| |
New Therapeutic HIV Vaccine Study Results....A Dendritic Cell-Based Vaccine Elicits T Cell Responses Associated with Control of HIV-1 Replication
|
| |
| |
Download the PDF here
"The concept of "functional cure"-defined as control of HIV replication without cART-is based on the observation that a limited number of HIV-infected patients (termed as long-term nonprogressors or elite controllers) can remain persistently infected for decades but are able to control HIV replication effectively enough to remain aviremic as measured by standard assays and without appreciable depletion of CD4+ T cells........Therapeutic immunization is intended to increase existing immune responses against HIV or induce de novo beneficial antiviral immune responses by vaccination with a suitable immunogen (3, 4). In the ideal scenario, these responses would be able to control viral replication......In the present blinded placebo-controlled clinical trial, we successfully immunized antiretroviral-treated chronic HIV-1-infected patients with a high dose of MD-DCs pulsed with heat-inactivated autologous virus to assess whether induced HIV-specific immune responses were able to change significantly pVL setpoint after cART interruption.........At weeks 12 and 24, a decrease of pVL setpoint ≥1 log was observed in 12 of 22 (55%) versus 1 of 11 (9%) individuals, and in 7 of 20 (35%) versus 0 of 10 (0%) individuals in DC-HIV-1 and DC-control, respectively (P = 0.02 and P = 0.03).......Despite these reductions in pVL setpoint, VL rebounded to detectable levels in all patients. pVL after the first interruption of cART before any immunization was similar to baseline pVL before any cART.......CD4 T cell counts declined to pre-cART values without significant differences between groups......In summary, these results suggest that HIV-1-specific immune responses elicited by therapeutic DC vaccines could significantly change pVL setpoint after cART interruption in most chronic HIV-1-infected patients treated in early stages. This is a proof of concept justifying further investigation of new candidates and/or new optimized strategies of vaccination with the final objective of obtaining a functional cure as an alternative to cART for life."
Therapeutic HIV Vaccine Shows Promise - see full report below
By Michael Smith, North American Correspondent, MedPage Today
Published: January 03, 2013
Action Points
· An experimental therapeutic vaccine against HIV was able temporarily to lower the level of virus in the blood of infected volunteers.
· Note that although the effect did not persist, it is "proof of concept" that such a vaccine might lead to what is called a functional cure, defined as control of HIV replication without antiretroviral drugs.
An experimental therapeutic vaccine against HIV was able temporarily to lower the level of virus in the blood of infected volunteers, researchers reported.
In a randomized, blinded, placebo-controlled trial, the vaccine - using modified antigen-presenting dendritic cells - lowered the so-called viral set point for several months, according to Felipe Garcia, MD, of Spain's University of Barcelona in Barcelona, and colleagues.
Although the effect did not persist, it is "proof of concept" that such a vaccine might lead to what is called a functional cure, defined as control of HIV replication without antiretroviral drugs, Garcia and colleagues concluded online in Science Translational Medicine.
Such control is already seen in the small minority of HIV-positive people known as "elite controllers," whose immune systems are able to keep the virus in check for decades without the aid of drugs, the researchers noted.
The new findings "open the possibility that a therapeutic vaccine could be used as a strategy to obtain a functional cure," Garcia said in a video interview with the journal.
Dendritic cells play a key role in the immune response to infectious disease, presenting antigens to the T cells so that they can identify the invading pathogens.
But in HIV infection, the dendritic cells can also carry live virus to the CD4-positive T cells, causing them to die instead of mount an immune response, Garcia and colleagues noted.
To avoid that in this study, they pulsed the patients' own monocyte-derived dendritic cells with virus collected from their blood and rendered inactive with heat.
The 36 patients were all on long-term combined antiretroviral therapy; 24 were randomly assigned to get three injections of the HIV pulsed cells and 12 to get three shots of unmodified cells.
Antiretroviral therapy was then stopped, and the patients were followed for up to 48 weeks.
The goal was to see if the vaccine lowered the plasma viral set point of HIV from a baseline established during an earlier interruption of therapy, Garcia and colleagues reported.
The vaccine was safe, they reported, and well tolerated; the main adverse effects were asymptomatic lymph node enlargement in four patients and one case each of local redness at the injection site and flu-like symptoms.
On the other hand, several patients in each arm had to resume therapy when their CD4 cell count dropped below prespecified levels.
Twelve weeks after antiretroviral drugs were stopped, 12 of 22 patients remaining in the active arm had at least a 10-fold reduction in the plasma viral load set point, compared with one of 11 in the control arm. The difference was significant at P=0.02.
After another 12 weeks, seven of the 20 remaining patients in the active arm still had at least a 10-fold drop in the viral load set point, compared with none of the remaining 10 patients in the control arm. The difference was significant at P=0.03.
The decrease in plasma viral load was associated with increases in HIV-specific T cell responses, Garcia and colleagues reported.
Despite the declines, however, viral load rebounded to detectable levels in all patients.
Garcia and colleagues cautioned that the goal of any therapeutic vaccine would be to keep viral load undetectable without the use of drugs and "this objective has not been reached with this vaccine."
One possible reason is that the patients were off medication for several weeks about 12 months before the first shot, in order to allow the collection of autologous cells and virus. That, Garcia and colleagues argued, might have "compromised the results" by allowing viral replication despite a subsequent drop to below the level of detectability.
Also, they noted, the vaccine did not prevent a drop in CD4 cells, which meant that several vaccinated patients had to resume therapy.
-------------------------
Sci Transl Med 2 January 2013
A Dendritic Cell-Based Vaccine Elicits T Cell Responses Associated with Control of HIV-1 Replication
Felipe Garcia,1 * Nuria Climent,1 * Alberto C. Guardo,1 Cristina Gil,1 Agathe Leon,1
Brigitte Autran,2 Jeffrey D. Lifson,3 Javier Martinez-Picado,4,5 Judit Dalmau,4 Bonaventura Clotet,4
JosepM. Gatell,1 Montserrat Plana,1 * Teresa Gallart,1 * For the DCV2/MANON07-ORVACS Study Group
Abstract
Combination antiretroviral therapy (cART) greatly improves survival and quality of life of HIV-1-infected patients; however, cART must be continued indefinitely to prevent viral rebound and associated disease progression. Inducing HIV-1-specific immune responses with a therapeutic immunization has been proposed to control viral replication after discontinuation of cART as an alternative to "cART for life." We report safety, tolerability, and immunogenicity results associated with a control of viral replication for a therapeutic vaccine using autologous monocyte-derived dendritic cells (MD-DCs) pulsed with autologous heat-inactivated whole HIV. Patients on cART with CD4+ >450 cells/mm3 were randomized to receive three immunizations with MD-DCs or with nonpulsed MD-DCs. Vaccination was feasible, safe, and well tolerated and shifted the virus/host balance. At weeks 12 and 24 after cART interruption, a decrease of plasma viral load setpoint ≥1 log was observed in 12 of 22 (55%) versus 1 of 11 (9%) and in 7 of 20 (35%) versus 0 of 10 (0%) patients in the DC-HIV-1 and DC-control groups, respectively. This significant decrease in plasma viral load observed in immunized recipients was associated with a consistent increase in HIV-1-specific T cell responses. These data suggest that HIV-1-specific immune responses elicited by therapeutic DC vaccines could significantly change plasma viral load setpoint after cART interruption in chronic HIV-1-infected patients treated in early stages. This proof of concept supports further investigation of new candidates and/or new optimized strategies of vaccination with the final objective of obtaining a functional cure as an alternative to cART for life.
Introduction
Although combination antiretroviral therapy (cART) improves survival and quality of life of HIV-infected patients, cART does not represent definitive therapy for HIV infection, in part because treatment must be continued indefinitely to prevent viral recrudescence and associated disease progression. Viral eradication and functional cure have been proposed as two alternatives to "cART for life" (1). The concept of "functional cure"-defined as control of HIV replication without cART-is based on the observation that a limited number of HIV-infected patients (termed as long-term nonprogressors or elite controllers) can remain persistently infected for decades but are able to control HIV replication effectively enough to remain aviremic as measured by standard assays and without appreciable depletion of CD4+ T cells. It has been proposed that the strong HIV-specific immune responses observed in these patients explain this natural functional cure (2), raising the possibility that therapeutic immunization of patients in whom HIV replication is suppressed by cART might result in a similar outcome, obviating the need for lifelong cART (3, 4).
Therapeutic immunization is intended to increase existing immune responses against HIV or induce de novo beneficial antiviral immune responses by vaccination with a suitable immunogen (3, 4). In the ideal scenario, these responses would be able to control viral replication in at least a proportion of patients, even after discontinuation of cART. Even if it fell short of achieving such a functional cure if a therapeutic vaccine were shown to be capable of changing plasma viral load (pVL) setpoint after a diagnostic interruption of cART, it would provide a proof of concept that would justify further investigation of new candidate therapeutic immunization approaches.
Autologous myeloid dendritic cells (DCs), such as monocyte-derived DCs (MD-DCs) (5), pulsed ex vivo with a variety of inactivated pathogens and tumor antigens, have been shown to induce a potent protective immunity in experimental murine models of human infections and tumors (6-8). Some studies in animal models suggest that animals immunized with DCs loaded with HIV-1 viral lysate, envelope glycoproteins, or inactivated virus mount a potent immune response against HIV-1 (9-12). Although at least 12 published clinical trials of DC-based immunotherapy for HIV infection have been performed in humans (13-24) [reviewed in (25)], most of them were noncontrolled, nonrandomized studies. In the present blinded placebo-controlled clinical trial, we successfully immunized antiretroviral-treated chronic HIV-1-infected patients with a high dose of MD-DCs pulsed with heat-inactivated autologous virus to assess whether induced HIV-specific immune responses were able to change significantly pVL setpoint after cART interruption.
Results
Characteristics of study patients and side effects of immunizations
Thirty-six patients were enrolled. The baseline characteristics of the patients in each arm, shown in Table 1, were well balanced. One patient in the DC-control group was excluded from the analysis because of consent withdrawal before receiving any immunization. Seven patients in the DC-HIV-1 and five in the DC-control started cART (DC-HIV-1: at week 4 due to consent withdrawal; at weeks 8, 12, 12, 36, and 36 due to a drop in CD4 T cell count below specified criteria; and at week 36 due to a drop in platelets; DC-control: at weeks 16, 24, 36, and 36 due to a drop in CD4 T cell count below specified criteria and at week 36 due to consent withdrawal) (Fig. 1). Overall, the immunizations were well tolerated, with asymptomatic enlargement of local lymph nodes after vaccination in four patients (in three DC-HIV-1 patients after 6 to 12 hours after three immunizations, and in one DC-control recipient after the first injection), one episode of mild local redness (one in DC-HIV-1 patients after the second immunization), and one episode of flu-like symptoms (one in DC-HIV-1 patients after the second immunization). The enlargement of lymph nodes regressed after 48 to 72 hours, without intervention, in each instance. The redness and flu-like symptoms subsided after 24 hours. Eleven DC-HIV-1 patients reported at least one adverse event during the follow-up, compared with five patients in the DC-control group. Except for the lymph node enlargement and the episode of local redness and flu-like symptoms, the adverse events were classified as unrelated to immunizations. The DC injections were not associated with any clinical or serologic evidence of autoimmunity, and no rheumatoid factor or antinuclear antibodies were detected after DC injections.
Changes in viral load and CD4+ T cell count after DC immunizations and cART interruption
DC-HIV-1 patients experienced significant changes of pVL setpoint after cART interruption compared with DC-controls. The drop in pVL setpoint after the second cART interruption is shown in Table 2 and Fig. 2 (A and B). The results of the analysis did not change at week 24, when a sensitivity-type analysis using the last observation carried forward for the missing pVLs was performed [mean (SE) change pVL (log10 RNA copies/ml), -0.80 versus -0.19 in DC-HIV-1 versus DC-control, respectively (P = 0.01)]. At weeks 12 and 24, a decrease of pVL setpoint ≥1 log was observed in 12 of 22 (55%) versus 1 of 11 (9%) individuals, and in 7 of 20 (35%) versus 0 of 10 (0%) individuals in DC-HIV-1 and DC-control, respectively (P = 0.02 and P = 0.03) (Fig. 3 and Table 2). Proportions of patients with a drop of pVL ≥0.5 log in both arms at different time points are shown in Fig. 3 and Table 2. Over a 48-week period, the AUC analysis showed a significant difference for a change of pVL setpoint between the groups [mean (SE), -0.73 (0.14) versus -0.24 (0.16), DC-HIV-1 and DC-control, respectively; P = 0.04]. The highest and lowest decreases in pVL setpoint (defined as the highest and lowest differences between pVL setpoint at any time point after cART interruption and baseline pVL setpoint before any cART) were also significantly different between arms [highest decrease: mean (SE), -1.2 (0.14) versus -0.56 (0.21), in DC-HIV-1 versus DC-control, P = 0.01; lowest decrease: mean (SE), -0.54 (0.11) versus -0.06 (0.19), in DC-HIV-1 versus DC-control, P = 0.04]. Finally, a pairwise analysis with a Wilcoxon test comparing pVL at baseline with pVL at weeks 12, 24, 36, and 48 showed that the differences were significant in the DC-HIV-1 group (P < 0.0001, P < 0.0001, P = 0.0006, and P = 0.0028, respectively) but not in the DC-control group (P = 0.06, P = 0.44, P = 0.69, and P = 0.10, respectively). Despite these reductions in pVL setpoint, VL rebounded to detectable levels in all patients. pVL after the first interruption of cART before any immunization was similar to baseline pVL before any cART (see Table 1).
CD4 T cell counts declined to pre-cART values without significant differences between groups (Fig. 4).
Changes in HIV-1-specific responses after DC immunizations
Baseline median values of the total sum of HIV-specific responses against HIV peptide pools were similar in both arms [2625 versus 2283 spot-forming cells (SFCs)/106 peripheral blood mononuclear cells (PBMCs), P = 0.462]. The median [interquartile range (IQR)] change in the frequency of total HIV-specific T cell responses after immunizations is shown in Table 2 and Fig. 5A. This difference was more evident when analyzing responses at week 24 against Gag p17 and Nef peptide pools (P = 0.0288 and P = 0.03615, respectively). Nevertheless, we also observed at week 24 an increased response against Gag p24, Gag small proteins, and Env gp41 peptide pools in the immunized arm, although the difference was not statistically significant when compared to the placebo arm (852 versus 328 SFCs/106 PBMCs for Gag p24, P = 0.705; 426 versus 60 SFCs/106 PBMCs for Gag small proteins, P = 0.909; and 415 versus 73 SFCs/106 PBMCs for Env gp4, P = 0.167, respectively). A complete immunophenotype was performed on T cells from all individuals. We observed, at different time points, a significant increase in activation markers such as CD38 and human leukocyte antigen (HLA)-DR especially on CD4 T cells from the DC-HIV-1 group (Fig. 5B). On the other hand, CD8 T cells, which usually correlate with progression of HIV infection, did not change significantly between groups. The median increase of peptide pools recognized was similar between the two groups of patients.
HIV-specific T cell responses observed at week 24 tended to be inversely associated with the drop in pVL in DC-HIV-1 group (r = -0.38, P = 0.08); however, they were directly and significantly correlated with changes in pVL in the DC-control group (r = 0.66, P = 0.03) (Fig. 6, A and B).
Although only transient positive responses to HIV p24 were observed, the median change in lymphoproliferative response (LPR) to HIV p24 at week 24 from baseline was 0.96 versus -0.50 (P = 0.02) in the DC-HIV-1 versus DC-control groups. Additionally, we found a significant positive correlation between changes in LPR to HIV p24 and changes in the magnitude of HIV-specific T cell responses measured by enzyme-linked immunospot (ELISPOT) in the DC-HIV group (r = 0.86, P = 0.0045), whereas in the case of the DC-control group, there was a negative tendency between these changes (r = -0.6, P = 0.096).
Discussion
Here, therapeutic vaccination of antiretrovirally treated nonadvanced chronic HIV-1-infected patients with high doses of autologous MD-DCs pulsed with high doses of autologous heat-inactivated HIV-1 was feasible, safe, and well tolerated. A significant decrease in VL was observed in immunized recipients combined with a consistent increase in HIV-1-specific T cell responses. Although our data fell short of achieving a functional cure, this therapeutic vaccine was capable of changing pVL setpoint after a diagnostic interruption of cART.
To date, results have been reported for 191 patients (60 off cART and 131 on cART) recruited into 12 clinical trials with DC-based immunotherapeutic vaccines (25). The safety profile has been excellent, with only minor local side effects reported in some studies. No severe side events or induction of autoimmunity has been reported. This excellent tolerance profile for DC administration to HIV-1-infected patients corresponds with experiences with DC-based cancer therapy. Our clinical trial confirms that a therapeutic MD-DC vaccine in chronically HIV-1-infected patients receiving antiretroviral therapy is feasible, safe, and well tolerated. However, this is a small trial in a highly select group of patients, and the overall safety over the long term and in a substantial number of unselected participants remains to be established.
The 12 clinical trials published so far suggest that DC immunotherapy in HIV-1 infection can elicit HIV-1-specific immunological responses. However, only four of these studies reported virological responses to immunization (14, 15, 21, 22), three have not assessed virological responses (17, 20, 23), and five failed to show any response (13, 16, 18, 19, 24). The most promising results have been reported in two noncontrolled, nonrandomized studies (14, 22). The first preliminary noncontrolled, nonrandomized clinical trial described by Lu et al. (14) found that, after administration of three immunizations with DCs loaded with AT-2-inactivated autologous virus, VL decreased a mean of 0.7 log10 copies/ml in antiretroviral treatment of naïve HIV-1-infected patients. Moreover, they found a drop of 1 log10 in the viral load of 8 of 18 (44%) patients. Similar results were found by Routy et al. (22) in antiretroviral-treated patients. Conversely, in the other two randomized clinical trials performed previously by our group [one in patients off cART (21) and the other in patients on cART (15)], only a modest virological response associated with weak increase in HIV-1-specific CD8+ T cell responses was observed (15, 21, 26, 27).
In the present blinded placebo-controlled study in antiretroviral-treated patients, we found a significant and consistent virological response that was maintained for at least 24 weeks in the vaccinated group and seemed to wane thereafter. Immunization shifted the virus/host balance; the change in pVL setpoint in the immunized patients compared to the control group was significant (mean peak drop of pVL of -1.2 log10 copies/ml and mean drop of pVL at weeks 12 and 24 of -0.91 and -0.81 log10 copies/ml). The protocol endpoint for control of pVL (≥1 log10) was achieved in 12 of 22 (55%) vaccine recipients at week 12 after cART interruption and was observed in only 1 of the control recipients during the 48 weeks of follow-up. Moreover, over this 48-week period, the AUC analysis showed a significant difference for a change of pVL setpoint between the groups with a mean drop of -0.73 in vaccinated and -0.24 in controls. To our knowledge, these are the best virological responses to any therapeutic vaccine used to date. However, comparison between the results of this clinical trial and those of published studies is difficult because, although the baseline characteristics of the patients were similar between different clinical trials, the design of these studies (including route of administration, type of immunogen, number of doses, and schedule) varied (25). In any case, it is worth considering whether autologous virus is a good immunogen. Clinical trials performed with heterologous antigens (13, 16-19, 23, 24) did not find any virological response. Conversely, the four studies reporting virological responses to immunization (14, 15, 21, 22) used autologous virus. Recently, Routy et al. (20, 28) reported the preliminary results of an immunotherapy noncontrolled, nonrandomized trial consisting of MD-DCs and RNA encoding autologous HIV-1 antigens (Gag, Nef, Rev, and Vpr) administered monthly in 33 subjects in four intradermal doses in combination with cART, followed by two more doses during a 12-week cART interruption. They found that this strategy induced a control of pVL similar to that reported by Lu et al. (14). These and our current data suggest that a combination of autologous antigens administered to patients on cART could have a higher virological effect. In addition, the difference in efficacy of this current trial compared with our previous clinical trials (15, 21) could be explained by the much lower quantities of MD-DCs and virus used in the first trial [106 versus 107 (MD-DCs) and 106 versus109 (virus) in the first and current trial, respectively] (15) and that the second trial was performed in antiretroviral untreated patients (21).
The vaccine tested here induced moderate HIV-specific T cell responses, as measured by ELISPOT. At week 24 after cART interruption, the pVL in immunized patients tended to be inversely correlated with HIV-1-specific T cell responses. In contrast, as other authors have reported previously, in the controls, HIV-1-specific T cells responses were directly correlated with an increase in pVL (29). We also observed a clear increase of activated CD4+ T lymphocytes in vaccinated patients. The latter suggests that pulsed DCs may be able to appropriately stimulate T cells to obtain an efficient immune response. The clear positive correlation we found between the increase in HIV-1-specific T cell proliferative response and interferon-γ (IFN-γ) production in immunized patients suggests a coordinated response to the therapeutic immunization and reinforces this idea. We have previously reported that a transient activation of HIV-specific CD4+, but not CD8+ T cells with HIV-1 recombinant canarypox vaccine (vCP1452), might have a detrimental effect on HIV outcomes (30). Conversely, the present data suggest that limited activation of HIV-specific CD4+ associated with stimulation of CD8+ T cells might have a beneficial effect in the control of viral replication.
Our study has a number of drawbacks. First, despite important reductions in pVL setpoint, VL rebounded to detectable levels in all patients. The goal of any therapeutic vaccine would be to control viral replication to an undetectable level in at least a proportion of patients in the absence of cART (functional cure), and this objective has not been reached with this vaccine. A replenishment of the reservoir during the first interruption of cART (performed to isolate autologous virus for pulsing MD-DCs) could be a major problem with the study design. After this interruption, patients were on cART for only 48 additional weeks. It could be expected to cause significant persistent viral replication despite a decline in viral RNA to <50 copies/ml and may have compromised the results. Regretfully, we have not been able to perform any other measures of the reservoir at the time of second treatment interruption after vaccination. Second, immunization did not prevent the drop of CD4+ T cells, and a third of randomized patients had to reinitiate cART during the follow-up. The observed decreases in CD4+ T cells are likely due to persistent viral replication, and it is possible that, if a therapeutic vaccine would be able to control viral replication to undetectable level, this deleterious effect in CD4 T cell count would not be observed. Finally, viral load response to vaccine waned with time. A new strategy including booster doses after cART interruption could potentially avoid this decline of the vaccine effect. This is suggested by the preliminary data reported by Routy et al. (22). The results of an ongoing clinical trial using four immunizations while on cART plus two additional booster doses after cART interruption could help to answer this question (25).
In summary, these results suggest that HIV-1-specific immune responses elicited by therapeutic DC vaccines could significantly change pVL setpoint after cART interruption in most chronic HIV-1-infected patients treated in early stages. This is a proof of concept justifying further investigation of new candidates and/or new optimized strategies of vaccination with the final objective of obtaining a functional cure as an alternative to cART for life.
| |
| |
| |
|
|
|
