In vivo delivery of a multiepitope peptide and Nef protein using novel cell-penetrating peptides for development of HIV-1 vaccine candidate

Engineered ClearColi™-derived outer membrane vesicles as functional carriers for development of HIV-1 therapeutic vaccine candidate

Bacteria-derived outer membrane vesicles (OMVs) can be engineered to incorporate foreign antigens. This study explored the potential of ClearColi™-derived OMVs as a natural adjuvant and a carrier (recombinant OMVs or rOMVs) for development of an innovative therapeutic vaccine candidate harboring HIV-1 Nef and Nef-Tat antigens. Herein, the rOMVs containing CytolysinA (ClyA)-Nef and ClyA-Nef-Tat fusion proteins were isolated from ClearColi™ strain. The presence of Nef and Nef-Tat proteins on their surface (rOMVNef and rOMVNef-Tat) was confirmed by western blotting after proteinase K treatment. Immune responses induced by Nef and Nef-Tat proteins emulsified with Montanide® ISA720 or mixed with OMVs, and also rOMVNef and rOMVNef-Tat were investigated in BALB/c mice. Additionally, the potency of splenocytes exposed to single-cycle replicable (SCR) HIV-1 virions was assessed for the secretion of cytokines in vitro. Our findings showed that the rOMVs as an antigen carrier (rOMVNef and rOMVNef-Tat) induced higher levels of IgG2a, IFN-γ and granzyme B compared to OMVs as an adjuvant (Nef + OMV and Nef-Tat + OMV), and also Montanide® ISA720 (Nef + Montanide and Nef-Tat + Montanide). Moreover, IFN-γ level in splenocytes isolated from mice immunized with rOMVNef-Tat was higher than other regimens after exposure to SCR virions. Generally, ClearColi™-derived rOMVs can serve as potent carriers for developing effective vaccines against HIV-1 infection.

Uptake pathways of cell-penetrating peptides in the context of drug delivery, gene therapy, and vaccine development

Cell-penetrating peptides have been extensively utilized for the purpose of facilitating the intracellular delivery of cargo that is impermeable to the cell membrane. The researchers have exhibited proficient delivery capabilities for oligonucleotides, thereby establishing cell-penetrating peptides as a potent instrument in the field of gene therapy. Furthermore, they have demonstrated a high level of efficiency in delivering several additional payloads. Cell penetrating peptides (CPPs) possess the capability to efficiently transport therapeutic molecules to specific cells, hence offering potential remedies for many illnesses. Hence, their utilization is imperative for the improvement of therapeutic vaccines. In contemporary studies, a plethora of cell-penetrating peptides have been unveiled, each characterized by its own distinct structural attributes and associated mechanisms. Although it is widely acknowledged that there are multiple pathways through which particles might be internalized, a comprehensive understanding of the specific mechanisms by which these particles enter cells has to be fully elucidated. The absorption of cell-penetrating peptides can occur through either direct translocation or endocytosis. However, it is worth noting that categories of cell-penetrating peptides are not commonly linked to specific entrance mechanisms. Furthermore, research has demonstrated that cell-penetrating peptides (CPPs) possess the capacity to enhance antigen uptake by cells and facilitate the traversal of various biological barriers. The primary objective of this work is to examine the mechanisms by which cell-penetrating peptides are internalized by cells and their significance in facilitating the administration of drugs, particularly in the context of gene therapy and vaccine development. The current study investigates the immunostimulatory properties of numerous vaccine components administered using different cell-penetrating peptides (CPPs). This study encompassed a comprehensive discussion on various topics, including the uptake pathways and mechanisms of cell-penetrating peptides (CPPs), the utilization of CPPs as innovative vectors for gene therapy, the role of CPPs in vaccine development, and the potential of CPPs for antigen delivery in the context of vaccine development.

Immunostimulatory effects of Hsp70 fragments and Hsp27 in design of novel HIV-1 vaccine formulations

BACKGROUND

Heat shock proteins (HSPs) as an adjuvant induce antigen-specific immunity through facilitating antigen presentation and stimulating T cells. In this study, the immunostimulatory properties of two major fragments of Hsp70 (N-Hsp70(aa 1-387) with ATPase property and C-Hsp70 (aa 508-641) with peptide-binding capacity) and the full length of Hsp27 as vaccine adjuvants were evaluated to boost HIV-1 Nef antigen-specific immunity in both in vitro and in vivo experiments.

METHODS

At first, the nanoparticles harbouring DNA fusion constructs (i.e. N-Hsp70-Nef, C-Hsp70-Nef and Hsp27-Nef) complexed with HIV Rev (34-50) cell-penetrating peptide were generated to deliver DNA into the cells. Then, the recombinant Nef, Hsp27-Nef, N-Hsp70-Nef and C-Hsp70-Nef proteins were generated in E.coli expression system. Next, the immunostimulatory properties of these fusion constructs were evaluated in both in vitro and in vivo studies. Finally, the secretion of main cytokines from single-cycle replicable (SCR) HIV-1 virion-exposed splenocytes was investigated.

RESULTS

Our data showed that the stable and non-toxic DNA/Rev nanoparticles could successfully deliver the genes of interest into the cells. Moreover, higher secretion of antibodies and cytokines was detected in mice receiving the Hsp-Nef constructs than in mice receiving Nef antigen. The C-Hsp70 was also superior for inducing Nef-specific Th1 and CTL immunity compared with N-Hsp70 and Hsp27. The T-cell activity was maintained in the SCR-exposed splenocytes, especially the splenocytes of mice receiving the C-Hsp70-Nef regimen.

CONCLUSION

Altogether, these findings demonstrate the significance of Hsps as enhancers of antigen-specific immunity. Notably, the C-Hsp70 region showed better adjuvant properties for inducing cellular immunity in the improvement of HIV-1 therapeutic vaccines.

Heterologous DNA Prime/Protein Boost Immunization Targeting Nef-Tat Fusion Antigen Induces Potent T-cell Activity and in vitro Anti-SCR HIV-1 Effects

BACKGROUND

Heterologous combinations in vaccine design are an effective approach to promote T cell activity and antiviral effects. The goal of this study was to compare the homologous and heterologous regimens targeting the Nef-Tat fusion antigen to develop a human immunodeficiency virus-1 (HIV-1) therapeutic vaccine candidate.

METHODS

At first, the DNA and protein constructs harboring HIV-1 Nef and the first exon of Tat as linked form (pcDNA-nef-tat and Nef-Tat protein) were prepared in large scale and high purity. The generation of the Nef-Tat protein was performed in the E. coli expression system using an IPTG inducer. Then, we evaluated and compared immune responses of homologous DNA prime/ DNA boost, homologous protein prime/ protein boost, and heterologous DNA prime/protein boost regimens in BALB/c mice. Finally, the ability of mice splenocytes to secret cytokines after exposure to single-cycle replicable (SCR) HIV-1 was compared between immunized and control groups in vitro.

RESULTS

The nef-tat gene was successfully subcloned in eukaryotic pcDNA3.1 (-) and prokaryotic pET-24a (+) expression vectors. The recombinant Nef-Tat protein was generated in the E. coli Rosetta strain under optimized conditions as a clear band of ~ 35 kDa detected on SDS-PAGE. Moreover, transfection of pcDNA-nef-tat into HEK-293T cells was successfully performed using Lipofectamine 2000, as confirmed by western blotting. The immunization studies showed that heterologous DNA prime/protein boost regimen could significantly elicit the highest levels of Ig- G2a, IFN-γ, and Granzyme B in mice as compared to homologous DNA/DNA and protein/protein regimens. Moreover, the secretion of IFN-γ was higher in DNA/protein regimens than in DNA/DNA and protein/protein regimens after exposure of mice splenocytes to SCR HIV-1 in vitro.

CONCLUSION

The chimeric HIV-1 Nef-Tat antigen was highly immunogenic, especially when applied in a heterologous prime/ boost regimen. This regimen could direct immune response toward cellular immunity (Th1 and CTL activity) and increase IFN-γ secretion after virus exposure.

LL-37 antimicrobial peptide and heterologous prime-boost vaccination regimen significantly induce HIV-1 Nef-Vpr antigen- and virion-specific immune responses in mice

OBJECTIVES

HIV infection still remains a leading cause of morbidity and mortality worldwide. The inability of highly-active antiretroviral therapy in HIV-1 eradication led to development of therapeutic vaccines. Exploiting effective immunogenic constructs and potent delivery systems are important to generate effective therapeutic vaccines, and overcome their poor membrane permeability. Among HIV-1 proteins, the Nef and Vpr proteins can be considered as antigen candidates in vaccine design.

METHODS

In this study, the immunogenicity of Nef-Vpr antigen candidate in different regimens along with antimicrobial peptide LL-37 (as a DNA carrier) and Montanide 720 (as an adjuvant) was studied in mice. Moreover, the secretion of cytokines was assessed in virion-exposed mice lymphocytes in vitro.

RESULTS

Our data indicated that groups immunized with the homologous protein + Montanide regimen (group 1), and also the heterologous DNA + LL-37 prime/protein + Montanide boost regimen (group 2) could significantly generate strong immune responses as compared to groups immunized with the DNA constructs (groups 3 & 4). Moreover, immunization of mice with the homologous DNA + LL-37 regimen in low dose of DNA (5 µg) could induce higher immune responses than the homologous naked DNA regimen in high dose of DNA (50 µg) indicating the role of LL-37 as a cell penetrating peptide. Additionally, the heterologous DNA + LL-37 prime/protein + Montanide boost regimen (group 2) induced significantly IFN-gamma secretion from virion-exposed lymphocytes in vitro.

CONCLUSION

Generally, the use of LL-37 for DNA delivery, Montanide 720 as an adjuvant, and heterologous DNA prime/protein boost strategy could significantly increase IgG2a, IFN-gamma, and Granzyme B, and maintain cytokine secretion after exposure to virions. Indeed, the heterologous DNA + LL-37 prime/protein + Montanide boost regimen can be considered as a potent strategy for development of therapeutic HIV vaccines.

Cell penetrating peptide: A potent delivery system in vaccine development

One of the main obstacles to most medication administrations (such as the vaccine constructs) is the cellular membrane's inadequate permeability, which reduces their efficiency. Cell-penetrating peptides (CPPs) or protein transduction domains (PTDs) are well-known as potent biological nanocarriers to overcome this natural barrier, and to deliver membrane-impermeable substances into cells. The physicochemical properties of CPPs, the attached cargo, concentration, and cell type substantially influence the internalization mechanism. Although the exact mechanism of cellular uptake and the following processing of CPPs are still uncertain; but however, they can facilitate intracellular transfer through both endocytic and non-endocytic pathways. Improved endosomal escape efficiency, selective cell targeting, and improved uptake, processing, and presentation of antigen by antigen-presenting cells (APCs) have been reported by CPPs. Different in vitro and in vivo investigations using CPP conjugates show their potential as therapeutic agents in various medical areas such as infectious and non-infectious disorders. Effective treatments for a variety of diseases may be provided by vaccines that can cooperatively stimulate T cell-mediated immunity (T helper cell activity or cytotoxic T cell function), and immunologic memory. Delivery of antigen epitopes to APCs, and generation of a potent immune response is essential for an efficacious vaccine that can be facilitated by CPPs. The current review describes the delivery of numerous vaccine components by various CPPs and their immunostimulatory properties.

Immunopotentiation by linking Hsp70 T-cell epitopes to Gag-Pol-Env-Nef-Rev multiepitope construct and increased IFN-gamma secretion in infected lymphocytes

Therapeutic human immunodeficiency virus (HIV) vaccines can boost the anti-HIV host immunity to control viral replication and eliminate viral reservoirs in the absence of anti-retroviral therapy. In this study, two computationally designed multiepitope Gag-Pol-Env-Nef-Rev and Hsp70-Gag-Pol-Env-Nef-Rev constructs harboring immunogenic and highly conserved HIV T cell epitopes were generated in E. coli as polypeptide vaccine candidates. Furthermore, the multiepitope gag-pol-env-nef-rev and hsp70-gag-pol-env-nef-rev DNA vaccine constructs were prepared and complexed with MPG cell-penetrating peptide. The immunogenicity of the multiepitope constructs were evaluated using the homologous and heterologous prime/boost strategies in mice. Moreover, the secretion of IFN-γ was assessed in infected lymphocytes in vitro. Our data showed that the homologous polypeptide regimens could significantly induce a mixture of IgG1 and IgG2a antibody responses, activate T cells to secret IFN-γ, IL-5, IL-10, and generate Granzyme B. Moreover, IFN-γ secretion was significantly enhanced in single-cycle replicable (SCR) HIV-1 virions-infected splenocytes in these groups compared to uninfected splenocytes. The linkage of heat shock protein 70 (Hsp70) epitopes to Gag-Pol-Env-Nef-Rev polypeptide in the homologous regimen increased significantly cytokines and Granzyme B levels, and IFN-γ secretion in virions-infected splenocytes. Briefly, both designed constructs in the homologous regimens can be used as a promising vaccine candidate against HIV infection.

Emerging landscape of cell-penetrating peptide-mediated nucleic acid delivery and their utility in imaging, gene-editing, and RNA-sequencing

The safety issues like immunogenicity and unacceptable cancer risk of viral vectors for DNA/mRNA vaccine delivery necessitate the development of non-viral vectors with no toxicity. Among the non-viral strategies, cell-penetrating peptides (CPPs) have been a topic of interest recently because of their ability to cross plasma membranes and facilitate nucleic acids delivery both in vivo and in vitro. In addition to the application in the field of gene vaccine and gene therapy, CPPs based nucleic acids delivery have been proved by its potential application like gene editing, RNA-sequencing, and imaging. Here, we focus on summarizing the recent applications and progress of CPPs-mediated nucleic acids delivery and discuss the current problems and solutions in this field.