Comparison of T-Cell Subsets' Reconstitution After 12 Months of Highly Active Antiretroviral Therapy Initiated During Early Versus Advanced States of HIV Disease:

Discordance of Aqueous/Plasma HIV Replication on ART

BACKGROUND

The study was conducted to analyze HIV dynamics across blood-retinal barrier (BRB) and the relevant risk factors for HIV-associated ocular complications.

METHODS

This study included a case series of 40 HIV-positive patients with ocular lesions, which were studied retrospectively. Clinical and laboratory examinations included plasma and intraocular viral load (VL).

RESULTS

HIV VL on paired aqueous/plasma samples was available for 40 patients. Aqueous VL was negatively associated with antiretroviral treatment (ART) duration (p = 0.02 and p < 0.05), and plasma VL was independent of ART duration (p = 0.53). An aqueous/plasma discordance was found in 19/40 (47.5%) patients, eight of whom (20%) had detectable aqueous VL despite a suppressed plasma VL (escape). There were significant differences in CD4+ T-lymphocyte levels (p = 0.011 and p < 0.05) and ART duration (p = 0.007 and p < 0.05) between the patients with HIV-associated ocular complications and the patients without.

CONCLUSION

This study provides a rationale for initiating ART early in the course of infection to reduce HIV VL in the aqueous humor, and raises the possibility of the ocular sanctuary where HIV replicates. Meanwhile, early and standard ART would be an optimal option to protect against ocular opportunistic infection.

Impact of HIV on CD8+ T cell CD57 expression is distinct from that of CMV and aging

Background

Chronic antigenic stimulation by cytomegalovirus (CMV) is thought to increase “immunosenesence” of aging, characterized by accumulation of terminally differentiated CD28- CD8+ T cells and increased CD57, a marker of proliferative history. Whether chronic HIV infection causes similar effects is currently unclear.

Methods

We compared markers of CD8+ T cell differentiation (e.g., CD28, CD27, CCR7, CD45RA) and CD57 expression on CD28- CD8+ T cells in healthy HIV-uninfected adults with and without CMV infection and in both untreated and antiretroviral therapy (ART)-suppressed HIV-infected adults with asymptomatic CMV infection.

Results

Compared to HIV-uninfected adults without CMV (n = 12), those with asymptomatic CMV infection (n = 31) had a higher proportion of CD28-CD8+ T cells expressing CD57 (P = 0.005). Older age was also associated with greater proportions of CD28-CD8+ T cells expressing CD57 (rho: 0.47, P = 0.007). In contrast, untreated HIV-infected CMV+ participants (n = 55) had much lower proportions of CD28- CD8+ cells expressing CD57 than HIV-uninfected CMV+ participants (P<0.0001) and were enriched for less well-differentiated CD28- transitional memory (T_TR) CD8+ T cells (P<0.0001). Chronically HIV-infected adults maintaining ART-mediated viral suppression (n = 96) had higher proportions of CD28-CD8+ T cells expressing CD57 than untreated patients (P<0.0001), but continued to have significantly lower levels than HIV-uninfected controls (P = 0.001). Among 45 HIV-infected individuals initiating their first ART regimen, the proportion of CD28-CD8+ T cells expressing CD57 declined (P<0.0001), which correlated with a decline in percent of transitional memory CD8+ T cells, and appeared to be largely explained by a decline in CD28-CD57- CD8+ T cell counts rather than an expansion of CD28-CD57+ CD8+ T cell counts.

Conclusions

Unlike CMV and aging, which are associated with terminal differentiation and proliferation of effector memory CD8+ T cells, HIV inhibits this process, expanding less well-differentiated CD28- CD8+ T cells and decreasing the proportion of CD28- CD8+ T cells that express CD57.

CD4(+) T-cell depletion in HIV infection: mechanisms of immunological failure

The hallmark of acquired immunodeficiency syndrome (AIDS) pathogenesis is a progressive depletion of CD4(+) T-cell populations in close association with progressive impairment of cellular immunity and increasing susceptibility to opportunistic infections (OI). Disease progression in untreated human immunodeficiency virus (HIV) infection can take many years, and it was originally hypothesized to be a consequence of slow, viral-mediated CD4(+) T-cell destruction. However, massive CD4(+) memory T-cell destruction is now known to occur quite early in infection, almost always without overt immunodeficiency. In most individuals, this initial destruction is countered by CD4(+) memory T-cell regeneration that preserves CD4(+) T-cell numbers and functions above the threshold associated with overt immunodeficiency. This regeneration, which occurs in the setting of chronic immune activation and immune dysregulation does not, however, restore all functionally important CD4(+) T-cell populations and is not stable over the long term. Ultimately, CD4(+) memory T-cell homeostasis fails and critical effector populations decline below the level necessary to prevent OI. Thus, the onset of overt immune deficiency appears to be intimately linked with CD4(+) memory T-cell dynamics and reflects the complex interplay of direct viral cytopathogenicity and the indirect effects of persistent immune activation on CD4(+) memory T-cell proliferation, differentiation, and survival.

Lower CD4+ T lymphocyte nadirs may indicate limited immune reconstitution in HIV-1 infected individuals on potent antiretroviral therapy: analysis of immunophenotypic marker results of AACTG 5067

BACKGROUND

Although initiation of potent antiretroviral therapy (ART) has significantly improved immune perturbations in individuals with AIDS, it is unclear which factors are most important in determining the degree of immune reconstitution.

METHODS

Whole blood was analyzed at baseline and week 12 in six groups of subjects (n = 81): those with acute or following immune reconstitution after Pneumocystis jirovecii (previously known as Pneumocystis carinii) pneumonia (PcP) (two groups) and cytomegalovirus (CMV) retinitis (two groups), HIV-infection without AIDS (one group), and healthy volunteers (one group). Absolute CD4+ and CD8+ T lymphocytes, naive (CD45RA+) and memory (CD45RO+) CD4+ T lymphocytes and percentages of activated CD8+ T lymphocytes (CD8+/CD38+/HLA-DR), and CD28 expression on CD4+ and CD8+ T lymphocytes were enumerated.

RESULTS

The reconstituted CMV group, which had a history of a lower CD4+ T lymphocyte nadir compared to the reconstituted PcP group (15 cells/mm(3) versus 48 cells/mm(3); p = .013), had significantly lower absolute CD4+, CD8+ and naive CD4+ T lymphocytes and a trend toward lower memory CD4+ T lymphocytes compared to the reconstituted PcP group. Moreover, no difference was noted between the reconstituted groups in the proportion of subjects with undetected HIV-1 RNA. The reconstituted subjects had significantly lower absolute CD4+, memory CD4+ and naive CD4+ T lymphocytes than the HIV-positive controls and a significantly higher percentage of activated CD8+ T lymphocytes with a lower percentage of CD8+CD28 expression than the HIV-negative controls.

CONCLUSION

The association of CD4+ T lymphocyte nadir with the extent of immune reconstitution in HIV-infected individuals suggests that HIV-1 may cause irreparable immune system damage despite potent ART.

Differential Upregulation of CD38 on Different T-Cell Subsets May Influence the Ability to Reconstitute CD4+ T Cells Under Successful Highly Active Antiretroviral Therapy

BACKGROUND

Immune activation is an independent surrogate marker of CD4 T-cell depletion in HIV-infected patients. Highly active antiretroviral therapy (HAART) reduces disease progression as a direct consequence of suppressing HIV replication. Immune function does not normalize completely in most subjects on HAART, however, perhaps reflecting residual HIV replication. So far, it is unclear to what extent immune activation may influence the evolution of CD4 T-cell counts in patients on HAART.

PATIENTS AND METHODS

The expression of CD38 on naive and memory subsets of CD4+ and CD8+ T cells was measured quantitatively by flow cytometry in 62 drug-naive HIV-positive and 30 HIV-uninfected controls. In addition, the evolution of this marker as well as that of some virologic parameters (plasma viremia and proviral load) and CD4 counts were assessed in 25 HIV-infected individuals who initiated HAART and were followed for 12 months.

RESULTS

The mean level of CD38 on memory CD4+ and CD8+ T cells as well as in naive CD8+ cells was significantly higher in drug-naive HIV-positive subjects than in HIV-negative controls. Moreover, it was highly correlated with viral load titers. In patients on successful HAART, immune activation declined in all T-cell subsets, particularly among memory CD8+ cells. It remained elevated with respect to HIV-negative controls, however, even after 12 months of HAART. There was a significant correlation between the CD8+ T-cell activation decay and the increase of CD4+ T cells on HAART. Patients with the highest decline in CD8 activation were those showing the highest CD4 T-cell gains after 12 months of therapy.

CONCLUSIONS

The level of CD38 expression on different T-cell subsets is differentially upregulated in drug-naive HIV-infected patients. After successful HAART, immune activation decreases in all T-cell subsets, although it still remains elevated in most cases after 12 months of HAART. The extent of immune deactivation under successful HAART correlates with the ability to reconstitute CD4 counts.

Memory responses in human immunodeficiency virus type 1-infected individuals with long-term viral load suppression are independent of CD4 cell nadir

The persistence of memory responses in suppressive highly active antiretroviral therapy (HAART) has been an area of controversy. By using a previously described proliferation assay that augments specific responses, peripheral blood lymphocytes (PBL) from 61 human immunodeficiency virus type 1-seropositive individuals with CD4 counts of >300/mm3 and suppressed viral burdens were studied for response to p24 antigen as a function of time of viral load suppression on HAART. In the majority of cases, proliferative responses could be measured in PBL from patients with plasma viral load suppression. No differences could be found in proliferative responses from PBL between individuals with a low and those with a high CD4 cell nadir. PBL that did not respond to either Casta antigen or p24 were found to have a higher percentage of naive cells than did PBL that responded well to antigen. These data support the contention that, after long-term viral load suppression, PBL from infected individuals have memory cell populations that can respond to antigenic stimulation under inducible conditions.

Clinical, Virologic, and Immunologic Response to Efavirenz-or Protease Inhibitor???Based Highly Active Antiretroviral Therapy in a Cohort of Antiretroviral-Naive Patients With Advanced HIV Infection (EfaVIP 2 Study)

OBJECTIVE

To compare the clinical, immunologic, and virologic outcomes of efavirenz (EFV)-based versus protease inhibitor (PI)-based highly active antiretroviral therapy (HAART) in severely immunosuppressed HIV-1-infected patients.

DESIGN

Retrospective observational cohort study.

METHODS

Responses were analyzed according to the intent-to-treat principle among antiretroviral-naive patients with < 100 CD4 cells/muL who started EFV (n = 92) or a PI (n = 218) plus 2 nucleoside reverse transcriptase inhibitors. The primary end point was time to treatment failure. Secondary end points were percentage of patients with a viral load < 400 copies/mL, time to virologic failure, time to CD4 lymphocyte count > 200 cells/microL, and incidence of opportunistic events or death.

RESULTS

The median baseline CD4 cell count and viral load were 34 cells/microL and 5.54 log10 copies/mL (EFV group) and 38 cells/microL and 5.40 log10 copies/mL (PI group). Time to treatment failure was shorter with a PI-based regimen than with an EFV-based regimen (adjusted relative hazard [RH] = 2.19, 95% confidence interval [CI]: 1.23-3.89). After 12 months of therapy, a significantly higher proportion of patients receiving EFV reached a viral load < 400 copies/mL (69.4 vs. 45.1%; P < 0.05). The probability of virologic failure was higher with a PI than with EFV (adjusted HR = 2.52, 95% CI: 1.14-5.61; P = 0.024). There was no difference in time to CD4 cell count > 200 cells/microL or in incidence of opportunistic events or death.

CONCLUSION

: In severely immunosuppressed, antiretroviral-naive, HIV-1-infected patients, treatment with an EFV-based regimen compared with a nonboosted PI-based regimen resulted in a superior virologic response with no difference in immunologic or clinical effectiveness.

Endothelial function in HIV-infected patients receiving protease inhibitor therapy: does immune competence affect cardiovascular risk?

BACKGROUND

The use of HIV protease inhibitors (PIs) as a component of combination antiretroviral therapy in HIV-infected patients has been associated with dyslipidaemia, but its significance as a risk factor for cardiovascular disease is unclear. Endothelial dysfunction is an early phase of atherogenesis that may be assessed non-invasively with ultrasonography in vivo.

AIM

To evaluate vascular function and investigate potential determinants of endothelial dysfunction of the peripheral circulation in PI-treated, HIV-infected men with dyslipidaemia.

DESIGN

Observational, case-control study.

METHODS

We studied 24 HIV-infected, PI-treated men with dyslipidaemia and 24 normolipidaemic, healthy male controls matched for age and body mass index. Brachial artery endothelial function was studied using high-resolution ultrasound and computerized edge-detection software. This non-invasive technique measured post-ischaemic flow-mediated dilatation (FMD), and the endothelium-independent vasodilatory response to glyceryl trinitrate (GTN).

RESULTS

Within the HIV patient group, FMD was significantly associated with percentage of 'naïve' CD4 + 45RA + T cells (p = 0.03), while plasma lipid/lipoprotein and insulin levels, body mass, and smoking status did not correlate with endothelial function. FMD was not significantly different between the study group and the controls.

CONCLUSIONS

The atherogenic potential of PI-associated dyslipidaemia may be attenuated in HIV-infected patients with decreased immune competence, reflecting a possible contribution of cell-mediated immune responses to the pathogenesis of atherosclerosis.

Nadir CD4+ T-cell count and numbers of CD28+ CD4+ T-cells predict functional responses to immunizations in chronic HIV-1 infection

OBJECTIVE

To ascertain whether delaying the initiation of highly active antiretroviral therapy (HAART) compromises functional immune reconstitution in HIV-1 infection in persons who regain 'normal' CD4 T-cell counts after suppressive antiretroviral therapies.

DESIGN

Prospective open-label study carried out at two University-affiliated HIV-outpatient clinics in the USA.

SUBJECTS AND METHODS

Response to immunization was used as a model for in vivo functional immune competence in 29 HIV-1 infected patients with CD4 T-cell counts > 450 x 106 cells/l and HIV-RNA < 400 copies/ml for > 12 months after HAART and nine HIV-1 seronegative controls. After immunization with tetanus toxoid, diphtheria-toxoid, and keyhole limpet hemocyanin, immune response scores (IRS) were calculated using postimmunization antibody concentrations, lymphocyte proliferation, and delayed-type hypersensitivity responses to vaccine antigens.

RESULTS

Despite normal numbers of circulating CD4 T-cells, the CD4 T-cell nadir before HAART initiation predicted the immune response to immunization (rho = 0.5; P < 0.005) while current CD4 T-cell count did not. Likewise, CD4 T-lymphocyte expression of the co-stimulatory molecule CD28 was also an independent predictor of response to immunization (rho = 0.5; P < 0.005).

CONCLUSIONS

Even among persons who controlled HIV replication and normalized CD4 T-cell counts with HAART, pretreatment CD4 T-cell count and numbers of circulating CD4+CD28+ T-cells at immunization, but not current CD4 T-cell count, predict the ability to respond to vaccination. Delaying the initiation of HAART in chronic HIV-1 infection results in impaired functional immune restoration despite normalization of circulating CD4 T-cell numbers.

Antigen-presenting cell modulation induces a memory response to p24 in peripheral blood leukocytes from human immunodeficiency virus-infected individuals

The accurate determination of human immunodeficiency virus type 1 (HIV-1)-specific proliferative responses is critically important when evaluating immune recovery after highly active antiretroviral therapy. Using a new assay to enhance proliferative responses to recall and HIV antigen, we addressed the questions of whether viral load affects cellular immunity and whether long-term viral load suppression results in loss of antigen-specific responder cells. This assay is based on the fact that lipopolysaccharide (LPS) can augment proliferative responses to antigen after monocyte adherence to a tissue culture plate. Twenty-six HIV-1-infected individuals donated peripheral blood leukocytes (PBL). Proliferation assays against p24, using LPS and cell adherence, were performed on all samples. Medical record abstraction provided information on CD4 cell nadir and time of viral load suppression. PBL from HIV-1-infected individuals with a viral load of <200 copies/ml had a significant proliferative response and a stimulation index of >5 to p24 (12 of 15) compared to those with a viral burden (2 of 11), using the LPS-adherence assay. Proliferative responses to p24 could be found in PBL from virally suppressed donors independent of the CD4 cell nadirs and in the majority of the donors who were virally suppressed for >10 months (7 of 10). The data presented here demonstrate that LPS and monocyte adherence provide a sensitive and specific way to boost proliferative responses to recall and HIV antigens.

CD4+ T-lymphocyte nadir and the effect of highly active antiretroviral therapy on phenotypic and functional immune restoration in HIV-1 infection

To evaluate the effects of the timing of highly active antiretroviral therapy (HAART) on immune reconstitution, we compared lymphocyte subpopulations and lymphocyte proliferation (LP) in response to Candida albicans, cytomegalovirus, HIV p24, Mycobacterium avium complex, pokeweed mitogen, streptokinase, and tetanus toxoid in 43 patients with pretherapy advanced, moderately advanced, and early chronic HIV-1 infection. All patients had recent CD4+ T-cell counts >450/microl and HIV RNA <400 copies/ml for >12 months. CD4+ nadirs were positively correlated with recent numbers of CD4+ T-cells (P < 0.001), memory cells (P < 0.001), and naïve CD4+ T-cells (P < 0.05) and CD4+ CD28+ T-lymphocytes (P < 0.05) and were negatively correlated with recent CD8+ T-lymphocyte counts (P < 0.05). Only CD4+ naïve T-cells normalized when HAART was initiated at lower CD4+ T-cell levels. Fifty-three percent of patients had LP responses to HIV p24 antigen. While LP responses to prevalent antigens were usually present, responses to tetanus toxoid were more common with higher CD4+ T-lymphocyte nadirs (P < 0.05). Delaying HAART may limit phenotypic and functional immune restoration in HIV-1 infection.

Virologic and Immunologic Response to Highly Active Antiretroviral Therapy

Highly active antiretroviral therapy (HAART) delays clinical progression to AIDS by suppressing viral replication, allowing the immune system to reconstitute. These virologic and immunologic consequences do not occur uniformly among HAART users; markers of HIV disease stage at the time of HAART initiation are critical determinants of the progression while under HAART. In this paper, we review studies describing the heterogeneous virologic and immunologic progression following the initiation of HAART, and update findings obtained in the Multicenter AIDS Cohort Study that show that CD4 cell count and history of antiretroviral therapy at the time of initiation are independent determinants of response.

The virological and immunological consequences of structured treatment interruptions in chronic HIV-1 infection

BACKGROUND

Some individuals with chronic HIV-1 infection have discontinued their drug therapy with consequent plasma virus rebound. In a small number of patients, a delayed or absent rebound in plasma virus load has been noted after drug cessation, apparently associated with prior drug interruptions and autologous boosting of HIV-1 specific immune responses. We hypothesized that cyclic structured treatment interruptions structured treatment interruptions (STI) could augment HIV-1 specific immune responses in chronic HIV-1 infection, which might help to control HIV-1 replication off therapy.

METHODS

We initiated an STI pilot study in 10 antiretroviral treatment-naive HIV-1 chronically infected subjects with baseline CD4 T-cell counts > 500 x 10(6) cells/l and plasma viral load > 5000 copies/ml who received highly active antiretroviral therapy (HAART) for 1 year with good response (plasma viral load < 20 copies/ml for at least 32 weeks). Three cycles of HAART interruption were performed.

RESULTS

In all of the patients viral load rebounded, but doubling times increased significantly between the first and third stops (P = 0.008), and by the third stop, six out of nine subjects had a virological set-point after a median 12 months off therapy that was lower than baseline before starting HAART (ranging from 0.6 log(10) to 1.3 log(10) lower than baseline) and in four it remained stable below 5000 copies/ml. Those subjects who controlled viral replication developed significantly stronger HIV-1 specific cellular immune responses than subjects lacking spontaneous decline (P < 0.05). During viral rebounds no genotypic or phenotypic changes conferring resistance to reverse trancriptase inhibitors or protease inhibitors was detected, but mean absolute CD4 T-cell counts declined significantly, although never below 450 x 10(6)/l and the mean value at 12 months off therapy was significantly higher than the pre-treatment level (P = 0.004).

CONCLUSIONS

Our findings suggest that STI in chronic HIV-1 infection might augment HIV-1-specific cellular immune responses associated with a spontaneous and sustained drop in plasma viral load in some subjects but at the potential cost of lower CD4 T-cell counts.