The absence of CD4+ T cell count recovery despite receipt of virologically suppressive highly active antiretroviral therapy: clinical risk, immunological gaps, and therapeutic options

No pol mutation is associated independently with the lack of immune recovery in patients infected with HIV and failing antiretroviral therapy

An investigation was undertaken to determine whether specific pol mutations hinder long-term immune recovery regardless of virological response. In total, 826 patients with >50 HIV RNA copies/ml, who underwent genotypic resistance testing between 1 January 2000 and 31 December 2003 after >3 years of antiretroviral treatment, and were followed up for >3 years after genotypic resistance testing, were analyzed retrospectively. The outcome of the study was the lack of immune recovery after >3 years of follow-up, defined as a slope by linear regression <0. The viremia detectability ratio was defined as the number of HIV RNA values of >50 copies/ml divided by the number of HIV RNA measurements during follow-up. Logistic regression was used for univariable and multivariable analysis. Median (Q1, Q3) values at baseline were the following: age 40 (37, 45) years, years on antiretroviral therapy 4.45 (3.65, 5.47), HIV RNA 3.91 (3.39, 4.53) log(10) copies/ml, CD4+ T-cell 358 (211, 524)/µl. After 3.13 years of follow-up, 375 patients (45.4%) showed a lack of immune recovery. The risk of lack of immune recovery increased independently with increasing baseline CD4+ counts (OR=1.104 per 50-cell increase, 95% CI=1.069-1.142, P<0.0001), increasing viremia detectability ratio during follow-up (OR=1.145 per 0.1-unit increase, 95% CI=1.093-1.202, P<0.0001), and with earlier calendar years of resistance testing (overall effect: P=0.0007). In conclusion, no pol mutation is associated independently with the lack of immune recovery.

Long-term CD4+ lymphocyte response following HAART initiation in a U.S. Military prospective cohort

Background

Among HIV-infected persons initiating highly active antiretroviral therapy (HAART), early CD4+ lymphocyte count increases are well described. However, whether CD4+ levels continue to increase or plateau after 4-6 years is controversial.

Methods

To address this question and identify other determinants of CD4+ response, we analyzed data for 1,846 persons from a prospective HIV military cohort study who initiated HAART, who had post-HAART CD4+ measurements, and for whom HIV seroconversion (SC) date was estimated.

Results

CD4+ count at HAART initiation was ≤ 200 cells/mm³ for 23%, 201-349 for 31%, 350-499 for 27%, and ≥500 for 19%. The first 6 months post-HAART, the greatest CD4+ increases (93-151 cells) occurred, with lesser increases (22-36 cells/year) through the first four years. Although CD4+ changes for the entire cohort were relatively flat thereafter, HIV viral load (VL) suppressors showed continued increases of 12-16 cells/year. In multivariate analysis adjusting for baseline CD4+ and post-HAART time interval, CD4+ responses were poorer in those with: longer time from HIV SC to HAART start, lower pre-HAART CD4+ nadir, higher pre-HAART VL, and clinical AIDS before HAART (P < 0.05).

Conclusions

Small but positive long-term increases in CD4+ count in virally suppressed patients were observed. CD4+ response to HAART is influenced by multiple factors including duration of preceding HIV infection, and optimized if treatment is started with virally suppressive therapy as early as possible.

Increased bone marrow interleukin-7 (IL-7)/IL-7R levels but reduced IL-7 responsiveness in HIV-positive patients lacking CD4+ gain on antiviral therapy

BACKGROUND

The bone marrow (BM) cytokine milieu might substantially affect T-lymphocyte homeostasis in HIV-positive individuals. Interleukin-7 (IL-7) is a bone marrow-derived cytokine regulating T-cell homeostasis through a CD4+-driven feedback loop. CD4+ T-lymphopenia is associated with increased free IL-7 levels and reduced IL-7R expression/function, which are only partially reverted by highly active antiretroviral therapy (HAART). We investigated the BM production, peripheral expression and signaling (pStat5+ and Bcl-2+ CD4+/CD8+ T cells) of IL-7/IL-7Rα in 30 HAART-treated HIV-positive patients who did not experience CD4+ recovery (CD4+ ≤200/µl) and who had different levels of HIV viremia; these patients included 18 immunological nonresponders (INRs; HIV-RNA≤50), 12 complete failures (CFs; HIV-RNA>1000), and 23 HIV-seronegative subjects.

METHODS

We studied plasma IL-7 levels, IL-7Rα+CD4+/CD8+ T-cell proportions, IL-7Rα mRNA expression in PBMCs, spontaneous IL-7 production by BM mononuclear cells (BMMCs), and IL-7 mRNA/IL-7Rα mRNA in BMMC-derived stromal cells (SCs). We also studied T-cell responsiveness to IL-7 by measuring the proportions of pStat5+ and Bcl-2+ CD4+/CD8+ T cells.

RESULTS

Compared to HIV-seronegative controls, CFs and INRs presented elevated plasma IL-7 levels and lower IL-7Rα CD4+/CD8+ cell-surface expression and peripheral blood production, confirming the most relevant IL-7/IL-7R disruption. Interestingly, BM investigation revealed a trend of higher spontaneous IL-7 production in INRs (p = .09 vs. CFs) with a nonsignificant trend toward higher IL-7-Rα mRNA levels in BMMC-derived stromal cells. However, upon IL-7 stimulation, the proportion of pStat5+CD4+ T cells did not increase in INRs despite higher constitutive levels (p = .06); INRs also displayed lower Bcl-2+CD8+ T-cell proportions than controls (p = .04).

CONCLUSIONS

Despite severe CD4+ T-lymphopenia and a disrupted IL-7/IL-7R profile in the periphery, INRs display elevated BM IL-7/IL-7Rα expression but impaired T-cell responsiveness to IL-7, suggesting the activity of a central compensatory pathway targeted to replenish the CD4+ compartment, which is nevertheless inappropriate to compensate the dysfunctional signaling through IL-7 receptor.

Qualitative immune modulation by interleukin-2 (IL-2) adjuvant therapy in immunological non responder HIV-infected patients

Background

Treatment of HIV-infected patients with interleukin-2 (IL-2) produces significant increases in CD4 T cell counts; however an associated qualitative improvement in cells function has yet to be conclusively demonstrated. By measuring mycobacterial killing activity, we evaluated IL-2-mediated functional immune enhancement ex vivo in immunological non-responders (INRs).

Methods and Findings

PBMC from 12 immunological non-responders (INRs) (CD4+<200/µl, HIV-RNA<50 cp/ml) on combination antiretroviral treatment (cART) were collected at baseline, and after 3 IL-2 cycles. Eight INRs receiving only cART were studied as controls. After 21 days of PBMC incubation with a virulent M. avium suspension, counts of residual colony forming units (CFUs) and concentrations of TNF-α, IL-10 and IFN-γ were determined. In IL-2 treated patients, a significant reduction in mean residual CFUs of PBMC cultures was observed (p<0.01). Moreover, following IL-2 treatment, significant increases in PBMC's IFNγ production (p = 0.02) and substantial reductions in IL-10 levels were observed.

Conclusions

IL-2 therapy restores the ability of the lympho-monocyte system in eliciting an effective response against mycobacterial infections. Our data indicate the possibility of a clinical role held by IL-2 in enhancing the immune function of subjects unable to achieve immune competence through cART alone.

Long-term mortality in HIV patients virally suppressed for more than three years with incomplete CD4 recovery: a cohort study

BACKGROUND

The mortality in patients with persistent low CD4 count despite several years of HAART with sustained viral suppression is poorly documented. We aimed to identify predictors for inadequate CD4 cell recovery and estimate mortality in patients with low CD4 count but otherwise successful HAART.

METHOD

In a nationwide cohort of HIV patients we identified all individuals who started HAART before 1 January 2005 with CD4 cell count ≤ 200 cells/μL and experienced three years with sustained viral suppression. Patients were categorized according to CD4 cell count after the three years suppressed period (≤ 200 cells/μL; immunological non-responders (INRs), >200 cells/μL; immunological responders (IRs)). We used logistic regression and Kaplan-Meier analysis to estimated risk factors and mortality for INRs compared to IRs.

RESULTS

We identified 55 INRs and 236 IRs. In adjusted analysis age > 40 years and > one year from first CD4 cell count ≤ 200 cells/μL to start of the virologically suppressed period were associated with increased risk of INR. INRs had substantially higher mortality compared to IRs. The excess mortality was mainly seen in the INR group with > one year of immunological suppression prior to viral suppression and injection drug users (IDUs).

CONCLUSION

Age and prolonged periods of immune deficiency prior to successful HAART are risk factors for incomplete CD4 cell recovery. INRs have substantially increased long-term mortality mainly associated with prolonged immunological suppression prior to viral suppression and IDU.

Low postseroconversion CD4 count and rapid decrease of CD4 density identify HIV+ fast progressors

CD4 expression in HIV replication is paradoxical: HIV entry requires high cell-surface CD4 densities, but replication requires CD4 down-modulation. However, is CD4 density in HIV+ patients affected over time? Do changes in CD4 density correlate with disease progression? Here, we examined the role of CD4 density for HIV disease progression by longitudinally quantifying CD4 densities on CD4+ T cells and monocytes of ART-naive HIV+ patients with different disease progression rates. This was a retrospective study. We defined three groups of HIV+ patients by their rate of CD4+ T cell loss, calculated by the time between infection and reaching a CD4 level of 200 cells/microl: fast (<7.5 years), intermediate (7.5-12 years), and slow progressors (>12 years). Mathematical modeling permitted us to determine the maximum CD4+ T cell count after HIV seroconversion (defined as "postseroconversion CD4 count") and longitudinal profiles of CD4 count and density. CD4 densities were quantified on CD4+ T cells and monocytes from these patients and from healthy individuals by flow cytometry. Fast progressors had significantly lower postseroconversion CD4 counts than other progressors. CD4 density on T cells was lower in HIV+ patients than in healthy individuals and decreased more rapidly in fast than in slow progressors. Antiretroviral therapy (ART) did not normalize CD4 density. Thus, postseroconversion CD4 counts define individual HIV disease progression rates that may help to identify patients who might benefit most from early ART. Early discrimination of slow and fast progressors suggests that critical events during primary infection define long-term outcome. A more rapid CD4 density decrease in fast progressors might contribute to progressive functional impairments of the immune response in advanced HIV infection. The lack of an effect of ART on CD4 density implies a persistent dysfunctional immune response by uncontrolled HIV infection.

Randomized, controlled clinical trial of zinc supplementation to prevent immunological failure in HIV-infected adults

BACKGROUND

Adequate zinc is critical for immune function; however, zinc deficiency occurs in >50% of human immunodeficiency virus (HIV)-infected adults. We examined the safety and efficacy of long-term zinc supplementation in relation to HIV disease progression.

METHODS

A prospective, randomized, controlled clinical trial was conducted involving 231 HIV-infected adults with low plasma zinc levels (<0.75 mg/L), who were randomly assigned to receive zinc (12 mg of elemental zinc for women and 15 mg for men) or placebo for 18 months. The primary end point was immunological failure. HIV viral load and CD4(+) cell count were determined every 6 months. Questionnaires, pill counts, and plasma zinc and C-reactive protein levels were used to monitor adherence to study supplements and antiretroviral therapy. Intent-to-treat analysis used multiple-event analysis, treating CD4(+) cell count <200 cells/mm(3) as a recurrent immunological failure event. Cox proportional hazard models and the general-linear model were used to analyze morbidity and mortality data.

RESULTS

Zinc supplementation for 18 months reduced 4-fold the likelihood of immunological failure, controlling for age, sex, food insecurity, baseline CD4(+) cell count, viral load, and antiretroviral therapy (relative rate, 0.24; 95% confidence interval, 0.10-0.56; P<.002). Viral load indicated poor control with antiretroviral therapy but was not affected by zinc supplementation. Zinc supplementation also reduced the rate of diarrhea by more than half (odds ratio, 0.4; 95% confidence interval, 0.183-0.981; P=.019), compared with placebo. There was no significant difference in mortality between the 2 groups.

CONCLUSIONS

This study demonstrated that long-term (18-month) zinc supplementation at nutritional levels delayed immunological failure and decreased diarrhea over time. This evidence supports the use of zinc supplementation as an adjunct therapy for HIV-infected adult cohorts with poor viral control. Trial registration. ClinicalTrials.gov identifier: NCT00149552.

Effect of baseline HIV disease parameters on CD4+ T cell recovery after antiretroviral therapy initiation in Kenyan women

BACKGROUND

Antiretroviral therapy (ART) for HIV infection reconstitutes the immune system and improves survival. However, the rate and extent of CD4+ T cell recovery varies widely. We assessed the impact of several factors on immune reconstitution in a large Kenyan cohort.

METHODOLOGY/PRINCIPAL FINDINGS

HIV-infected female sex workers from a longitudinal cohort, with at least 1 year of pre-ART and 6 months of post-ART follow-up (n = 79), were enrolled in the current study. The median pre-ART follow-up was 4,040 days. CD4 counts were measured biannually and viral loads where available. The median CD4 count at ART initiation was 180 cells/ul, which increased to 339 cells/ul at the most recent study visit. The rate of CD4+ T cell increase on ART was 7.91 cells/month (mean = 13, range -25.92 to 169.4). LTNP status prior to ART initiation did not associate with the rate of CD4 recovery on ART. In univariate analyses, associations were observed for CD4 recovery rate and duration of pre-ART immunosuppression (r = -0.326, p = 0.004) and CD4 nadir (r = 0.284, p = 0.012). In multivariate analysis including age, CD4 nadir, duration of HIV infection, duration of pre-ART immunosuppression, and baseline viral load, only CD4 nadir (p = 0.007) and not duration of immunosuppression (p = 0.87) remained significantly associated with the rate of CD4 recovery.

CONCLUSIONS/SIGNIFICANCE

These data suggest that prior duration of immune suppression does not predict subsequent recovery once ART is initiated and confirm the previous observation that the degree of CD4 depletion prior to ART initiation is the most important determinant of subsequent immune reconstitution.

Micronutrients and HIV infection

The immune system requires several essential micronutrients to maintain an effective immune response. HIV infection destroys the immune system and promotes nutritional deficiencies, which further impair immunity. This article reviews the role of several micronutrients (vitamins A, C, E and D, the B vitamins, and minerals, selenium, iron and zinc) that are relevant for maintaining immune function. In addition, the deficiencies of these micronutrients have been associated with faster progression of HIV-1 disease. This review examines the evidence from observational studies of an association between micronutrient status and HIV disease, as well as the effectiveness of micronutrient supplementation on HIV-disease progression, pregnancy outcomes and nutritional status, among others, utilizing randomized clinical trials. Each micronutrient is introduced with a summary of its functions in human physiology, followed by the presentation of studies conducted in HIV-infected patients in relation to this specific micronutrient. Overall findings and recommendations are then summarized.

Incident tuberculosis during antiretroviral therapy contributes to suboptimal immune reconstitution in a large urban HIV clinic in sub-Saharan Africa

BACKGROUND

Antiretroviral therapy (ART) effectively decreases tuberculosis (TB) incidence long-term, but is associated with high TB incidence rates in the first 6 months. We sought to determine the incidence and the long-term effects of TB during ART on HIV treatment outcome, and the risk factors for incident TB during ART in a large urban HIV clinic in Uganda.

METHODOLOGY/PRINCIPAL FINDINGS

Routinely collected longitudinal clinical data from all patients initiated on first-line ART was retrospectively analysed. 5,982 patients were included with a median baseline CD4+ T cell count (CD4 count) of 117 cells/mm(3) (interquartile range [IQR]; 42, 182). In the first 2 years, there were 336 (5.6%) incident TB events in 10,710 person-years (py) of follow-up (3.14 cases/100 pyar [95% CI 2.82-3.49]); incidence rates at 0-3, 3-6, 6-12 and 12-24 months were 11.25 (9.58-13.21), 6.27 (4.99-7.87), 2.47 (1.87-3.36) and 1.02 (0.80-1.31), respectively. Incident TB during ART was independently associated with baseline CD4 count of <50 cells/mm(3) (hazard ratio [HR] 1.84 [1.25-2.70], P = 0.002) and male gender (HR 1.68 [1.34-2.11], P<0.001). After two years on ART, the patients who had developed TB in the first 12 months had a significantly lower median CD4 count increase (184 cells/mm(3) [IQR; 107, 258, n = 118] vs 209 cells/mm(3) [124, 309, n = 2166], P = 0.01), a larger proportion of suboptimal immune reconstitution according to two definitions (increase in CD4 count <200 cells/mm(3): 57.4% vs 46.9%, P = 0.03, and absolute CD4 count <200 cells/mm(3): 30.4 vs 19.9%, P = 0.006), and a higher percentage of immunological failure according to the WHO criteria (13.6% vs 6.5%, P = 0.003). Incident TB during ART was independently associated with poor CD4 count recovery and fulfilling WHO immunological failure definitions.

CONCLUSIONS/SIGNIFICANCE

Incident TB during ART occurs most often within 3 months and in patients with CD4 counts less than 50 cells/mm(3). Incident TB during ART is associated with long-term impairment in immune recovery.

Gene expression before HAART initiation predicts HIV-infected individuals at risk of poor CD4+ T-cell recovery

OBJECTIVE

To identify a pre-HAART gene expression signature in peripheral blood mononuclear cells (PBMCs) predictive of CD4 T-cell recovery during HAART in HIV-infected individuals.

DESIGN

This retrospective study evaluated PBMC gene expression in 24 recently HIV-infected individuals before the initiation of HAART to identify genes whose expression is predictive of CD4 T-cell recovery after 48 weeks of HAART.

METHODS

The change in CD4 T-cell count (DeltaCD4) over the 48-week study period was calculated for each of the 24 participants. Twelve participants were assigned to the 'good' (DeltaCD4 > or = 200 cells/microl) and 12 to the 'poor' (DeltaCD4 < 200 cells/microl) CD4 T-cell recovery group. Gene expression profiling of the entire transcriptome using Illumina BeadChips was performed with PBMC samples obtained before HAART. Gene expression classifiers capable of predicting CD4 T-cell recovery group (good vs. poor), as well as the specific DeltaCD4 value, at week 48 were constructed using methods of Class Prediction.

RESULTS

The expression of 40 genes in PBMC samples taken before HAART predicted CD4 T-cell recovery group (good vs. poor) at week 48 with 100% accuracy. The expression of 22 genes predicted a specific DeltaCD4 value for each HIV-infected individual that correlated well with actual values (R = 0.82). Predicted DeltaCD4 values were also used to assign individuals to good vs. poor CD4 T-cell recovery groups with 79% accuracy.

CONCLUSION

Gene expression in PBMCs can be used as biomarkers to successfully predict disease outcomes among HIV-infected individuals treated with HAART.

Modelling the association between patient characteristics and the change over time in a disease measure using observational cohort data

In observational cohort studies we may wish to examine the associations between fixed patient characteristics and the longitudinal changes from baseline in a repeated outcome measure. Many biological and other outcome measures are known to be subject to measurement error and biological variation. In an initial analysis we may fit a regression model to all outcome measurements, accounting for all the identified sources of variability, and see how the characteristics are linked to the change for typical patients. However, the characteristics may also be linked to different distributions of the underlying outcome value at baseline, which itself may be correlated with the change over time. Therefore, if we wish to examine the change over time for patients of different characteristics but with the same underlying baseline value then the initial approach is confounded by the baseline values. Furthermore, if we attempt to remove this confounding by including the observed baseline measure as a covariate in a model for later measurements, then this may provide an approximate solution but is likely to introduce some bias. We propose a method based on first following the initial approach but then, applying a correction to the parameter estimates. This allows the predicted trajectories to be plotted and valid significance tests of association with characteristics. Our approach is compared with other methods and illustrated through a simulation study and an analysis of the association between HIV-1 subtype and immunological response after starting antiretroviral therapy.

Role of the CD4 count in HIV management

As a result of successful antiretroviral treatment over the last 20 years, HIV has become more of a chronic disease for practitioners to manage, requiring careful, but routine, clinical monitoring. Laboratory markers, such as the HIV-1 RNA viral load and CD4 cell count, are regularly used for patient management in addition to predicting disease progression and/or treatment outcomes. The HIV viral load is considered to be the gold standard for evaluating treatment success, although it is often limited by the cost. Furthermore, in certain cases, there is a mismatch between an undetectable viral load (<50 copies/ml) and the absence of immune reconstitution, which can be confusing to both the treatment provider and patient. In this review, the utility of the CD4 count as a predictor for HIV disease progression in patients not on therapy is evaluated, as well as a method for monitoring a patient’s response to therapy. Its use in predicting immune reconstitution in patients initiating antiretrovirals is also identified. We hope to aid the clinician by examining the most recent literature and discussing the added value of the CD4 count in the management of a person with HIV infection.

Clinical implications of new findings in HIV basic research

HIV has been studied extensively over the past 25 years. Insights into the different stages of the virus' replication cycle and its interaction with host-cell proteins have led to the development of an armamentarium of effective antiretroviral medications. These antiviral drugs have dramatically changed the prognosis for HIV-infected subjects from an inevitable march towards death to a chronic disease with a potentially normal lifespan. Even with these successes, there is a continuing need to provide new drugs, especially those effective against drug-resistant viruses, to devise optimal strategies to prevent adverse events from either immunosuppression or the antiretroviral medications, and to develop treatments aimed at eliminating virus replication in the absence of antiviral drugs. In this review, how these important issues are being addressed will be highlighted, emphasizing clinical implications from some recent basic science studies and demonstrating how they could change the face of HIV therapeutics over the next 5-10 years.

Recent Publications on Medications and Pharmacy

Hospital Pharmacy presents this feature to keep pharmacists abreast of new publications in the medical/pharmacy literature. Articles of interest regarding a broad scope of topics are abstracted monthly.