The red alga Porphyridium as a host for molecular farming: Efficient production of immunologically active hepatitis C virus glycoprotein.

Microalgae are promising production platforms for the cost-effective production of recombinant proteins. We have recently established that the red alga Porphyridium purpureum provides superior transgene expression properties, due to the episomal maintenance of transformation vectors as multicopy plasmids in the nucleus. Here, we have explored the potential of Porphyridium to synthesize complex pharmaceutical proteins to high levels. Testing expression constructs for a candidate subunit vaccine against the hepatitis C virus (HCV), we show that the soluble HCV E2 glycoprotein can be produced in transgenic algal cultures to high levels. The antigen undergoes faithful posttranslational modification by N-glycosylation and is recognized by conformationally selective antibodies, suggesting that it adopts a proper antigenic conformation in the endoplasmic reticulum of red algal cells. We also report the experimental determination of the structure of the N-glycan moiety that is attached to glycosylated proteins in Porphyridium. Finally, we demonstrate the immunogenicity of the HCV antigen produced in red algae when administered by injection as pure protein or by feeding of algal biomass.

The "humanized" N-glycosylation pathway in CRISPR/Cas9-edited Nicotiana benthamiana significantly enhances the immunogenicity of a S/preS1 Hepatitis B Virus antigen and the virus-neutralizing antibody response in vaccinated mice.

The recent SARS-CoV-2 pandemic has taught the world a costly lesson about the devastating consequences of viral disease outbreaks but also, the remarkable impact of vaccination in limiting life and economic losses. Vaccination against human Hepatitis B Virus (HBV), a major human pathogen affecting 290 million people worldwide, remains a key action towards viral hepatitis elimination by 2030. To meet this goal, the development of improved HBV antigens is critical to overcome non-responsiveness to standard vaccines based on the yeast-produced, small (S) envelope protein. We have recently shown that combining relevant immunogenic determinants of S and large (L) HBV proteins in chimeric antigens markedly enhances the anti-HBV immune response. However, the demand for cost-efficient, high-quality antigens remains challenging. This issue could be addressed by using plants as versatile and rapidly scalable protein production platforms. Moreover, the recent generation of plants lacking ß-1,2-xylosyltransferase and α-1,3-fucosyltransferase activities (FX-KO), by CRISPR/Cas9 genome editing, enables production of proteins with "humanized" N-glycosylation. In this study, we investigated the impact of plant N-glycosylation on the immunogenic properties of a chimeric HBV S/L vaccine candidate produced in wild-type and FX-KO Nicotiana benthamiana. Prevention of ß-1,2-xylose and α-1,3-fucose attachment to the HBV antigen significantly increased the immune response in mice, as compared with the wild-type plant-produced counterpart. Notably, the antibodies triggered by the FX-KO-made antigen neutralized more efficiently both wild-type HBV and a clinically relevant vaccine escape mutant. Our study validates in premiere the glyco-engineered Nicotiana benthamiana as a substantially improved host for plant production of glycoprotein vaccines.

Adenylate cyclases involvement in pathogenicity, a minireview.

Cyclic AMP (cAMP), one of the most important secondary messengers, is produced by adenylate cyclase (AC) from adenosine triphosphate (ATP). AC is a widespread enzyme, being present both in prokaryotes and eukaryotes. Although they have the same enzymatic activity (ATP cyclization), the structure of these proteins varies, depending on their function and the producing organism. Some pathogenic bacteria utilize these enzymes as toxins which interact with calmodulin (or another eukaryote activator), causing intense cAMP synthesis and disruption of infected cell functions. In contrast, other pathogenic bacteria benefit of augmentation of AC activity for their own function. Based on sequence analysis ofAC catalytic domain from two pathogenic bacteria (Bacillus anthracis and Bordetellapertussis) with known three-dimensional structures, a possible secondary structure for 1-255 amino acid fragment from Pseudomonas aeruginosa AC (with 80TKGFSVKGKSS90 as the ATP binding site) is proposed.

Comparison of truncated human angiotensin-converting enzyme 2 (hACE2) expression in pET28a(+) versus pET-SUMO vector and two Escherichia coli strains.

PURPOSE: Truncated human angiotensin-converting enzyme 2 (hACE2) expression rises a great scientific interest, considering its possible therapeutic and diagnostic applications. A promising research direction is the therapeutic use of smaller hACE2 versions with high binding affinity as decoy receptors for S1 glycoprotein of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Another possible application is the use of these truncated versions for the functionalization of appropriate nanomaterials for constructing novel biosensors with a rapid and sensitive response for coronavirus disease 2019 (COVID-19) detection. The present study aimed to find a suitable system for high yield expression of different versions of truncated hACE2. MATERIALS AND METHODS: The encoding DNA for the hACE2 fragments (7-507 aa, 16-128 aa, and 30-357 aa) was obtained by PCR amplification using as template pcDNA3.1-hACE2 plasmid and further cloned into pET28a(+) and pET-SUMO vectors. The positive clones were selected and the correct DNA insertion was confirmed through gene sequencing. The truncated hACE2 proteins were further expressed in two E. coli strains, Rosetta(DE3) and BL21(DE3). RESULTS: For all three truncated hACE2 mini proteins, pET28a(+) does not lead to protein expression, regardless of the bacterial strain. The situation changes with the use of the pET-SUMO expression system when all hACE2 fragments are expressed, but with higher efficiency in E. coli BL21(DE3) than E. coli Rosetta. CONCLUSION: In the present study, we showed that different versions of recombinant hACE2 are successfully expressed in E. coli BL21(DE3) by using pET-SUMO expression system.

Use of recombinant purified protein derivative (PPD) antigens as specific skin test for tuberculosis.

BACKGROUND & OBJECTIVES: Purified protein derivative (PPD) is currently the only available skin test reagent used worldwide for the diagnosis of tuberculosis (TB). The aim of this study was to develop a Mycobacterium tuberculosis specific skin test reagent, without false positive results due to Bacillus Calmette-Guerin (BCG) vaccination using recombinant antigens. METHODS: Proteins in PPD IC-65 were analyzed by tandem mass spectrometry and compared to proteins in M. tuberculosis culture filtrate; 54 proteins were found in common. Top candidates MPT64, ESAT 6, and CFP 10 were overexpressed in Escherichia coli expression strains and purified as recombinant proteins. To formulate optimal immunodiagnostic PPD cocktails, the antigens were evaluated by skin testing guinea pigs sensitized with M. tuberculosis H37Rv and BCG. RESULTS: For single antigens and a cocktail mixture of these antigens, best results were obtained using 3 µg/0.1 ml, equivalent to 105 TU (tuberculin units). Each animal was simultaneously tested with PPD IC-65, 2 TU/0.1 ml, as reference. Reactivity of the multi-antigen cocktail was greater than that of any single antigen. The skin test results were between 34.3 and 76.6 per cent the level of reactivity compared to that of the reference when single antigens were tested and 124 per cent the level of reactivity compared to the reference for the multi-antigen cocktail. INTERPRETATION & CONCLUSIONS: Our results showed that this specific cocktail could represent a potential candidate for a new skin diagnostic test for TB.

Efficient cellular and humoral immune response and production of virus-neutralizing antibodies by the Hepatitis B Virus S/preS116-42 antigen.

Despite the availability of improved antiviral therapies, infection with Hepatitis B virus (HBV) remains a3 significant health issue, as a curable treatment is yet to be discovered. Current HBV vaccines relaying on the efficient expression of the small (S) envelope protein in yeast and the implementation of mass vaccination programs have clearly contributed to containment of the disease. However, the lack of an efficient immune response in up to 10% of vaccinated adults, the controversies regarding the seroprotection persistence in vaccine responders and the emergence of vaccine escape virus mutations urge for the development of better HBV immunogens. Due to the critical role played by the preS1 domain of the large (L) envelope protein in HBV infection and its ability to trigger virus neutralizing antibodies, including this protein in novel vaccine formulations has been considered a promising strategy to overcome the limitations of S only-based vaccines. In this work we aimed to combine relevant L and S epitopes in chimeric antigens, by inserting preS1 sequences within the external antigenic loop of S, followed by production in mammalian cells and detailed analysis of their antigenic and immunogenic properties. Of the newly designed antigens, the S/preS116-42 protein assembled in subviral particles (SVP) showed the highest expression and secretion levels, therefore, it was selected for further studies in vivo. Analysis of the immune response induced in mice vaccinated with S/preS116-42- and S-SVPs, respectively, demonstrated enhanced immunogenicity of the former and its ability to activate both humoral and cellular immune responses. This combined activation resulted in production of neutralizing antibodies against both wild-type and vaccine-escape HBV variants. Our results validate the design of chimeric HBV antigens and promote the novel S/preS1 protein as a potential vaccine candidate for administration in poor-responders to current HBV vaccines.

Characterization of guanylate kinase from gram positive and gram negative microorganisms; preliminary results.

Guanylate kinase is a member of the nucleoside monophosphate (NMP) kinase family, a family of enzymes that despite having a low primary structure identity share a similar fold, which consists of three structurally distinct regions termed the CORE, LID, and NMP-binding regions. Guanylate kinase (GMPK) is an essential enzyme for the biosynthesis of GTP and dGTP by catalyzing the phosphoryl transfer from ATP to (d)GMP resulting in ADP and (d)GDP. Despite the similar fold of the monomer there is an important difference between GMPKs from prokaryotes and eukaryotes: eukaryotes GMPK are monomers while prokaryotes GMPK are dimmers, tetramers or hexamers. For this reason bacterial GMPKs are possible targets for new antibacterial drugs. Finding new targets for antibacterial therapies is a prior subject in today's medical research. The purpose of this work was to characterize guanylate kinases from both gram positive and gram negative pathogenic bacteria. We started with GMPK from Enterococcus faecalis as gram positive microorganism and Pseudomonas aeruginosa as gram negative representative.

Use of recombinant purified protein derivative (PPD) antigens as specific skin test for tuberculosis.

Background & objectives: Purified protein derivative (PPD) is currently the only available skin test reagent used worldwide for the diagnosis of tuberculosis (TB). The aim of this study was to develop a Mycobacterium tuberculosis specific skin test reagent, without false positive results due to Bacillus Calmette-Guerin (BCG) vaccination using recombinant antigens. Methods: Proteins in PPD IC-65 were analyzed by tandem mass spectrometry and compared to proteins in M. tuberculosis culture filtrate; 54 proteins were found in common. Top candidates MPT64, ESAT 6, and CFP 10 were overexpressed in Escherichia coli expression strains and purified as recombinant proteins. To formulate optimal immunodiagnostic PPD cocktails, the antigens were evaluated by skin testing guinea pigs sensitized with M. tuberculosis H37Rv and BCG. Results: For single antigens and a cocktail mixture of these antigens, best results were obtained using 3 μg/0.1 ml, equivalent to 105 TU (tuberculin units). Each animal was simultaneously tested with PPD IC-65, 2 TU/0.1 ml, as reference. Reactivity of the multi-antigen cocktail was greater than that of any single antigen. The skin test results were between 34.3 and 76.6 per cent the level of reactivity compared to that of the reference when single antigens were tested and 124 per cent the level of reactivity compared to the reference for the multi-antigen cocktail. Interpretation & conclusions: Our results showed that this specific cocktail could represent a potential candidate for a new skin diagnostic test for TB.