Abstract
The influence of DNA vaccine formulations on immune responses in combination with adjuvants was investigated with the aim to increase cell-mediated immunity against plasmid DNA (pDNA) encoding Mycobacterium tuberculosis antigen 85A. Different ratios of pDNA with cationic trimethyl chitosan (TMC) nanoparticles were characterized for their morphology and physicochemical characteristics (size, zeta potential, loading efficiency and pDNA release profile) applied in vitro for cellular uptake studies and in vivo, to determine the dose-dependent effects of pDNA on immune responses. A selected pDNA/TMC nanoparticle formulation was optimized by the incorporation of muramyl dipeptide (MDP) as an immunostimulatory agent. Cellular uptake investigations in vitro showed saturation to a maximum level upon the increase in the pDNA/TMC nanoparticle ratio, correlating with increasing Th1-related antibody responses up to a definite pDNA dose applied. Moreover, TMC nanoparticles induced clear polarization towards a Th1 response, indicated by IgG2c/IgG1 ratios above unity and enhanced numbers of antigen-specific IFN-γ producing T-cells in the spleen. Remarkably, the incorporation of MDP in TMC nanoparticles provoked a significant additional increase in T-cell-mediated responses induced by pDNA. In conclusion, pDNA-loaded TMC nanoparticles are capable of provoking strong Th1-type cellular and humoral immune responses, with the potential to be further optimized by the incorporation of MDP.
Highlights
Activation of potent Th1 cellular immune responses has been shown to play a role againstMycobacterium tuberculosis (Mtb) infection and reactivation
Other than the final amount of each component used in the formulation composition, no differences in the physicochemical characteristics of the final product of plasmid DNA (pDNA)/trimethyl chitosan (TMC) nanoparticle formulations were observed
Our studies provided evidence that the combination of adjuvants to Ag85A-encoding pDNA in a single nanoparticle formulation can lead to an effective targeting of the cellular immune system and developed profound Th1 cell-mediated immune responses in mice
Summary
Activation of potent Th1 cellular immune responses has been shown to play a role against. It is contemplated as a promising strategy for developing new effective vaccines against tuberculosis [1,2,3]. DNA (pDNA) induce specific immune responses against the pathogen, without the risk of reversion into virulence associated with live-attenuated vaccines [4]. DNA vaccines have the potential to induce both humoral and cellular immune responses, including cytotoxic T-cell responses, which is crucial to prevent the reactivation of latent tuberculosis infection and to mediate the elimination of intracellular Mtb [5]. Ag85A is among the major Mtb secretory proteins, and immune responses against this antigen play a key role in tuberculosis infection [6].
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