An intranasal stringent response vaccine targeting dendritic cells as a novel adjunctive therapy against tuberculosis

Abstract

Lengthy tuberculosis (TB) treatment is required to overcome the ability of a subpopulation of persistent Mycobacterium tuberculosis (Mtb) to remain in a non-replicating, antibiotic-tolerant state characterized by metabolic remodeling, including induction of the Rel Mtb -mediated stringent response. We developed a novel therapeutic DNA vaccine containing a fusion of the rel Mtb gene with the gene encoding the immature dendritic cell-targeting chemokine, MIP-3a/CCL20. To augment mucosal immune responses, intranasal delivery was also evaluated. We found that intramuscular delivery of the MIP-3a/rel Mtb (fusion) vaccine or intranasal delivery of the rel Mtb (nonfusion) vaccine potentiate isoniazid activity more than intramuscular delivery of the DNA vaccine expressing rel Mtb alone in a chronic TB mouse model (absolute reduction of Mtb burden: 0.63 log 10 and 0.5 log 10 colony-forming units, respectively; P=0.0002 and P=0.0052), inducing pronounced Mtbprotective immune signatures. The combined approach involving intranasal delivery of the DNA MIP-3a/rel Mtb fusion vaccine demonstrated the greatest mycobactericidal activity together with isoniazid when compared to each approach alone (absolute reduction of Mtb burden: 1.13 log 10 , when compared to the intramuscular vaccine targeting rel Mtb alone; P<0.0001), as well as robust systemic and local Th1 and Th17 responses. This DNA vaccination strategy may be a promising adjunctive approach combined with standard Frontiers in Immunology frontiersin.org 01

A SARS-CoV-2 RBD vaccine fused to the chemokine MIP-3α elicits sustained murine antibody responses over 12 months and enhanced lung T-cell responses

“…Vaccine plasmid construction and verification pUC57 plasmid containing DNA encoding codon-optimized RBD (spike amino acids 319-545 of Wuhan-Hu-1 isolate) was purchased from GenScript (Piscataway, NJ, USA). DNA was extracted and ligated into a previously generated pSecTag2b plasmid by HindIII and BamHI to generate RBD alone and also by KasI and BamHI to generate MIP-3a-RBD (restriction enzymes from Thermo Fisher, Waltham, MA, USA) (22). Proper insertion was confirmed by agarose gel electrophoresis and sequencing, and the expression of target genes was confirmed by immunoblots probed by anti-C-myc (BioLegend, San Diego, CA, USA) of cell lysates and supernatants following transfection of HEK293T cells (American Type Culture Collection, Manassas, VA, USA) utilizing the Trans-IT 293 transfection system (Mirus Bio, Madison, WI, USA) (Supplementary Figure S1).…”

“…These studies evaluated immunogenicity within a shorter time frame and did not analyze the duration of the observed immune responses (Figure 2A). The IN vaccination regimen employed was identical to that successfully employed in our previously described TB vaccine formulation (22), in which higher DNA plasmid doses were used to compensate for the lack of electroporation. Mice were immunized on four occasions at 3week intervals and received either IN immunization with 200 mg of vaccine (100 mg in each nostril in 50 mL of PBS) or IM immunization with 50 mg of vaccine administered with electroporation and use of the CpG adjuvant, as described.…”

“…While MIP-3a serves as a chemoattractant for iDC (33-38), previous studies have demonstrated the requirement of fusing the vaccine antigen to chemokine to achieve maximum efficacy. In our recent study in a mouse challenge model using a therapeutic vaccine targeting the Mycobacterium tuberculosis stringent response, we found that IN immunization elicited significantly greater antibacterial activity than intramuscular (IM) immunization, and that IN vaccination with the MIP-3a-fused vaccine was also significantly more effective than immunization with vaccine antigen alone (22). Optimal immune responses were observed with a DNA vaccine construct that required no encapsulation of the DNA or use of adjuvant to achieve the observed therapeutic efficacy.…”

“…Unlike the situation for circulating neutralizing antibodies elicited by immunization or previous infection that are readily accessible at the time of pathogen exposure, T-cell immunity is most effective if pathogen-specific T cells pre-exist within the targeted organ (16)(17)(18)(19). To counter respiratory pathogens, multiple studies have indicated that intranasal (IN) immunization is more effective than systemic immunization at eliciting T-cell responses in the lungs (20)(21)(22).…”

“…Targeting immature DC (iDC) distinguishes this vaccine construct from other dendritic cell-targeting vaccines, which engage receptors expressed by more differentiated DC (24-29) to enhance vaccine efficacy. Employment of this vaccine platform has generated greater and, in some model systems, more sustained responses than those observed when the vaccine antigen is not fused to the chemokine (22,23,(30)(31)(32). While MIP-3a serves as a chemoattractant for iDC (33-38), previous studies have demonstrated the requirement of fusing the vaccine antigen to chemokine to achieve maximum efficacy.…”