Safety and immunogenicity of recombinant poxvirus HIV-1 vaccines in young adults on highly active antiretroviral therapy

Abstract

A trial to evaluate the safety and immunogenicity of recombinant modified vaccinia Ankara (MVA) and fowlpox (FP) vectors expressing multiple HIV-1 proteins was conducted in twenty HIV-1 infected youth with suppressed viral replication on HAART. The MVA and FP-based multigene HIV-1 vaccines were safe and well tolerated. Increased frequencies of HIV-1 specific CD4+ proliferative responses and cytokine secreting cells were detected following immunization. Increased frequencies and breadth of HIV-1 specific CD8 T-cell responses were also detected. Plasma HIV-1-specific antibody levels and neutralizing activity were unchanged following vaccination. Poxvirus-based vaccines may merit further study in therapeutic vaccine protocols.

Fig. 1. Flow diagram of enrollment, immunization, viral loads and antiretroviral therapy

*Viremia detected: HIV-1 RNA copies/ml (c/ml) plasma (weeks when detected); ARV – antiretrovirals. ** Viremia detected at early time points (≤ week 26) highlighted in underlined italics. *** Subject 11 had progressive increases in viremia on ARV; the three time points with viremia detected are listed

Fig. 2. Detection and enumeration of vaccinia-specific CD8 T-cells

A. The CD8 T-cell responses to live vaccinia stimulation (subject 9); dot plot. Top panels display cytokine and degranulation responses to vaccinia at study entry compared with background values. Bottom panels display these responses at study week 26, after all four immunizations. B. The CD8 T-cell responses to live vaccinia stimulation (subject 9); functional profile. Depicted values are background subtracted using the no antigen control assay. Pie chart depicts the percentages of responding CD8 T-cells that express these markers individually and in combinations up to 5. Bar chart depicts the percentages of responding CD8 T-cells that express each of the possible combinations of markers (dots indicate positive responses). C. Summation of CD8 T-cell cytokine responses to live vaccinia stimulation. Frequencies of responses at baseline and post-immunization among 5 individuals studied by this technique. Median, interquartile range and SD are shown by heavy line, bar and whiskers, respectively. Background subtracted values less than the threshold defined by the 90^th percentile of a normal distribution around zero were assigned a value of 0 for calculation purposes. Wilcoxon sign rank test comparing post-immunization with baseline frequencies.

Fig. 2. Detection and enumeration of vaccinia-specific CD8 T-cells

A. The CD8 T-cell responses to live vaccinia stimulation (subject 9); dot plot. Top panels display cytokine and degranulation responses to vaccinia at study entry compared with background values. Bottom panels display these responses at study week 26, after all four immunizations. B. The CD8 T-cell responses to live vaccinia stimulation (subject 9); functional profile. Depicted values are background subtracted using the no antigen control assay. Pie chart depicts the percentages of responding CD8 T-cells that express these markers individually and in combinations up to 5. Bar chart depicts the percentages of responding CD8 T-cells that express each of the possible combinations of markers (dots indicate positive responses). C. Summation of CD8 T-cell cytokine responses to live vaccinia stimulation. Frequencies of responses at baseline and post-immunization among 5 individuals studied by this technique. Median, interquartile range and SD are shown by heavy line, bar and whiskers, respectively. Background subtracted values less than the threshold defined by the 90^th percentile of a normal distribution around zero were assigned a value of 0 for calculation purposes. Wilcoxon sign rank test comparing post-immunization with baseline frequencies.

Fig. 2. Detection and enumeration of vaccinia-specific CD8 T-cells

A. The CD8 T-cell responses to live vaccinia stimulation (subject 9); dot plot. Top panels display cytokine and degranulation responses to vaccinia at study entry compared with background values. Bottom panels display these responses at study week 26, after all four immunizations. B. The CD8 T-cell responses to live vaccinia stimulation (subject 9); functional profile. Depicted values are background subtracted using the no antigen control assay. Pie chart depicts the percentages of responding CD8 T-cells that express these markers individually and in combinations up to 5. Bar chart depicts the percentages of responding CD8 T-cells that express each of the possible combinations of markers (dots indicate positive responses). C. Summation of CD8 T-cell cytokine responses to live vaccinia stimulation. Frequencies of responses at baseline and post-immunization among 5 individuals studied by this technique. Median, interquartile range and SD are shown by heavy line, bar and whiskers, respectively. Background subtracted values less than the threshold defined by the 90^th percentile of a normal distribution around zero were assigned a value of 0 for calculation purposes. Wilcoxon sign rank test comparing post-immunization with baseline frequencies.

Fig. 3. HIV-specific CD4 T-cell responses

A. Percentage of individuals with positive CD4 T-cell proliferation responses to stimulation with p24^Gag at time points pre and post immunizations. Two groups shown are those who received all immunizations (n=10) and those who received at least two of the immunizations (n=19; including two who discontinued ARV before week 26). B. HIV-specific CD4 T-cell proliferation. Proliferation index (PI) in response to p24^Gag are shown at baseline and week 6 for all participants who received at least two immunizations; and shown at week 26 and 48 are only those who received all 4 immunizations (one assay at week 48 was not performed due to sample handling problems). C. HIV-specific CD4 T-cell cytokine responses; IL-2 producing, p55^Gag-specific CD4 T-cells. D. HIV-specific CD4 T-cell cytokine responses; IFNγ producing, p55^Gag-specific CD4 T-cells. Panels C and D show baseline and week 6 values for all participants who received at least two immunizations; and values at week 26 for those who received all 4 immunizations. In panels B, C, and D, Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19); baseline with week 26 (n=10), and baseline with week 48 (n=9).

Fig. 3. HIV-specific CD4 T-cell responses

A. Percentage of individuals with positive CD4 T-cell proliferation responses to stimulation with p24^Gag at time points pre and post immunizations. Two groups shown are those who received all immunizations (n=10) and those who received at least two of the immunizations (n=19; including two who discontinued ARV before week 26). B. HIV-specific CD4 T-cell proliferation. Proliferation index (PI) in response to p24^Gag are shown at baseline and week 6 for all participants who received at least two immunizations; and shown at week 26 and 48 are only those who received all 4 immunizations (one assay at week 48 was not performed due to sample handling problems). C. HIV-specific CD4 T-cell cytokine responses; IL-2 producing, p55^Gag-specific CD4 T-cells. D. HIV-specific CD4 T-cell cytokine responses; IFNγ producing, p55^Gag-specific CD4 T-cells. Panels C and D show baseline and week 6 values for all participants who received at least two immunizations; and values at week 26 for those who received all 4 immunizations. In panels B, C, and D, Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19); baseline with week 26 (n=10), and baseline with week 48 (n=9).

Fig. 3. HIV-specific CD4 T-cell responses

A. Percentage of individuals with positive CD4 T-cell proliferation responses to stimulation with p24^Gag at time points pre and post immunizations. Two groups shown are those who received all immunizations (n=10) and those who received at least two of the immunizations (n=19; including two who discontinued ARV before week 26). B. HIV-specific CD4 T-cell proliferation. Proliferation index (PI) in response to p24^Gag are shown at baseline and week 6 for all participants who received at least two immunizations; and shown at week 26 and 48 are only those who received all 4 immunizations (one assay at week 48 was not performed due to sample handling problems). C. HIV-specific CD4 T-cell cytokine responses; IL-2 producing, p55^Gag-specific CD4 T-cells. D. HIV-specific CD4 T-cell cytokine responses; IFNγ producing, p55^Gag-specific CD4 T-cells. Panels C and D show baseline and week 6 values for all participants who received at least two immunizations; and values at week 26 for those who received all 4 immunizations. In panels B, C, and D, Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19); baseline with week 26 (n=10), and baseline with week 48 (n=9).

Fig. 3. HIV-specific CD4 T-cell responses

A. Percentage of individuals with positive CD4 T-cell proliferation responses to stimulation with p24^Gag at time points pre and post immunizations. Two groups shown are those who received all immunizations (n=10) and those who received at least two of the immunizations (n=19; including two who discontinued ARV before week 26). B. HIV-specific CD4 T-cell proliferation. Proliferation index (PI) in response to p24^Gag are shown at baseline and week 6 for all participants who received at least two immunizations; and shown at week 26 and 48 are only those who received all 4 immunizations (one assay at week 48 was not performed due to sample handling problems). C. HIV-specific CD4 T-cell cytokine responses; IL-2 producing, p55^Gag-specific CD4 T-cells. D. HIV-specific CD4 T-cell cytokine responses; IFNγ producing, p55^Gag-specific CD4 T-cells. Panels C and D show baseline and week 6 values for all participants who received at least two immunizations; and values at week 26 for those who received all 4 immunizations. In panels B, C, and D, Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19); baseline with week 26 (n=10), and baseline with week 48 (n=9).

Fig. 4. HIV-specific CD8 T-cell responses

A. Overlapping pools of peptides were used to detect HIV-1–specific, IFNγ producing cells in an ELISPOT assay. PBMC were stimulated with pools as listed in Table 2. Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19), and baseline with week 26 (n=10). B. Sum of IFNγ producing cells in response to OLP (sum of Gag, Nef, Pol, Rev, Tat responses; background subtracted) as measured by ELISPOT. Baseline is average of screen and entry values. Median values are indicated with a horizontal bar. Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19), and baseline with week 26 (n=10).

Fig. 4. HIV-specific CD8 T-cell responses

A. Overlapping pools of peptides were used to detect HIV-1–specific, IFNγ producing cells in an ELISPOT assay. PBMC were stimulated with pools as listed in Table 2. Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19), and baseline with week 26 (n=10). B. Sum of IFNγ producing cells in response to OLP (sum of Gag, Nef, Pol, Rev, Tat responses; background subtracted) as measured by ELISPOT. Baseline is average of screen and entry values. Median values are indicated with a horizontal bar. Wilcoxon sign rank test p-values shown compare baseline with week 6 (n=19), and baseline with week 26 (n=10).

Fig. 5. HIV-specific CD8 T-cell responses

Participants with pronounced increases in IFNγ producing cells to pools of Gag and Pol OLP were selected to study the production of additional cytokines and degranulation markers in response to the same peptide pools. A. Functional profile of CD8 T-cells responses to Gag Pool 1 at week 26 (subject 9; see also vaccinia responses; Fig. 2B). Frequencies of Gag Pool 1 CD8 T-cell responses at entry were insufficient to represent data in this format. B. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.18; week 6 = 0.15; week 26 = 0.68. C. Functional profile of CD8 T-cells responses to Gag Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Gag Pool 1-specific CD8 T-cells: entry = 0.13; week 6 = 0.09; week 26 = 0.15. D. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline and week 26 (subject 11). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.65; week 26 = 1.03.

Fig. 5. HIV-specific CD8 T-cell responses

Participants with pronounced increases in IFNγ producing cells to pools of Gag and Pol OLP were selected to study the production of additional cytokines and degranulation markers in response to the same peptide pools. A. Functional profile of CD8 T-cells responses to Gag Pool 1 at week 26 (subject 9; see also vaccinia responses; Fig. 2B). Frequencies of Gag Pool 1 CD8 T-cell responses at entry were insufficient to represent data in this format. B. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.18; week 6 = 0.15; week 26 = 0.68. C. Functional profile of CD8 T-cells responses to Gag Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Gag Pool 1-specific CD8 T-cells: entry = 0.13; week 6 = 0.09; week 26 = 0.15. D. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline and week 26 (subject 11). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.65; week 26 = 1.03.

Fig. 5. HIV-specific CD8 T-cell responses

Participants with pronounced increases in IFNγ producing cells to pools of Gag and Pol OLP were selected to study the production of additional cytokines and degranulation markers in response to the same peptide pools. A. Functional profile of CD8 T-cells responses to Gag Pool 1 at week 26 (subject 9; see also vaccinia responses; Fig. 2B). Frequencies of Gag Pool 1 CD8 T-cell responses at entry were insufficient to represent data in this format. B. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.18; week 6 = 0.15; week 26 = 0.68. C. Functional profile of CD8 T-cells responses to Gag Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Gag Pool 1-specific CD8 T-cells: entry = 0.13; week 6 = 0.09; week 26 = 0.15. D. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline and week 26 (subject 11). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.65; week 26 = 1.03.

Fig. 5. HIV-specific CD8 T-cell responses

Participants with pronounced increases in IFNγ producing cells to pools of Gag and Pol OLP were selected to study the production of additional cytokines and degranulation markers in response to the same peptide pools. A. Functional profile of CD8 T-cells responses to Gag Pool 1 at week 26 (subject 9; see also vaccinia responses; Fig. 2B). Frequencies of Gag Pool 1 CD8 T-cell responses at entry were insufficient to represent data in this format. B. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.18; week 6 = 0.15; week 26 = 0.68. C. Functional profile of CD8 T-cells responses to Gag Pool 1 at baseline, week 6 and week 26 (subject 2; note that week 26 profile possibly influenced by episode of viremia at week 24). Frequencies (percentages) of Gag Pool 1-specific CD8 T-cells: entry = 0.13; week 6 = 0.09; week 26 = 0.15. D. Functional profile of CD8 T-cells responses to Pol Pool 1 at baseline and week 26 (subject 11). Frequencies (percentages) of Pol Pool 1-specific CD8 T-cells: entry = 0.65; week 26 = 1.03.