DNA/MVA HIV-1/AIDS vaccine elicits long-lived vaccinia virus-specific immunity and confers protection against a lethal monkeypox challenge

Abstract

Modified vaccinia Ankara (MVA) is being tested in humans as an alternative to the current smallpox vaccine Dryvax. Here, we compare the magnitude and longevity of protective immune responses elicited by a DNA/MVA HIV-1 vaccine with those elicited by Dryvax using a monkeypox virus/macaque model. The DNA/MVA vaccine elicited similar levels of vaccinia virus (VV)-specific antibody and 5-10-fold lower levels of VV-specific cellular responses than Dryvax. This MVA-elicited cellular and humoral immunity was long-lived. A subset of the DNA/MVA- and Dryvax-vaccinated macaques were subjected to a lethal monkeypox virus challenge at 3 years after vaccination. All of the vaccinated monkeys survived, whereas the unvaccinated controls succumbed to monkeypox. The viral control correlated with early postchallenge levels of monkeypox-specific neutralizing antibody but not with VV-specific cellular immune response. Thus, our results demonstrate the elicitation of long lasting protective immunity for a lethal monkeypox challenge by a DNA/MVA HIV-1 vaccine.

Fig. 1

Schematic for macaque trials. DNA/HIV and MVA/HIV are recombinant DNA and MVA vectors expressing HIV-1 vaccine inserts, respectively. i.v., intravenous; i.m, intramuscular; pfu, plaque forming units.

Fig. 2

Temporal VV-specific cellular immunity elicited by the DMM and Dryvax vaccines. VV-specific IFN-γ producing CD4 and CD8 T cells were measured using an ICS assay. (A) A representative ICS assay. PBMC were stimulated with vaccinia as described in Materials and methods and stained for CD3, CD8 and IFN-γ. Cells were gated on lymphocytes based on the scatter pattern, followed by CD3 expression and analyzed for the expression of CD8 and IFN-γ. Cells in the right quadrants represent CD8 cells and left quadrants represent CD4 cells (CD3 positive, CD8 negative). The frequencies in the upper quadrants are IFN-γ producing cells as a % of total CD4 cells (left quadrants) or total CD8 cells (right quadrants). (B) VV-specific CD4 response in DMM-vaccinated macaques. (C) VV-specific CD4 response in Dryvax-vaccinated macaques. (D) VV-specific CD8 response in DMM-vaccinated macaques. (E) VV-specific CD8 response in Dryvax vaccinated macaques. Each symbol represents an individual macaque. There are 15 animals in the DMM group. For week 9, data are for 5 macaques and for week 174, data are for 10 macaques. The numbers on the graphs represent the geometric means for the groups at different time points. The shaded area on the graph represents the level of detection.

Fig. 3

VV-specific neutralizing antibody elicited by HIV DMM vaccine. (A) Neutralizing antibody response against intracellular mature virion form of vaccinia virus measured using a GFP/flow based assay. Each symbol represents an individual macaque. The shaded area on the graph represents the background level of neutralizing activity observed in the sera of unvaccinated macaques. (B) Neutralizing antibody response against the extracellular form of vaccinia virus using a comet assay. VIG, vaccinia immunoglobulin.

Fig. 4

Comparison of VV-specific cellular and humoral responses elicited by Dryvax, and DMM vaccines in macaques. (A) VV-specific CD4 T cell response. (B) VV-specific CD8 T cell response. VV-specific IFN-γ producing CD4 and CD8 T cells were measured using an ICS assay. (C) Vaccinia virus MV-specific neutralizing antibody response. MV-specific neutralizing antibody response was measured using GFP based assay. Each symbol represents an individual macaque. The numbers on the graph represent the geometric means for the group at different time points. The shaded area on the graph represents the level of detection. ‘n’ represents the number of animals in the respective group. Peak CD4 and CD8 responses for Dryvax and DMM represent weeks 2 and 33 of the respective trials. Memory CD4 and CD8 responses for Dryvax and DMM represent weeks 12 and 40 of the respective trials. Peak neutralizing antibody response for Dryvax and DMM represents weeks 2 and 35 of the respective trials. Memory neutralizing antibody response for Dryvax and DMM represents weeks 84 and 167 of the respective trials. DMM, DNA/MVA/MVA.

Fig. 5

Cellular and humoral immunity, and correlates for protection following MPXV challenge. (A) MPXV-specific neutralizing antibody. Neutralization of monkeypox Zaire strain was performed using a plaque reduction assay. (B) VV-specific CD8 T cell response. VV-specific IFN-γ producing CD8 T cells were measured using an ICS assay. (C) Correlation between the peak viremia and immune responses on the day of challenge. (D) Correlation between the peak viremia and immune responses at day 8, postchallenge.