Prime/boost immunization with HIV-1 MPER-V3 fusion construct enhances humoral and cellular immune responses

Expression and Characterization of Two DNA Constructs Derived from HIV-1-vif in Escherichia coli and Mammalian Cells

Background

Acquired immunodeficiency syndrome (HIV/AIDS) is still a major global concern and no effective therapeutic vaccine has been produced to prevent the problem. Among HIV-1 proteins, vif as a basic cytoplasmic protein of HIV-1 is involved in late stages of viral generation and plays important role in HIV-1 virion replication. It also increases the stability of virion cores, which probably inhibits early degradation of viral entry. Therefore, it seems rational to apply this protein as a vaccine based on its impact on HIV-1 life cycle. This study aimed at cloning, expression and production of vif protein as an HIV-1 vaccine candidate.

Methods

In this study, vif sequence was amplified from pLN4-3 plasmid including HIV-1 vif gene and then cloned in pET23a to generate the recombinant plasmids of pET23a/vif with hexahistidine tags. BL21 competent cells were transformed to obtain the protein of interest. Ni-NTA column was used to purify the protein of interest and western blotting confirmed vif protein using anti-His tag antibody. In order to express the gene of interest in eukaryotic cells, vif was sub-cloned into pEGFP plasmids and HEK 293-T cells were transfected. Flow cytometry was then applied to evaluate GFP expression.

Results

vif protein was expressed in BL21(DE3) strain and identified as a23 kDa band in SDS-PAGE and confirmed by anti-His antibody in western blotting. The purified protein concentration was 173.3 μg/ml using Bradford assay. HEK-293T cells were successfully transfected by recombinant pEGFP plasmids and flow cytometry confirmed the cell transfection.

Conclusion

vif protein can be expressed in mammalian cells and may be a proper protein subunit vaccine candidate against HIV-1.

Internalisation and Biological Activity of Nucleic Acids Delivering Cell-Penetrating Peptide Nanoparticles Is Controlled by the Biomolecular Corona

Nucleic acid molecules can be transferred into cells to alter gene expression and, thus, alleviate certain pathological conditions. Cell-penetrating peptides (CPPs) are vectors that can be used for transfecting nucleic acids as well as many other compounds. CPPs associate nucleic acids non-covalently, forming stable nanoparticles and providing efficient transfection of cells in vitro. However, in vivo, expected efficiency is achieved only in rare cases. One of the reasons for this discrepancy is the formation of protein corona around nanoparticles, once they are exposed to a biological environment, e.g., blood stream. In this study, we compared protein corona of CPP-nucleic acid nanoparticles formed in the presence of bovine, murine and human serum. We used Western blot and mass-spectrometry to identify the major constituents of protein corona forming around nanoparticles, showing that proteins involved in transport, haemostasis and complement system are its major components. We investigated physical features of nanoparticles and measured their biological efficiency in splice-correction assay. We showed that protein corona constituents might alter the fate of nanoparticles in vivo, e.g., by subjecting them to phagocytosis. We demonstrated that composition of protein corona of nanoparticles is species-specific that leads to dissimilar transfection efficiency and should be considered while developing delivery systems for nucleic acids.

Small Interfering RNAs and their Delivery Systems: A Novel Powerful Tool for the Potential Treatment of HIV Infections

Small interfering RNAs (siRNAs) have rapidly developed into biomedical research as a novel tool for the potential treatment of various human diseases. They are based on altered gene expression. In spite of the availability of highly active antiretroviral therapy (HAART), there is a specific interest in developing siRNAs as a therapeutic agent for human immunodeficiency virus (HIV) due to several problems including toxicity and drug resistance along with long term treatment. The successful use of siRNAs for therapeutic goals needs safe and effective delivery to specific cells and tissues. Indeed, the efficiency of gene silencing depends on the potency of the carrier used for siRNA delivery. The combination of siRNA and nano-carriers is a potent method to prevent the limitations of siRNA formulation. Three steps were involved in non-viral siRNA carriers such as the complex formation of siRNA with a cationic carrier, conjugation of siRNA with small molecules, and encapsulation of siRNA within nanoparticles. In this mini-review, the designed siRNAs and their carriers are described against HIV-1 infections both in vitro and in vivo.

Antiviral therapy for the sexually transmitted viruses: recent updates on vaccine development

INTRODUCTION

The sexually transmitted infections (STIs) caused by viruses including human T cell leukemia virus type-1 (HTLV-1), human immunodeficiency virus-1 (HIV-1), human simplex virus-2 (HSV-2), hepatitis C virus (HCV), hepatitis B virus (HBV), and human papillomavirus (HPV) are major public health issues. These infections can cause cancer or result in long-term health problems. Due to high prevalence of STIs, a safe and effective vaccine is required to overcome these fatal viruses.

AREAS COVERED

This review includes a comprehensive overview of the literatures relevant to vaccine development against the sexually transmitted viruses (STVs) using PubMed and Sciencedirect electronic search engines. Herein, we discuss the efforts directed toward development of effective vaccines using different laboratory animal models including mice, guinea pig or non-human primates in preclinical trials, and human in clinical trials with different phases.

EXPERT OPINION

There is no effective FDA approved vaccine against the sexually transmitted viruses (STVs) except for HBV and HPV as prophylactic vaccines. Many attempts are underway to develop vaccines against these viruses. There are several approaches for improving prophylactic or therapeutic vaccines such as heterologous prime/boost immunization, delivery system, administration route, adjuvants, etc. In this line, further studies can be helpful for understanding the immunobiology of STVs in human. Moreover, development of more relevant animal models is a worthy goal to induce effective immune responses in humans.

An overview of in silico vaccine design against different pathogens and cancer

INTRODUCTION

Due to overcome the hardness of the vaccine design, computational vaccinology is emerging widely. Prediction of T cell and B cell epitopes, antigen processing analysis, antigenicity analysis, population coverage, conservancy analysis, allergenicity assessment, toxicity prediction, and protein-peptide docking are important steps in the process of designing and developing potent vaccines against various viruses and cancers. In order to perform all of the analyses, several bioinformatics tools and online web servers have been developed. Scientists must take the decision to apply more suitable and precise servers for each part based on their accuracy.

AREAS COVERED

In this review, a wide-range list of different bioinformatics tools and online web servers has been provided. Moreover, some studies were proposed to show the importance of various bioinformatics tools for predicting and developing efficient vaccines against different pathogens including viruses, bacteria, parasites, and fungi as well as cancer.

EXPERT OPINION

Immunoinformatics is the best way to find potential vaccine candidates against different pathogens. Thus, the selection of the most accurate tools is necessary to predict and develop potent preventive and therapeutic vaccines. To further evaluation of the computational and in silico vaccine design, in vitro/in vivo analyses are required to develop vaccine candidates.

B1 protein: a novel cell penetrating protein for in vitro and in vivo delivery of HIV-1 multi-epitope DNA constructs

Objectives

Enhancement of the potential ability of biomacromolecules to cross cell membranes is a critical step for development of effective therapeutic vaccine especially DNA vaccine against human immunodeficiency virus-1 (HIV-1) infection. The supercharged proteins were known as powerful weapons for delivery of different types of cargoes such as DNA and protein. Hence, we applied B1 protein with + 43 net charges obtained from a single frameshift in the gene encoding enhanced green fluorescent protein (eGFP) for delivery of two multi-epitope DNA constructs (nef-vpu-gp160-p24 and nef-vif-gp160-p24) in vitro and in vivo for the first time. For this purpose, B1 protein was generated in bacterial expression system under native conditions, and used to interact with both DNA constructs.

Results

Our data indicated that B1 protein (~ 27 kDa) was able to form a stable nanoparticle (~ 80–110 nm) with both DNA constructs at nitrogen: phosphate (N: P) ratio of 1:1. Moreover, the transfection efficiency of B1 protein for DNA delivery into HEK-293T cell line indicated that the cellular uptake of nef-vif-gp160-p24 DNA/ B1 and nef-vpu-gp160-p24 DNA/ B1 nanoparticles was about 32–35% with lower intensity as compared to TurboFect commercial reagent. On the other hand, immunization of BALB/c mice with different modalities demonstrated that B1 protein could enhance the levels of antibody, IFN-gamma and Granzyme B eliciting potent and strong Th1-directed cellular immunity.

Conclusion

Generally, our findings showed the potency of B1 protein as a promising gene delivery system to improve an effective therapeutic vaccine against HIV-1 infection.

Combination of Mechanical and Chemical Methods Improves Gene Delivery in Cell-based HIV Vaccines

OBJECTIVE

Novel vaccination approaches are required to control human immunodeficiency virus (HIV) infections. The membrane proximal external region (MPER) of Env gp41 subunit and the V3/glycans of Env gp120 subunit were known as potential antigenic targets for anti-HIV-1 vaccines. In this study, we prepared the modified dendritic cells (DCs) and mesenchymal stem cells (MSCs) with HIV-1 MPER-V3 gene using mechanical and chemical approaches.

METHODS

At first, MPER-V3 fusion DNA delivery was optimized in dendritic cells (DCs) and mesenchymal stem cells (MSCs) using three mechanical (i.e., uniaxial cyclic stretch, equiaxial cyclic stretch and shear stress bioreactors), and two chemical (i.e., TurboFect or Lipofectamine) methods. Next, the modified DCs and MSCs with MPER-V3 antigen were compared to induce immune responses in vivo.

RESULTS

Our data showed that the combination of equiaxial cyclic stretch loading and lipofectamine twice with 48 h intervals increased the efficiency of transfection about 60.21 ± 1.05 % and 65.06 ± 0.09 % for MSCs and DCs, respectively. Moreover, DCs and MSCs transfected with MPER-V3 DNA in heterologous DC or MSC prime/ peptide boost immunizations induced high levels of IgG2a, IgG2b, IFN-γ and IL-10 directed toward Th1 responses as well as an increased level of Granzyme B. Indeed, the modified MSCs and DCs with MPER-V3 DNA could significantly enhance the MPER/V3-specific T-cell responses compared to MPER/V3 peptide immunization.

CONCLUSIONS

These findings showed that the modified MSC-based immunization could elicit effective immune responses against HIV antigen similar to the modified DC-based immunization.

Comparison of HIV-1 Vif and Vpu accessory proteins for delivery of polyepitope constructs harboring Nef, Gp160 and P24 using various cell penetrating peptides

To develop an effective therapeutic vaccine against HIV-1, prediction of the most conserved epitopes derived from major proteins using bioinformatics tools is an alternative achievement. The epitope-driven vaccines against variable pathogens represented successful results. Hence, to overcome this hyper-variable virus, we designed the highly conserved and immunodominant peptide epitopes. Two servers were used to predict peptide-MHC-I binding affinity including NetMHCpan4.0 and Syfpeithi servers. The NetMHCIIpan3.2 server was utilized for MHC-II binding affinity. Then, we determined immunogenicity scores and allergenicity by the IEDB immunogenicity predictor and Algpred, respectively. Next, for estimation of toxicity and population coverage, ToxinPred server and IEDB population coverage tool were applied. After that, the MHC-peptide binding was investigated by GalexyPepDock peptide-protein flexible docking server. Finally, two different DNA and peptide constructs containing Nef-Vif-Gp160-P24 and Nef-Vpu-Gp160-P24 were prepared and complexed with four various cell penetrating peptides (CPPs) for delivery into mammalian cells (MPG and HR9 CPPs for DNA delivery, and CyLoP-1 and LDP-NLS CPPs for protein delivery). Our results indicated that the designed DNA and peptide constructs could form non-covalent stable nanoparticles at certain ratios as observed by scanning electron microscope (SEM) and Zetasizer. The flow cytometry results obtained from in vitro transfection of the nanoparticles into HEK-293T cell lines showed that the percentage of GFP expressing cells was about 38.38 ± 1.34%, 25.36% ± 0.30, 54.95% ± 0.84, and 25.11% ± 0.36 for MPG/pEGFP-nef-vif-gp160-p24, MPG/pEGFP-nef-vpu-gp160-p24, HR9/pEGFP-nef-vif-gp160-p24 and HR9/pEGFP-nef-vpu-gp160-p24, respectively. Thus, these data showed that the DNA construct harboring nef-vif-gp160-p24 multi-epitope gene had higher efficiency than the DNA construct harboring nef-vpu-gp160-p24 multi-epitope gene to penetrate into the cells. Moreover, delivery of the recombinant Nef-Vif-Gp160-P24 and Nef-Vpu-Gp160-P24 polyepitope peptides in HEK-293T cells was confirmed as a single band about 32 kDa using western blot analysis. Although, both DNA and peptide constructs could be successfully transported by a variety of CPPs into the cells, but the difference between them in transfection rate will influence the levels of immune responses for development of therapeutic vaccines.

Cell penetrating peptides: the potent multi-cargo intracellular carriers

Introduction: Cell penetrating peptides (CPPs) known as protein translocation domains (PTD), membrane translocating sequences (MTS), or Trojan peptides (TP) are able to cross biological membranes without clear toxicity using different mechanisms, and facilitate the intracellular delivery of a variety of bioactive cargos. CPPs could overcome some limitations of drug delivery and combat resistant strains against a broad range of diseases. Despite delivery of different therapeutic molecules by CPPs, they lack cell specificity and have a short duration of action. These limitations led to design of combined cargo delivery systems and subsequently improvement of their clinical applications. Areas covered: This review covers all our studies and other researchers in different aspects of CPPs such as classification, uptake mechanisms, and biomedical applications. Expert opinion: Due to low cytotoxicity of CPPs as compared to other carriers and final degradation to amino acids, they are suitable for preclinical and clinical studies. Generally, the efficiency of CPPs was suitable to penetrate the cell membrane and deliver different cargos to specific intracellular sites. However, no CPP-based therapeutic approach has approved by FDA, yet; because there are some disadvantages for CPPs including short half-life in blood, and nonspecific CPP-mediated delivery to normal tissue. Thus, some methods were used to develop the functions of CPPs in vitro and in vivo including the augmentation of cell specificity by activatable CPPs, specific transport into cell organelles by insertion of corresponding localization sequences, incorporation of CPPs into multifunctional dendrimeric or liposomal nanocarriers to improve selectivity and efficiency especially in tumor cells.

Induction of a Robust Humoral Response using HIV-1 VLPMPER-V3 as a Novel Candidate Vaccine in BALB/c Mice

Background:

Several approaches have not been successful to suppress HIV (Human immunodeficiency virus) infection among infected individuals or to prevent it yet. In order to expand strong HIV specific humoral and cellular responses, Virus-like particles (VLPs) as potential vaccines show significant increase in neutralizing antibodies secretion, T-cell count and also secretion of cytokines.

Objective:

This study aimed at immunological evaluation of VLPs harboring high copy of MPERV3 in BALB/c mice.

Methods:

Female BALB/c mice were immunized with homologous and heterologous primeboosting regimens of HIV-1 VLPMPER-V3. Their immune responses were evaluated for humoral responses (Total IgG and IgG isotyping) and cellular responses (IFN-γ, IL-5 secretion, in vitro CTL assay and T cell proliferation) and compared in immunized mice.

Results:

The data showed robust induction of humoral response in mice groups which received different regimens of VLP. Furthermore, analysis of cytokine profile indicated that the highest IL-5 secretion was related to VLP+M50 group and confirmed the dominance of Th2 immunity in this group.

Conclusion:

This study showed that VLP MPER-V3 as a potential vaccine candidate has the potency as an effective prophylactic vaccine and this finding guarantees further investigations to achieve a promising HIV-1 vaccine candidate.

Identification of a HIV Gp41-Specific Human Monoclonal Antibody With Potent Antibody-Dependent Cellular Cytotoxicity

Antibody-Dependent Cellular Cytotoxicity (ADCC) is a major mechanism of protection against viral infections in vivo. Identification of HIV-1-specific monoclonal antibodies (mAbs) with potent ADCC activity may help develop an effective HIV-1 vaccine. In present study, we isolated such human mAb, designated E10, from an HIV-1-infected patient sample by single B cell sorting and single cell PCR. E10 bound to gp140 trimer and linear peptides derived from gp41 membrane proximal external region (MPER). E10 epitope (QEKNEQELLEL) overlapped with mAb 2F5 epitope. However, E10 differentiated from 2F5 in neutralization breadth and potency, as well as ADCC activity. E10 showed low neutralization activity and narrow spectrum of neutralization compared to 2F5, but it mediated higher ADCC activity than 2F5 at low antibody concentration. Fine mapping of E10 epitope may potentiate MPER-based subunit vaccine development.

Membranotropic peptides mediating viral entry

The means used by enveloped viruses to bypass cellular membranes are well characterized; however, the mechanisms used by non-enveloped viruses to deliver their genome inside the cell remain unresolved and poorly defined. The discovery of short, membrane interacting, amphipathic or hydrophobic sequences (known as membranotropic peptides) in both enveloped and non-enveloped viruses suggests that these small peptides are strongly involved in breaching the host membrane and in the delivery of the viral genome into the host cell. Thus, in spite of noticeable differences in entry, this short stretches of membranotropic peptides are probably associated with similar entry-related events. This review will uncover the intrinsic features of viral membranotropic peptides involved in viral entry of both naked viruses and the ones encircled with a biological membrane with the objective to better elucidate their different functional properties and possible applications in the biomedical field.

The development of HIV vaccines targeting gp41 membrane-proximal external region (MPER): challenges and prospects

A human immunodeficiency virus type-1 (HIV-1) vaccine which is able to effectively prevent infection would be the most powerful method of extinguishing pandemic of the acquired immunodeficiency syndrome (AIDS). Yet, achieving such vaccine remains great challenges. The membrane-proximal external region (MPER) is a highly conserved region of the envelope glycoprotein (Env) gp41 subunit near the viral envelope surface, and it plays a key role in membrane fusion. It is also the target of some reported broadly neutralizing antibodies (bNAbs). Thus, MPER is deemed to be one of the most attractive vaccine targets. However, no one can induce these bNAbs by immunization with immunogens containing the MPER sequence(s). The few attempts at developing a vaccine have only resulted in the induction of neutralizing antibodies with quite low potency and limited breadth. Thus far, vaccine failure can be attributed to various characteristics of MPER, such as those involving structure and immunology; therefore, we will focus on these and review the recent progress in the field from the following perspectives: (1) MPER structure and its role in membrane fusion, (2) the epitopes and neutralization mechanisms of MPER-specific bNAbs, as well as the limitations in eliciting neutralizing antibodies, and (3) different strategies for MPER vaccine design and current harvests.

Small heat shock protein 27: An effective adjuvant for enhancement of HIV-1 Nef antigen-specific immunity

Novel vaccine modalities have been designed to improve the efficiency of vaccines against HIV infections. In this way, the HIV-1 Nef protein has been known as an attractive antigenic candidate in therapeutic vaccine development. Moreover, the endogenous adjuvants such as heat shock proteins (HSPs) and high mobility group box 1 protein (HMGB1) have been suggested effectively to induce antigen-specific humoral and cellular immune responses. In this study, different Nef DNA and protein constructs were produced in eukaryotic and prokaryotic expression systems, and their immunostimulatory properties were evaluated using small heat shock protein 27 (Hsp27) and the HMGB1-derived peptide (Hp91) in a mouse model. Generally, our results indicated that the Hsp27-Nef fusion DNA or protein could significantly elicit higher humoral and cellular immune responses than Nef DNA or protein, respectively. Analysis of the immune responses demonstrated that the Hsp27-Nef fusion protein, and also the mixture of Nef and Hp91 significantly enhanced the Nef-specific T cell responses. Indeed, these regimens induced high levels of IgG2a and IFN-γ directed toward Th1 responses and also Granzyme B secretion as compared to other immunization strategies. The immunostimulatory properties of Freund's adjuvant were significantly less than Hsp27 and Hp91 peptide in various immunization strategies. These findings showed that the use of Hsp27 and Hp91 in protein strategy could improve HIV-1 Nef-specific B- and T-cell immune responses, and also represent a promising HIV-1 vaccine candidate in future.

Interleukin-21 administration leads to enhanced antigen-specific T cell responses and natural killer cells in HIV-1 vaccinated mice

Interleukin-21 (IL-21), which belongs to IL-2 γ chain receptor cytokine family, is as an important regulator of immune responses. In this study, we developed a novel strategy for immunizing mice with a DNA/vaccinia/protein vaccine in the presence or absence of mouse IL-21 (mIL-21) to evaluate whether mIL-21 could enhance immune responses. Our results demonstrated that co-immunization with mIL-21 did not increase significantly the capacity of vaccine induced antibodies to bind to HIV-1 GP140. An effect of mIL-21 in adjusting the efficacy of HIV-1 vaccine through enhancing Th1 type immune response was however observed. The frequencies of HIV-1-specific cytokine-producing CD4+ T and CD4+ TEM cells, especially multifunctional T cell responses, were significantly increased by co-administrating with mIL-21. A significant increase was also observed in the frequency of NK cells in mIL-21 adjuvant groups. Taken together, combination of mIL-21 with HIV-1 vaccines led to distinct enhancement of NK cells and T cell immune responses associated with immune protection.