Designing and evaluation of an antibody-targeted chimeric recombinant vaccine encoding Shigella flexneri outer membrane antigens

Production of egg yolk antibody (IgY) against a chimeric protein containing IpaD, StxB, and TolC antigens from Shigella: An investigation of its prophylactic effects against Shiga toxin (Stx) and Shigella dysenteriae in vitro and in vivo

Shigella is a major problem in developing countries. Immunoglobulin Y (IgY) can be used for prophylaxis and neutralize bacteria. The aim of this study was to produce IgY against the chimeric protein containing IpaD, StxB, and TolC antigens from Shigella, investigate its prophylactic and neutralizing effects against Stx and Shigella dysenteriae. The nucleotide sequence corresponding to the chimeric protein was cloned into pET28a plasmid and expressed in E. coli BL21 (DE3). Protein expression was confirmed by SDS-PAGE and the recombinant protein was purified by Ni-NTA affinity chromatography. The 150 μg of chimeric protein was mixed with Freund's adjutant and injected into laying hens (Leghorn). IgY was purified using PEG6000 precipitation. Antibody titer in the serum and egg yolk was evaluated by ELISA. IgY challenge against 1,10 and 50 LD50 of Stx and S. dysenteriae was investigated. A 60.6 kDa recombinant protein was confirmed by SDS-PAGE. ELISA showed that the antibody titer was significantly increased. MTT assay [3-(4,5-Dimethylthiazol-2-yl)-2,5-Diphenyltetrazolium Bromide] showed that at 16 μmol/L, IgY protected HeLa cells against Stx. Treatment of mice with 1000 and 1500 μg IgY leads to complete survival of the mice against 1LD50 toxin and 4000 μg of IgY led to complete survival against 1LD50, also 70% and 30% survival against 10 and 50 LD50S. dysenteriae. This study showed that IgY produced against Stx and Shigella virulence factors could cause high protective effects against bacteria and toxins.

Antimicrobial and Antibiofilm Efficacy and Mechanism of Oregano Essential Oil Against Shigella flexneri

The aim of this study was to assess the antimicrobial activity of oregano essential oil (OEO) against Shigella flexneri and eradication efficacy of OEO on biofilm. The results showed that the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) of OEO against S. flexneri were 0.02% (v/v) and 0.04% (v/v), respectively. OEO effectively killed S. flexneri in Luria-Bertani (LB) broth and contaminated minced pork (the initial population of S. flexneri was about 7.0 log CFU/mL or 7.2 log CFU/g), and after treatment with OEO at 2 MIC in LB broth or at 15 MIC in minced pork, the population of S. flexneri decreased to an undetectable level after 2 or 9 h, respectively. OEO increased intracellular reactive oxygen species concentration, destroyed cell membrane, changed cell morphology, decreased intracellular ATP concentration, caused cell membrane depolarization, and destroyed proteins or inhibited proteins synthesis of S. flexneri. In addition, OEO effectively eradicated the biofilm of S. flexneri by effectively inactivating S. flexneri in mature biofilm, destroying the three-dimensional structure, and reducing exopolysaccharide biomass of S. flexneri. In conclusion, OEO exerts its antimicrobial action effectively and also has a valid scavenging effect on the biofilm of S. flexneri. These findings suggest that OEO has the potential to be used as a natural antibacterial and antibiofilm material in the control of S. flexneri in meat product supply chain, thereby preventing meat-associated infections.

Oral vaccination with novel Lactococcus lactis mucosal live vector-secreting Brucella lumazine synthase (BLS) protein induces humoral and cellular immune protection against Brucella abortus

This work aimed to provide recombinant Lactococcus lactis as a potential live vector for the manufacture of recombinant Brucella abortus (rBLS-Usp45). The sequences of the genes were collected from the GenBank database. Using Vaxijen and ccSOL, the proteins' immunogenicity and solubility were evaluated. Mice were given oral vaccinations with recombinant L. lactis. Anti-BLS-specific IgG antibodies were measured by ELISA assay. Cytokine reactions were examined using real-time PCR and the ELISA technique. The BLS protein was chosen for immunogenicity based on the vaccinology screening findings since it had maximum solubility and antigenic values ​​of 99% and 0.75, respectively. The BLS gene, digested at 477 bp, was electrophoretically isolated to demonstrate that the recombinant plasmid was successfully produced. Protein-level antigen expression showed that the target group produced the 18 kDa-sized BLS protein, whereas the control group did not express any proteins. In the sera of mice given the L. lactis-pNZ8148-BLS-Usp45 vaccine 14 days after priming, there was a significant level of BLS-specific IgG1, IgG2a (P < 0.001) compared to the PBS control group. Vaccinated mice showed higher levels of IFN-γ, TNFα, IL-4, and IL-10 in samples obtained on days 14 and 28, after receiving the L. lactis-pNZ8148-BLS-Usp45 and IRBA vaccines (P < 0.001). The inflammatory reaction caused less severe spleen injuries, alveolar edema, lymphocyte infiltration, and morphological damage in the target group's spleen sections. Based on our findings, an oral or subunit-based vaccine against brucellosis might be developed using L. lactis-pNZ8148-BLS-Usp45 as a novel, promising, and safe alternative to the live attenuated vaccines now available.

Effects of cinnamaldehyde against planktonic bacteria and biofilm formation of Shigella flexneri

Cinnamaldehyde (CA) has demonstrated anti-inflammatory, anti-tumor and anti-cancer activities; Its antimicrobial and antibiofilm actions against Shigella flexneri, on the other hand, have not been investigated. Sh. flexneri is a gram-negative foodborne pathogen that can be widely found in nature and some industrial production environments. In this current research, our aim was to examine the influences of CA on planktonic bacteria and biofilm formation. The minimum inhibitory concentration (MIC) of CA against Sh. flexneri strain was 100 μg/mL, while bacteria treated with CA showed a longer lag phase compared with the untreated control. CA effectively inactivated the Sh. flexneri in LB broth and fresh lettuce juice. CA treatment resulted in cell membrane permeability changes and dysfunction, as proven by cell membrane depolarization, decreased intracellular ATP concentration. In addition, CA was also discovered to increase the level of reactive oxygen species (ROS) in cells, and induce morphological changes in cells. Crystal violet staining showed that the biomass of biofilm was decreased significantly with CA in 24 h. Light microscopy and field emission scanning electron microscopy (FESEM) observations demonstrated decreased biofilm adhesion and destruction of biofilm architecture after treatment with CA. These findings indicated that CA acts as a natural bacteriostatic agent to control Sh. flexneri in food processing and production.

Shigella iron-binding proteins: An insight into molecular physiology, pathogenesis, and potential target vaccine development

Shigella is a well-known etiological agent responsible for intestinal infection among children, the elderly, and immunocompromised people ranging from mild to severe cases. Shigellosis remains endemic in Malaysia and yet there is no commercial vaccine available to eradicate the disease. Iron is an essential element for the survival of Shigella within the host. Hence, it is required for regulating metabolic mechanisms and virulence determinants. Alteration of iron status in the extracellular environment directly triggers the signal in enteropathogenic bacterial, providing information that they are in a hostile environment. To survive in an iron-limited environment, molecular regulation of iron-binding proteins plays a vital role in facilitating the transportation and utilization of sufficient iron sources. Given the importance of iron molecules for bacterial survival and pathogenicity, this review summarizes the physiological role of iron-binding proteins in bacterial survival and their potential use in vaccine and therapeutic developments.

Identification of a Novel Therapeutic Target against XDR Salmonella Typhi H58 Using Genomics Driven Approach Followed Up by Natural Products Virtual Screening

Typhoid fever is caused by a pathogenic, rod-shaped, flagellated, and Gram-negative bacterium known as Salmonella Typhi. It features a polysaccharide capsule that acts as a virulence factor and deceives the host immune system by protecting phagocytosis. Typhoid fever remains a major health concern in low and middle-income countries, with an estimated death rate of ~200,000 per annum. However, the situation is exacerbated by the emergence of the extensively drug-resistant (XDR) strain designated as H58 of S. Typhi. The emergence of the XDR strain is alarming, and it poses serious threats to public health due to the failure of the current therapeutic regimen. A relatively newer computational method called subtractive genomics analyses has been widely applied to discover novel and new drug targets against pathogens, particularly drug-resistant ones. The method involves the gradual reduction of the complete proteome of the pathogen, leading to few potential and novel drug targets. Thus, in the current study, a subtractive genomics approach was applied against the Salmonella XDR strain to identify potential drug targets. The current study predicted four prioritized proteins (i.e., Colanic acid biosynthesis acetyltransferase wcaB, Shikimate dehydrogenase aroE, multidrug efflux RND transporter permease subunit MdtC, and pantothenate synthetase panC) as potential drug targets. Though few of the prioritized proteins are treated in the literature as the established drug targets against other pathogenic bacteria, these drug targets are identified here for the first time against S. Typhi (i.e., S. Typhi XDR). The current study aimed at drawing attention to new drug targets against S. Typhi that remain largely unexplored. One of the prioritized drug targets, i.e., Colanic acid biosynthesis acetyltransferase, was predicted as a unique, new drug target against S. Typhi XDR. Therefore, the Colanic acid was further explored using structure-based techniques. Additionally, ~1000 natural compounds were docked with Colanic acid biosynthesis acetyltransferase, resulting in the prediction of seven compounds as potential lead candidates against the S. Typhi XDR strain. The ADMET properties and binding energies via the docking program of these seven compounds characterized them as novel drug candidates. They may potentially be used for the development of future drugs in the treatment of Typhoid fever.

Application of Reverse Vaccinology and Immunoinformatic Strategies for the Identification of Vaccine Candidates Against Shigella flexneri

Reverse vaccinology (RV) was first introduced by Rappuoli for the development of an effective vaccine against serogroup B Neisseria meningitidis (MenB). With the advances in next generation sequencing technologies, the amount of genomic data has risen exponentially. Since then, the RV approach has widely been used to discover potential vaccine protein targets by screening whole genome sequences of pathogens using a combination of sophisticated computational algorithms and bioinformatic tools. In contrast to conventional vaccine development strategies, RV offers a novel method to facilitate rapid vaccine design and reduces reliance on the traditional, relatively tedious, and labor-intensive approach based on Pasteur"s principles of isolating, inactivating, and injecting the causative agent of an infectious disease. Advances in biocomputational techniques have remarkably increased the significance for the rapid identification of the proteins that are secreted or expressed on the surface of pathogens. Immunogenic proteins which are able to induce the immune response in the hosts can be predicted based on the immune epitopes present within the protein sequence. To date, RV has successfully been applied to develop vaccines against a variety of infectious pathogens. In this chapter, we apply a pipeline of bioinformatic programs for identification of Shigella flexneri potential vaccine candidates as an illustration immunoinformatic tools available for RV.