Immunity to Pathogens

Trivalent outer membrane vesicles-based combination vaccine candidate induces protective immunity against Campylobacter and invasive non-typhoidal Salmonella in adult mice

Campylobacter and invasive non-typhoidal Salmonella (iNTS) are among the most common causative agents of gastroenteritis worldwide. As of now, no single combination licensed vaccine is available for public health use against both iNTS and Campylobacter species. Outer-membrane vesicles (OMVs) are nanoscale proteoliposomes released from the surface of gram-negative bacteria during log phase and harbor a variety of immunogenic proteins. Based on epidemiology of infections, we formulated a novel trivalent outer membrane vesicles (TOMVs)-based vaccine candidate against Campylobacter jejuni (CJ), Salmonella Typhimurium (ST) and Salmonella Enteritidis (SE). Isolated OMVs from CJ, ST and SE were combined in equal ratios for formulation of TOMVs and 5 µg of the developed vaccine candidate was used for intraperitoneal immunization of adult BALB/c mice. Immunization with TOMVs significantly activated both the humoral and cellular arm of adaptive immune response. Robust bactericidal effect was elicited by TOMVs immunized adult mice sera. TOMVs immunization induced long-term protective efficacy against CJ, ST and SE infections in mice. The study illustrates the ability of TOMVs-based combination immunogen in eliciting broad-spectrum protective immunity against prevalent Campylobacter and iNTS pathogens. According to the findings, TOMVs can work as a potent combination-based acellular vaccine candidate for amelioration of Campylobacter and iNTS-mediated gastroenteritis.

The crosstalk between SUMOylation and immune system in host-pathogen interactions

Pathogens can not only cause infectious diseases, immune system diseases, and chronic diseases, but also serve as potential triggers or initiators for certain tumors. They directly or indirectly damage human health and are one of the leading causes of global deaths. Small ubiquitin-like modifier (SUMO) modification, a type of protein post-translational modification (PTM) that occurs when SUMO groups bond covalently to particular lysine residues on substrate proteins, plays a crucial role in both innate and adaptive immunologic responses, as well as pathogen-host immune system crosstalk. SUMOylation participates in the host's defense against pathogens by regulating immune responses, while numerically vast and taxonomically diverse pathogens have evolved to exploit the cellular SUMO modification system to break through innate defenses. Here, we describe the characteristics and multiple functions of SUMOylation as a pivotal PTM mechanism, the tactics employed by various pathogens to counteract the immune system through targeting host SUMOylation, and the character of the SUMOylation system in the fight between pathogens and the host immune system. We have also included a summary of the potential anti-pathogen SUMO enzyme inhibitors. This review serves as a reference for basic research and clinical practice in the diagnosis, prognosis, and treatment of pathogenic microorganism-caused disorders.

Role of interferons in the antiviral battle: from virus-host crosstalk to prophylactic and therapeutic potential in SARS-CoV-2 infection

Mammalians sense antigenic messages from infectious agents that penetrate the respiratory and digestive epithelium, as well as signals from damaged host cells through membrane and cytosolic receptors. The transduction of these signals triggers a personalized response, depending on the nature of the stimulus and the host's genetics, physiological condition, and comorbidities. Interferons (IFNs) are the primary effectors of the innate immune response, and their synthesis is activated in most cells within a few hours after pathogen invasion. IFNs are primarily synthesized in infected cells, but their anti-infective effect is extended to the neighboring cells by autocrine and paracrine action. The emergence of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic in 2019 was a stark reminder of the potential threat posed by newly emerging viruses. This pandemic has also triggered an overwhelming influx of research studies aiming to unveil the mechanisms of protective versus pathogenic host immune responses induced by SARS-CoV-2. The purpose of this review is to describe the role of IFNs as vital players in the battle against SARS-CoV-2 infection. We will briefly characterize and classify IFNs, present the inductors of IFN synthesis, their sensors, and signaling pathways, and then discuss the role of IFNs in controlling the evolution of SARS-CoV-2 infection and its clinical outcome. Finally, we will present the perspectives and controversies regarding the prophylactic and therapeutic potential of IFNs in SARS-CoV-2 infection.

Toward rational vaccine engineering

Technological revolutions in several fields have pushed the boundaries of vaccine design and provided new avenues for vaccine development. Next-generation vaccine platforms have shown promise in targeting challenging antigens, for which traditional approaches have been ineffective. With advances in protein engineering, structural biology, computational biology and immunology, the structural vaccinology approach, which uses protein structure information to develop immunogens, holds promise for future vaccine design. In this review, we highlight various vaccine development strategies, along with their advantages and limitations. We discuss the rational vaccine design approach, which focuses on structure-based vaccine design. Finally, we discuss antigen engineering using the epitope-scaffold approach, gaps in structural vaccinology, and remaining challenges in vaccine design.

Enhanced antibacterial properties on superhydrophobic micro-nano structured titanium surface

Micro/nano scale surface modifications of titanium based orthopedic and cardiovascular implants has shown to augment biocompatibility. However, bacterial infection remains a serious concern for implant failure, aggravated by increasing antibiotic resistance and over usage of antibiotics. Bacteria cell adhesion on implant surface leads to colonization and biofilm formation resulting in morbidity and mortality. Hence, there is a need to develop new implant surfaces with high antibacterial properties. Recent developments have shown that superhydrophobic surfaces prevent protein and bacteria cell adhesion. In this study, a thermochemical treatment was used modify the surface properties for high efficacy antibacterial activity on titanium surface. The modification led to a micro-nano surface topography and upon modification with polyethylene glycol (PEG) and silane the surfaces were superhydrophilic and superhydrophobic, respectively. The modified surfaces were characterized for morphology, wettability, chemistry, corrosion resistance and surface charge. The antibacterial capability was characterized with Staphylococcus aureus and Escherichia coli by evaluating the bacteria cell inhibition, adhesion kinetics, and biofilm formation. The results indicated that the superhydrophobic micro-nano structured titanium surface reduced bacteria cell adhesion significantly (>90%) and prevented biofilm formation compared to the unmodified titanium surface after 24 h of incubation.

Impact of iron fortification on anaemia and iron deficiency among pre-school children living in Rural Ghana

Anaemia in young sub-Saharan African children may be due to the double burden of malaria and iron deficiency. Primary analysis of a double-blind, cluster randomized trial of iron containing micronutrient powder supplementation in Ghanaian children aged 6 to 35 months found no difference in malaria risk between intervention and placebo groups. Here, we performed a secondary analysis of the trial data to assess the impact of long-term prophylactic iron fortificant on the risk of iron deficiency and anaemia in trial subjects. This population-based randomized-cluster trial involved 1958 children aged between 6 to 35 months, identified at home and able to eat semi-solid foods. The intervention group (n = 967) received a daily dose containing 12.5 mg elemental iron (as ferrous fumarate), vitamin A (400 μg), ascorbic acid (30 mg) and zinc (5 mg). The placebo group (n = 991) received a similar micronutrient powder but without iron. Micronutrient powder was provided daily to both groups for 5 months. At baseline and endline, health assessment questionnaires were administered and blood samples collected for analysis. The two groups had similar baseline anthropometry, anaemia, iron status, demographic characteristics, and dietary intakes (p > 0.05). Of the 1904 (97.2%) children who remained at the end of the intervention, the intervention group had significantly higher haemoglobin (p = 0.0001) and serum ferritin (p = 0.0002) levels than the placebo group. Soluble transferrin receptor levels were more saturated among children from the iron group compared to non-iron group (p = 0.012). Anaemia status in the iron group improved compared to the placebo group (p = 0.03). Continued long-term routine use of micronutrient powder containing prophylactic iron reduced anaemia, iron deficiency and iron deficiency anaemia among pre-school children living in rural Ghana's malaria endemic area.

Identification and evaluation of novel vaccine candidates against Shigella flexneri through reverse vaccinology approach

Shigellosis is a significant type of diarrhea that causes 160,000 deaths annually in a global scale. The mortality occurs mainly in children less than 5 years of age. No licensed vaccine is available, and conventional efforts for developing an effective and safe vaccine against shigellosis have not been succeeded yet. The reverse vaccinology is a novel promising method that screens genome or proteome of an organism for finding new vaccine candidates. In this study, through reverse vaccinology approach, new vaccine candidates against Shigella flexneri were identified and experimentally evaluated. Proteomes of S. flexneri were obtained from UniProt, and then outer membrane and extracellular proteins were predicted and selected for the evaluation of transmembrane domains, protein conservation, host homology, antigenicity, and solubility. From 103 proteins, 7 high-scored proteins were introduced as novel vaccine candidates, and after B- and T-cell epitope prediction, the best protein was selected for experimental studies. Recombinant protein was expressed, purified, and injected to BALB/c mice. The adhesion inhibitory effect of sera was also studied. The immunized mice demonstrated full protection against the lethal dose challenge. The sera remarkably inhibited S. flexneri adhesion to Caco-2 epithelial cells. The results indicate that identified antigen can serve for vaccine development against shigellosis and support reverse vaccinology for discovering novel effective antigens. KEY POINTS: • Seven Shigella new antigens were identified by reverse vaccinology (RV) approach. • The best antigen experimented demonstrated full protection against lethal dose. • In vivo results verified RV analyses and suggest FimG as a new potent vaccine candidate.

Role of duty cycle on Pseudomonas aeruginosa growth inhibition mechanisms by positive electric pulses

BACKGROUND

P. aeruginosa considered as a notoriously difficult organism to be controlled by antibiotics or disinfectants. The potential use of alternative means as an aid to avoid the wide use of antibiotics against bacteria pathogen has been recently arisen remarkably.

OBJECTIVE

Effect of extremely low frequency positive electric pulse with different duty cycles on Pseudomonas aeruginosa (ATCC: 27853) growth by constructed and implemented exposure device was investigated in this study.

METHODS

The exposure device was applied to give extremely low frequency in the range of 0.1 up to 20 Hz with the capability to control the duty cycle of each pulse with variation from 10% up to 100%. Growth curves of Pseudomonas aeruginosa were investigated before and after exposure to different frequencies (0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9 Hz) through measuring the optical density and cell count. Exposures to selected frequencies in the whole ranges of duty cycles were done. These studies were followed by DNA fragmentation, transmission electron microscope (TEM), antibiotic susceptibility tests, and dielectric measurements.

RESULTS

Findings revealed inhibition effect by 48.56% and 47.4% together with change in the DNA structural properties for samples exposed to 0.5 Hz and 0.7 Hz respectively. Moreover the data indicated important role of duty cycle on the inhibition mechanism.

CONCLUSION

It is concluded that there are two different mechanisms of interaction between positive electric pulse and microorganism occurred; 0.5 Hz caused rupture in cell wall while 0.7 Hz caused denaturation of the inner consistent of the cell.