Oral Salmonella msbB Mutant as a Carrier for a Salmonella-Based Vaccine for Prevention and Reversal of Type 1 Diabetes

A therapy that includes an oral vaccine for type 1 diabetes (T1D) using live attenuated Salmonella MvP728 (ΔhtrA/ΔpurD), cytokines (IL10 and TGFβ) and preproinsulin (PPI) antigen in combination with a sub-therapeutic dose of anti-CD3 mAb was developed by our team. The vaccine combination therapy reduced insulitis and prevented and reversed diabetes in non-obese diabetic (NOD) mice. Here, we show the effectiveness of an alternative Salmonella mutant (ΔmsbB) as a carrier strain, which is anticipated to have lower risks of an inflammatory response and septicemia as a result of modification in the lipopolysaccharide (LPS) via detoxification of lipid A. This mutant strain proved to have highly reduced pathogenic side effects. Salmonella strain ΔmsbB expressed autoantigens and in combination with cytokines and anti-CD3 mAb, successfully prevented and reversed T1D to levels comparable to the previously used carrier strain ΔhtrA/ΔpurD. Additionally, the Salmonella msbB mutant resulted in higher rates of host cell infection. These results further demonstrate the potential of an oral Salmonella-based combined therapy in the treatment of early T1D.

Strategies for Enhancement of Live-Attenuated Salmonella-Based Carrier Vaccine Immunogenicity

The use of live-attenuated bacterial vaccines as carriers for the mucosal delivery of foreign antigens to stimulate the mucosal immune system was first proposed over three decades ago. This novel strategy aimed to induce immunity against at least two distinct pathogens using a single bivalent carrier vaccine. It was first tested using a live-attenuated Salmonella enterica serovar Typhi strain in clinical trials in 1984, with excellent humoral immune responses against the carrier strain but only modest responses elicited against the foreign antigen. Since then, clinical trials with additional Salmonella-based carrier vaccines have been conducted. As with the original trial, only modest foreign antigen-specific immunity was achieved in most cases, despite the incorporation of incremental improvements in antigen expression technologies and carrier design over the years. In this review, we will attempt to deconstruct carrier vaccine immunogenicity in humans by examining the basis of bacterial immunity in the human gastrointestinal tract and how the gut detects and responds to pathogens versus benign commensal organisms. Carrier vaccine design will then be explored to determine the feasibility of retaining as many characteristics of a pathogen as possible to elicit robust carrier and foreign antigen-specific immunity, while avoiding over-stimulation of unacceptably reactogenic inflammatory responses.

Description of Antibiotic Susceptibility Pattern Analysis on Methicillin-Susceptible Staphylococcus aureus and Methicillin-Resistant Staphylococcus aureus Clothing Gene Panton-Valentine Leukocidin from Clinic Isolate

Staphylococcus aureus is the most common cause of health care acquired infection and has a high rate of morbidity and mortality. S. aureus has a number of virulent factors that facilitate these bacteria to adhesion to the tissues of the host, avoiding the body’s defense system, and damaging the host cell. PVL cytotoxin is one of the virulent factors that causes hypervirulent in S. aureus. The infections caused are varied, ranging from severe skin infections, peneumonia, and sepsis. To obtain a description of the antibiotic susceptibility pattern in Methicillin-sensitive Staphylococcus aureus (MSSA) and Methicillin-resistant Staphylococcus aureus (MRSA) carriers of the pvl gene that causes infection. Isolate S. aureus derived from clinical isolates of inpatients who have identified and tested phenotypic antibiotic susceptibility using BD Phoenix TM Automated Microbiology System or Vitek2 Compact bioMérieux system followed by genotypic testing using PCR to detect the presence of the pvl gene. Of 85 S. aureus isolates, 65 isolates (76.5%) included MSSA bacterial strains and 20 isolates (23.5%) including strains of MRSA bacteria. Of the 65 isolates of MSSA bacterial strains, 9 isolates (13.84%) had the pvl gene, and of the 20 isolates of the MRSA strain, 1 isolate (5%) had the pvl gene. The susceptibility of non betalactam antibiotics to MSSA virus strains of pvl gene carriers ranged from 77.8%-100%. MSSA bacterial strains that did not carry the pvl gene also showed a non-betallactam antibiotic susceptibility ranging from 69.1%-100%. The susceptibility of tetracycline antibiotics to both MSSA strains of both pvl and non-carriers of pvl genes was 55.6% and 39.3% respectively. There was no significant difference between the antibiotic susceptibility pattern in the MSSA carrier strain of the pvl gene carrier and the proportion of the MRSA carrier strain of the pvl gene carrier.

Acquisition of virulence genes by a carrier strain gave rise to the ongoing epidemics of meningococcal disease in West Africa

In the African meningitis belt, a region of sub-Saharan Africa comprising 22 countries from Senegal in the west to Ethiopia in the east, large epidemics of serogroup A meningococcal meningitis have occurred periodically. After gradual introduction from 2010 of mass vaccination with a monovalent meningococcal A conjugate vaccine, serogroup A epidemics have been eliminated. Starting in 2013, the northwestern part of Nigeria has been affected by yearly outbreaks of meningitis caused by a novel strain of serogroup C Neisseria meningitidis (NmC). In 2015, the strain spread to the neighboring country Niger, where it caused a severe epidemic. Following a relative calm in 2016, the largest ever recorded epidemic of NmC broke out in Nigeria in 2017. Here, we describe the recent evolution of this new outbreak strain and show how the acquisition of capsule genes and virulence factors by a strain previously circulating asymptomatically in the African population led to the emergence of a virulent pathogen. This study illustrates the power of long-read whole-genome sequencing, combined with Illumina sequencing, for high-resolution epidemiological investigations.

A Single Amino Acid Replacement in the Sensor Kinase LiaS Contributes to a Carrier Phenotype in Group A Streptococcus

ABSTRACTDespite the high frequency of asymptomatic carriage of bacterial pathogens, we understand little about the bacterial molecular genetic underpinnings of this phenomenon. To obtain new information about the molecular genetic mechanisms underlying carriage of group AStreptococcus(GAS), we performed whole-genome sequencing of GAS strains recovered from a single individual during acute pharyngitis and subsequent asymptomatic carriage. We discovered that compared to the initial infection isolate, the strain recovered during asymptomatic carriage contained three single nucleotide polymorphisms, one of which was in a highly conserved region of a gene encoding a sensor kinase,liaS, resulting in an arginine-to-glycine amino acid replacement at position 135 of LiaS (LiaSR135G). Using gene replacement, we demonstrate that introduction of the carrier allele (liaSR135G) into a serotype-matched invasive strain increased mouse nasopharyngeal colonization and adherence to cultured human epithelial cells. The carrier mutation also resulted in a reduced ability to grow in human blood and reduced virulence in a mouse model of necrotizing fasciitis. Repair of the mutation in the GAS carrier strain restored virulence and decreased adherence to cultured human epithelial cells. We also provide evidence that the carrier mutation alters the GAS transcriptome, including altered transcription of GAS virulence genes, providing a potential mechanism for the pleiotropic phenotypic effects. Our data obtained using isogenic strains suggest that theliaSR135Gmutation in the carrier strain contributes to the transition from disease to asymptomatic carriage and provides new information about this poorly described regulatory system in GAS.

Lactococcus lactis IBB477 presenting adhesive and muco-adhesive properties as a candidate carrier strain for oral vaccination against influenza virus.

In the gastrointestinal tract (GIT), adhesion is a prerequisite for bacterial colonization. Lactococci can be used in functional food (probiotics) and health-related applications (mucosal vaccines, therapeutic drug delivery), both potentially involving adhesive properties. A candidate lactic acid bacterium for influenza antigen delivery through the GIT should display the ability to adhere. The present work probes the interactions between Lactococcus lactis and mucins using pig gastric mucin (PGM) as a model. Two strains were used for the optimization of the screening method for adhesion: L. lactis subsp. cremoris IBB477 persistent in the GIT of germ-free rats, and the low-adhering control strain MG1820. High adhesion to bare and mucin-coated polystyrene of IBB477 in comparison with MG1820 was observed. We searched for genetic determinants potentially involved in the adhesion/muco-adhesion of IBB477, identifying two such genes: prtP and a gene coding for a protein with MUB and MucBP domains. Based on its persistence in the GIT and adhesive properties, L. lactis IBB477 is a candidate carrier strain for expression of influenza haemagglutinin (HA) protein for induction of mucosal immune response.