Bacterial Ghosts-Based Vaccine and Drug Delivery Systems

Bacterial ghosts (BGs) are empty bacterial envelopes of Gram-negative bacteria produced by controlled expressions of cloned gene E, forming a lysis tunnel structure within the envelope of the living bacteria. Globally, BGs have been used as vaccine delivery systems and vaccine adjuvants. There is an increasing interest in the development of novel delivery systems that are based on BGs for biomedical applications. Due to intact reservation of bacterial cell membranes, BGs have an inherent immunogenicity, which enables targeted drug delivery and controlled release. As carrier vehicles, BGs protect drugs from interference by external factors. In recent years, there has been an increasing interest in BG-based delivery systems against tumors, inflammation, and infection, among others. Herein, we reviewed the preparation methods for BGs, interactions between BGs and the host, and further highlighted research progress in BG development.

Immunization of chicken with flagellin adjuvanted Salmonella enteritidis bacterial ghosts confers complete protection against chicken salmonellosis

The present study describes the generation of Salmonella enteritidis (SE) ghosts with a surface decorated Salmonella Typhimurium (ST) flagellin (FliC) antigen for immune enhancement and strain-specific protection. The ghosts were generated by biological means using pJHL184::fliC temperature inducible plasmid where the lysis occurs by phage PhiX174 lysis gene E expression. Being an inactivated strain, no environmental contamination was observed by fecal shedding upon inoculation into the chicken. To test the protective immune responses, ghost vaccination was conducted via the intramuscular route using chicken as the model organism. The development of antigen-specific humoral, cell-mediated, and protective immune responses was assessed. Compared to vector alone and phosphate-buffered saline (PBS) control groups, pJHL184::fliC ghost could generate significantly high antigen-specific IgY and cell-mediated immune (CMI) responses measured by a peripheral blood mononuclear cell proliferation, flow cytometer, and cytokine responses elicited by stimulated splenic T-cells (P < 0.05). The adjuvant effect induced by FliC was demonstrated by elicitation of Toll-like receptor 5 (TLR5). To test the protection efficacy, chickens were challenged with both SE and ST wild type (WT) strains, and the protection efficacy was assessed by determining the presence of challenging strains in the spleen and liver, and by assessing the histopathological alterations. Complete clearance of the challenged strain and least inflammatory signs were evident in the SE ghosts vaccinated group compared to the vector and PBS control. The elimination of both SE and ST in chicken organs ensures the intramuscular immunization of the present SE ghost vaccine can reduce SE and ST contamination levels in chicken that can be beneficial to prevent enteric infections in humans.

Genetic Diversity Among SARS-CoV2 Strains in South America may Impact Performance of Molecular Detection

Since its emergence in Wuhan (China) on December 2019, the Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) has rapidly spread worldwide. After its arrival in South America in February 2020, the virus has expanded throughout the region, infecting over 900,000 individuals with approximately 41,000 reported deaths to date. In response to the rapidly growing number of cases, a number of different primer-probe sets have been developed. However, despite being highly specific, most of these primer-probe sets are known to exhibit variable sensitivity. Currently, there are more than 300 SARS-CoV2 whole genome sequences deposited in databases from Brazil, Chile, Ecuador, Colombia, Uruguay, Peru, and Argentina. To test how regional viral diversity may impact oligo binding sites and affect test performance, we reviewed all available primer-probe sets targeting the E, N, and RdRp genes against available South American SARS-CoV-2 genomes checking for nucleotide variations in annealing sites. Results from this in silico analysis showed no nucleotide variations on the E-gene target region, in contrast to the N and RdRp genes which showed massive nucleotide variations within oligo binding sites. In lines with previous data, our results suggest that the E-gene stands as the most conserved and reliable target when considering single-gene target testing for molecular diagnosis of SARS-CoV-2 in South America.