Ad26/MVA therapeutic vaccination with TLR7 stimulation in SIV-infected rhesus monkeys

Abstract

The development of immunologic interventions that can target the viral reservoir in HIV-1-infected individuals is a major goal of HIV-1 research. However, little evidence exists that the viral reservoir can be sufficiently targeted to improve virologic control following discontinuation of antiretroviral therapy. Here we show that therapeutic vaccination with Ad26/MVA (recombinant adenovirus serotype 26 (Ad26) prime, modified vaccinia Ankara (MVA) boost) and stimulation of TLR7 (Toll-like receptor 7) improves virologic control and delays viral rebound following discontinuation of antiretroviral therapy in SIV-infected rhesus monkeys that began antiretroviral therapy during acute infection. Therapeutic vaccination with Ad26/MVA resulted in a marked increase in the magnitude and breadth of SIV-specific cellular immune responses in virologically suppressed, SIV-infected monkeys. TLR7 agonist administration led to innate immune stimulation and cellular immune activation. The combination of Ad26/MVA vaccination and TLR7 stimulation resulted in decreased levels of viral DNA in lymph nodes and peripheral blood, and improved virologic control and delayed viral rebound following discontinuation of antiretroviral therapy. The breadth of cellular immune responses correlated inversely with set point viral loads and correlated directly with time to viral rebound. These data demonstrate the potential of therapeutic vaccination combined with innate immune stimulation as a strategy aimed at a functional cure for HIV-1 infection.

Extended Data Figure 1. Activation of CD8+ T cells following GS-986 administration

Representative data on days 0, 1, and 2 following GS-986 administration. Activation was assessed by CD69 expression on CD3+CD8+ T cells.

Extended Data Figure 2. Activation of CD4+ T cells following GS-986 administration

Representative data on days 0, 1, and 2 following GS-986 administration. Activation was assessed by CD69 expression on CD3+CD4+ T cells.

Extended Data Figure 3. Innate immune stimulation following GS-986 administration

Plasma IFN-α (pg/ml) levels are shown on day 1 following GS-986 administration. Red bars represent mean values for each group. Data points reflect all animals following all GS-986 administrations combined with pre-dose levels subtracted.

Extended Data Figure 4. CD8+ T cells following Ad26/MVA vaccination

SIVmac239 Gag/Pol/Env-specific, IFN-γ+CD3+CD8+ central memory T cells were assessed by multiparameter intracellular cytokine staining assays.

Extended Data Figure 5. CD4+ T cells following Ad26/MVA vaccination

SIVmac239 Gag/Pol/Env-specific, IFN-γ+CD3+CD4+ central memory T cells were assessed by multiparameter intracellular cytokine staining assays.

Extended Data Figure 6. Cellular immune breadth

Responses to subpools of 10 peptides spanning SIVmac239 Gag, Pol, and Env are shown prior to vaccination (week 20, blue), following Ad26 priming (week 29, red), and following MVA boosting (week 50, green). Colored squares indicate positive responses.×indicates missing data as a result of insufficient PBMC.

Extended Data Figure 7. Correlations of cellular immune breadth to day 7 SIV RNA

Correlations are shown for the breadth of Gag, Pol, Env, and Total (Gag+Pol+Env) cellular immune responses at the time of ART discontinuation at week 72 and pre-ART day 7 log SIV RNA.

Extended Data Figure 8. Correlations of cellular immune breadth to setpoint viral loads

Correlations are shown for the breadth of Gag, Pol, Env, and total (Gag+Pol+Env) cellular immune responses at peak immunity at week 50 and setpoint log SIV RNA following ART discontinuation.

Extended Data Figure 9. Correlations of cellular immune breadth to time to viral rebound

Correlations are shown for the breadth of Gag, Pol, Env, and total (Gag+Pol+Env) cellular immune responses at peak immunity at week 50 and time to viral rebound following ART discontinuation.

Extended Data Figure 10. Rebound kinetic parameters estimated from viral dynamics modeling

Viral load values following ART discontinuation in each animal were fit to a viral dynamics model using a Bayesian framework. Plots show the median and 95% credible intervals for estimations of (a) the rate of reactivation of cells from the latent reservoir, (b) the initial exponential growth rate, (c) the immune proliferation rate, and (d) the time at which viral load reaches the detection threshold of 200 copies/ml for each treatment group. Monkeys treated with both the vaccine and TLR7 agonist exhibited slower viral growth rates and stronger immune responses than all other groups (P < 0.01 for each comparison). These monkeys and monkeys treated with only the vaccine exhibited a lower reservoir exit rate than untreated monkeys (P < 0.05 for each comparison).

Figure 1. SIV RNA and vaccine immunogenicity prior to ART discontinuation

(a) Rhesus monkeys were infected with SIVmac251 on day 0 and initiated ART on day 7 (N=9 animals/group). Ad26 and MVA vaccination timepoints are shown with the vertical arrows. The timeframe for TLR7 agonist administration (10 doses every 2 weeks) is shown by the horizontal bar. Log SIV RNA copies/ml are shown (limit of detection 2.3 log RNA copies/ml). (b) IFN-γ ELISPOT responses in response to Gag, Pol, and Env peptide pools from SIVmac239 and SIVsmE543. Group numbers and timepoints are denoted on the x-axis. Group 1 received the Ad26/MVA vaccine alone, and Group 2 received the Ad26/MVA vaccine + TLR7 agonist. P values indicate 2-sided Wilcoxon rank-sum tests compared with week 24 (pre-vaccination). (c) Cellular immune breadth in the vaccinated animals as measured by subpools of 10 peptides spanning the SIVmac239 Gag, Pol, and Env proteins at week 0 (naïve), week 20 (pre-vaccination), week 29 (Ad26), and week 50 (MVA). The numbers of positive subpools are indicated in red. P values indicate 2-sided Wilcoxon rank-sum tests.

Figure 2. SIV DNA prior to ART discontinuation

Log SIV DNA copies/10⁶ CD4+ T cells are shown (limit of detection 3 DNA copies/10⁶ cells) in (a) inguinal lymph node mononuclear cells and (b) peripheral blood mononuclear cells (PBMC). Week 48 reflects post-Ad26 priming, and week 70 reflects post-MVA boosting. P values indicate 2-sided Wilcoxon rank-sum tests.

Figure 3. SIV RNA following ART discontinuation

(a) Log SIV RNA copies/ml are shown (limit of detection 2.3 log RNA copies/ml) following ART discontinuation at study week 72. Days following ART discontinuation are shown on the x-axis. (b) Median log SIV RNA in each group. (c) Statistical analysis of setpoint levels of SIV RNA and time to viral rebound in each group. P values indicate 2-sided Wilcoxon rank-sum tests.

Figure 4. Correlations of cellular immune breadth with setpoint viral loads and time to viral rebound

Correlations are shown for the breadth of Gag, Pol, Env, and total (Gag+Pol+Env) cellular immune responses as defined as the number of positive subpools at the time of ART discontinuation at week 72 and (a) setpoint log SIV RNA or (b) time to viral rebound following ART discontinuation. P values indicate 2-sided Spearman rank-correlation tests.