Influenza and Other Respiratory Viruses: Vaccine against SARS-CoV-2: Challenges and considerations

It is essential to consider challenges previously faced and addressed while developing a vaccine against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Considering the severity of the health crisis that SARS-CoV-2 has caused worldwide, and with so little known about the virus, our focus should be drawn towards approaches that can bring better development outcomes in a relatively short period of time. This commentary discusses the use of nucleic acid (deoxyribonucleic acid and ribonucleic acid) vaccines against viral infections and pandemic-like settings. The potential advantages of the nucleic acid vaccines over conventional vaccines are presented, and the nucleic acid vaccines currently in development against viral infections and the challenges these vaccines face entering clinical trial are discussed.     

Sequential nucleic acid and recombinant adenovirus vaccination induces host-protective immune responses against Taenia ovis infection in sheep

Sheep were immunized with a protective recombinant antigen (45W) from the cestode parasite Taenia ovis using three different vaccine delivery systems, either alone or in different combinations. The DNA encoding 45W was cloned into the expression plasmid pcDNA 3 and an ovine adenovirus to create nucleic acid and recombinant viral vector vaccines, respectively. Sheep received two vaccinations with various combinations of these two delivery systems and/or purified recombinant 45W protein in a conventional vaccine formulation containing Quil A as adjuvant (protein/Quil A vaccine). Sheep receiving two inoculations of either the nucleic acid or the recombinant adenovirus alone, demonstrated only low levels of 45W-specific antibody. However, immunization with either nucleic acid or recombinant adenovirus primed animals to mount an enhanced immune response after a subsequent vaccination with the protein/Quil A vaccine. The most striking result was that sheep initially immunized with the nucleic acid vaccine and boosted with the recombinant adenovirus, mounted IgG₁ responses >65 fold higher than those of sheep receiving either vaccine alone. The level of antibody in these sheep was commensurate with that observed in animals vaccinated twice with the protein/Quil A adjuvanted vaccine. In both cases, host-protection from experimental challenge infection with T. ovis was obtained.     

Poly-beta amino ester-containing microparticles enhance the activity of nonviral genetic vaccines

Current nonviral genetic vaccine systems are less effective than viral vaccines, particularly in cancer systems where epitopes can be weakly immunogenic and antigen-presenting cell processing and presentation to T cells is down-regulated. A promising nonviral delivery method for genetic vaccines involves microencapsulation of antigen-encoding DNA, because such particles protect plasmid payloads and target them to phagocytic antigen-presenting cells. However, conventional microparticle formulations composed of poly lactic-co-glycolic acid take too long to release encapsulated payload and fail to induce high levels of target gene expression. Here, we describe a microparticle-based DNA delivery system composed of a degradable, pH-sensitive poly-beta amino ester and poly lactic-co-glycolic acid. These formulations generate an increase of 3-5 orders of magnitude in transfection efficiency and are potent activators of dendritic cells in vitro. When used as vaccines in vivo, these microparticle formulations, unlike conventional formulations, induce antigen-specific rejection of transplanted syngenic tumor cells.     

Transiently Transfected Mammalian Cell Cultures: An Adaptable and Effective Platform for Virus-like Particle-Based Vaccines against Foot-and-Mouth Disease Virus

RNA viruses, such as foot-and-mouth disease virus (FMDV), have error-prone replication resulting in the continuous emergence of new viral strains capable of evading current vaccine coverage. Vaccine formulations must be regularly updated, which is both costly and technically challenging for many vaccine platforms. In this report, we describe a plasmid-based virus-like particle (VLP) production platform utilizing transiently transfected mammalian cell cultures that combines both the rapid response adaptability of nucleic-acid-based vaccines with the ability to produce intact capsid epitopes required for immunity. Formulated vaccines which employed this platform conferred complete protection from clinical foot-and-mouth disease in both swine and cattle. This novel platform can be quickly adapted to new viral strains and serotypes through targeted exchanges of only the FMDV capsid polypeptide nucleic acid sequences, from which processed structural capsid proteins are derived. This platform obviates the need for high biocontainment manufacturing facilities to produce inactivated whole-virus vaccines from infected mammalian cell cultures, which requires upstream expansion and downstream concentration of large quantities of live virulent viruses.     

狂犬病mRNA疫苗的应用和研究进展

狂犬病是一个古老而又传统的疾病,其公共安全威胁持续存在,人类需要新型、快速和价格更为低廉的疫苗技术对其进行防治。mRNA疫苗作为一种新型的核酸疫苗, 在感染性疾病的预防控制和癌症的治疗等领域已经取得阶段性进展,因此狂犬病mRNA疫苗有望成为抗击狂犬病的新生力量。本文将从狂犬病mRNA疫苗的结构、递送系统和临床前及临床研究等方面进行简要综述,阐明狂犬病mRNA疫苗目前的研究现状。     

A Glimmer of Hope: Recent Updates and Future Challenges in Zika Vaccine Development

The emergence and rapid spread of Zika virus (ZIKV) on a global scale as well as the establishment of a causal link between Zika infection and congenital syndrome and neurological disorders triggered unprecedented efforts towards the development of a safe and effective Zika vaccine. Multiple vaccine platforms, including purified inactivated virus, nucleic acid vaccines, live-attenuated vaccines, and viral-vectored vaccines, have advanced to human clinical trials. In this review, we discuss the recent advances in the field of Zika vaccine development and the challenges for future clinical efficacy trials. We provide a brief overview on Zika vaccine platforms in the pipeline before summarizing the vaccine candidates in clinical trials, with a focus on recent, promising results from vaccine candidates that completed phase I trials. Despite low levels of transmission during recent years, ZIKV has become endemic in the Americas and the potential of large Zika outbreaks remains real. It is important for vaccine developers to continue developing their Zika vaccines, so that a potential vaccine is ready for deployment and clinical efficacy trials when the next ZIKV outbreak occurs.     

La nueva generación de vacunas de ARN mensajero (ARNm) frente a la gripe

Today there are multiple types of flu vaccines. The emergence of nucleic acid technology used in vaccines against SARS-CoV-2 suggests its future application against this infection. Against influenza, two types of vaccines have been developed based on messenger RNA (mRNA): conventional or non-replicative and self-amplifying or replicative (auRNA), both included in lipid nanoparticles. Animal studies carried out with the former have shown their strong capacity to induce Th-1 antibodies and cellular immunity against influenza haemagglutinin (HA) with few side effects. Human trials have shown 87% seroconversion and 100% seroprotection. The auRNA vaccines have obtained similar results in animals but at a concentration 64 times lower than the conventional one. Vaccines based on mRNA platforms meet the WHO requirements for next generation influenza vaccines.     

衣原体疫苗的研究策略与进展

衣原体(Chlamydia)是一种专性胞内寄生菌,衣原体的反复感染及其诱发的严重后遗症是人类健康的巨大威胁,因此,迫切需要开发安全有效的疫苗来预防和控制衣原体感染.尽管人类在衣原体免疫保护机制的研究和疫苗开发方面已经取得了一定的突破,但是结合疫苗安全性和免疫效果的全面考量,有效衣原体疫苗的成功出世仍然面临很多问题.本文...     

Respiratory Viruses in Solid Organ Transplant Recipients

Solid organ transplantation is often lifesaving, but does carry an increased risk of infection. Respiratory viral infections are one of the most prevalent infections, and are a cause of significant morbidity and mortality, especially among lung transplant recipients. There is also data to suggest an association with acute rejection and chronic lung allograft dysfunction in lung transplant recipients. Respiratory viral infections can appear at any time post-transplant and are usually acquired in the community. All respiratory viral infections share similar clinical manifestations and are all currently diagnosed using nucleic acid testing. Influenza has good treatment options and prevention strategies, although these are hampered by resistance to neuraminidase inhibitors and lower vaccine immunogenicity in the transplant population. Other respiratory viruses, unfortunately, have limited treatments and preventive methods. This review summarizes the epidemiology, clinical manifestations, therapies and preventive measures for clinically significant RNA and DNA respiratory viruses, with the exception of SARS-CoV-2. This area is fast evolving and hopefully the coming decades will bring us new antivirals, immunologic treatments and vaccines.     

弓形虫病疫苗研究进展概述

弓形虫是一种专性细胞内寄生原虫,能引起人畜共患弓形虫病,严重威胁着人类健康且对畜牧业的发展造成巨大的经济损失。研制安全有效的疫苗是防制弓形虫病的策略之一。目前,弓形虫病疫苗包括灭活疫苗、减毒活疫苗、核酸疫苗、亚单位疫苗和卡介苗。本文对弓形虫病疫苗的研究现状进行了综述。     

Massively parallel sequencing for monitoring genetic consistency and quality control of live viral vaccines

Intrinsic genetic instability of RNA viruses may lead to the accumulation of revertants during manufacture of live viral vaccines, requiring rigorous quality control to ensure vaccine safety. Each lot of oral poliovirus vaccine (OPV) is tested for neurovirulence in animals and also for the presence of neurovirulent revertants. Mutant analysis by PCR and restriction enzyme cleavage (MAPREC) is used to measure the frequency of neurovirulent mutations at the 5' untranslated region (UTR) of the viral genome that correlate with the level of neurovirulence determined by the monkey neurovirulence test. However, MAPREC can only monitor mutations at a few genomic loci and miss mutations at other sites that could adversely affect vaccine quality. Here we propose to use massively parallel sequencing (MPS) for sensitive detection and quantification of all mutations in the entire genome of attenuated viruses. Analysis of vaccine samples and reference preparations demonstrated a perfect agreement with MAPREC results. Quantitative MPS analysis of validated reference preparations tested by MAPREC produced identical results, suggesting that the method could take advantage of the existing reference materials and be used as a replacement for the MAPREC procedure in lot release of OPV. Patterns of mutations present at a low level in vaccine preparations were characteristic of seed viruses used for their manufacture and could be used for identification of individual batches. This approach may represent the ultimate tool for monitoring genetic consistency of live viral vaccines.     

结核病DNA疫苗及其作用机制研究进展

为实现到2050年在全球范围内根除结核病(Tuberculosis,TB)这一宏伟目标,迫切需要开发新的TB疫苗和疫苗接种策略.虽然卡介苗(Bacille Calmette-Guérin,BCG)在保护儿童免受粟粒性结核和结核性脑膜炎等方面获得了成功,但其对成人肺结核(Pulmonary tuberculosis,PT...     

HIV UTR,LTR, and Epigenetic Immunity

The duel between humans and viruses is unending. In this review, we examine the HIV RNA in the form of un-translated terminal region (UTR), the viral DNA in the form of long terminal repeat (LTR), and the immunity of human DNA in a format of epigenetic regulation. We explore the ways in which the human immune responses to invading pathogenic viral nucleic acids can inhibit HIV infection, exemplified by a chromatin vaccine (cVaccine) to elicit the immunity of our genome—epigenetic immunity towards a cure.     

Nanoparticles in influenza subunit vaccine development: Immunogenicity enhancement

The threat of novel influenza infections has sparked research efforts to develop subunit vaccines that can induce a more broadly protective immunity by targeting selected regions of the virus. In general, subunit vaccines are safer but may be less immunogenic than whole cell inactivated or live attenuated vaccines. Hence, novel adjuvants that boost immunogenicity are increasingly needed as we move toward the era of modern vaccines. In addition, targeting, delivery, and display of the selected antigens on the surface of professional antigen‐presenting cells are also important in vaccine design and development. The use of nanosized particles can be one of the strategies to enhance immunogenicity as they can be efficiently recognized by antigen‐presenting cells. They can act as both immunopotentiators and delivery system for the selected antigens. This review will discuss on the applications, advantages, limitations, and types of nanoparticles (NPs) used in the preparation of influenza subunit vaccine candidates to enhance humoral and cellular immune responses.     

Immunopathogenesis of tuberculosis: Implications for vaccine development

Abstract:   Tuberculosis (TB) remains a leading infectious disease worldwide despite the availability of Bacille Calmette Guérin (BCG) vaccine and chemotherapy. A better understanding of how immune system controls TB and latent TB is critical for understanding disease pathogenesis and for devising immune-mediated strategies for prevention and treatment of disease. A brief update on the immunopathogenesis of TB will be provided, and how this knowledge can be used for rational vaccine design will be briefly addressed. Due to poor BCG protective efficacy in humans, there is currently a great deal of activity in new vaccine development. Various vaccine candidates; BCG replacement vaccines including recombinant BCG; live-attenuated Mycobacterium tuberculosis ; and booster vaccines such as vaccinia virus overexpressing antigen 85, nucleic acid vaccines, and subunit protein vaccines with novel adjuvants, are at different stages of development. There is significant interest in using a prime-boost strategy for improved vaccine efficacy. However, the optimal dose, route, frequency and timing of the booster vaccines remain to be determined, and the potential side effects of booster vaccines in causing increased pathology needs to be tested. The recent genome sequencing of avirulent strain M. tuberculosis H37Ra provides a rational approach for reconstructing a new live-attenuated vaccine that could be even more attenuated than BCG and useful for HIV-positive and HIV-negative settings. The challenges of TB vaccine development such as lack of immune markers for protection in humans, shortage of clinical trial sites, lengthy time required for vaccine evaluation, and the high cost will also be briefly discussed.     

Dendritic cell-targeted protein vaccines: a novel approach to induce T-cell immunity

Current vaccines primarily work by inducing protective antibodies. However, in many infections like HIV, malaria and tuberculosis as well as cancers, there remains a need for durable and protective T-cell immunity. Here, we summarize our efforts to develop a safe T-cell-based protein vaccine that exploits the pivotal role of dendritic cells (DC) in initiating adaptive immunity. Focusing on HIV, gag-p24 protein antigen is introduced into a monoclonal antibody (mAb) that efficiently and specifically targets the DEC-205 antigen uptake receptor on DC. When administered together with synthetic double-stranded RNA, polyriboinosinic:polyribocytidylic acid (poly IC) or its analogue poly IC stabilized with carboxymethylcellulose and poly-L-lysine (poly ICLC), as adjuvant, HIV gag-p24 within anti-DEC-205 mAb is highly immunogenic in mice, rhesus macaques, and in ongoing research, healthy human volunteers. Human subjects form both T- and B-cell responses to DC-targeted protein. Thus, DC-targeted protein vaccines are a potential new vaccine platform, either alone or in combination with highly attenuated viral vectors, to induce integrated immune responses against microbial or cancer antigens, with improved ease of manufacturing and clinical use.     

An overview of the regulation of influenza vaccines in the United States

Influenza virus vaccines are unique among currently licensed viral vaccines. The vaccines designed to protect against seasonal influenza illness must be updated periodically in an effort to match the vaccine strain with currently circulating viruses, and the vaccine manufacturing timeline includes multiple, overlapping processes with a very limited amount of flexibility. In the United States (U.S.), over 150 million doses of seasonal trivalent and quadrivalent vaccine are produced annually, a mammoth effort, particularly in the context of a vaccine with components that usually change on a yearly basis. In addition, emergence of an influenza virus containing an HA subtype that has not recently circulated in humans is an ever present possibility. Recently, pandemic influenza vaccines have been licensed, and the pathways for licensure of pandemic vaccines and subsequent strain updating have been defined. Thus, there are formidable challenges for the regulation of currently licensed influenza vaccines, as well as for the regulation of influenza vaccines under development. This review describes the process of licensing influenza vaccines in the U.S., the process and steps involved in the annual updating of seasonal influenza vaccines, and some recent experiences and regulatory challenges faced in development and evaluation of novel influenza vaccines.     

基于登革病毒prME序列mRNA候选疫苗的构建与评价

目的 利用mRNA结合脂质纳米颗粒(lipid nanoparticle, LNP)包裹递送技术,设计构建mRNA疫苗,以期为登革热疫苗研发提供新思路。方法 以DENV1 Hawaii株prME序列为靶基因,体外合成D1ME-mRNA,利用流式细胞术及免疫荧光染色鉴定其在细胞内表达后,用LNP包裹mRNA,制备D1ME mRNA-LNP候选疫苗;利用C57BL/6小鼠模型,肌肉注射10μg进行二剂次免疫接种,评价疫苗的保护作用及免疫原性。结果 流式细胞术及免疫荧光检测证实D1ME-mRNA在细胞内高效表达;经颅内注射DENV1攻毒后,疫苗组小鼠体重下降幅度明显小于对照组,且无明显临床症状;疫苗组小鼠的中和抗体平均效价为1∶20,高于对照组;疫苗组小鼠的脾淋巴细胞经特异性抗原刺激可分泌高水平的Th1细胞相关的细胞因子IFN-γ、TNF-α。结论 本研究成功构建了针对DENV1的mRNA-LNP疫苗,二剂次免疫接种可诱导小鼠产生DENV1特异性的、以Th1型细胞免疫为主的免疫应答,并可为小鼠提供保护作用以抵抗DENV1的感染。     

Virus-Vectored Influenza Virus Vaccines

Despite the availability of an inactivated vaccine that has been licensed for >50 years, the influenza virus continues to cause morbidity and mortality worldwide. Constant evolution of circulating influenza virus strains and the emergence of new strains diminishes the effectiveness of annual vaccines that rely on a match with circulating influenza strains. Thus, there is a continued need for new, efficacious vaccines conferring cross-clade protection to avoid the need for biannual reformulation of seasonal influenza vaccines. Recombinant virus-vectored vaccines are an appealing alternative to classical inactivated vaccines because virus vectors enable native expression of influenza antigens, even from virulent influenza viruses, while expressed in the context of the vector that can improve immunogenicity. In addition, a vectored vaccine often enables delivery of the vaccine to sites of inductive immunity such as the respiratory tract enabling protection from influenza virus infection. Moreover, the ability to readily manipulate virus vectors to produce novel influenza vaccines may provide the quickest path toward a universal vaccine protecting against all influenza viruses. This review will discuss experimental virus-vectored vaccines for use in humans, comparing them to licensed vaccines and the hurdles faced for licensure of these next-generation influenza virus vaccines.     

Multivalent DNA Vaccines as a Strategy to Combat Multiple Concurrent Epidemics: Mosquito-Borne and Hemorrhagic Fever Viruses

The emergence of multiple concurrent infectious diseases localized in the world creates a complex burden on global public health systems. Outbreaks of Ebola, Lassa, and Marburg viruses in overlapping regions of central and West Africa and the co-circulation of Zika, Dengue, and Chikungunya viruses in areas with A. aegypti mosquitos highlight the need for a rapidly deployable, safe, and versatile vaccine platform readily available to respond. The DNA vaccine platform stands out as such an application. Here, we present proof-of-concept studies from mice, guinea pigs, and non-human primates for two multivalent DNA vaccines delivered using in vivo electroporation (EP) targeting mosquito-borne (MMBV) and hemorrhagic fever (MHFV) viruses. Immunization with MMBV or MHFV vaccines via intradermal EP delivery generated robust cellular and humoral immune responses against all target viral antigens in all species. MMBV vaccine generated antigen-specific binding antibodies and IFNγ-secreting lymphocytes detected in NHPs up to six months post final immunization, suggesting induction of long-term immune memory. Serum from MHFV vaccinated NHPs demonstrated neutralizing activity in Ebola, Lassa, and Marburg pseudovirus assays indicating the potential to offer protection. Together, these data strongly support and demonstrate the versatility of DNA vaccines as a multivalent vaccine development platform for emerging infectious diseases.