Protection against SHIV-KB9 infection by combining rDNA and rFPV vaccines based on HIV multiepitope and p24 protein in Chinese rhesus macaques

Abstract

Developing an effective vaccine against HIV infection remains an urgent goal. We used a DNA prime/fowlpox virus boost regimen to immunize Chinese rhesus macaques. The animals were challenged intramuscularly with pathogenic molecularly cloned SHIV-KB9. Immunogenicity and protective efficacy of vaccines were investigated by measuring IFN-γ levels, monitoring HIV-specific binding antibodies, examining viral load, and analyzing CD4/CD8 ratio. Results show that, upon challenge, the vaccine group can induce a strong immune response in the body, represented by increased expression of IFN-γ, slow and steady elevated antibody production, reduced peak value of acute viral load, and increase in the average CD4/CD8 ratio. The current research suggests that rapid reaction speed, appropriate response strength, and long-lasting immune response time may be key protection factors for AIDS vaccine. The present study contributes significantly to AIDS vaccine and preclinical research.

Figure 1

Schematic representation of the rDNA and rFPV vaccine constructs. The functional elements of the expression vector are the following. P_CMV: human cytomegalovirus (CMV) immediate-early promoter/enhancer; Kozak: a Kozak translation-initiation sequence and an initiation codon (ATG) for proper initiation of translation; ER signal: endoplasmic reticulum signal peptide; MEG(4): multi-epitope gene (including 4 epitopes); P24: HIV-1 capsid protein; MEG(25): multi-epitope gene (including 25 epitopes); BGHpA: Bovine growth hormone (BGH) polyadenylation signal; TKL: the left recombinant fowlpox virus; P_E/L: early and late promoter of fowlpox virus; T5NT: terminal signal of fowlpox virus; TKR: the right recombinant fowlpox virus.

Figure 2

Immunization and challenge schedule. rDNA: recombinant DNA; rFPV: recombinant FPV.

Figure 3

Number of IFN-γ-secreting PBMC was detected by ELISPOT after stimulation with p24 peptide pools at various times after immunization and challenge. (a) Histogram bars represent the average number of spots per million cells detected in duplicate cultures for each animal, after subtraction of the average number of spots found in duplicate control cultures of PBMC without stimulation. (b) Dynamics of the IFN-γ response was observed throughout the experiment for each group.

Figure 4

Plasma viral load analysis post-SHIV-KB9 challenge. Viremia was quantified by RT-PCR. (a) Dynamics of viral load for each group. (b) Average value of viral load for each group.

Figure 5

CD4/CD8 ratio analysis and total CD4 counts post-SHIV-KB9 challenge.