Residual human immunodeficiency virus type 1 RNA in lymphoid tissue of patients with sustained plasma RNA of <200 copies/mL

An active HIV reservoir during ART is associated with maintenance of HIV-specific CD8+ T cell magnitude and short-lived differentiation status

Before initiation of antiretroviral therapy (ART), HIV-specific CD8+ T cells are dysfunctional and short lived. To better understand the relationship between the HIV reservoir in CD4+ T cells and the magnitude and differentiation status of HIV-specific CD8+ T cells, we investigated these cells from acute and chronic HIV-infected individuals after 2 years of ART. Although both the HIV reservoir and the CD8+ T cell responses declined significantly after 2 years of ART, sustained HIV-specific CD8+ T cell responses correlated with a greater reduction of integrated HIV provirus. However, the magnitude of CD8+ T cells specific for HIV Gag, Pol, Nef, and Vif proteins positively associated with the active reservoir size during ART, measured as cell-associated RNA. Importantly, high HIV DNA levels strongly associate with maintenance of short-lived HIV-specific CD8+ T cells, regardless of ART initiation time. Our data suggest that the active reservoir maintains HIV-specific CD8+ T cell magnitude but prevents their differentiation into functional cells.

Current strategies to induce selective killing of HIV-1-infected cells

Although combination antiretroviral therapy (ART) has led to significant HIV-1 suppression and improvement in immune function, persistent viral reservoirs remain that are refractory to intensified ART. ART poses many challenges such as adherence to drug regimens, the emergence of resistant virus, and cumulative toxicity resulting from long-term therapy. Moreover, latent HIV-1 reservoir cells can be stochastically activated to produce viral particles despite effective ART and contribute to the rapid viral rebound that typically occurs within 2 weeks of ART interruption; thus, lifelong ART is required for continued viral suppression. Several strategies have been proposed to address the HIV-1 reservoir such as reactivation of HIV-1 transcription using latency reactivating agents with a combination of ART, host immune clearance and HIV-1-cytotoxicity to purge the infected cells-a "shock and kill" strategy. However, these approaches do not take into account the multiple transcriptional and translational blocks that contribute to HIV-1 latency or the complex heterogeneity of the HIV-1 reservoir, and clinical trials have thus far failed to produce the desired results. Here, we describe alternative strategies being pursued that are designed to kill selectively HIV-1-infected cells while sparing uninfected cells in the absence of enhanced humoral or adaptive immune responses.

CD9 and ITGA3 are regulated during HIV-1 infection in macrophages to support viral replication

Monocytes/macrophages are important target cells for HIV-1. Here, we investigated whether HIV-1 induces changes in the macrophage gene expression profile to support viral replication. We observed that the macrophage gene expression profiles dramatically changed upon HIV-1 infection. The majority of the HIV-1 regulated genes were also differentially expressed in M2a macrophages. The biological functions associated with the HIV-1 induced gene expression profile in macrophages were mainly related to inflammatory responses. CD9 and ITGA3 were among the top genes upregulated upon HIV-1 infection. We showed that these genes support viral replication and that downregulation of these genes decreased HIV-1 replication in macrophages. Here we showed that HIV-1 infection of macrophages induces a gene expression profile that may dampen inflammatory responses. CD9 and ITGA3 were among the top genes regulated by HIV-1 and were shown to support viral production most likely at the level of viral budding and release.

The Role of Macrophages in HIV-1 Persistence and Pathogenesis

Current antiretroviral therapy (ART) effectively suppresses Human Immunodeficiency Virus type 1 (HIV-1) in infected individuals. However, even long term ART does not eradicate HIV-1 infected cells and the virus persists in cellular reservoirs. Beside memory CD4⁺ T cells, cells of the myeloid lineage, especially macrophages, are believed to be an important sanctuary for HIV-1. Monocytes and macrophages are key players in the innate immune response to pathogens and are recruited to sites of infection and inflammation. Due to their long life span and ability to reside in virtually every tissue, macrophages have been proposed to play a critical role in the establishment and persistence of the HIV-1 reservoir. Current HIV-1 cure strategies mainly focus on the concept of “shock and kill” to purge the viral reservoir. This approach aims to reactivate viral protein production in latently infected cells, which subsequently are eliminated as a consequence of viral replication, or recognized and killed by the immune system. Macrophage susceptibility to HIV-1 infection is dependent on the local microenvironment, suggesting that molecular pathways directing differentiation and polarization are involved. Current latency reversing agents (LRA) are mainly designed to reactivate the HIV-1 provirus in CD4+ T cells, while their ability to abolish viral latency in macrophages is largely unknown. Moreover, the resistance of macrophages to HIV-1 mediated kill and the presence of infected macrophages in immune privileged regions including the central nervous system (CNS), may pose a barrier to elimination of infected cells by current “shock and kill” strategies. This review focusses on the role of monocytes/macrophages in HIV-1 persistence. We will discuss mechanisms of viral latency and persistence in monocytes/macrophages. Furthermore, the role of these cells in HIV-1 tissue distribution and pathogenesis will be discussed.

The Role of Macrophages in HIV-1 Persistence and Pathogenesis

Current antiretroviral therapy (ART) effectively suppresses Human Immunodeficiency Virus type 1 (HIV-1) in infected individuals. However, even long term ART does not eradicate HIV-1 infected cells and the virus persists in cellular reservoirs. Beside memory CD4⁺ T cells, cells of the myeloid lineage, especially macrophages, are believed to be an important sanctuary for HIV-1. Monocytes and macrophages are key players in the innate immune response to pathogens and are recruited to sites of infection and inflammation. Due to their long life span and ability to reside in virtually every tissue, macrophages have been proposed to play a critical role in the establishment and persistence of the HIV-1 reservoir. Current HIV-1 cure strategies mainly focus on the concept of "shock and kill" to purge the viral reservoir. This approach aims to reactivate viral protein production in latently infected cells, which subsequently are eliminated as a consequence of viral replication, or recognized and killed by the immune system. Macrophage susceptibility to HIV-1 infection is dependent on the local microenvironment, suggesting that molecular pathways directing differentiation and polarization are involved. Current latency reversing agents (LRA) are mainly designed to reactivate the HIV-1 provirus in CD4+ T cells, while their ability to abolish viral latency in macrophages is largely unknown. Moreover, the resistance of macrophages to HIV-1 mediated kill and the presence of infected macrophages in immune privileged regions including the central nervous system (CNS), may pose a barrier to elimination of infected cells by current "shock and kill" strategies. This review focusses on the role of monocytes/macrophages in HIV-1 persistence. We will discuss mechanisms of viral latency and persistence in monocytes/macrophages. Furthermore, the role of these cells in HIV-1 tissue distribution and pathogenesis will be discussed.

Perspectives on Human Immunodeficiency Virus (HIV) Cure: HIV Persistence in Tissue

The uneven anatomic distribution of cell subsets that harbor human immunodeficiency virus (HIV) during antiretroviral therapy (ART) complicates investigation of the barriers to HIV cure. Here we propose that while previous studies done largely in blood cells have led to important investigations into HIV latency, other important mechanisms of HIV persistence during ART may not be readily apparent in the bloodstream. We specifically consider as an example the question of ongoing HIV replication during ART. We discuss how growing understanding of key anatomic sanctuaries for the virus can inform future experiments aimed at further clarifying this issue.

Nanodrug formulations to enhance HIV drug exposure in lymphoid tissues and cells: clinical significance and potential impact on treatment and eradication of HIV/AIDS

Although oral combination antiretroviral therapy effectively clears plasma HIV, patients on oral drugs exhibit much lower drug concentrations in lymph nodes than blood. This drug insufficiency is linked to residual HIV in cells of lymph nodes. While nanoformulations improve drug solubility, safety and delivery, most HIV nanoformulations are intended to extend plasma levels. A stable nanodrug combination that transports, delivers and accumulates in lymph nodes is needed to clear HIV in lymphoid tissues. This review discusses limitations of current oral combination antiretroviral therapy and advances in anti-HIV nanoformulations. A 'systems approach' has been proposed to overcome these limitations. This concept has been used to develop nanoformulations for overcoming drug insufficiency, extending cell and tissue exposure and clearing virus for treating HIV/AIDS.

Anti-HIV drug-combination nanoparticles enhance plasma drug exposure duration as well as triple-drug combination levels in cells within lymph nodes and blood in primates

HIV patients on combination oral drug therapy experience insufficient drug levels in lymph nodes, which is linked to viral persistence. Following success in enhancing lymph node drug levels and extending plasma residence time of indinavir formulated in lipid nanoparticles, we developed multidrug anti-HIV lipid nanoparticles (anti-HIV LNPs) containing lopinavir (LPV), ritonavir (RTV), and tenofovir (PMPA). These anti-HIV LNPs were prepared, characterized, scaled up, and evaluated in primates with a focus on plasma time course and intracellular drug exposure in blood and lymph nodes. Four macaques were subcutaneously administered anti-HIV LNPs and free drug suspension in a crossover study. The time course of the plasma drug concentration as well as intracellular drug concentrations in blood and inguinal lymph nodes were analyzed to compare the effects of LNP formulation. Anti-HIV LNPs incorporated LPV and RTV with high efficiency and entrapped a reproducible fraction of hydrophilic PMPA. In primates, anti-HIV LNPs produced over 50-fold higher intracellular concentrations of LPV and RTV in lymph nodes compared to free drug. Plasma and intracellular drug levels in blood were enhanced and sustained up to 7 days, beyond that achievable by their free drug counterpart. Thus, multiple antiretroviral agents can be simultaneously incorporated into anti-HIV lipid nanoparticles to enhance intracellular drug concentrations in blood and lymph nodes, where viral replication persists. As these anti-HIV lipid nanoparticles also prolonged plasma drug exposure, they hold promise as a long-acting dosage form for HIV patients in addressing residual virus in cells and tissue.

Long-acting three-drug combination anti-HIV nanoparticles enhance drug exposure in primate plasma and cells within lymph nodes and blood

Insufficient HIV drug levels in lymph nodes have been linked to viral persistence. To overcome lymphatic drug insufficiency, we developed and evaluated in primates a lipid-drug nanoparticle containing lopinavir, ritonavir, and tenofovir. These nanoparticles produced over 50-fold higher intracellular lopinavir, ritonavir and tenofovir concentrations in lymph nodes compared to free drug. Plasma and intracellular drug levels in blood were enhanced and sustained for 7 days after a single subcutaneous dose, exceeding that achievable with current oral therapy.

Protease inhibitor monotherapy is not associated with increased viral replication in lymph nodes

There are concerns about residual viremia in sanctuary sites among patients on protease inhibitor monotherapy, so we aimed to study viro-immunological parameters in tonsil's lymphoid tissue of patients on highly active antiretroviral therapy (HAART) and on protease inhibitor monotherapy. Despite fully suppressed serum HIV viral load, we found viral replication in both groups; in addition, more patients had detectable proviral DNA among those on HAART, compared to those on protease inhibitor monotherapy (P = 0.08), supporting the absence of a deleterious effect of protease inhibitor monotherapy.

Evolution of broadly cross-reactive HIV-1-neutralizing activity: therapy-associated decline, positive association with detectable viremia, and partial restoration of B-cell subpopulations

Little is known about the stability of HIV-1 cross-neutralizing responses. Taking into account the fact that neutralization breadth has been positively associated with plasma viral load, there is no explanation for the presence of broadly neutralizing responses in a group of patients on treatment with undetectable viremia. In addition, the B-cell profile responsible for broadly cross-neutralizing responses is unknown. Here we studied the evolution of neutralizing responses and the B-cell subpopulation distribution in a group of patients with broadly cross-reactive HIV-1-neutralizing activity. We studied neutralization breadth evolution in a group of six previously identified broadly cross-neutralizing patients and six control patients during a 6-year period with a previously described minipanel of recombinant viruses from five different subtypes. B-cell subpopulation distribution during the study was also determined by multiparametric flow cytometry. Broadly cross-neutralizing activity was transient in four broad cross-neutralizers and stable, up to 4.6 years, in the other two. In four out of five broad cross-neutralizers who initiated treatment, a neutralization breadth loss occurred after viremia had been suppressed for as much as 20 months. B-cell subpopulation analyses revealed a significant increase in the frequency of naive B cells in broadly cross-reactive samples, compared with samples with less neutralization breadth (increased from 44% to 62%). We also observed a significant decrease in tissue-like and activated memory B cells (decreased from 19% to 12% and from 17% to 9%, respectively). Our data suggest that HIV-1 broadly cross-neutralizing activity is variable over time and associated with detectable viremia and partial B-cell restoration.

Effect of a short-term HAART on SIV load in macaque tissues is dependent on time of initiation and antiviral diffusion

BACKGROUND

HIV reservoirs are rapidly established after infection, and the effect of HAART initiated very early during acute infection on HIV reservoirs remains poorly documented, particularly in tissue known to actively replicate the virus. In this context, we used the model of experimental infection of macaques with pathogenic SIV to assess in different tissues: (i) the effect of a short term HAART initiated at different stages during acute infection on viral dissemination and replication, and (ii) the local concentration of antiviral drugs.

RESULTS

Here, we show that early treatment with AZT/3TC/IDV initiated either within 4 hours after intravenous infection of macaques with SIVmac251 (as a post exposure prophylaxis) or before viremia peak (7 days post-infection [pi]), had a strong impact on SIV production and dissemination in all tissues but did not prevent infection. When treatment was initiated after the viremia peak (14 days pi) or during early chronic infection (150 days pi), significant viral replication persists in the peripheral lymph nodes and the spleen of treated macaques despite a strong effect of treatment on viremia and gut associated lymphoid tissues. In these animals, the level of virus persistence in tissues was inversely correlated with local concentrations of 3TC: high concentrations of 3TC were measured in the gut whereas low concentrations were observed in the secondary lymphoid tissues. IDV, like 3TC, showed much higher concentration in the colon than in the spleen. AZT concentration was below the quantification threshold in all tissues studied.

CONCLUSIONS

Our results suggest that limited antiviral drug diffusion in secondary lymphoid tissues may allow persistent viral replication in these tissues and could represent an obstacle to HIV prevention and eradication.

Factors associated with collagen deposition in lymphoid tissue in long-term treated HIV-infected patients

OBJECTIVE

The factors associated with fibrosis in lymphoid tissue in long-term treated HIV-infected patients and their correlation with immune reconstitution were assessed.

METHODS

Tonsillar biopsies were performed in seven antiretroviral-naive patients and 29 successfully treated patients (median time on treatment, 61 months). Twenty patients received protease inhibitors-sparing regimens and nine protease inhibitor-containing regimens. Five tonsillar resections of HIV-negative individuals were used as controls. Lymphoid tissue architecture, collagen deposition (fibrosis) and the mean interfollicular CD4(+) cell count per mum were assessed.

RESULTS

Naive and long-term treated HIV-infected patients had a higher proportion of fibrosis than did HIV-uninfected persons (P < 0.001). Patients with greater collagen deposition showed lower levels of CD4 cells in lymphoid tissue (P = 0.03) and smaller increase in peripheral CD4(+) T cells (r = -0.40, P = 0.05). The factors independently associated with fibrosis in lymphoid tissue were age (P < 0.0001), treated patients with detectable lymphoid tissue viral load when compared with patients with undetectable lymphoid tissue viral load (median 5 vs. 12%, respectively, P = 0.017) and patients receiving a protease inhibitor-sparing vs. a protease inhibitor-containing regimen (median 8 vs. 2.5%, respectively, P = 0.04).

CONCLUSION

Fibrosis in lymphoid tissue was associated with a poor reconstitution of CD4(+) T cells and long-term antiretroviral therapy did not reverse this abnormality. HIV infection, older age, a detectable level of lymphoid tissue viral load in treated patients and protease inhibitor-sparing regimens seem to favour fibrosis in lymphoid tissue.

Switch from enfuvirtide to raltegravir in virologically suppressed HIV-1 infected patients: effects on level of residual viremia and quality of life

BACKGROUND

Raltegravir is a potential treatment option for virologically suppressed HIV-1 infected patients on enfuvirtide with injection site reactions.

OBJECTIVES

To characterize safety and efficacy of an enfuvirtide to raltegravir switch including changes in T-cells, quality of life, and residual viremia.

STUDY DESIGN

In patients with viral load <50 copies/mL and injection site reactions, enfuvirtide was switched to raltegravir without additional changes to the antiretroviral regimen. Virologic failure was defined as a viral load >1000 copies/mL or two consecutive viral load measurements between 50 and 1000 copies/mL (low-level viremia). Over the 24 week study, we compared changes in T-cells, injection site reactions, quality of life, and residual viremia, as measured through the single-copy assay which can detect plasma virus down to a single copy, using paired t-tests.

RESULTS

Fourteen patients with a median CD4+ T-cell count of 420 cells/microL were enrolled. After the switch, two patients experienced virologic failure due to confirmed low-level viremia. However, both patients subsequently were re-suppressed, one without any changes to his regimen. There was no change in CD4+ T-cell count. Injection site reactions resolved. However, there was little reported change in quality of life. The baseline median level of residual viremia was 6 copies/mL and did not change after the switch to raltegravir.

CONCLUSIONS

A switch to raltegravir in virologically suppressed patients on enfuvirtide is effective in maintaining immunologic and virologic control at 24 weeks but did not result in a change in residual viremia.

Evaluation of the pathogenesis of decreasing CD4(+) T cell counts in human immunodeficiency virus type 1-infected patients receiving successfully suppressive antiretroviral therapy

Most human immunodeficiency virus (HIV)-infected individuals experience increases in peripheral CD4(+) T cell counts with suppressive antiretroviral therapy (ART) that achieves plasma HIV RNA levels that are less than the limit of detection. However, some individuals experience decreasing CD4(+) T cell counts despite suppression of plasma viremia. We evaluated 4 patients with a history of CD4(+) T cell decline despite successfully suppressive ART, from a median of 719 cells/mm(3) (range, 360-1141 cells/mm(3)) to 227 cells/mm(3) (range, 174-311 cells/mm(3)) over a period of 18-24 months; 3 of the patients were receiving tenofovir and didanosine, which may have contributed to this decrease. There was no evidence of HIV replication, nor of antiretroviral drug resistance in the blood or lymphoid tissue, or increased proliferation or decreased thymic production of naive CD4(+) T cells. All 4 patients had significant fibrosis of the T cell zone of lymphoid tissue, which appeared to be an important factor in the failure to reconstitute T cells.

HIV expression in surgical specimens

We determined the HIV-1 RNA and Gag p24 protein expression in gastrointestinal tract-associated lymphoid tissue (GALT), deep lymph nodes (LNs), and inflammatory lesions, acquired during surgery on HIV-infected patients. Surgically excised gastrointestinal tract specimens, LNs, and cervices removed from HIV-1-infected patients for various clinical conditions were studied by immunohistochemistry (IHC) for Gag p24 HIV protein and in situ hybridization (ISH) for HIV-specific RNA. Fragments of some specimens were also submitted in glutaraldehyde for TEM analysis. Germinal centers (GC) in the GALT had at least as much HIV RNA and p24 protein deposited on their follicular dendritic cell (FDC) networks as did GC in LNs draining or associated with areas of inflammation or ulceration. The level of viral expression in the deep LNs, e.g., mesenteric and retroperitoneal, was at least equivalent to that seen in superficial LNs, i.e., inguinal, axillary, and cervical, and tonsils and adenoids. HIV expressing T and B lymphocytes and macrophages were seen in GALT and LNs. Virus-expressing mononuclear cells (MNC) were also seen in inflammatory lesions such as gastrointestinal ulcers and acute appendicitis. Abundant virus was seen in the cervix of patients with and without cancer and in LNs of patients with metastatic cancer. Individual and clusters of mature HIV particles were identified by TEM in LN GC and in GALT. Gastrointestinal tract lymphoid tissue, inflammatory lesions, and deep LNs showed levels of HIV RNA and Gag p24 protein expression in the range seen in superficial LNs.

Intensification of a suppressive HAART regimen increases CD4 counts and decreases CD8+ T-cell activation

A significant proportion of HIV-1-infected individuals on suppressive HAART regimens do not reconstitute CD4 counts well. If viral reservoirs persist and impact on CD4 reconstitution in a percentage of cases then addition of another antiretroviral agent could further suppress these reservoirs resulting in enhanced CD4 recovery. To evaluate this possibility, we studied the effect of adding abacavir to a chronically suppressive NNRTI containing HAART regimen for 8 patients on their CD4 count and expression of activation markers. Over the first 24 weeks of intensification, CD4 counts increased significantly (p=0.028). This increase continued after a year in follow-up with a significant rate of change in CD4 T-cells of 0.959+/-1.27 per week. In addition, during intensification changes in the percentage of CD38+CD8+ T-cells over time were significantly negatively correlated with changes in CD4 cell number over time above increases predicted without intensification (r(2)=0.716, p=0.008). These data support the possibility that in certain cases where suboptimal CD4 reconstitution occurs that intensification of the regimen can impact immunologic parameters.

Naive T-cell depletion related to infection by X4 human immunodeficiency virus type 1 in poor immunological responders to highly active antiretroviral therapy

The reasons for poor CD4+ T-cell recovery in some human immunodeficiency virus (HIV)-infected subjects despite effective highly active antiretroviral therapy (HAART) remain unclear. We recently reported that CXCR4-using (X4) HIV-1 could be gradually selected in cellular reservoirs during sustained HAART. Because of the differential expression of HIV-1 coreceptors CCR5 and CXCR4 on distinct T-cell subsets, the residual replication of R5 and X4 viruses could have different impacts on T-cell homeostasis during immune reconstitution on HAART. We examined this hypothesis and the mechanisms of CD4+ T-cell restoration by comparing the virological and immunological features of 15 poor and 15 good immunological responders to HAART. We found a high frequency of X4 viruses in the poor immunological responders. But the levels of intrathymic proliferation of the two groups were similar regardless of whether they were infected by R5 or X4 virus. The frequency of recent thymic emigrants in the poor immunological responders was also similar to that found in the good immunological responders, despite their reduced numbers of naïve CD4+ T cells. Our data, rather, suggest that the naïve T-cell compartment is drained by a high rate of mature naïve cell loss in the periphery due to bystander apoptosis or activation-induced differentiation. X4 viruses could play a role in the depletion of naïve T cells in poor immunological responders to HAART by triggering persistent T-cell activation and bystander apoptosis via gp120-CXCR4 interactions.

Persistence of distinct HIV-1 populations in blood monocytes and naive and memory CD4 T cells during prolonged suppressive HAART

OBJECTIVE

Reservoirs of HIV-1 are a major obstacle to virus eradication. There is therefore a need to clearly understand the molecular nature of the virus populations that persist in patients with sustained suppression of plasma viraemia on highly active antiretroviral therapy (HAART).

DESIGN

We performed a detailed analysis of the genotypes of HIV-1 quasispecies isolated from highly purified blood cell types taken from three selected patients with sustained undetectable viral loads on HAART for 7 years.

METHODS

We used polychromatic flow cytometry to sort naive and memory CD4 T cells, CD14 monocytes, and CD56+CD3- natural killer (NK) cells from the total peripheral blood mononuclear cells after 7 years of HAART. Clonal analysis was used to determine coreceptor use and drug-resistance genotypes of HIV-1 quasispecies in the sorted blood cell types.

RESULTS

We detected HIV-1 DNA in memory and naive CD4 T cells and in CD14 monocytes, but not in the CD56+CD3- NK cells. Phylogenetic analysis demonstrated that the various blood cells types of two of the three patients harboured genetically distinct HIV-1 quasispecies. Drug-resistance mutations were also distributed differently from one cell type to another. This compartmentalization suggests a minimal virus trafficking between blood cell types during suppressive HAART.

CONCLUSIONS

We observed a cell-specific compartmentalization of the residual virus populations during prolonged suppressive HAART. The coexistence of numerous HIV-1 quasispecies with different resistance genotypes and coreceptor use in cellular reservoirs may be relevant for future antiretroviral treatment strategies.

R5 to X4 Switch of the Predominant HIV-1 Population in Cellular Reservoirs During Effective Highly Active Antiretroviral Therapy

HIV-1 coreceptor usage plays a critical role for virus tropism and pathogenesis. A switch from CCR5 to CXCR4-using viruses can occur in the natural course of infection and correlates with subsequent disease progression. To investigate whether HIV-1 genetic evolution might lead to changes in virus coreceptor usage during highly active antiretroviral therapy (HAART), a longitudinal genotypic analysis of the virus found in cellular reservoirs was conducted in 32 patients with undetectable viral loads on HAART for 5 years. The genotype of the 3rd variable region of the env gene predicting coreceptor usage was retrospectively determined in the plasma or in peripheral blood mononuclear cells (PBMC) at baseline and then in PBMCs at months 30 and 60 of HAART. There was a switch from R5 to X4 variants in 11 of the 23 patients who harbored a majority virus population of R5 variants at baseline. X4 variants remained predominant in the 9 patients who harbored mainly X4 variants at baseline. The patients harboring predominantly X4 variants during HAART, either from baseline or after an R5 to X4 switch, tended to have lower CD4+ T-cell counts on HAART than did patients harboring continuously a majority population of R5 variants. These results suggest that potent antiretroviral therapy produces the conditions necessary for the gradual emergence of X4 variants in cellular reservoirs.

Long-term suppression of plasma viremia with highly active antiretroviral therapy despite virus evolution and very limited selection of drug-resistant genotypes

HIV-1 evolution and the possible emergence of mutations associated with resistance to antiretroviral inhibitors have been evaluated in a cohort of sixty-three patients successfully treated with highly active antiretroviral therapy (HAART). The patients under effective HAART were recruited in three different hospitals in Spain, and none of them had been treated (naïve) before entering this study. HIV-1 RNA levels, CD4+, and CD8+ T-cell counts were determined, and nucleotide sequences of proviral regions encoding protease and reverse transcriptase (RT) were obtained for longitudinal blood samples spanning a mean follow-up period of 88 weeks. Phylogenetic reconstructions and calculations of genetic distances among the different sequences of each patient were performed. All except one of the patients under study showed an early and sustained decrease in plasma HIV-1 RNA to levels that were below 200 copies/ml. The plasma viral decline paralleled a significant increase in the CD4+ T-lymphocyte counts. Amino acid sequence analyses revealed the occurrence of mutations associated with antiretroviral resistance in nine patients (14.3%) during HAART treatment, that in some cases could be attributed to excess G to A transitions. In six of the nine patients, the mutations conferred resistance to inhibitors administered in the treatment regime, although the mutations did not result in treatment failure. Sequence comparisons revealed viral evolution during the period of treatment in 47.5% of the patients. The results indicate successful suppression of HIV-1 under HAART for extended time periods, indistinguishable for patients in which evidence of virus evolution could or could not be documented.

Predictors of Tonsillar Tissue HIV-1 Viral Burden at Baseline and after 1 Year of Antiretroviral Therapy

In 81 antiretroviral-naive HIV-1 chronic-infected patients, we found a correlation among tonsillar tissue viral load, and virological and immunological measures in blood at baseline. No correlation was observed after 1 year of antiretroviral therapy. A protease inhibitor-containing regimen was the best predictor of good tonsillar tissue virological response.

Mutational patterns of paired blood and rectal biopsies in HIV-infected patients on HAART

Blood and concurrent rectal biopsy samples of human immunodeficiency virus type 1 (HIV-1)-positive highly active antiretroviral therapy (HAART)-treated patients were tested for genotypic resistance by direct sequencing of reverse transcriptase (RT) and protease (PR) regions to compare the patterns of resistance in these compartments. Fourteen subjects (five with undetectable plasma viral load (pVL) and nine persistently viremic) were studied. Four of five patients with undetectable pVL also had undetectable mucosal HIV RNA; sequence analyses from proviral DNA (PBMCs and rectal biopsy) were obtained with none or few resistance-associated mutations and no alteration of susceptibility profile. All viremic patients, and one with negative pVL, had detectable levels of mucosal HIV RNA (1.93-4.21 log(10) copies/mg); sequences of HIV RNA (plasma and/or rectal biopsy) were also obtained, and multiple mutations generally compatible with current/past medications were detected. Overall, 40 HIV-1 PR and 42 RT sequences were analyzed, yielding a total of 42 PR and 47 RT sequence pairs (plasma/tissue-RNA; plasma-RNA/tissue-DNA; PBMC/tissue-DNA; tissue-DNA/RNA; tissue-RNA/PBMC-DNA; PBMC-DNA/plasma-RNA), which almost always differed at the total amino acid level (median percentage discordance 8.08% in the PR, 4.8% in RT). The median percentage of resistance position discordance equaled 88.8% (IQR = 20-100) in the PR and 74.55% (IQR = 31.75-100%) in the RT pairs, respectively. Different resistance levels were detected by means of a computer-assisted interpretation of mutational profiles. The results support the multiform evolution of HIV genotype in various body compartments and emphasize the participation of intestinal mucosa in HIV genotype selection. Samples from diverse tissues should be used for resistance evaluation to obtain a complete picture of drug resistance for antiretroviral-treated patients.

Comparison of three kinetic models of HIV-1 infection: implications for optimization of treatment

Clinical markers in the peripheral blood guide the treatment of human immunodeficiency virus type 1 (HIV-1). Likewise, many of the theoretical models developed to simulate infection only incorporate variables in the blood. To test the suitability of blood-only models, three distinct models of HIV infection kinetics are compared: "full model" including latently and actively infected cells and virus in the peripheral blood and lymphoid tissue (LT); "reduced model", including peripheral blood and LT without latent cells; and "blood model" including only actively infected cells and virus in the peripheral blood. Using the same parameter values for all three, qualitative differences are demonstrated between the blood model and its more inclusive counterparts. Additionally, optimization studies show that the reduced and blood models generate progressively lower optimal treatment levels relative to the full model when constant-level treatment is considered. These findings indicate that including the lymphoid tissue and latently infected cells into kinetic models may lead to differing conclusions with regard to optimal treatment and could be useful in guiding therapy even when plasma viral levels are below detectable limits.

In a subset of subjects on highly active antiretroviral therapy, human immunodeficiency virus type 1 RNA in plasma decays from 50 to <5 copies per milliliter, with a half-life of 6 months

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.

Discrepancies between protease inhibitor concentrations and viral load in reservoirs and sanctuary sites in human immunodeficiency virus-infected patients

The variable penetration of antiretroviral drugs into sanctuary sites may contribute to the differential evolution of human immunodeficiency virus (HIV) and the emergence of drug resistance. We evaluated the penetration of indinavir, nelfinavir, and lopinavir-ritonavir (lopinavir/r) in the central nervous system, genital tract, and lymphoid tissue and assessed the correlation with residual viral replication. Plasma, cerebrospinal fluid (CSF), semen, and lymph node biopsy samples were collected from 41 HIV-infected patients on stable highly active antiretroviral therapy regimens to determine drug concentrations and HIV RNA levels. When HIV RNA was detectable, sequencing of the reverse transcriptase and protease genes was performed. Ratios of the concentration in semen/concentration in plasma were 1.9 for indinavir, 0.08 for nelfinavir, and 0.07 for lopinavir. Only indinavir was detectable in CSF, with a concentration in CSF/concentration in plasma ratio of 0.17. Differential penetration into lymphoid tissue was observed, with concentration in lymph node tissue/concentration in plasma ratios of 2.07, 0.58, and 0.21 for indinavir, nelfinavir, and lopinavir, respectively. HIV RNA levels were <50 copies/ml in all CSF samples of patients in whom HIV RNA was not detectable in plasma. HIV RNA was detectable in the semen of three patients (two patients receiving nelfinavir and one patient receiving lopinavir/r), and its detection was associated with multiple resistance mutations, while the viral load in plasma was undetectable. HIV RNA was detectable in all lymph node tissue samples. Differential drug penetration was observed among the three protease inhibitors in the sanctuary sites, but there was no correlation between drug levels and HIV RNA levels, suggesting that multiple factors are involved in the persistence of viral reservoirs. Further studies are required to clarify the role and clinical relevance of drug penetration in sanctuaries in terms of long-term efficacy and drug resistance.

Evolution of total and integrated HIV-1 DNA and change in DNA sequences in patients with sustained plasma virus suppression

Blood samples from patients with plasma HIV-1 RNA <20 copies/ml for more than 2 years were studied. Significant decreases in total and integrated HIV-1 DNA were observed during the first 15 months of suppressive therapy before the concentrations became stable. Clonal analysis of HIV-1 pol demonstrated that the proportions of resistance mutations in DNA sequences after 2 years were lower than those in baseline DNA and RNA sequences. The changes in the clonal composition of HIV-1 env populations in three patients with evidence of changes in HIV-1 pol populations indicated a shift from predominantly R5-like viruses to predominantly X4-like viruses in two patients and the persistence of predominantly X4-like viruses in the third. Our analyses indicate the reemergence of ancestral sequences from long-lived cells or the residual production of wild-type virus from anatomic sites with limited access to antiretroviral drugs and the preferential infection of cells expressing CXCR4.

HIV-1 reservoirs

In most infected individuals, HIV-1 replicates high levels throughout the duration of infection, including the clinically quiescent phase of disease. The level of this active viral replication correlates directly with disease progression and survival. The advent of combination therapeutics for HIV-1 (i.e., highly active antiretroviral therapy [HAART]) has led to dramatic reductions in viral replication in vivo and morbidity and mortality, at least in the developed world.

Improved long-term suppression of HIV-1 replication with a triple-class multidrug regimen compared with standard of care antiretroviral therapy

BACKGROUND

The treatment of HIV-1-infected patients with triple-drug combination therapy results in profound suppression of viral replication. In most therapy-naive patients plasma HIV-1-RNA levels (pVL) drop below the lower limit of quantification (LLQ) of currently used assays. In a large percentage of such patients, more sensitive assays provide evidence of residual viral replication. The question is whether more potent therapy can further suppress this residual replication.

METHODS

Thirty control patients who, using very strict criteria, had not experienced virological failure during 3 years of standard therapy, were compared with 10 patients treated with a five-drug regimen, consisting of three different classes of antiretroviral drugs (alternative multidrug regimen). A modified ultrasensitive assay with an LLQ of 5 copies/ml was used to re-test plasma obtained at week 48 and at three timepoints at and around week 144.

RESULTS

At weeks 48 and 144 pVL could be quantified significantly more frequently in control patients than in patients using the alternative multidrug regimen (week 48: 42 versus 0% with quantifiable pVL, P = 0.017; week 144: 60 versus 14% with at least one quantifiable pVL, P = 0.036, respectively). A low baseline CD4T cell count was predictive of quantifiable pVL in control patients, but not in alternative multidrug patients.

CONCLUSION

This proof-of-principle study demonstrates that the use of an alternative multidrug regimen results in stronger long-term suppression of pVL compared with clinically successful treatment with standard therapy.

The extent of HIV-1-related immunodeficiency and age predict the long-term CD4 T lymphocyte response to potent antiretroviral therapy

OBJECTIVE

To study the long-term immunological recovery in HIV-1-infected individuals receiving potent antiretroviral therapy (ART).

DESIGN

Prospective, observational study.

METHODS

Plasma HIV-1 RNA, CD4 and CD8 T lymphocyte counts were determined at 3-6 monthly intervals in 95 HIV-1-infected subjects receiving ART who suppressed plasma HIV-1 RNA to levels below 400 copies/ml during a median observation period of 45 months.

RESULTS

The median CD4 cell count rose from 325 to 624 cells/microl at 48 months, increasing by 22.6 cells/microl per month in the first 3 months, 8.1 cells/microl per month from months 3 to 12, 6.8 cells/microl per month in the second year, 3.3 cells/microl per month in the third, and 1.7 cells/microl per month in the fourth year. At 48 months, 98% of subjects reached CD4 cell counts > 200 cells/microl, 86% > 350 cells/microl, and 74% > 500 cells/microl. A higher nadir CD4 cell count and younger age were independently associated with greater increases in CD4 cell counts, and higher absolute CD4 cell counts at 48 months. Poor immunological responders who did not reach 500 CD4 lymphocytes/microl at 48 months showed lower nadir and baseline CD4 cell counts than good responders (99 versus 300 cells/microl and 160 versus 373 cells/microl, respectively).

CONCLUSION

The recovery of CD4 T lymphocytes occurs mainly in the first 2 years after the initiation of ART, and is associated with age and the pre-existing degree of HIV-1-related immunodeficiency, suggesting that the long-term exposure to HIV-1 infection has caused damage to the immune system that is difficult to correct.

Short-cycle structured intermittent treatment of chronic HIV infection with highly active antiretroviral therapy: effects on virologic, immunologic, and toxicity parameters

Although continuous highly active antiretroviral therapy (HAART) is effective for many HIV-infected patients, it can be toxic and prohibitive in cost. By decreasing the total amount of time patients receive medications, intermittent HAART could reduce toxicity and cost. Therefore, we initiated a pilot study in which 10 HIV-infected individuals receiving effective therapy that resulted in levels of HIV RNA <50 copies per ml of plasma and CD4(+) T cell counts >300 cells per mm(3) of whole blood received repeated cycles of 7 days on HAART followed by 7 days off of HAART. Patients maintained suppression of plasma viremia for 32-68 weeks. There was no significant increase in HIV proviral DNA or replication-competent HIV in peripheral CD4(+) T cells or HIV RNA in peripheral blood or lymph node mononuclear cells. There was no significant change in CD4(+) T cell counts, no significant increase in CD4(+) or CD8(+) T cells expressing activation markers or producing IFN-gamma in response to HIV, no increase in CD4(+) T cell proliferation to p24 antigen, and no evidence for the development of resistance to HAART medications. There was a significant decrease in serum cholesterol and triglyceride levels. Thus, in this proof-of-concept study, short-cycle intermittent HAART maintained suppression of plasma viremia as well as HIV replication in reservoir sites while preserving CD4(+) T cell counts. In addition, there was a decrease in serum cholesterol and triglyceride levels. Intermittent therapy may be an important strategy to reduce cost and toxicity for HIV-infected individuals.

Persistence of HIV-1 resistance in lymph node mononuclear cell RNA despite effective HAART

OBJECTIVE

To analyse the presence of genotypic and phenotypic resistance in lymph node mononuclear cells from patients with sustained undetectable plasma HIV-1 RNA with highly active antiretroviral therapy.

DESIGN

Cross-sectional study on 27 HIV-infected patients receiving triple therapy for a mean period of 232.8 +/- 22.1 weeks.

METHODS

HIV-1 RNA was measured in plasma and lymph node cells using PCR. Reverse transcriptase and protease genes were sequenced from HIV-1 RNA obtained from lymph node cells and from peripheral blood mononuclear cell proviral DNA using a commercially available kit (TruGene). Phenotypic resistance was assessed by using a recombinant virus assay (AntiVirogram).

RESULTS

Mutations were not found in lymph node mononuclear cell RNA in six out of nine patients on first-line regimens although they were detected in 15 out of 18 who received prior suboptimal combinations. Phenotypic resistance was confirmed in most of these cases. These patterns of resistance were closely related to patients' history of antiretroviral therapy and genotypic analysis of plasma HIV-1 RNA taken just before initiation of the current regimen. In half the patients analysed, resistance mutations found in lymph nodes were not always detected in archival proviral DNA from blood cells. Mean levels of HIV-1 RNA in lymph node cells were not different in patients exhibiting resistance compared with those harbouring wild-type viruses.

CONCLUSION

These data demonstrate that resistant HIV-1 is produced in lymphoid tissues for prolonged periods despite effective therapy. The mechanism could represent a release from previously infected cells rather than new cycles of cellular infection.

Human immunodeficiency virus pathogenesis: insights from studies of lymphoid cells and tissues

Although plasma virus load is invaluable for monitoring human immunodeficiency virus (HIV) infection, key pathogenesis events and most viral replication take place in lymphoid tissues. Decreases in virus load associated with therapy occur in plasma and tissues, but persistent latent infection and ongoing viral replication are evident. Many unanswered questions remain regarding mechanisms of HIV-associated lymphocyte depletion, but partial CD4(+) cell reconstitution after therapy likely reflects retrafficking from inflamed tissues, increased thymic or peripheral production, and decreased destruction. Rapid establishment of latent infection and the follicular dendritic cell-associated viral pool within lymphoid tissues suggest that only early intervention could substantially alter the natural history of HIV. If therapy is started prior to seroconversion, some individuals retain potent HIV-specific cellular immune responsiveness that is suggestive of delayed progression. Although complete virus eradication appears out of reach at present, more attention is being directed toward the prospect of boosting HIV-specific immune responses to effect another type of "clinical cure": immune-mediated virus suppression in the absence of therapy.

Lymphoid tissue viral burden and duration of viral suppression in plasma

OBJECTIVES

To assess virological response in lymphoid tissue and its impact on the durability of response in plasma in HIV-1-infected persons who achieved sustained suppression of plasma viraemia with different antiretroviral regimens.

METHODS

Consecutive patients on first-line antiretroviral therapy were included if they had a plasma HIV-1 RNA viraemia < 20 copies/ml within the last 6 months and tonsillar tissue accessible for biopsy. First-line therapy contained two nucleoside analogues: alone (2NRTI group, n = 3); plus a HIV-1 protease inhibitor (PI group, n = 11) or plus nevirapine (NVP group; n = 16). Patients were followed until virus was detectable in plasma, they changed therapy or were lost to follow-up.

RESULTS

Tonsillar HIV-1 RNA could be detected (> 100 copies/mg) in 10 patients: one in the PI group (9%), six (38%) in the NVP group and in all three patients in the 2NRTI group. Primary resistance mutations could be detected in only 2 of these 10 patients. After a median of 9 months after the biopsies, viral suppression in plasma had failed in 6 of these 10 patients whereas failure had only occurred in 1 out of 20 with initially undetectable viral load in lymphoid tissue (P = 0.01; log rank test).

CONCLUSIONS

In patients with sustained viral suppression in plasma, triple therapy including a HIV-1 protease inhibitor was more potent than triple therapy containing nevirapine or dual therapy with nucleoside analogues to reduce viral burden in lymphoid tissue. A worse response in lymphoid tissue could not be explained by local selection of resistance and was associated with a less durable virological response in plasma.

Cerebrospinal fluid response to structured treatment interruption after virological failure

OBJECTIVE

Structured antiretroviral treatment interruption (STI) has been advocated as a therapeutic strategy for HIV-1 infection. We report initial observations of cerebrospinal fluid (CSF) HIV-1 infection in five patients undergoing serial lumbar punctures (LPs) during STI undertaken following virological failure.

DESIGN AND METHODS

In this prospective observational study we quantified HIV-1 RNA concentrations and assessed both phenotypic drug susceptibility profiles and genotypic antiviral drug resistance mutations in CSF and plasma during the period of treatment interruption. CSF white blood cells were also counted, and patients' neurological status monitored.

RESULTS

In four of the patients, CSF HIV-1 concentration increased more rapidly than that of the plasma, with consequent reduction in the ratio between plasma and CSF viral loads (pVL : cVL). Three individuals developed robust, though asymptomatic CSF lymphocytic pleocytosis. In all patients the predominant HIV-1 quasispecies shifted simultaneously in CSF and plasma from a drug-resistant to a more drug-susceptible phenotype with identical and simultaneous changes in genotypes associated with drug resistance.

CONCLUSIONS

STI may be accompanied by previously unrecognized changes in tissue viral exposures and lymphocyte traffic. Hence, despite 'virological failure' as evidenced by persistent plasma viremia, ongoing antiretroviral treatment prior to its interruption appeared to suppress CSF HIV-1 infection (indeed more effectively than that of plasma) and restrain lymphocyte traffic into the CSF. Simultaneous change of resistance mutations in CSF and plasma was likely due to re-emergence and overgrowth of pre-existing strains with ready exchange of virus between these two compartments, either facilitated by or provoking a local CSF lymphocytosis.

Sensitive and reproducible quantitation of mucosal HIV-1 RNA and DNA viral burden in patients with detectable and undetectable plasma viral HIV-1 RNA using endoscopic biopsies

Mucosal tissue is the main portal of entry for HIV-1 infection and, in macaques, has been demonstrated to be a significant compartment for viral replication and CD4+ T lymphocyte depletion. Quantitating tissue viral burden in addition to plasma viral load provides insights into HIV-1 pathogenesis and an additional means to gauge antiretroviral response. The aim of this study was to develop reliable, reproducible, and sensitive assays to quantitate tissue viral burden of HIV-1 RNA and DNA using 1-3 endoscopically acquired, rectosigmoid biopsies. Total DNA and RNA were simultaneously extracted following homogenization from the same tissue samples. Quantitative polymerase chain reaction (PCR) assay in the HIV-1 LTR region was used to detect viral DNA and RT-PCR for viral RNA. It was determined that HIV-1 RNA and DNA can be reproducibly quantified from a single rectosigmoid biopsy with minimal intra-assay or intra-patient variability. These results reflect high recovery of extracted nucleic acids with calculated results accurately reflecting in vivo levels. The techniques outlined differ from currently available approaches by incorporating control standards to identify loss or degradation of RNA and DNA from acquisition through the in vitro assay and permit extraction with high yields of RNA and DNA from the same tissue sample.

HIV-specific effector cytotoxic T lymphocytes and HIV-producing cells colocalize in white pulps and germinal centers from infected patients

Human immunodeficiency virus (HIV) infection is characterized by the massive infiltration of secondary lymphoid organs with activated CD8(+) T lymphocytes. While converging data indicated that these cells were HIV-specific cytotoxic T lymphocytes (CTLs) responsible for HIV spread limitation, direct evidence was lacking. Here, the presence of HIV-specific effector CTLs was demonstrated directly ex vivo in 15 of 24 microdissected splenic white pulps from an untreated patient and in 1 of 24 tonsil germinal centers from a second patient with incomplete viral suppression following bitherapy. These patients had plasma HIV RNA loads of 5900 and 820 copies per milliliter. The frequencies of HIV-1 DNA(+) cells in their lymphoid organs were more than 1 in 50 and 1 in 175, respectively. Spliced viral messenger RNA (a marker for ongoing viral replication) was present in most immunocompetent structures tested. Conversely, CTL activity was not found in spleens from 2 patients under highly active antiretroviral therapy, with undetectable plasma viral load. These patients had much lower spleen DNA(+) cell frequencies (1 in 2700 and 1 in 3800) and no white pulps containing spliced RNA. CTL effector activity as well as spliced viral messenger RNA were both concentrated in the white pulps and germinal centers. This colocalization indicates that viral replication in immunocompetent structures of secondary lymphoid organs triggers anti-HIV effector CTLs to these particular locations, providing clues to target therapeutic intervention.

In vitro exposure to highly cytopathic HIV-1 X4 strains increases expression of mucosa-associated integrins on CD4(+) T cells

To determine whether infection with HIV-1 strains of different tropisms would influence expression of the mucosa-associated integrins alpha 4 beta 7 and alpha E beta 7 or the lymph node homing receptor L-selectin on peripheral T lymphocytes, cells were infected with the CXCR4-tropic (X4)/syncytium-inducing (SI) HIV-1(IIIB) strain or with X4/SI or CCR5-tropic (R5)/non-SI (NSI) primary human isolates. Flow cytometric analyses of CD4(+) T cells from cultures infected with HIV-1(IIIB) and one X4/SI primary HIV-1 isolate revealed a significant increase in surface expression of alpha 4 beta 7 and alpha E beta 7 12 days after infection. L-selectin expression was not significantly affected on CD4(+) T cells. However, infection with another X4/SI and two R5/NSI primary HIV-1 isolates did not significantly alter homing receptor expression on CD4(+) T cells. Since a higher degree of CD4 cytopathicity occurred in those cultures having increased integrin expression, these data suggest that significantly altered mucosal homing receptor expression on CD4(+) T cells may result as a "bystander" effect after infection with some cytopathic isolates of HIV-1.

Residual HIV-1 RNA in blood plasma of patients taking suppressive highly active antiretroviral therapy

Residual HIV-1 disease remains in the vast majority of patients treated with even the most intensive highly active antiretroviral therapy (HAART). There are at least two well-described molecular mechanisms for HIV-1 persistence in these patients. These include proviral latency in resting CD4+ T-cells, as well as 'cryptic' residual viral replication. As well, potential sanctuary sites, including the brain and testes, may be important areas which will hinder HIV-1 eradication attempts. It is not clear whether other sites of HIV-1 persistence, including tissue-bound infected monocytes/macrophages, may also be involved in residual HIV-1 disease during virally-suppressive HAART.

Predictors of Virological Response in HIV-Infected Patients to Salvage Antiretroviral Therapy that Includes Nelfinavir

Different salvage strategies have been used to regain control in patients with HIV who have virological failure on combination antiretroviral therapy. We conducted a cohort study of 63 extensively antiretroviral pretreated patients who initiated nelfinavir as part of salvage therapy, to determine predictors of virological response. The maximum HIV RNA response was >0.5 log10 copies/ml reduction in 43 patients (68%), including 21 patients (33%) who had suppression to <500 copies/ml. Corresponding response rates at 24 weeks were 41 and 19%, respectively. Responders and non-responders could not be distinguished by mean baseline HIV RNA or CD4 cell count, duration of prior protease inhibitor (PI) use, introduction of an initial non-nucleoside reverse transcriptase inhibitor or the number of antiretroviral agents changed when nelfinavir was added, likely reflecting the homogeneity of the population studied. The only parameter predictive of response was virus genotype. Response rates were lower in patients with increasing numbers of primary ( P=0.045) or secondary ( P=0.001) PI mutations. The addition of increasing numbers of reverse transcriptase mutations further impaired response rates ( P=0.004).

HIV RNA and HIV DNA in peripheral blood mononuclear cells are consistent markers for estimating viral load in patients undergoing long-term potent treatment

The aim of this study was to evaluate residual viral replication by assessing the HIV load of circulating infected cells in patients given an effective antiprotease-containing treatment for 1 year. PBMC HIV RNA and HIV DNA was quantified by techniques standardized and evaluated by interlaboratory quality control testing. Viral markers identified in a multicenter study were validated in a cross-sectional study of 121 patients beginning treatment. A longitudinal study of 3 viral markers was carried out in 18 patients, each of whom had fewer than 200 copies of HIV RNA per milliliter of plasma after 12 months of treatment. The cross-sectional study showed that viral replication in PBMCs was correlated with the number of circulating infected cells (Spearman rank correlation; p = 0.0001, r = 0.35) and the concentration of virus particles in the plasma (Spearman; p = 0.0001, r = 0.54). The longitudinal study showed that the decrease in HIV RNA levels was smaller in PBMCs than in the plasma. The largest decrease in HIV DNA levels after 12 months of treatment was recorded in patients with low levels of intracellular replication (Spearman; p = 0.005, r = 0.69). PBMC HIV RNA and HIV DNA levels were very informative markers, complementary to plasma HIV RNA levels. They should be used in future trials evaluating the long-term efficacy of new associations of highly active antiretroviral treatments.

Rapid restoration of CD4 T cell subsets in subjects receiving antiretroviral therapy during primary HIV-1 infection

OBJECTIVE

To compare the effect of highly active antiretroviral therapy on immune reconstitution in subjects with acute and chronic HIV-1 infection.

DESIGN

Prospective study including 58 treatment-naive subjects who commenced indinavir or nelfinavir and two nucleosides during primary (PHI; n = 28) or chronic HIV-1 infection (CHI; n = 30).

METHODS

Naive (CD45RA+ 62L+), memory (CD45RA-) and activated (CD38+ HLA-DR+) T cell subsets were quantified at 1-2 monthly time intervals using 4-colour flow cytometry.

RESULTS

At 1 year, HIV-1 RNA declined in both cohorts to undetectable levels (< 50 copies/ml), while median CD4 lymphocyte count increased from 470 to 758 x 10(6) cells/l in PHI and from 204 to 310 x 10(6) cells/l in CHI, reaching > 500 x 10(6) cells/l in 93% of PHI, but only in 37% of CHI subjects (P < 0.001). Naive CD4 lymphocytes increased from 106 to 176 x 10(6) cells/l in PHI and from 41 to 44 x 10(6) cells/l in CHI (PHI versus CHI at 12 months: P = 0.003), while memory cells rose from 368 to 573 x 10(6) cells/l in PHI and from 148 to 223 x 10(6) cells/l in CHI (P < 0.001). Early increases (< 3 months) of CD4 lymphocytes were larger in subjects with PHI, consisting of naive CD45RA+ CD62L+ as well as memory CD45RA- CD62L+ cells (P = 0.001). CD4 activation declined from 5 to 2% in PHI and from 13 to 6% in CHI (P = 0.001), while CD8 cell activation was reduced from 33 to 15% in PHI and from 42 to 19% in CHI (P = 0.02).

CONCLUSION

Immune reconstitution was more complete, occurred earlier and comprised both naive and memory CD4 T lymphocytes in subjects who commenced antiretroviral therapy during primary HIV-1 infection.

Therapeutic targeting of human immunodeficiency virus type-1 latency: current clinical realities and future scientific possibilities

Factors affecting HIV-1 latency present formidable obstacles for therapeutic intervention. As these obstacles have become a clinical reality, even with the use of potent anti-retroviral regimens, the need for novel therapeutic strategies specifically targeting HIV-1 latency is evident. However, therapeutic targeting of HIV-1 latency requires an understanding of the mechanisms regulating viral quiescence and activation. These mechanisms have been partially delineated using chronically infected cell models and, clearly, HIV-1 activation from latency involves several key viral and cellular components. Among these distinctive therapeutic targets, cellular factors involved in HIV-1 transcription especially warrant further consideration for rational drug design. Exploring the scientific possibilities of new therapies targeting HIV-1 latency may hold new promise of eventual HIV-1 eradication.

Effect of lamivudine in HIV-infected persons with prior exposure to zidovudine/didanosine or zidovudine/zalcitabine

Nucleoside analog-based regimens remain an integral component of combination therapy for use in both antiretroviral treatment-naive and experienced HIV-infected patients. To further define treatment responses to new antiretroviral therapy in patients with long-term experience to dual nucleoside analog therapy (zidovudine [ZDV] plus didanosine [ddI] or ZDV plus zalcitabine [ddC]), 325 subjects derived from the AIDS Clinical Trials Group (ACTG) 175 trial were randomized to three different combination regimens: (1) continuation of ZDV + ddI or ZDV + ddC (continuation arm), (2) addition of 3TC to ZDV + ddI or ZDV + ddC (addition arm), or (3) a switch to ZDV + 3TC therapy (switch arm). Both the addition and switch arms sustained significantly greater short-term (baseline to week 4) mean CD4+ cell count increases compared with the continuation arm (+36, +28 versus -4 cells/mm3; p = 0.012) and long-term CD4+ cell count responses (baseline to weeks 40/48: +32, +19 versus -9 cells/mm3; p = 0.003). Superior short-term (baseline to week 8) mean decreases in plasma HIV RNA (p < 0.001) were achieved by both the addition and switch arms (0.53 log10 and 0.54 log10 copies/ml, respectively) compared with the continuation arm (0.13 copies/ml) whereas no differences in long-term virologic suppression were observed (p = 0.30). At week 48, no differences were observed in the proportions of subjects who had HIV RNA levels below 500 copies/mL: 18% of subjects in each treatment arm (3-way p = 1.0). Overall, the treatments were well tolerated and only nine subjects (3%) died or developed one or more AIDS-defining events. While this study confirms the intrinsic antiretroviral activity of 3TC, only modest marker changes and limited short-term viral suppression are seen with incremental addition of the drug. The current approach of using 3TC in maximally suppressive regimens is preferred.

Rapid activation of lymph nodes and mononuclear cell HIV expression upon interrupting highly active antiretroviral therapy in patients after prolonged viral suppression

OBJECTIVE

To compare the architecture and HIV-1 RNA and Gag p24 protein expression in lymph nodes (LN) excised from individuals during chronic highly active antiretroviral therapy (HAART) with LN removed from the same patient after plasma virus rebound following the interruption of HAART.

MATERIALS AND METHODS

Six HIV-1-infected patients on HAART, with CD4 cell counts greater than 350 cells/microl, and plasma HIV-1 RNA less than 50 copies/ml, underwent inguinal LN excision upon discontinuation of HAART, and again after rebound of plasma virus. Lymph nodes were evaluated by immunohistochemical staining for Gag p24 antigen and Ki67, in-situ hybridization for HIV-1 RNA and H3-histone, and transmission electron microscopy (TEM).

RESULTS

LN at baseline were quiescent to mildly hyperplastic and generally contained more primary than secondary follicles. Only one LN had detectable follicular dendritic cell (FDC)-associated p24 antigen, none had HIV RNA. Few mononuclear cells (MNC) expressed RNA or p24 antigen. Plasma virus at the second biopsy ranged from 329 to 3.2 x 10(6) copies/ml. CD4 cell count decline ranged from 5 to 51% during drug hiatus, and was greatest in patients with highest viral rebound. Four of six of the second LN were more hyperplastic than the initial LN, two showed paracortical hyperplasia. MNC expression of HIV RNA in the second LN paralleled the level of plasma viremia. Increased Ki67 and H3-histone signal occurred in the second LN.

CONCLUSION

Quiescent LN from individuals on HAART rapidly become hyperplastic and activated within 1-2 months after treatment interruption. As in acute HIV infection, virus expression by LN MNC parallels the rebound in plasma viremia and fall in CD4 cell count.

Amprenavir in Combination with Lamivudine and Zidovudine versus Lamivudine and Zidovudine Alone in HIV-1-Infected Antiretroviral-Naive Adults

Objectives

To compare the antiviral activity and safety of a new protease inhibitor, amprenavir (141W94) in combination with lamivudine and zidovudine, versus lamivudine and zidovudine alone in HIV-1 infected, antiretroviral-naive subjects.

Design

Subjects ( n=232) with a CD4 T cell count of ≥200 cells/mm3, plasma HIV-1 RNA levels of ≥10000 copies/ml, and ≤4 weeks of prior nucleoside antiretroviral therapy, were stratified according to baseline plasma HIV-1 RNA level (10000–30000; 30000–100000; or >100000 copies/ml). Subjects received double-blind treatment with either 1200 mg amprenavir twice daily in combination with lamivudine (150 mg twice daily) and zidovudine (300 mg twice daily) (amprenavir/lamivudine/zidovudine) or matched placebo, lamivudine and zidovudine for 16 weeks. Thereafter, subjects with confirmed plasma HIV-1 RNA levels of ≥400 copies/ml could add open-label amprenavir or switch to other antiretrovirals and continue treatment for up to a minimum of 48 weeks. The primary endpoint of the study was defined as the proportion of subjects with plasma HIV-1 RNA of <400 copies/ml at 48 weeks.

Results

At 48 weeks, a significantly greater proportion of amprenavir/lamivudine/zidovudine subjects had plasma HIV-1 RNA levels <400 copies/ml than lamivudine/ zidovudine subjects in the overall population: 41 versus 3% (intent-to-treat missing equals failure analysis) ( P<0.001); 93 versus 42% (as-treated analysis) ( P<0.001); and within each of the three randomization strata ( P<0.001). Subjects on amprenavir/lamivudine/ zidovudine experienced longer time to event (permanent discontinuation of randomized therapy or viral rebound) than those on lamivudine/ zidovudine (median of 33 versus 13 weeks; P<0.001). A significantly greater incidence of drug-related nausea, vomiting, rash and oral/perioral paresthesia was observed with amprenavir/lamivudine/zidovudine than with lamivudine/zidovudine.

Conclusions

Amprenavir, in combination with lamivudine and zidovudine, has potent and durable antiviral activity in antiretroviral-naive subjects over 48 weeks. Amprenavir was safe and generally well tolerated.