Jorge A. Salazar-González

Immunological aspects of using plant cells as delivery vehicles for oral vaccines.

Genetically engineered plants can be used for the biomanufacture and delivery of oral vaccines. Although a myriad of antigens have been produced using this approach, improving our knowledge of their oral immunogenic properties is a priority as this aspect has not been well researched. Some studies have provided evidence of a higher immunogenic activity for antigens that were orally administered in the form of plant-based vaccines in comparison with conventional pure antigens. The characteristics of the plant-derived vaccines that may influence oral immunogenicity are identified and discussed in this review. Among the hypotheses explaining these immunogenic properties are the following: bioencapsulation favors antigen uptake and displays a resistance to degradation; plant metabolites exert adjuvant activity; plant compounds, such as polysaccharides, exert mucoadhesive properties; differential glycosylation conferred by the plant cell machinery enhances immunogenicity. Perspectives on how these hypotheses may be assessed are examined.

Chikungunya virus vaccines: Current strategies and prospects for developing plant-made vaccines

Chikungunya virus is an emerging pathogen initially found in East Africa and currently spread into the Indian Ocean Islands, many regions of South East Asia, and in the Americas. No licensed vaccines against this eminent pathogen are available and thus intensive research in this field is a priority. This review presents the current scenario on the developments of Chikungunya virus vaccines and identifies the use of genetic engineered plants to develop attractive vaccines. The possible avenues to develop plant-made vaccines with distinct antigenic designs and expression modalities are identified and discussed considering current trends in the field.

A Plant-Derived Multi-HIV Antigen Induces Broad Immune Responses in Orally Immunized Mice

Abstract Multi-HIV, a multiepitopic protein derived from both gp120 and gp41 envelope proteins of the human immunodeficiency virus (HIV), has been proposed as a vaccine prototype capable of inducing broad immune responses, as it carries various B and T cell epitopes from several HIV strains. In this study, the immunogenic properties of a Multi-HIV expressed in tobacco chloroplasts are evaluated in test mice. BALB/c mice orally immunized with tobacco-derived Multi-HIV have elicited antibody responses, including both the V3 loop of gp120 and the ELDKWA epitope of gp41. Based on splenocyte proliferation assays, stimulation with epitopes of the C4, V3 domain of gp120, and the ELDKWA domain of gp41 elicits positive cellular responses. Furthermore, specific interferon gamma production is observed in both CD4+ and CD8+ T cells stimulated with HIV peptides. These results demonstrate that plant-derived Multi-HIV induces T helper-specific responses. Altogether, these findings illustrate the immunogenic potential of plant-derived Multi-HIV in an oral immunization scheme. The potential of this low-cost immunization approach and its implications on HIV/AIDS vaccine development are discussed.

Gold nanoparticles and vaccine development

Mucosal vaccines constitute an advantageous immunization approach to achieve broad immunization against widespread diseases; however, improvements in this field are still required to expand their exploitation. As gold nanoparticles are biocompatible and can be easily functionalized with antigens, they have been proposed as carriers for the delivery of vaccines. The study of gold nanoparticles (AuNPs) in vaccinology has been of interest for a number of research groups in recent years and important advances have been made. This review provides a summary of the AuNPs synthesis methodologies and an updated overview of the current AuNPs-based vaccines under development. The implications of these advances for the development of new mucosal vaccines as well as future prospects for the field are discussed.

A perspective for atherosclerosis vaccination: is there a place for plant-based vaccines?

Alternatives to pharmacological treatments for atherosclerosis are highly desirable in terms of cost and compliance. During the last two decades several vaccination strategies have been reported as an effort to develop immunotherapeutic treatments. This approach consists on eliciting immune responses able to modulate either the atherosclerosis-associated inflammatory processes or the activity of some physiological mechanisms that are up-regulated under this pathologic condition. In particular, the apolipoprotein B100 (ApoB100) and the cholesterilester transferase protein (CETP) have been targeted in these strategies. It is considered that recent progress in the development of experimental models of oral vaccines against atherosclerosis has opened a new avenue in the field: as plant-based vaccines are considered a viable platform for vaccine production and delivery at low costs, they could serve as an oral-delivered therapeutic approach for atherosclerosis in an economical and patient-friendly manner. The rationale of the design, development and evaluation of possible plant-based vaccines against atherosclerosis is discussed in this review. We identify within this approach a significant trend that will positively impact the field of atherosclerosis vaccination.

Implications of plant glycans in the development of innovative vaccines

ABSTRACT Plant glycans play a central role in vaccinology: they can serve as adjuvants and/or delivery vehicles or backbones for the synthesis of conjugated vaccines. In addition, genetic engineering is leading to the development of platforms for the production of novel polysaccharides in plant cells, an approach with relevant implications for the design of new types of vaccines. This review contains an updated outlook on this topic and provides key perspectives including a discussion on how the molecular pharming field can be linked to the production of innovative glycan-based and conjugate vaccines.

Progress and future opportunities in the development of vaccines against atherosclerosis

ABSTRACT Introduction: Atherosclerosis represents a serious global health problem that demands new therapeutic and prophylactic interventions. Considering that atherosclerosis has autoimmune and inflammatory components, immunotherapy is a possible focus to treat this disease. Areas covered: Based on the analysis of the current biomedical literature, this review describes the status on the development of vaccines against atherosclerosis. Several targets have been identified including sequences of apolipoprotein B100 (ApoB100), cholesteryl ester transfer protein (CETP), heat shock proteins (HSP), extracellular matrix proteins, T cell receptor β chain variable region 31 (TRBV31), the major outer membrane protein (MOMP), and the outer membrane protein 5 (Pomp5) from Chlamydia pneumoniae. Humoral and cellular immunities to these targets have been associated with therapeutic effects in murine models and humans. The evaluation of some candidates in clinical trials is ongoing. Expert commentary: New research paths based on the use of next generation vaccine production platforms are envisioned.

Viral Vector-Based Expression Strategies

The need for high recombinant protein yields for the formulation of plant-derived vaccines has led to the development of innovative expression strategies. The efficient capacity of viruses to replicate themselves is a highly desirable characteristic with implications on achieving this goal. Plant viral vectors have been positioned as one of the most efficient approaches in terms of protein yield following strategies of full or deconstructed virus. Expression strategies based on the use of RNA and DNA plant virus are described in this chapter. Plant virus vectors based on Potexvirus, Tobamovirus, Comovirus, and Geminivirus are prominently used because of their high recombinant protein yields. The strategy of using virus-like particles has resulted in highly effective immunogens due to their complex structure, offering the production of chimeric particles bearing unrelated epitopes. Other viral elements that represent new developments are the internal ribosome entry sites (IRES) and the 2A peptide of foot-and-mouth disease virus, which may allow for the co-expression of distinct antigens from a single expression cassette, thus having implications on the formulation of improved bivalent or adjuvanted vaccines. Promising vaccination approaches using viral vector-based platforms are also presented, including vaccines against influenza, human immunodeficiency virus, human papillomavirus, and Norwalk virus.

Plastid-Based Expression Strategies

Since the development of methodologies for achieving genetic modification of chloroplast genomes, termed transplastomic technologies, a straightforward use in the field of plant-based vaccines was initiated. Chloroplast transformation is mediated by homologous recombination that allows for site-specific insertion of foreign DNA into the plastome. This focus offers substantial advantages that include high yields, improved biosafety given by maternal inheritance in most plant species, and multigene expression through polycistrons allowing in theory for the straightforward production of multicomponent vaccines. One limitation of the system consists of the lack of glycosylation pathways, which are of relevance in some cases. State of the art in this area reflects a number of well-characterized vaccination models, although no one has passed clinical evaluations, which contrasts with other nuclear transient expression systems. Transplastomic technologies are envisioned as a relevant tool for developing new convenient vaccines.

Plant-Based Vaccines Against the Human Immunodeficiency Virus

The spread of the human immunodeficiency virus (HIV) has evolved in an alarming manner in terms of human mortality and morbidity, and thus development of an effective and affordable vaccine is a priority to fight this viral disease. As candidate vaccines assessed in clinical trials have shown limited efficacies, efforts to test new candidates capable of inducing strong and neutralizing humoral and cellular responses are underway. This chapter presents a general overview of vaccine candidates produced in plant systems, focusing on the most advanced and promising approaches. This group of candidates comprise strategies targeting structural (Env, Gag) and early non-structural HIV-1 proteins (Rev, Tat, and Nef), which have been expressed in plant tissues using a variety of expression approaches. A number of plant-based vaccines are in preclinical evaluation trials with promising results in terms of immunogenicity.