A phase I trial of preventive HIV vaccination with heterologous poxviral-vectors containing matching HIV-1 inserts in healthy HIV-uninfected subjects

Abstract

We evaluated replication-defective poxvirus vectors (modified vaccinia Ankara [MVA] and fowlpox [FPV]) in a homologous and heterologous vector prime-boost vaccination regimen containing matching HIV inserts (MVA-HIV and FPV-HIV) given at months 0, 1, 3, 5 and 7 in 150 healthy HIV-negative vaccinia-naïve participants. FPV-HIV alone was poorly immunogenic, while the high dose (10(9)pfu/2 ml) of MVA-HIV alone elicited maximal responses after two injections: CD4+ and CD8+ T-cell responses in 26/55 (47.3%) and 5/60 (8.3%) of participants, respectively, and IFN-γ ELISpot responses in 28/62 (45.2%). The infrequent CD8+ T-cell responses following MVA-HIV priming were boosted only by the heterologous (FPV-HIV) construct in 14/27 (51.9%) of participants post 4th vaccination. Alternatively, HIV envelope-specific binding antibodies were demonstrated in approximately two-thirds of recipients of the homologous boosting regimen, but in less than 20% of subjects after the heterologous vector boost. Thus, a heterologous poxvirus vector prime-boost regimen can induce HIV-specific CD8+ T-cell and CD4+ T-cell responses, which may be an important feature of an optimal regimen for preventive HIV vaccination.

Trial registration: ClinicalTrials.gov NCT00083603.

Figure 1. Maximum severity of local pain or tenderness (panel A) and of systemic symptoms (panel B) following each of the 5 study injections

Onset of a reaction was within the first 3 days following a study injection. Reactions were followed to resolution to determine the maximum severity. Systemic reactions included malaise/fatigue, headache, chills, myalgia, arthralgia, nausea and vomiting. Groups include both vaccinees and controls who received empty pox vectors. Data are included from all participants in Part B of the study, plus those from Part A who received the same regimen and dosage as the Part B groups.

Figure 2. Ex-vivo HIV-specific CD4+ and CD8+ T-cells induced by heterologous vector (M/F) and homologous vector (M/M) regimens

The percentage of CD4+ (panels A, C and E) and CD8+ (panels B, D and F) T-cells producing γ-interferon (IFN- γ) and/or interleukin-2 (IL-2) in response to Env, Gag, Pol and/or Nef peptide pools (panels A and B), Env peptide pools alone (panels C and D) or Gag peptide pools alone (panels E and F) 2 weeks after the indicated immunization and at the final study visit as measured by intracellular staining assay. Responders are shown in colored circles (red = M/F; blue = M/M; groups include all participants in Part B of the study, plus those from Part A who received the same regimen and dosage as the Part B groups) and non-responders in gray triangles. The boxplots show the distribution of responses in positive responders only. The box indicates the median and interquartile range (IQR); whiskers extend to the furthest point within 1.5 times the IQR from the upper or lower quartile. Numbers at the top of each panel show the number of responders / number with assay result and the percent with positive response. Pol and Nef are not shown due to infrequent responses.

Figure 3. HIV protein-specific CD4+ and CD8+ T-cell responses induced by heterologous vector (M/F) and homologous vector (M/M) regimens

Number of study participants with HIV gene-specific responses among CD4+ T-cells at 2 weeks post 2^nd vaccination (panel A); CD8+ T-cells at 2 weeks post 2nd vaccination (panel B), CD4+ T-cells at 2 weeks post 4th vaccination (panel C), and CD8+ T-cells at 2 weeks post 4^th vaccination (panel D).as measured by intracellular staining assay. Groups include all participants in Part B of the study, plus those from Part A who received the same regimen and dosage as the Part B groups. No participants had positive responses to >2 proteins at these timepoints.

Figure 4. HIV-specific CD4+ and CD8+ T-cells producing multiple cytokines induced by heterologous vector (M/F) and homologous vector (M/M) regimens at 2 weeks post 4^th vaccination

For each panel, the left graph shows the percentage of the HIV-specific CD4+ (panel A) or CD8+ (panel B) T-cells (red = MVA/FP; blue = MVA/MVA; groups include all participants in Part B of the study, plus those from Part A who received the same regimen and dosage as the Part B groups) that are producing one, two or three cytokines for positive responders detected by intracellular staining assay. The right graph depicts the γ-interferon (IFN-γ), interleukin-2 (IL-2) or tumor necrosis factor-α (TNF-α) in those cells producing one cytokine (1^st panel on right), and the percentage of cells co-producing cytokine pairs in those producing two cytokines (2^nd panel on the right). The boxplots indicate the median and IQR; whiskers extend to the furthest point within 1.5 times the IQR from the upper or lower quartile.

Figure 5. HIV-specific Interferon-γ ELISpot assay response rates and magnitude of background-adjusted spot forming cells (SFCs) per 10⁶ PBMC induced by heterologous vector (M/F) and homologous vector (M/M) regimens

Total is the response to Env, Gag, Pol and/or Nef peptide pools. Responders are shown in colored circles (red = M/F; blue = M/M; groups include all participants in Part B of the study, plus those from Part A who received the same regimen and dosage as the Part B groups) and non-responders in gray triangles. The boxplots show the distribution of responses in positive responders only. The box indicates the median and interquartile range (IQR); whiskers extend to the furthest point within 1.5 times the IQR from the upper or lower quartile. Numbers at the top of each panel show the number of responders / number with assay result and the percent with positive response. Pol and Nef are not shown due to infrequent responses.