Protein-based nanoparticles in cancer vaccine development

Peptide and protein-based cancer vaccines usually fail to elicit efficient immune responses against tumors. However, delivery of these peptides and proteins as components within caged protein nanoparticles has shown promising improvements in vaccine efficacy. Advantages of protein nanoparticles over other vaccine platforms include their highly organized structures and symmetry, biodegradability, ability to be specifically functionalized at three different interfaces (inside and outside the protein cage, and between subunits in macromolecular assembly), and ideal size for vaccine delivery. In this review, we discuss different classes of virus-like particles and caged protein nanoparticles that have been used as vehicles to transport and increase the interaction of cancer vaccine components with the immune system. We review the effectiveness of these protein nanoparticles towards inducing and elevating specific immune responses, which are needed to overcome the low immunogenicity of the tumor microenvironment.     

Effects of varying antigens and adjuvant systems on the immunogenicity and safety of investigational tetravalent human oncogenic papillomavirus vaccines: Results from two randomized trials

Background

A prophylactic human papillomavirus (HPV) vaccine targeting oncogenic HPV types in addition to HPV-16 and -18 may broaden protection against cervical cancer. Two Phase I/II, randomized, controlled studies were conducted to compare the immunogenicity and safety of investigational tetravalent HPV L1 virus-like particle (VLP) vaccines, containing VLPs from two additional oncogenic genotypes, with the licensed HPV-16/18 AS04-adjuvanted vaccine (control) in healthy 18–25 year-old women.

Methods

In one trial (NCT00231413), subjects received control or one of 6 tetravalent HPV-16/18/31/45 AS04 vaccine formulations at months (M) 0,1,6. In a second trial (NCT00478621), subjects received control or one of 5 tetravalent HPV-16/18/33/58 vaccines formulated with different adjuvant systems (AS04, AS01 or AS02), administered on different schedules (M0,1,6 or M0,3 or M0,6).

Results

One month after the third injection (Month 7), there was a consistent trend for lower anti-HPV-16 and -18 geometric mean antibody titers (GMTs) for tetravalent AS04-adjuvanted vaccines compared with control. GMTs were statistically significantly lower for an HPV-16/18/31/45 AS04 vaccine containing 20/20/10/10 μg VLPs for both anti-HPV-16 and anti-HPV-18 antibodies, and for an HPV-16/18/33/58 AS04 vaccine containing 20/20/20/20 μg VLPs for anti-HPV-16 antibodies. There was also a trend for lower HPV-16 and -18-specific memory B-cell responses for tetravalent AS04 vaccines versus control. No such trends were observed for CD4⁺ T-cell responses. Immune interference could not always be overcome by increasing the dose of HPV-16/18 L1 VLPs or by using a different adjuvant system. All formulations had acceptable reactogenicity and safety profiles. Reactogenicity in the 7-day post-vaccination period tended to increase with the introduction of additional VLPs, especially for formulations containing AS01.

Conclusions

HPV-16 and -18 antibody responses were lower when additional HPV L1 VLPs were added to the HPV-16/18 AS04-adjuvanted vaccine. Immune interference is a complex phenomenon that cannot always be overcome by changing the antigen dose or adjuvant system.     

Progress on pursuit of human cytomegalovirus vaccines for prevention of congenital infection and disease

Congenital infection of human cytomegalovirus (HCMV) is the leading cause of childhood hearing loss and mental retardation. Unfortunately, a preventive vaccine remains elusive. Two strategies have been employed to develop HCMV vaccines, including (1) attenuating HCMV to generate modified virus vaccines and (2) isolating subunit viral antigen(s) to create individual antigen vaccines. The most studied candidate in each category is live attenuated Towne virus and recombinant gB/MF59 vaccine, respectively. Although both were moderately efficacious, neither could induce the durable, robust humoral and cellular immunity commonly seen in HCMV seropositive subjects. In addition, both vaccines failed to induce neutralizing antibodies against viral infection of endothelial cells, epithelial cells and leukocytes. This review summarizes the recent understanding of host natural immunity to HCMV, including the importance of antibodies targeting HCMV epithelial tropism, and discusses its implications for vaccine design. We also highlight some recent key discoveries that may lead to the development of an effective HCMV vaccine.     

Production and characterization of mammalian virus-like particles from modified vaccinia virus Ankara vectors expressing influenza H5N1 hemagglutinin and neuraminidase

Several studies have described the production of influenza virus-like particles (VLP) using a variety of platform systems. These VLPs are non-replicating particles that spontaneously self-assemble from expressed influenza virus proteins and have been proposed as vaccine candidates for both seasonal and pandemic influenza. Although still in the early stages of development and evaluation as influenza vaccines, influenza VLPs have a variety of other valuable uses such as examining and understanding correlates of protection against influenza and investigating virus-cell interactions. The most common production system for influenza VLPs is the baculovirus-insect cell expression which has several attractive features including the ease in which new gene combinations can be constructed, the immunogenicity elicited and protection afforded by the produced VLPs, and the scalability offered by the system. However, there are differences between the influenza VLPs produced by baculovirus expression systems in insect cells and the influenza viruses produced for use as current vaccines or the virus produced during a productive clinical infection. We describe here the development of a modified vaccinia virus Ankara (MVA) system to generate mammalian influenza VLPs containing influenza H5N1 proteins. The MVA vector system is flexible for manipulating and generating various VLP constructs, expresses high level of influenza hemagglutinin (HA), neuraminidase (NA), and matrix (M) proteins, and can be scaled up to produce VLPs in quantities sufficient for in vivo studies. We show that mammalian VLPs are generated from recombinant MVA vectors expressing H5N1 HA alone, but that increased VLP production can be achieved if NA is co-expressed. These mammalian H5N1 influenza VLPs have properties in common with live virus, as shown by electron microscopy analysis, their ability to hemagglutinate red blood cells, express neuraminidase activity, and to bind influenza specific antibodies. Importantly, these VLPs are able to elicit a protective immune response in a mouse challenge model, suggesting their utility in dissecting the correlates of immunity in such models. Mammalian derived VLPs may also provide a useful tool for studying virus-cell interactions and may have potential for development as pandemic vaccines.     

Modification of human papillomavirus-like particle vaccine by insertion of the cross-reactive L2-epitopes

Infection with human papillomavirus 16 (HPV16), which is one of the 15 types of HPV causally associated with cervical cancer and accounts for 50% of the cases, can be prevented in a type-specific manner by an HPV16 virus-like particle (VLP) vaccine comprised of particles of the L1 protein alone. We attempted to modify the VLP vaccine by inserting the HPV16 L2-peptides including cross-neutralization epitopes into the L1 polypeptide. The chimeric L1 had, between L1 amino acids (aa) 430 and 433, the L2 sequence of aa 18-38, 56-75, or 96-115 (with the replacements of S at aa 101 and T at aa 112 with L and S, respectively). The three chimeric L1s were each expressed from the recombinant baculovirus in insect Sf9 cells, and the resultant VLPs were characterized. The chimeric VLPs were shown to present the L2-peptides on their surface. By immunizing rabbits with the VLPs, it was shown that they retained capability to induce the antibody neutralizing HPV16 and acquired capability to elicit antibodies cross-neutralizing the infectious HPV18, 31, 52, and 58 pseudovirions. Although the cross-neutralizing titers were lower than the type-specific neutralizing titer, the results suggest that the chimeric VLPs have potential to serve as a vaccine candidate for a broad spectrum of high-risk HPVs.     

Recombinant retrovirus-derived virus-like particle-based vaccines induce hepatitis C virus-specific cellular and neutralizing immune responses in mice

While the immunological correlates of hepatitis C virus (HCV)-specific immunity are not well understood, it is now admitted that an effective vaccine against HCV will need to induce both cellular and humoral immune responses and address viral heterogeneity to prevent immune escape. We developed a vaccine platform specifically aimed at inducing such responses against HCV antigens displayed by recombinant retrovirus-based virus-like particles (VLPs) made of Gag of murine leukemia virus. Both ex vivo produced VLPs and plasmid DNA encoding VLPs can be used as vaccines. Here, we report that immunizations with plasmid DNA forming VLPs pseudotyped with HCV E1 and E2 envelope glycoproteins (HCV-specific plasmo-retroVLPs) induce strong T-cell-mediated immune responses that can be optimized by using proper DNA delivery methods and/or genetic adjuvants. Additionally, multigenotype or multi-specific T-cell responses were observed after immunization with plasmids that encode VLPs pseudotyped with E1E2 derived from numerous viral genotypes and/or displaying NS3 antigen in capsid proteins. While homologous prime-boost immunizations with HCV-specific plasmo-retroVLPs or ex vivo produced VLPs induce a low level of specific antibody responses, optimal combination of plasmo-retroVLPs and VLPs was identified for inducing HCV-specific T-cell and B-cell responses as well as neutralizing antibodies. Altogether, these results have important meanings for the development of anti-HCV preventive vaccines and exemplify the flexibility and potential of our retrovirus-based platform in inducing broad cellular and humoral immune responses.     

急性心肌梗死伴室性心律失常晚电位临床意义

目的　对急性心肌梗死 (AMI)进行心室晚电位 (VLP)测定 ,分析室性心律失常 (VAR)和VLP的相关性。方法　采用美国生产ECGLABTM工作站 ,VLP采用Frankd导联测定。结果　发现AMI伴VAR者VLP比未伴VAR者阳性率明显增高 ,两组相比差异显著 ,并发现多部位比单部位阳性率高。结论　VLP与心律失常有着密切联系 ,VLP阳性者 ,室内电活动呈不稳定状态 ,有发生恶性心律失常的可能。     

Immunogenicity of adjuvanted plant-produced SARS-CoV-2 Beta spike VLP vaccine in New Zealand white rabbits

The outbreak of the SARS-CoV-2 global pandemic heightened the pace of vaccine development with various vaccines being approved for human use in a span of 24 months. The SARS-CoV-2 trimeric spike (S) surface glycoprotein, which mediates viral entry by binding to ACE2, is a key target for vaccines and therapeutic antibodies. Plant biopharming is recognized for its scalability, speed, versatility, and low production costs and is an increasingly promising molecular pharming vaccine platform for human health. We developed Nicotiana benthamiana-produced SARS-CoV-2 virus-like particle (VLP) vaccine candidates displaying the S-protein of the Beta (B.1.351) variant of concern (VOC), which triggered cross-reactive neutralising antibodies against Delta (B.1.617.2) and Omicron (B.1.1.529) VOCs. In this study, immunogenicity of the VLPs (5 µg per dose) adjuvanted with three independent adjuvants i.e. oil-in-water based adjuvants SEPIVAC SWE^TM (Seppic, France) and “AS IS” (Afrigen, South Africa) as well as a slow-release synthetic oligodeoxynucleotide (ODN) adjuvant designated NADA (Disease Control Africa, South Africa) were evaluated in New Zealand white rabbits and resulted in robust neutralising antibody responses after booster vaccination, ranging from 1:5341 to as high as 1:18204. Serum neutralising antibodies elicited by the Beta variant VLP vaccine also showed cross-neutralisation against the Delta and Omicron variants with neutralising titres ranging from 1:1702 and 1:971, respectively. Collectively, these data provide support for the development of a plant-produced VLP based candidate vaccine against SARS-CoV-2 based on circulating variants of concern.     

A multivalent polyomavirus vaccine elicits durable neutralizing antibody responses in macaques

In 2019, there were about 100,000 kidney transplants globally, with more than a quarter of them performed in the United States. Unfortunately, some engrafted organs are lost to polyomavirus-associated nephropathy (PyVAN) caused by BK and JC viruses (BKPyV and JCPyV). Both viruses cause brain disease and possibly bladder cancer in immunosuppressed individuals. Transplant patients are routinely monitored for BKPyV viremia, which is an accepted hallmark of nascent nephropathy. If viremia is detected, a reduction in immunosuppressive therapy is standard care, but the intervention comes with increased risk of immune rejection of the engrafted organ. Recent reports have suggested that transplant recipients with high levels of polyomavirus-neutralizing antibodies are protected against PyVAN. Virus-like particle (VLP) vaccines, similar to approved human papillomavirus vaccines, have an excellent safety record and are known to induce high levels of neutralizing antibodies and long-lasting protection from infection. In this study, we demonstrate that VLPs representing BKPyV genotypes I, II, and IV, as well as JCPyV genotype 2 produced in insect cells elicit robust antibody titers. In rhesus macaques, all monkeys developed neutralizing antibody titers above a previously proposed protective threshold of 10,000. A second inoculation, administered 19 weeks after priming, boosted titers to a plateau of $\ge$ 25,000 that was maintained for almost two years. No vaccine-related adverse events were observed in any macaques. A multivalent BK/JC VLP immunogen did not show inferiority compared to the single-genotype VLP immunogens. Considering these encouraging results, we believe a clinical trial administering the multivalent VLP vaccine in patients waiting to receive a kidney transplant is warranted to evaluate its ability to reduce or eliminate PyVAN.