DNA/MVA Vaccination of HIV-1 Infected Participants with Viral Suppression on Antiretroviral Therapy, followed by Treatment Interruption: Elicitation of Immune Responses without Control of Re-Emergent Virus

Abstract

GV-TH-01, a Phase 1 open-label trial of a DNA prime—Modified Vaccinia Ankara (MVA) boost vaccine (GOVX-B11), was undertaken in HIV infected participants on antiretroviral treatment (ART) to evaluate safety and vaccine-elicited T cell responses, and explore the ability of elicited CD8+ T cells to control viral rebound during analytical treatment interruption (TI). Nine men who began antiretroviral therapy (ART) within 18 months of seroconversion and had sustained plasma HIV-1 RNA <50 copies/mL for at least 6 months were enrolled. Median age was 38 years, median pre-ART HIV-1 RNA was 140,000 copies/ml and mean baseline CD4 count was 755/μl. Two DNA, followed by 2 MVA, inoculations were given 8 weeks apart. Eight subjects completed all vaccinations and TI. Clinical and laboratory adverse events were generally mild, with no serious or grade 4 events. Only reactogenicity events were considered related to study drug. No treatment emergent viral resistance was seen. The vaccinations did not reduce viral reservoirs and virus re-emerged in all participants during TI, with a median time to re-emergence of 4 weeks. Eight of 9 participants had CD8+ T cells that could be stimulated by vaccine-matched Gag peptides prior to vaccination. Vaccinations boosted these responses as well as eliciting previously undetected CD8+ responses. Elicited T cells did not display signs of exhaustion. During TI, temporal patterns of viral re-emergence and Gag-specific CD8+ T cell expansion suggested that vaccine-specific CD8+ T cells had been stimulated by re-emergent virus in only 2 of 8 participants. In these 2, transient decreases in viremia were associated with Gag selection in known CD8+ T cell epitopes. We hypothesize that escape mutations, already archived in the viral reservoir, plus a poor ability of CD8+ T cells to traffic to and control virus at sites of re-emergence, limited the therapeutic efficacy of the DNA/MVA vaccine.

Trial registration: clinicaltrials.gov NCT01378156.

Conflict of interest statement

HLR is a co-founder of GeoVax, Inc., owns stock in GeoVax and is an employee of GeoVax. This does not alter her adherence to PLOS policies on sharing data and materials. YX and SK are former employees of GeoVax. RB and MSH are current employees of GeoVax. This does not alter their adherence to PLOS policies on sharing data and materials. There are no patents or pending patent applications for therapeutic immunization with this product. MT, BS, KW are employees of AIDS Research Consortium of Atlanta, which received funding from GeoVax for the conduct of the trial. SH is an employee of University of Alabama, Birmingham, which received funding from GeoVax for the conduct of the trial.

Figures

Fig 1. Patient Disposition (CONSORT) flow chart.

ITT, intent to treat.

Fig 2. Trial Schema.

The phases of the trial are indicated for screening, vaccination, treatment interruption and treatment reinstitution. An efavirenz washout period occurred for those on an efavirenz-containing regimen. ART, antiretroviral treatment; EFV, efavirenz.

Fig 3. Timing and Height of Re-emergent Virus and Viral Reservoirs.

Panel A. presents weeks to re-emergent virus and panel B presents temporal levels of viral RNA throughout the study. Temporal levels of viral RNA are given as medians and interquartile ranges. In panel B, the median pre-ART level of viral RNA is indicated with a square symbol. Panel C shows the frequency of circulating CD4+ T cells harboring integrated HIV DNA. Panel D shows the number of CD4+ cells with inducible Tat/ Rev mRNA as measured by TILDA. Insets in C and D give the medians and interquartile ranges for all participants. Participants are listed in the same order in A, C, and D. Participant 01–7 is not included in reservoir analyses because pre-vaccination cells were not available. Pre designates the day of vaccination and TI-1, the day of treatment interruption. Samples with HIV-1 RNA

Fig 4. Temporal Levels of Absolute CD4+ and CD8+ T Cells Throughout the Study.

All data are means with the error bars indicating standard deviations. Panels A and B present absolute CD4+ and CD8+ T cell counts as cells/μl. Panels C and D present activated cells as a percent of total CD4+ and CD8+ T cells respectively. Cells displaying CD38+ and HLA-DR surface markers are considered activated T cells.

Fig 5. Response rates.

Response rates are for (A) vaccine enhanced CD8+ and CD4+ T cells scored by ICS and (B) vaccine enhanced Ab to gp120 and gp41 scored by ELISA.

Fig 6. Temporal magnitudes of vaccine stimulated T cell and Ab responses.

Panels A-D: medians with interquartile ranges for Gag-stimulated T cell responses scored using ICS. IFNγ (panel A) and IFNγ + IL-2 co-producing (Panel B) CD8+ cells as % of total CD8+ T cells. IFNγ (Panel C) and IFNγ + IL-2 (Panel D) co-producing CD4+ cells as % of total CD4+ T cells. Panels E and F: gp120 and gp41 Ab (μg/ml). Data are for the vaccination, treatment interruption (indicated in grey) and treatment reinstitution phases of the trial. Dotted lines indicate the timing of DNA (D) and MVA (M) immunizations. All 9 participants are included in T cell data through the 1st MVA inoculation after which data are for the 8 participants that completed the trial. The Ab data are for the 8 participants that completed the trial.

Fig 7. Inhibitory receptor expression on Gag-specific IFNγ and IL-2 producing CD8+ and CD4+ T cells.

Panel A shows the mean fluorescent intensity (MFI) for PD1 and TIM-3 on Gag-specific CD8+ T cells. Panel B shows MFI for PD-1, CTLA-4 and TIM-3 on Gag-specific CD4+ T cells. HIV+ designates virologically suppressed, ART treated subjects undergoing therapeutic vaccination whereas HIV- designates uninfected individuals undergoing prophylactic vaccination in the HVTN 205 trial. Inhibitory receptor expression was determined for IFNγ and IL-2 responding cells, indicated below the X axis. Box plots show median values and interquartile ranges; the whiskers indicate the lowest and highest points within 1.5 interquartile ranges of the lower and higher quartiles. No significant difference in inhibitory receptor expression was found between HIV+ and HIV- subjects using Mann-Whitney T test.

Fig 8. Temporal viral RNA and responding T Cells.

Panels show data for the 8 participants in the trial who completed the study ordered from the individual who delayed treatment re-institution (01–1) and then participants with increasing levels of viral RNA during the TI phase (Table 2, measured by area under the curve). The red bar at the left side of each panel indicates pre-ART levels of viral RNA. Red lines indicate temporal levels of viral RNA and black lines, temporal levels of Gag-specific IFNγ expressing CD8+ T cells. DNA and MVA immunizations are indicated by dashed black vertical lines designated D and M respectively. The initiation of an efavirenz washout is indicated by a dashed vertical blue line, W. Levels of HIV-1 RNA

Fig 9. Mapping of Elicited T Cell Responses to 11 Pools of Sequential Gag Peptides.

Panel A shows examples of the CD8+ and CD4+ responses in three participants. Panel B summarizes responses for the eight participants that completed the trial. 101–3 had a high background at TI allowing only dominant responses to be scored. Pre, responses present before vaccination; PV, responses scored after the 2nd MVA inoculation; TI, Responses scored at 2 weeks post the re-emergence of virus during treatment interruption. Red indicates responses present at baseline, post vaccination and either present or absent post TI, yellow indicates responses observed post vaccination and post treatment interruption, blue indicates responses scored only post vaccination and green indicates responses scored only during treatment interruption.