using molecular beacons. This assay allows simultaneous detection of both the vaccine strain and the challenge virus in the same sample, enabling direct quantification of changes in each viral population. Our results show that CD8+ T cells were depleted within 1 h after administration of OKT8F, and were reduced by as much as 99% in the peripheral blood. CD8+ T cell depletion was associated with a 1–2 log increase in SIV...