An Enhanced Synthetic Multiclade DNA Prime Induces Improved Cross-Clade-Reactive Functional Antibodies when Combined with an Adjuvanted Protein Boost in Nonhuman Primates

Abstract

The search for an efficacious human immunodeficiency virus type 1 (HIV-1) vaccine remains a pressing need. The moderate success of the RV144 Thai clinical vaccine trial suggested that vaccine-induced HIV-1-specific antibodies can reduce the risk of HIV-1 infection. We have made several improvements to the DNA platform and have previously shown that improved DNA vaccines alone are capable of inducing both binding and neutralizing antibodies in small-animal models. In this study, we explored how an improved DNA prime and recombinant protein boost would impact HIV-specific vaccine immunogenicity in rhesus macaques (RhM). After DNA immunization with either a single HIV Env consensus sequence or multiple constructs expressing HIV subtype-specific Env consensus sequences, we detected both CD4؉ and CD8 ؉ T-cell responses to all vaccine immunogens. These T-cell responses were further increased after protein boosting to levels exceeding those of DNA-only or protein-only immunization. In addition, we observed antibodies that exhibited robust cross-clade binding and neutralizing and antibody-dependent cellular cytotoxicity (ADCC) activity after immunization with the DNA prime-protein boost regimen, with the multiple-Env formulation inducing a more robust and broader response than the single-Env formulation. The magnitude and functionality of these responses emphasize the strong priming effect improved DNA immunogens can induce, which are further expanded upon protein boost. These results support further study of an improved synthetic DNA prime together with a protein boost for enhancing anti-HIV immune responses. IMPORTANCEEven with effective antiretroviral drugs, HIV remains an enormous global health burden. Vaccine development has been problematic in part due to the high degree of diversity and poor immunogenicity of the HIV Env protein. Studies suggest that a relevant HIV vaccine will likely need to induce broad cellular and humoral responses from a simple vaccine regimen due to the resource-limited setting in which the HIV pandemic is most rampant. DNA vaccination lends itself well to increasing the amount of diversity included in a vaccine due to the ease of manufacturing multiple plasmids and formulating them as a single immunization. By increasing the number of Envs within a formulation, we were able to show an increased breadth of responses as well as improved functionality induced in a nonhuman primate model. This increased breadth could be built upon, leading to better coverage against circulating strains with broader vaccine-induced protection.T o prevent human immunodeficiency virus (HIV) infection, a vaccine will likely need to induce antibodies with a broad range of binding and Fc-mediated functions, including antibodydependent cellular cytotoxicity (ADCC) in addition to virus neutralization. The induction of broad multifunctional antibody responses with an HIV vaccine in nonhuman primates (NHPs) has been challenging. Previous studies of neutralizing antibodies have focused on rare tier 1 HIV-1 viruse...

New developments in an old strategy: heterologous vector primes and envelope protein boosts in HIV vaccine design

“…In macaques, both sequential and co-immunization DNA/Env protein strategies have been evaluated. Using a DNA prime consisting of pHIV Gag and Pol along with consensus clades A, B, C, D, and A/E Env gp140s, followed by boosting with SF162 gp140 protein, broadly cross-reactive Abs were induced that had both neutralizing and non-neutralizing activities [142]. The utilization of multiple antigenic targets in the priming vector contributed to greater breadth and functionality of induced Abs.…”

Application of area scaling analysis to identify natural killer cell and monocyte involvement in the GranToxiLux antibody dependent cell‐mediated cytotoxicity assay

“…We have previously described a high‐throughput quantitative flow cytometry‐based assay that allows for detection of the proteolytic activity of Granzyme B (GzB) at the single cell level to identify target cells that have received a cytotoxic hit as a result of antigen‐specific antibody‐Fc receptor interactions . We and others have broadly applied this assay, the ADCC‐GranToxiLux assay (ADCC‐GTL), to the measure of HIV‐ or SIV‐specific antibody responses generated by natural infection or by active and passive immunization strategies .…”

T- and B-cell responses to multivalent prime-boost DNA and viral vectored vaccine combinations against hepatitis C virus in non-human primates

“…The DNA immunization may not have provided an optimal priming, as use of specific formulations or delivery devices such as electroporation would have induced superior priming. 15,22 Notably, higher E2-specific lymphoproliferation and E2-specific cytokine production was induced after MVA boosting in the group immunized with SFV+MVA as compared with DNA+MVA, indicating that SFV priming was responsible for this effect, even though this did not lead to an antibody response to E2 in this group. This could be due to differences in the constructs rather than the delivery vector: for technical reasons, the E2 gene was inserted in a E1-E2 expressing SFV particle as opposed to a combined C-E1-E2 as in the DNA, adenovirus and MVA vectors.…”