HIV-1 Gag-virus-like particles induce natural killer cell immune responses via activation and maturation of dendritic cells

How promising are HIV-1-based virus-like particles for medical applications

New approaches aimed at identifying patient-specific drug targets and addressing unmet clinical needs in the framework of precision medicine are a strong motivation for researchers worldwide. As scientists learn more about proteins that drive known diseases, they are better able to design promising therapeutic approaches to target those proteins. The field of nanotechnology has been extensively explored in the past years, and nanoparticles (NPs) have emerged as promising systems for target-specific delivery of drugs. Virus-like particles (VLPs) arise as auspicious NPs due to their intrinsic properties. The lack of viral genetic material and the inability to replicate, together with tropism conservation and antigenicity characteristic of the native virus prompted extensive interest in their use as vaccines or as delivery systems for therapeutic and/or imaging agents. Owing to its simplicity and non-complex structure, one of the viruses currently under study for the construction of VLPs is the human immunodeficiency virus type 1 (HIV-1). Typically, HIV-1-based VLPs are used for antibody discovery, vaccines, diagnostic reagent development and protein-based assays. This review will be centered on the use of HIV-1-based VLPs and their potential biomedical applications.

Recombinant baculovirus expressing the FrC-OVA protein induces protective antitumor immunity in an EG7-OVA mouse model

Background

The baculovirus (BV) Autographa californica multiple nuclear polyhedrosis virus has been used in numerous protein expression systems because of its ability to infect insect cells and serves as a useful vaccination vector with several benefits, such as its low clinical risks and posttranslational modification ability. We recently reported that dendritic cells (DCs) infected with BV stimulated antitumor immunity. The recombinant BV (rBV) also strongly stimulated peptide-specific T-cells and antitumor immunity. In this study, the stimulation of an immune response against EG7-OVA tumors in mice by a recombinant baculovirus-based combination vaccine expressing fragment C-ovalbumin (FrC-OVA-BV; rBV) was evaluated.

Results

We constructed an rBV expressing fragment C (FrC) of tetanus toxin containing a promiscuous MHC II-binding sequence and a p30-ovalbumin (OVA) peptide that functions in the MHC I pathway. The results showed that rBV activated the CD8⁺ T-cell-mediated response much more efficiently than the wild-type BV (wtBV). Experiments with EG7-OVA tumor mouse models showed that rBV significantly decreased tumor volume and increased survival compared with those in the wild-type BV or FrC-OVA DNA vaccine groups. In addition, a significant antitumor effect of classic prophylactic or therapeutic vaccinations was observed for rBV against EG7-OVA-induced tumors compared with that in the controls.

Conclusion

Our findings showed that FrC-OVA-BV (rBV) induced antitumor immunity, paving the way for its use in BV immunotherapy against malignancies.

NK cells in host responses to viral infections

Natural killer (NK) cells are cytotoxic innate lymphocytes that play an important role in viral clearance. NK cell responses to viral infections were originally believed to be non-specific and lacked immune memory recall responses. It is now appreciated that NK cell responses to viral infections can be specific and in some cases memory recall responses are established. Increasing evidence also illuminates the complexity of NK cell interactions with both innate and adaptive immune cells. Here, we summarize the evidence for NK cell-specific memory responses to viral infections and the intricate reciprocal interactions between NK cells and other immune cells that dictate their activation and effector functions.

Coadministration of a Plasmid Encoding HIV-1 Gag Enhances the Efficacy of Cancer DNA Vaccines

DNA vaccination holds great promise for the prevention and treatment of cancer and infectious diseases. However, the clinical ability of DNA vaccines is still controversial due to the limited immune response initially observed in humans. We hypothesized that electroporation of a plasmid encoding the HIV-1 Gag viral capsid protein would enhance cancer DNA vaccine potency. DNA electroporation used to deliver plasmids in vivo, induced type I interferons, thereby supporting the activation of innate immunity. The coadministration of ovalbumin (OVA) and HIV-1 Gag encoding plasmids modulated the adaptive immune response. This strategy favored antigen-specific Th1 immunity, delayed B16F10-OVA tumor growth and improved mouse survival in both prophylactic and therapeutic vaccination approaches. Similarly, a prophylactic DNA immunization against the melanoma-associated antigen gp100 was enhanced by the codelivery of the HIV-1 Gag plasmid. The adjuvant effect was not driven by the formation of HIV-1 Gag virus-like particles. This work highlights the ability of both electroporation and the HIV-1 Gag plasmid to stimulate innate immunity for enhancing cancer DNA vaccine immunogenicity and demonstrates interesting tracks for the design of new translational genetic adjuvants to overcome the current limitations of DNA vaccines in humans.

Current Advances in Virus-Like Particles as a Vaccination Approach against HIV Infection

HIV-1 virus-like particles (VLPs) are promising vaccine candidates against HIV-1 infection. They are capable of preserving the native conformation of HIV-1 antigens and priming CD4+ and CD8+ T cell responses efficiently via cross presentation by both major histocompatibility complex (MHC) class I and II molecules. Progress has been achieved in the preclinical research of HIV-1 VLPs as prophylactic vaccines that induce broadly neutralizing antibodies and potent T cell responses. Moreover, the progress in HIV-1 dendritic cells (DC)-based immunotherapy provides us with a new vision for HIV-1 vaccine development. In this review, we describe updates from the past 5 years on the development of HIV-1 VLPs as a vaccine candidate and on the combined use of HIV particles with HIV-1 DC-based immunotherapy as efficient prophylactic and therapeutic vaccination strategies.

Baculovirus Infection of Human Monocyte-Derived Dendritic Cells Restricts HIV-1 Replication

Acquired immune deficiency syndrome (AIDS) is mainly caused by infection with human immunodeficiency virus-1 (HIV-1) and still poses a global threat for which we lack a protective or therapeutic vaccine. Dendritic cells (DCs) play a major role in the onset of HIV infection, providing one of the primary sites of HIV replication, and also act as viral reservoirs in vivo. Previous studies have shown that baculovirus (BV) induces strong host immune responses against infections and malignancies. In this study, we infected human monocyte-derived DCs with recombinant BV (AcCAG-gag) and showed that AcCAG-gag-infected human DCs underwent maturation and produced interferon alpha and other proinflammatory cytokines accompanied by increases in the mRNA and protein expression levels of APOBEC3 (A3A, A3F, and A3G), proteins associated with the inhibition of HIV-1 replication. Surprisingly, HIV-1 inhibition is also observed in human DCs infected with a wild-type BV, as determined by the production of inflammatory cytokines, the expression of A3, and a reduction in the p24 level. Our findings outline the mechanism underlying the inhibition of HIV-1 in BV-infected human DCs and pave the way for the use of BV as an effective tool for immunotherapy against HIV-1.

The immune-enhancing effect of the Cronobacter sakazakii ES2 phage results in the activation of nuclear factor-κB and dendritic cell maturation via the activation of IL-12p40 in the mouse bone marrow

The bacteriophage ES2 is a virus for bacterial host cells. Unlike other phages that are known for their therapeutic effects, the ES2 phage has never been clearly examined as a therapeutic agent. To systematically and conclusively evaluate its therapeutic efficacy, the expression of the surface markers CD86, CD40, and MHCII, the production of the proinflammatory cytokines IL-6, IL-1α, IL-1β, and TNF-α, and the underlying NF-κB signaling pathway in murine bone marrow-derived dendritic cells (BM-DCs) in response to ES2 phage infection were examined. The bacteriophage ES2, which was isolated from swine fecal samples an antigen, affected the expression of the cell surface molecules and proinflammatory cytokines that are associated with the DC maturation processes. Treatment with ES2 phage also led to NF-κBp65 activation and translocation to the nucleus, which indicates the activation of NF-κB signaling. Furthermore, the ES2 phage induced the promoter activity of IL-12p40. Our chromatin immunoprecipitation assay revealed that p65 was enriched at the IL12-p40 promoter as a direct target of chromatin. The present study demonstrates that the ES2 phage potently induces DC maturation via immune-enhancement processes.

HIV-1 Gag-virus-like particles inhibit HIV-1 replication in dendritic cells and T cells through IFN-α-dependent upregulation of APOBEC3G and 3F

Human immunodeficiency virus-1 (HIV-1) infection and the acquired immune deficiency syndrome (AIDS) pandemic remain global threats in the absence of a protective or a therapeutic vaccine. HIV-1 replication is reportedly inhibited by some cellular factors, including APOBEC3G (A3G) and APOBEC3F (A3F), which are well known inhibitors of HIV-1. Recently, HIV-1 Gag-virus-like particles (Gag-VLPs) have been shown to be safe and potent HIV-1 vaccine candidates that can elicit strong cellular and humoral immunity without need of any adjuvant. In this report, we stimulated human monocyte-derived dendritic cells (DCs) with Gag-VLPs and we demonstrated that Gag-VLP-treated DCs (VLP-DCs) produced interferon alpha (IFN-α), along with an increase in mRNA and protein expression of A3G and A3F. Gag-VLPs inhibited HIV-1 replication not only in DCs themselves, but also in cocultured T cells in an IFN-α-dependent manner. In addition, A3G/3F content in HIV virions released from VLP-DCs increased. Both the increase in A3G/3F expression and the inhibition of HIV-1 replication were reversed by anti-IFN-α or anti-IFNAR antibodies. Our findings in this study provide insight into the mechanism of Gag-VLP-induced inhibition of HIV-1 replication in DCs and T cells.