Optimised production of an anti-fungal antibody in Solanaceae hairy roots to develop new formulations against Candida albicans

Hairy root culture: a potent method for improved secondary metabolite production of Solanaceous plants

Secondary metabolites synthesized by the Solanaceous plants are of major therapeutic and pharmaceutical importance, many of which are commonly obtained from the roots of these plants. 'Hairy roots', mirroring the same phytochemical pattern of the corresponding root of the parent plant with higher growth rate and productivity, are therefore extensively studied as an effective alternative for the in vitro production of these metabolites. Hairy roots are the transformed roots, generated from the infection site of the wounded plants with Agrobacterium rhizogenes. With their fast growth, being free from pathogen and herbicide contamination, genetic stability, and autotrophic nature for plant hormones, hairy roots are considered as useful bioproduction systems for specialized metabolites. Lately, several elicitation methods have been employed to enhance the accumulation of these compounds in the hairy root cultures for both small and large-scale production. Nevertheless, in the latter case, the cultivation of hairy roots in bioreactors should still be optimized. Hairy roots can also be utilized for metabolic engineering of the regulatory genes in the metabolic pathways leading to enhanced production of metabolites. The present study summarizes the updated and modern biotechnological aspects for enhanced production of secondary metabolites in the hairy root cultures of the plants of Solanaceae and their respective importance.

Nicotiana hairy roots for recombinant protein expression, where to start? A systematic review

BACKGROUND

Hairy roots are a plant-tissue culture raised by Rhizobium rhizogenes infection (formerly known as Agrobacterium rhizogenes). Nowadays, these roots have been gaining more space in biotechnology due to their benefits for the recombinant expression of valuables proteins; it includes simplified downstream processing, protein rhizosecretion, and scalability in bioreactors. However, due to methodological inconsistency among reports, the tissue platform is still a promising technology.

METHODS AND RESULTS

In the current paper, we propose the first step to overcome this issue through a systematic review of studies that employ Nicotiana hairy roots for recombinant expression. We conducted a qualitative synthesis of 36 out of 387 publications initially selected. Following the PRISMA procedure, all papers were assessed for exclusion and inclusion criteria. Multiple points of root culture were explored, including transformation methods, root growth curve, external additives, and scale-up with bioreactors to determine which approaches performed best and what is still required to achieve a robust protocol.

CONCLUSION

The information presented here may help researchers who want to work with hairy roots in their laboratories trace a successful path to appraisal the literature status.

Immunomodulatory responses of differentially polarized macrophages to fungal infections

Macrophages, the first line of defense against invasive fungi in the innate immune system, are widely distributed in the blood and tissues of the body. In response to various internal and external stimulators, macrophages can polarize into classically activated macrophages (M1) and alternatively activated macrophages (M2). These two types of polarized macrophages play different roles in antifungal activity and in maintaining the steady-state balance between inflammation and tissue repair. However, the antifungal mechanisms of M1- and M2-type macrophages have not been fully described. In this review, the immune regulatory mechanisms against pathogenic fungi of these two classical types of macrophages in various tissues are summarized. The effects of antifungal factors on macrophage differentiation are also highlighted. The description of these data, on the one hand provides valuable insight for future investigations and also highlights new strategies for the treatment of pathogenic fungal infections.

Root Exudates: Mechanistic Insight of Plant Growth Promoting Rhizobacteria for Sustainable Crop Production

The breaking silence between the plant roots and microorganisms in the rhizosphere affects plant growth and physiology by impacting biochemical, molecular, nutritional, and edaphic factors. The components of the root exudates are associated with the microbial population, notably, plant growth-promoting rhizobacteria (PGPR). The information accessible to date demonstrates that PGPR is specific to the plant's roots. However, inadequate information is accessible for developing bio-inoculation/bio-fertilizers for the crop in concern, with satisfactory results at the field level. There is a need to explore the perfect candidate PGPR to meet the need for plant growth and yield. The functions of PGPR and their chemotaxis mobility toward the plant root are triggered by the cluster of genes induced by the components of root exudates. Some reports have indicated the benefit of root exudates in plant growth and productivity, yet a methodical examination of rhizosecretion and its consequences in phytoremediation have not been made. In the light of the afore-mentioned facts, in the present review, the mechanistic insight and recent updates on the specific PGPR recruitment to improve crop production at the field level are methodically addressed.

The Pathogenesis of Aspergillus fumigatus, Host Defense Mechanisms, and the Development of AFMP4 Antigen as a Vaccine

Aspergillus fumigatus is one of the ubiquitous fungi with airborne conidia, which accounts for most aspergillosis cases. In immunocompetent hosts, the inhaled conidia are rapidly eliminated. However, immunocompromised or immunodeficient hosts are particularly vulnerable to most Aspergillus infections and invasive aspergillosis (IA), with mortality from 50% to 95%. Despite the improvement of antifungal drugs over the last few decades, the therapeutic effect for IA patients is still limited and does not provide significant survival benefits. The drawbacks of antifungal drugs such as side effects, antifungal drug resistance, and the high cost of antifungal drugs highlight the importance of finding novel therapeutic and preventive approaches to fight against IA. In this article, we systemically addressed the pathogenic mechanisms, defense mechanisms against A. fumigatus, the immune response, molecular aspects of host evasion, and vaccines' current development against aspergillosis, particularly those based on AFMP4 protein, which might be a promising antigen for the development of anti-A. fumigatus vaccines.

The Instability of Dimeric Fc-Fusions Expressed in Plants Can Be Solved by Monomeric Fc Technology

The potential therapeutic value of many proteins is ultimately limited by their rapid in vivo clearance. One strategy to limit clearance by metabolism and excretion, and improving the stability of therapeutic proteins, is their fusion to the immunoglobulin fragment crystallizable region (Fc). The Fc region plays multiple roles in (i) dimerization for the formation of "Y"-shaped structure of Ig, (ii) Fc-mediated effector functions, (iii) extension of serum half-life, and (iv) a cost-effective purification tag. Plants and in particular Nicotiana benthamiana have proven to be suitable expression platforms for several recombinant therapeutic proteins. Despite the enormous success of their use for the production of full-length monoclonal antibodies, the expression of Fc-fused therapeutic proteins in plants has shown limitations. Many Fc-fusion proteins expressed in plants show different degrees of instability resulting in high amounts of Fc-derived degradation products. To address this issue, we used erythropoietin (EPO) as a reporter protein and evaluated the efforts to enhance the expression of full-length EPO-Fc targeted to the apoplast of N. benthamiana. Our results show that the instability of the fusion protein is independent from the Fc origin or IgG subclass and from the peptide sequence used to link the two domains. We also show that a similar instability occurs upon the expression of individual heavy chains of monoclonal antibodies and ScFv-Fc that mimic the "Y"-shape of antibodies but lack the light chain. We propose that in this configuration, steric hindrance between the protein domains leads to physical instability. Indeed, mutations of critical residues located on the Fc dimerization interface allowed the expression of fully stable EPO monomeric Fc-fusion proteins. We discuss the limitations of Fc-fusion technology in N. benthamiana transient expression systems and suggest strategies to optimize the Fc-based scaffolds on their folding and aggregation resistance in order to improve the stability.