Expansion of pre-terminally differentiated CD8 T cells in chronic HIV-positive patients presenting a rapid viral rebound during structured treatment interruption

Clinical trials of antiretroviral treatment interruption in HIV-infected individuals

: Despite the benefits of antiretroviral therapy (ART) for people living with HIV, there has been a long-standing research interest in interrupting ART as a strategy to minimize adverse effects of ART as well as to test interventions aiming to achieve a degree of virological control without ART. We performed a systematic review of HIV clinical studies involving treatment interruption from 2000 to 2017 to describe the differences between treatment interruption in studies that contained and didn't contain an intervention. We assessed differences in monitoring strategies, threshold to restart ART, duration and adverse outcomes of treatment interruption, and factors aimed at minimizing transmission. We found that treatment interruption has been incorporated into 159 clinical studies since 2000 and is increasingly being included in trials to assess the efficacy of interventions to achieve sustained virological remission off ART. Great heterogeneity was noted in immunological, virological and clinical monitoring strategies, as well as in thresholds to recommence ART. Treatment interruption in recent intervention studies were more closely monitored, had more conservative thresholds to restart ART and had a shorter treatment interruption duration, compared with older treatment interruption studies that didn't include an intervention.

An IL-15 Dependent CD8 T Cell Response to Selected HIV Epitopes is Related to Viral Control in Early-Treated HIV-Infected Subjects

In some early-treated HIV+ patients, Structured Treatment Interruption (STI) is associated to spontaneous control of viral rebound. Thus, in this clinical setting, we analyzed the immunological parameters associated to viral control. Two groups of early treated patients who underwent STI were retrospectively defined, according to the ability to spontaneously control HIV replication (Controller and Non-controller). Plasma cytokine levels were analyzed by multiplex analysis. CD8 T cell differentiation was determined by polychromatic flow cytometry. Antigen-specific IFN-Γ production was analyzed by ELISpot and intracellular staining after stimulation with HIV-peptides. Long-term Elispot assays were performed in the presence or absence of IL-15. Plasma IL-15 was found decreased over a period of time in Non-Controller patients, whereas a restricted response to Gag (aa.167–202 and 265–279) and Nef (aa.86–100 and 111–138) immunodominant epitopes was more frequently observed in Controller patients. Interestingly, in two Non-Controller patients the CD8-mediated T cells response to immunodominant epitopes could be restored in vitro by IL-15, suggesting a major role of cytokine homeostasis on the generation of protective immunity. In early-treated HIV+ patients undergoing STI, HIV replication control was associated to CD8 T cell maturation and sustained IL-15 levels, leading to HIV-specific CD8 T cell responses against selected Gag and Nef epitopes.

Poor functional immune recovery in aged HIV-1-infected patients following successfully treatment with antiretroviral therapy

Aging is now a well-recognized characteristic of the HIV-infected population and both AIDS and aging are characterized by a deficiency of the T-cell compartment. The objective of the present study was to evaluate the impact of antiretroviral (ARV) therapy in recovering functional response of T cells to both HIV-1-specific ENV peptides (ENV) and tetanus toxoid (TT), in young and aged AIDS patients who responded to ARV therapy by controlling virus replication and elevating CD4(+) T cell counts. Here, we observed that proliferative response of T-cells to either HIV-1-specific Env peptides or tetanus toxoid (TT) was significantly lower in older antiretroviral (ARV)-treated patients. With regard to cytokine profile, lower levels of IFN-γ, IL-17 and IL-21, associated with elevated IL-10 release, were produced by Env- or TT-stimulated T-cells from older patients. The IL-10 neutralization by anti-IL-10 mAb did not elevate IFN-γ and IL-21 release in older patients. Finally, even after a booster dose of TT, reduced anti-TT IgG titers were quantified in older AIDS patients and it was related to both lower IL-21 and IFN-γ production and reduced frequency of central memory T-cells. Our results reveal that ARV therapy, despite the adequate recovery of CD4(+) T cell counts and suppression of viremia, was less efficient in recovering adequate immune response in older AIDS patients.

The impact of pregnancy on the HIV-1-specific T cell function in infected pregnant women

Evidences indicate that pregnancy can alter the Ag-specific T-cell responses. This work aims to evaluate the impact of pregnancy on the in vitro HIV-1-specific immune response. As compared with non-pregnant patients, lower T-cell proliferation and higher IL-10 production were observed in T-cell cultures from pregnant patients following addition of either mitogens or HIV-1 antigens. In our system, the main T lymphocyte subset involved in producing IL-10 was CD4(+)FoxP3(-). Depletion of CD4(+) cells elevated TNF-α and IFN-γ production. Interestingly, the in vitro HIV-1 replication was lower in cell cultures from pregnant patients, and it was inversely related to IL-10 production. In these cultures, the neutralization of IL-10 by anti-IL-10 mAb elevated TNF-α release and HIV-1 replication. In conclusion, our results reveal that pregnancy-related events should favor the expansion of HIV-1-specific IL-10-secreting CD4(+) T-cells in HIV-1-infected women, which should, in the scenario of pregnancy, help to reduce the risk of vertical HIV-1 transmission.

Breast milk HIV-1 RNA levels and female sex are associated with HIV-1-specific CD8+ T-cell responses in HIV-1-exposed, uninfected infants in Kenya

BACKGROUND

Although evidence supports a relationship between human immunodeficiency virus (HIV)-1 exposure and HIV-1-specific CD8(+) T cell responses, studies have not demonstrated a direct association between the quantity of HIV-1 to which a person is exposed and the presence or absence of a response.

METHODS

From 1999 to 2005, maternal HIV-1 RNA levels were measured in blood, cervical secretions, and breast milk at delivery and 1 month after delivery. HIV-1-specific interferon (IFN)-γ Elispot assays were conducted to determine infant CD8(+) T-cell responses at 3 months of age.

RESULTS

Among 161 infants tested with Elispot assays, 23 (14%) had positive results. Mothers whose infants had a positive assay had higher breast milk HIV-1 RNA levels at month 1 compared with mothers whose infants had negative Elispot assays (3.1 vs 2.5 log(10) copies/mL; P = .017). Female infants were also more likely to have positive Elispot assays than male infants (P = .046), and in multivariate analyses, both female sex and high breast milk HIV-1 levels remained important predictors of a positive response (P = .022 and P = .015, respectively).

CONCLUSIONS

Exposure to breast milk HIV-1 and sex were associated with development of HIV-1-specific CD8(+) T-cell responses in infants. These data support a role for mucosal exposure via the oral route in induction of systemic HIV-1-specific cellular immunity.

Nonlinear observer output-feedback MPC treatment scheduling for HIV

BACKGROUND

Mathematical models of the immune response to the Human Immunodeficiency Virus demonstrate the potential for dynamic schedules of Highly Active Anti-Retroviral Therapy to enhance Cytotoxic Lymphocyte-mediated control of HIV infection.

METHODS

In previous work we have developed a model predictive control (MPC) based method for determining optimal treatment interruption schedules for this purpose. In this paper, we introduce a nonlinear observer for the HIV-immune response system and an integrated output-feedback MPC approach for implementing the treatment interruption scheduling algorithm using the easily available viral load measurements. We use Monte-Carlo approaches to test robustness of the algorithm.

RESULTS

The nonlinear observer shows robust state tracking while preserving state positivity both for continuous and discrete measurements. The integrated output-feedback MPC algorithm stabilizes the desired steady-state. Monte-Carlo testing shows significant robustness to modeling error, with 90% success rates in stabilizing the desired steady-state with 15% variance from nominal on all model parameters.

CONCLUSIONS

The possibility of enhancing immune responsiveness to HIV through dynamic scheduling of treatment is exciting. Output-feedback Model Predictive Control is uniquely well-suited to solutions of these types of problems. The unique constraints of state positivity and very slow sampling are addressable by using a special-purpose nonlinear state estimator, as described in this paper. This shows the possibility of using output-feedback MPC-based algorithms for this purpose.

Zoledronic acid and interleukin-2 treatment improves immunocompetence in HIV-infected persons by activating Vgamma9Vdelta2 T cells

OBJECTIVE

gammadelta T cells bearing the Vgamma9Vdelta2 T-cell receptor exert many antiviral effector functions in humans, including release of anti-HIV factors and direct cytotoxicity against virus-infected cells. Moreover, they are known to activate dendritic cells, improving antigen presentation function. After HIV infection, Vgamma9Vdelta2 T-cell number and reactivity are rapidly affected and they decrease upon disease progression. Bisphosphonate drugs such as zoledronic acid (Zol), used to treat bone diseases, have been shown to induce in vivo, in combination with interleukin-2, Vgamma9Vdelta2 T-cells' activation. The aim of this work was to verify whether the administration of Zol in combination with interleukin-2 in HIV-infected patients might improve Vgamma9Vdelta2 T-cell function, including immune adjuvancy mediated by gammadelta-dendritic cell cross-talk.

DESIGN AND METHODS

In HIV patients naive to antiretroviral therapy, we analyzed the effect of combined Zol and interleukin-2 treatment, in comparison to Zol alone, on Vgamma9Vdelta2 T-cell number, maturation and function, on dendritic cell activation and on HIV-specific CD8 T-cell response.

RESULTS

Zol and interleukin-2-combined treatment induced in-vivo Vgamma9Vdelta2 T-cell expansion and maturation. Paralleling Vgamma9Vdelta2 T-cell activation, increased dendritic cell maturation and HIV-specific CD8 T-cell responses were found.

CONCLUSION

The specific modulation of Vgamma9Vdelta2 T-cell number and responsiveness after HIV infection may be at least transiently restored in vivo by Zol and interleukin-2 treatment. In this way, the immune effector mechanisms, secondary to Vgamma9Vdelta2 T-cell activation, were improved, suggesting a possible adjuvancy role of Zol and interleukin-2 treatment in restoring innate and specific competence in HIV-infected persons.

Response to M. tuberculosis selected RD1 peptides in Ugandan HIV-infected patients with smear positive pulmonary tuberculosis: a pilot study

Background

Tuberculosis (TB) is the most frequent co-infection in HIV-infected individuals still presenting diagnostic difficulties particularly in developing countries. Recently an assay based on IFN-gamma response to M. tuberculosis RD1 peptides selected by computational analysis was developed whose presence is detected during active TB disease. Objective of this study was to investigate the response to selected RD1 peptides in HIV-1-infected subjects with or without active TB in a country endemic for TB and to evaluate the change of this response over time.

Methods

30 HIV-infected individuals were prospectively enrolled, 20 with active TB and 10 without. Among those with TB, 12 were followed over time. IFN-gamma response to selected RD1 peptides was evaluated by enzyme-linked immunospot (ELISPOT) assay. As control, response to RD1 proteins was included. Results were correlated with immune, microbiological and virological data.

Results

Among patients with active TB, 2/20 were excluded from the analysis, one due to cell artifacts and the other to unresponsiveness to M. tuberculosis antigens. Among those analyzable, response to selected RD1 peptides evaluated as spot-forming cells was significantly higher in subjects with active TB compared to those without (p = 0.02). Among the 12 TB patients studied over time a significant decrease (p =< 0.007) of IFN-gamma response was found at completion of therapy when all the sputum cultures for M. tuberculosis were negative. A ratio of RD1 peptides ELISPOT counts over CD4⁺ T-cell counts greater than 0.21 yielded 100% sensitivity and 80% specificity for active TB. Conversely, response to RD1 intact proteins was not statistically different between subjects with or without TB at the time of recruitment; however a ratio of RD1 proteins ELISPOT counts over CD4⁺ T-cell counts greater than 0.22 yielded 89% sensitivity and 70% specificity for active TB.

Conclusion

In this pilot study the response to selected RD1 peptides is associated with TB disease in HIV-infected individuals in a high TB endemic country. This response decreases after successful therapy. The potential of the novel approach of relating ELISPOT spot-forming cell number and CD4⁺ T-cell count may improve the possibility of diagnosing active TB and deserves further evaluation.

Response to region of difference 1 (RD1) epitopes in human immunodeficiency virus (HIV)-infected individuals enrolled with suspected active tuberculosis: a pilot study

Tuberculosis is the most frequent co-infection in human immunodeficiency virus (HIV)-infected individuals, and which still presents diagnostic difficulties. Recently we set up an assay based on interferon (IFN)-gamma response to region of difference 1 (RD1) peptides selected by computational analysis which is associated with active Mycobacterium tuberculosis replication. The objective of this study was to investigate the response to RD1 selected peptides in HIV-1-infected individuals in a clinical setting. The mechanisms of this immune response and comparison with other immune assays were also investigated. A total of 111 HIV-infected individuals with symptoms and signs consistent with active tuberculosis were enrolled prospectively. Interferon (IFN)-gamma responses to RD1 selected peptides and recall antigens were evaluated by enzyme-linked immunospot assay. Results were correlated with CD4(+) T cell counts, individuals' characteristics, tuberculin skin test, QuantiFERON-TB Gold and T-SPOT.TB. Results from 21 (19%) individuals were indeterminate due to in vitro cell anergy. Among 'non-anergic' individuals, sensitivity for active tuberculosis of the assay based on RD1 selected peptides was 67% (24 of 36), specificity was 94% (three of 54). The assay also resulted positive in cases of extra-pulmonary and smear-negative pulmonary active tuberculosis. The response was mediated by CD4(+) effector/memory T cells and correlated with CD4(+) T cell counts, but not with plasma HIV-RNA load. Moreover, the RD1 selected peptides assay had the highest diagnostic odds ratio for active tuberculosis compared to tuberculin skin test (TST), QuantiFERON-TB Gold and T-SPOT.TB. RD1 selected peptides assay is associated with M. tuberculosis replication in HIV-infected individuals, although T cell anergy remains an important obstacle to be overcome before the test can be proposed as a diagnostic tool.

Immunological and virological effects of structured treatment interruptions following exposure to hydroxyurea plus didanosine

Both hydroxyurea (HU) and structured treatment interruptions (STI) have been investigated as therapeutic approaches to enhance immune responses in chronically HIV-infected individuals. HIV-specific T cell responses as well as T cell activation were analyzed longitudinally in 31 HIV-infected individuals who had been treated for the prior 12 months with didanosine (ddI) plus HU and thereafter completed three STI cycles consisting of 2 months off and 2 months on ddI-HU. Similar increases in plasma HIV-RNA were seen in each of the three cycles off therapy, whereas CD4 counts remained fairly stable along the study period. T cell activation paralleled the evolution of plasma HIV-RNA during the first STI cycle and waned afterward. At baseline most patients presented a high level of CD8+ responses to different HIV peptide pools and 23% of them had CD4+ responses to Gag and/or Env. The level of CD8+ responses against each pool was stable and did not increase during STI cycles, while CD4 responses tended to decline. However, the contribution of Nef-specific response to the total CD8 response tended to increase. In a multivariate model, both a higher baseline plasma HIV-RNA and a higher level of Nef-specific response contribution to the total CD8+ response were independently associated with lower plasma HIV-RNA increases during each of the three STI cycles. Nef-specific CD8+ responses might contribute to a better virological control of HIV replication following treatment interruptions in HIV-infected individuals and might be boosted by the immunomodulatory effect of HU.

Structured treatment interruptions with tenofovir monotherapy for simian immunodeficiency virus-infected newborn macaques

We demonstrated previously that prolonged tenofovir treatment of infant macaques, starting early during infection with virulent simian immunodeficiency virus (SIVmac251), can lead to persistently low or undetectable viremia even after the emergence of mutants with reduced in vitro susceptibility to tenofovir as a result of a K65R mutation in reverse transcriptase; this control of viremia was demonstrated to be mediated by the generation of effective antiviral immune responses. To determine whether structured treatment interruptions (STI) can induce similar immunologic control of viremia, eight newborn macaques were infected with highly virulent SIVmac251 and started on a tenofovir STI regimen 5 days later. Treatment was withdrawn permanently at 33 weeks of age. All animals receiving STI fared much better than 22 untreated SIVmac251-infected infant macaques. However, there was a high variability among animals in the viral RNA set point after complete drug withdrawal, and none of the animals was able to achieve long-term immunologic suppression of viremia to persistently low levels. Early immunologic and viral markers in blood (including the detection of the K65R mutation) were not predictive of the viral RNA set point after drug withdrawal. These results, which reflect the complex interactions between drug resistance mutations, viral virulence, and drug- and immune-mediated inhibition of virus replication, highlight the difficulties associated with trying to develop STI regimens with predictable efficacy for clinical practice.

CD4-guided structured antiretroviral treatment interruption strategy in HIV-infected adults in west Africa (Trivacan ANRS 1269 trial): a randomised trial

BACKGROUND

Structured treatment interruptions of highly-active antiretroviral therapy (HAART) might be particularly relevant for sub-Saharan Africa, where cost-saving strategies could help to increase the number of patients on HAART. We did a randomised trial of structured treatment interruption in Abidjan, Côte d'Ivoire.

METHODS

HIV-infected adults were randomised to receive continuous HAART (CT), CD4-guided HAART (CD4GT) with interruption and reintroduction thresholds at 350 and 250 cells per mm3, respectively, or 2-months-off, 4-months-on HAART. Primary endpoints were death and severe morbidity (any WHO stage 3 or 4 events and any events leading to death) at month 24. We report data from the CT and CD4GT groups until Oct 31, 2005, when the data safety monitoring board recommended to prematurely stop the CD4GT arm. Analyses were intention-to-treat. This study is registered at ClinicalTrials.gov, number NCT00158405.

RESULTS

326 adults (median CD4 count nadir 272 per mm3) were randomised to the CT or CD4GT groups and followed up for median of 20 months. Incidence of mortality (per 100 person-years) was not different between groups (CT 0.6, CD4GT 1.2; p=0.57). Incidence of severe morbidity (per 100 person-years) was higher in the CDG4T group (17.6) than in the CT group (6.7; p=0.001). The most frequent severe events were invasive bacterial diseases. 79% of severe morbidity episodes occurred in patients with CD4 count 200-500 per mm3.

CONCLUSION

Patients on CD4GT had severe morbidity rates 2.5-fold higher than those on CT. This difference was mainly due to high rates of common diseases in patients with CD4 count 200-500 per mm3. This CD4-guided structured treatment interruption strategy should not be recommended in Abidjan.

Structured Treatment Interruptions in Primary HIV-1 Infection

BACKGROUND

Whether structured treatment interruptions (STIs) can induce anti-HIV immune response and control HIV replication following discontinuation of highly active antiretroviral therapy (HAART) in patients with primary HIV infection is controversial.

METHODS

In this multicenter, prospective trial, patients with early symptomatic primary HIV infection were given HAART continuously for 34 weeks. Afterward, patients with plasma viral load (PVL) <50 copies/mL entered the STI phase, which consisted of 3 consecutive periods of 2, 4, and 8 weeks off HAART, each separated by 12 weeks on HAART. HAART was permanently stopped at week 84 and patients were followed up for 24 weeks. The primary endpoint for definition of virologic success was a PVL <50 copies/mL during the 6 months following HAART discontinuation.

RESULTS

Of the 29 patients enrolled, 26 completed the trial. Six months after HAART discontinuation, only 1 patient (3.8%, 95% CI: 0.1% to 19.6%) had PVL <50 copies/mL, whereas 6 of 26 (23.1%, 95% CI: 9.0% to 43.7%) had PVL <1000 copies/mL. Female gender was the only parameter significantly associated with a PVL <1000 copies/mL. No other parameter, either at baseline or before HAART discontinuation, predicted virologic success at week 108. A major protease inhibitor resistance mutation (L90M) developed in 3 patients.

CONCLUSIONS

This trial failed to confirm that a significant proportion of patients with primary HIV infection can maintain suppression of viremia after a sequence of HAART/STIs followed by HAART discontinuation.

Structured treatment interruptions (STI) in chronic suppressed HIV infection in adults

BACKGROUND

Although antiretroviral treatment (ART) has led to a decline in morbidity and mortality of HIV-infected patients in developed countries, it has also presented challenges. These challenges include increases in pill burden; adherence to treatment; development of resistance and treatment failure; development of drug toxicities; and increase in cost of HIV treatment and care. These issues stimulated interest in investigating the short-term and long-term consequences of discontinuing ART, thus providing support for research in structured treatment interruptions (STI). Structured treatment interruptions of antiretroviral treatment involve taking supervised breaks from ART. STI are defined as one or more planned, timing pre-specified, cyclical interruptions in ART. STI are attempted in monitored clinical settings in eligible participants. STI have generated hopes of reducing drug toxicities, decreasing costs and total time on treatment in HIV-positive patients. The first STI was attempted in the case of a patient in Germany, who later permanently discontinued treatment. This successful anecdotal case report led to several trials on STI worldwide.

OBJECTIVES

The objective of this systematic review was to assess the effects of structured treatment interruptions (STI) of antiretroviral therapy (ART) in the management of chronic suppressed HIV infection, using all available high-quality studies.

SEARCH STRATEGY

Nine databases covering the time period from January 1996 to March 2005 were searched. Bibliographies were scanned and experts contacted in the field to identify unpublished research and ongoing trials. Two reviewers independently extracted data, and evaluated study eligibility and quality. Disagreements were resolved in consultation with a third reviewer. Data from 33 studies were included in the review.

SELECTION CRITERIA

STI is a planned, timing pre-specified experimental intervention. In our review, we decided to include all available intervention trials in HIV-infected patients, with or without control groups. We reviewed evidence from 18 randomized and non-randomized controlled trials, and 15 single arm trials. Single arm trials were included because these pilot studies made significant contribution to the early development and refutation of hypotheses in STI.

DATA COLLECTION AND ANALYSIS

Trials included in this review varied in study participants, methodology and reported inconsistent measures of effect. Due to this heterogeneity, we did not attempt to meta-analyse them. Results were tabulated and a qualitative systematic review was done

MAIN RESULTS

For the purpose of this review, STI strategies were classified either as a timed-cycle STI strategy or a CD4-guided STI strategy. In timed-cycle STI strategy, a predetermined period of fixed duration (e.g. one week, one month) off ART was attempted followed by resumption of ART, while closely monitoring changes in CD4 levels and viral load levels. Predetermined criteria for interruption and resumption were laid out in this strategy. Timed-cycle STI fell out of favor due to reports of development of resistance in many studies. Moreover, there were no significant immunological and virological benefits, and no reduction in toxicities, reported in these studies. In CD4-guided STI strategy, ART was interrupted for variable durations guided by CD4 levels. Participants with high nadir CD4 levels qualified for this approach. A reduction in costs of ART, a reduction in mutation, and a better tolerability of this CD4-guided STI strategy was reported. However, concerns about long-term safety of this strategy on immunological, virological, and clinical outcomes were also raised.

AUTHORS' CONCLUSIONS

Timed-cycle STI have not been proven to be safe in the short term. Although CD4-guided STI strategy has reported favorable outcomes in the short term, the long-term safety, efficacy and tolerability of this strategy has not been fully investigated. Based on the studies we reviewed, the evidence to support the use of timed-cycle STI and CD4-guided STI cycles as a standard of care in the management of chronic suppressed HIV infection is inconclusive.

A model predictive control based scheduling method for HIV therapy

Recently developed models of the interaction of the human immune system and the human immunodeficiency virus (HIV) suggest the possibility of using interruptions of highly active anti-retroviral therapy (HAART) to simulate a therapeutic vaccine and induce cytotoxic lymphocyte (CTL) mediated control of HIV infection. We have developed a model predictive control (MPC) based method for determining optimal treatment interruption schedules for this purpose. This method provides a clinically implementable framework for calculating interruption schedules that are robust to errors due to measurement and patient variations. In this paper, we discuss the medical motivation for this work, introduce the MPC-based method, show simulation results, and discuss future work necessary to implement the method.

Distinct patterns of HIV-specific memory T lymphocytes in HIV-exposed uninfected individuals and in HIV-infected patients

BACKGROUND

Repeated exposure to HIV is not always associated with infection and multiple cohorts of HIV-exposed but seronegative individuals (ESN) have been described. HIV-specific CD4 and CD8 T lymphocytes are detected both in HIV patients and in ESN; we verified whether different patterns of HIV-specific memory T lymphocytes would be detected in individuals in whom exposure to HIV results or does not result in infection.

METHODS

Gag-specific T cells were analysed in 15 ESN, 14 HIV patients, and 15 healthy controls using extensive flow cytometry analysis.

RESULTS

Data confirmed that gag-specific T lymphocytes are present in ESN. Gag-specific T cells mainly secrete interleukin-2 in ESN and interferon-gamma in HIV patients. In addition the CD4/CD8 and the memory/naive ratios are altered, central memory (45RA-/CCR7+) CD4 and CD8 T lymphocytes are more abundant, and terminally differentiated (45RA+/CCR7- and 27-/28-) CD8 T lymphocytes are augmented in ESN individuals.

CONCLUSIONS

Exposure to HIV occurs in high risk seronegative individuals; the observation that naive cells and CM are skewed in ESN indicate that this exposure is robust enough to modulate the CM/EM ratio. The increase in late effectors and in natural killer cells seen in ESN suggests a role for these cells in preventing actual infection.

Interrupting highly active antiretroviral therapy in patients with HIV

Scheduled treatment interruptions are preplanned interruptions of antiretroviral treatment, which may be directed by time (e.g., cycles of 8 weeks on treatment and 8 weeks off treatment); the concentration of CD4+ lymphocytes (the CD4 count); HIV-1 RNA concentration (viral load); or other factors. This review covers the rationale of scheduled treatment interruptions and the different strategies that have been explored. It examines the issue of autovaccination, resistance and other risks and benefits. Scheduled-treatment-interruption studies in three populations are discussed: patients who initiated highly active antiretroviral therapy during acute HIV infection; patients with successfully treated chronic HIV infection; and patients with highly active antiretroviral therapy failure.

HLA-E up-regulation induced by HIV infection may directly contribute to CD94-mediated impairment of NK cells

Alterations in NK cell numbers and function have been repeatedly shown during HIV infection. In this study, NK cell number and MHC class I expression on CD4+ T cells were studied in HIV patients at different stages of disease progression. An increased expression of HLA-E was seen on CD4+ T cells. In parallel, a reduced number of CD94+ NK cells was observed in advanced disease stages. Moreover, a decline in CD94 expression on NK cells was observed at the HIV replication peak in patients undergoing antiretroviral treatment interruption, suggesting a role of viral replication on NK cells alterations. In vitro HIV infection induced a rapid down-regulation of HLA-A,B,C expression, paralleled by an increased expression of HLA-E surface molecules, the formal ligands of CD94 NK receptors. HIV-infected HLA-E expressing cells were able to inhibit NK cell cytotoxicity through HLA-E expression, since cytotoxicity was restored by antibody masking experiments. These data indicate that the CD94/HLA-E interaction may contribute to NK cell dysfunction in HIV infection, suggesting a role of HIV replication in this process.

HIV-1 DNA burden dynamics in CD4 T cells and monocytes in patients undergoing a transient therapy interruption

Replication-competent HIV, as well as HIV-1 DNA, has been detected in CD4 T cells and in monocytes during antiretroviral therapy (ART), indicating that these cells could represent an important viral reservoir. We measured HIV-1 DNA in monocytes and CD4 T cells in patients undergoing transient therapy interruption (TTI), to establish the dynamic of HIV-1 DNA burden and to find possible correlations with immune restoration and re-establishment of virological control after ART resumption. In most patients CD4 depletion and viral load rebound followed TTI. Rapid resumption of virological and immunological control was achieved after ART reintroduction. After TTI, in most cases a transient increase of both monocyte and CD4 HIV-1 DNA burden was observed. After ART reintroduction, both CD4 T cell and monocyte HIV-1 DNA copy number decreased, reaching baseline levels at the end of observation. At this time monocyte HIV-1 DNA burden was always undetectable, while CD4 T cell HIV-1 DNA burden was lower than at baseline. As CD4 T cell HIV-1 DNA values are independently associated with CD4 depletion, the increase of HIV-1 DNA burden in these cells after TTI is presumably due to acute infection, causing cell death. This is also supported by the pattern of 2-LTR appearance in these cells after TTI. HIV-1 DNA burden in monocytes and CD4 T cells show high correlation, suggesting reciprocal re-feeding of two cell populations. Repopulation by HIV these cells after TTI is temporary, and no significant changes of HIV-1 DNA burden were observed after ART resumption respect to pre-TTI period.

Flow cytometry and T-cell response monitoring after smallpox vaccination

Orthopoxvirus zoonosis or smallpox as result of bioterrorism or biological warfare represents a risk for epidemic spread. By monitoring T-cell responses by flow cytometry, we observed a recall response after recent vaccination against smallpox. When the high similarity between the orthopoxviruses is considered, this rapid assay that uses vaccinia antigens could identify recently exposures.