Target Product Profile and Development Path for Shigellosis Treatment with Antibacterials

Berberine protects against dysentery by targeting both Shigella filamentous temperature sensitive protein Z and host pyroptosis: Resolving in vitro-vivo effect discrepancy

BACKGROUND

Berberine (BBR), an isoquinoline alkaloid, has been applied clinically to treat dysentery caused by Shigella for decades. Nevertheless, the precise mechanisms behind its anti-Shigella effect have not been fully elucidated.

PURPOSE

This study aims to investigate the mechanism of BBR on antibacterial activity against S. flexneri infection.

METHODS

We initially reproduced the mouse model of Shigella flexneri-induced dysentery, and then, assessed the therapeutic effect of BBR. In vitro, we measured the inhibitory effect of BBR against S. flexneri and the GTPase activity of FtsZ (filamentous temperature sensitive protein Z) using the minimum inhibitory concentration (MIC) test and an enzyme activity assay to investigate the bacteria-directed mechanisms. Subsequently, we utilized both the in vivo mouse model of dysentery and the in vitro macrophage infection model with S. flexneri to explore the host-directed anti-Shigella mechanisms of BBR. The canonical pyroptosis pathway mediated by caspase-1 and mitochondrial damage were examined by Western blot, immunofluorescence and RNA interference analysis.

RESULTS

Administration of BBR alleviated the symptoms of dysentery induced by S. flexneri infection. In vitro, BBR could inhibit the growth of S. flexneri by targeting the GTPase activity of FtsZ, thereby affecting bacterial cell division. Additionally, our in vivo findings revealed that BBR suppressed macrophage pyroptosis by inhibiting the expression of caspase-1 and subsequently the mitochondrial damage, which in turn reduced the intestinal inflammation and tissue damage.

CONCLUSIONS

Our results provide a novel mechanism of BBR's action, which targets both the bacterium and the host to exert its antibacterial effects. Furthermore, it also provides an explanation for the discrepancy between BBR's relatively modest antibacterial efficacy in vitro and its enhanced antibacterial effects in vivo, thus, giving support to its clinical use.

Tebipenem pivoxil as an alternative to ceftriaxone for clinically non-responding children with shigellosis: a randomised non-inferiority trial protocol

INTRODUCTION

Shigellosis is the second leading cause of diarrhoeal deaths among children worldwide. Oral azithromycin and intravenous ceftriaxone are the recommended first-line and second-line therapies for shigellosis in Bangladesh, respectively, but growing antibiotic resistance will require new antibiotic options. Tebipenem pivoxil, an orally administered carbapenem antibiotic with activity against many strains of antibiotic-resistant bacteria, may be a viable option.

METHODS

A phase IIb randomised controlled trial was planned to determine the efficacy and safety of oral tebipenem pivoxil, compared with intravenous ceftriaxone, for children with Shigella diarrhoea unresponsive to the first-line antibiotic therapy. We will enrol 132 children in the trial (66 in each arm). Children from Bangladesh aged 24-59 months suspected of having Shigella diarrhoea, with no clinical improvement within 48 hours of starting first-line therapy, will be randomised to a 3-day course of intravenous ceftriaxone (50 mg/kg, once a day) or a 3-day course of oral tebipenem pivoxil (4 mg/kg, three times a day). The children will be evaluated for key clinical, microbiological and safety outcomes during the subsequent 30-day period. Clinically, failure at day 3 will be defined as the presence of fever (axillary temperature ≥38°C), diarrhoea (three or more abnormally loose or watery stools in the last 24 hours), blood in stool, or abdominal pain/tenderness at day 3 of follow-up or death or hospitalisation prior to day 3. It is hypothesised that children treated with tebipenem pivoxil will have no worse clinical and microbiological failure rates compared with ceftriaxone.

ETHICS AND DISSEMINATION

This study protocol was approved by the institutional review board of the International Centre for Diarrhoeal Disease Research, Bangladesh, which comprises a research review committee and an ethics review committee. In addition, the use of tebipenem pivoxil in shigellosis was approved by the Directorate General of Drug Administration of Bangladesh.

TRIAL REGISTRATION NUMBER

NCT05121974.

Facilitating the use of the target product profile in academic research: a systematic review

BACKGROUND

The Target Product Profile (TPP) is a tool used in industry to guide development strategies by addressing user needs and fostering effective communication among stakeholders. However, they are not frequently used in academic research, where they may be equally useful. This systematic review aims to extract the features of accessible TPPs, to identify commonalities and facilitate their integration in academic research methodology.

METHODS

We searched peer-reviewed papers published in English developing TPPs for different products and health conditions in four biomedical databases. Interrater agreement, computed on random abstract and paper sets (Cohen's Kappa; percentage agreement with zero tolerance) was > 0.91. We interviewed experts from industry contexts to gain insight on the process of TPP development, and extracted general and specific features on TPP use and structure.

RESULTS

138 papers were eligible for data extraction. Of them, 92% (n = 128) developed a new TPP, with 41.3% (n = 57) focusing on therapeutics. The addressed disease categories were diverse; the largest (47.1%, n = 65) was infectious diseases. Only one TPP was identified for several fields, including global priorities like dementia. Our analyses found that 56.5% of papers (n = 78) was authored by academics, and 57.8% of TPPs (n = 80) featured one threshold level of product performance. The number of TPP features varied widely across and within product types (n = 3-44). Common features included purpose/context of use, shelf life for drug stability and validation aspects. Most papers did not describe the methods used to develop the TPP. We identified aspects to be taken into account to build and report TPPs, as a starting point for more focused initiatives guiding use by academics.

DISCUSSION

TPPs are used in academic research mostly for infectious diseases and have heterogeneous features. Our extraction of key features and common structures helps to understand the tool and widen its use in academia. This is of particular relevance for areas of notable unmet needs, like dementia. Collaboration between stakeholders is key for innovation. Tools to streamline communication such as TPPs would support the development of products and services in academia as well as industry.

Vaccination with a Protective Ipa Protein-Containing Nanoemulsion Differentially Alters the Transcriptomic Profiles of Young and Elderly Mice following Shigella Infection

Shigella spp. are responsible for bacillary dysentery or shigellosis transmitted via the fecal-oral route, causing significant morbidity and mortality, especially among vulnerable populations. There are currently no licensed Shigella vaccines. Shigella spp. use a type III secretion system (T3SS) to invade host cells. We have shown that L-DBF, a recombinant fusion of the T3SS needle tip (IpaD) and translocator (IpaB) proteins with the LTA1 subunit of enterotoxigenic E. coli labile toxin, is broadly protective against Shigella spp. challenge in a mouse lethal pulmonary model. Here, we assessed the effect of LDBF, formulated with a unique TLR4 agonist called BECC470 in an oil-in-water emulsion (ME), on the murine immune response in a high-risk population (young and elderly) in response to Shigella challenge. Dual RNA Sequencing captured the transcriptome during Shigella infection in vaccinated and unvaccinated mice. Both age groups were protected by the L-DBF formulation, while younger vaccinated mice exhibited more adaptive immune response gene patterns. This preliminary study provides a step toward identifying the gene expression patterns and regulatory pathways responsible for a protective immune response against Shigella. Furthermore, this study provides a measure of the challenges that need to be addressed when immunizing an aging population.

Impact of an intranasal L-DBF vaccine on the gut microbiota in young and elderly mice

Shigella spp. cause bacillary dysentery (shigellosis) with high morbidity and mortality in low- and middle-income countries. Infection occurs through the fecal-oral route and can be devastating for vulnerable populations, including infants and the elderly. These bacteria invade host cells using a type III secretion system (T3SS). No licensed vaccine yet exists for shigellosis, but we have generated a recombinant fusion protein, L-DBF, combining the T3SS needle tip protein (IpaD), translocator protein (IpaB), and the LTA1 subunit of enterotoxigenic E. coli labile toxin, which offers broad protection in a mouse model of lethal pulmonary infection. The L-DBF vaccine protects high-risk groups, including young and elderly mice. Here, we investigated how the gut microbiota of young and elderly mice responds to intranasal L-DBF vaccination formulated in an oil-in-water emulsion (ME). Samples from lungs, small intestines, and feces were collected on day 14 after 2 or 3 doses of L-DBF in ME. 16S rRNA gene sequencing revealed age-dependent changes in gut microbiota post-vaccination. The vaccine-induced changes were more prominent in the elderly mice and were most significant in the intestinal tract, indicating that vaccination by the intranasal route can have a tremendous impact on the gut environment. These findings provide insight into the communication between the intranasal mucosal surface following subunit vaccination and the microbiota at a distant mucosal site, thereby highlighting the impact of vaccination and the host's microbiome.

Impact of the TLR4 agonist BECC438 on a novel vaccine formulation against Shigella spp

Shigellosis (bacillary dysentery) is a severe gastrointestinal infection with a global incidence of 90 million cases annually. Despite the severity of this disease, there is currently no licensed vaccine against shigellosis. Shigella's primary virulence factor is its type III secretion system (T3SS), which is a specialized nanomachine used to manipulate host cells. A fusion of T3SS injectisome needle tip protein IpaD and translocator protein IpaB, termed DBF, when admixed with the mucosal adjuvant double-mutant labile toxin (dmLT) from enterotoxigenic E. coli was protective using a murine pulmonary model. To facilitate the production of this platform, a recombinant protein that consisted of LTA-1, the active moiety of dmLT, and DBF were genetically fused, resulting in L-DBF, which showed improved protection against Shigella challenge. To extrapolate this protection from mice to humans, we modified the formulation to provide for a multivalent presentation with the addition of an adjuvant approved for use in human vaccines. Here, we show that L-DBF formulated (admix) with a newly developed TLR4 agonist called BECC438 (a detoxified lipid A analog identified as Bacterial Enzymatic Combinatorial Chemistry candidate #438), formulated as an oil-in-water emulsion, has a very high protective efficacy at low antigen doses against lethal Shigella challenge in our mouse model. Optimal protection was observed when this formulation was introduced at a mucosal site (intranasally). When the formulation was then evaluated for the immune response it elicits, protection appeared to correlate with high IFN-γ and IL-17 secretion from mucosal site lymphocytes.

Identification and antibiotic pattern analysis of bacillary dysentery causing bacteria isolated from stool samples of infected patients

Bacillary dysentery is a type of dysentery and a severe form of shigellosis. This dysentery is usually restricted to Shigella infection, but Salmonella enterica and enteroinvasive Escherichia coli strains are also known as this infection's causative agents. The emergence of drug-resistant, bacillary dysentery-causing pathogens is a global burden, especially for developing countries with poor hygienic environments. This study aimed to isolate, identify, and determine the drug-resistant pattern of bacillary dysentery-causing pathogens from the stool samples of the Kushtia region in Bangladesh. Hence, biochemical tests, serotyping, molecular identification, and antibiotic profiling were performed to characterize the pathogens. Among one hundred fifty (150) stool samples, 18 enteric bacterial pathogens were isolated and identified, where 12 were Shigella strains, 5 were S. enterica sub spp. enterica strains and one was the E.coli strain. Among 12 Shigella isolates, 8 were Shigella flexneri 2a serotypes, and 4 were Shigella sonnei Phage-II serotypes. Except for three Salmonella strains, all isolated strains were drug-resistant (83%), whereas 50% were multidrug-resistant (MDR), an alarming issue for public health. In antibiotic-wise analysis, the isolated pathogens showed the highest resistance against nalidixic acid (77.78%), followed by tetracycline (38.89%), kanamycin (38.89%), amoxicillin (27.78%), streptomycin (27.78%), cefepime (22.22%), ceftriaxone (22.22%), ampicillin (16.67%), ciprofloxacin (16.67%), and chloramphenicol (16.67%). The existence of MDR organisms that cause bacillary dysentery in the Kushtia area would warn the public to be more health conscious, and physicians would administer medications cautiously. The gradual growth of MDR pathogenic microorganisms needs immediate attention, and the discovery of effective medications must take precedence.

Supplementary information

The online version contains supplementary material available at 10.1007/s11756-022-01299-x.

Development of a Self-Adjuvanting, Cross-Protective, Stable Intranasal Recombinant Vaccine for Shigellosis

With the acquirement of antibiotic resistance, Shigella has resulted in multiple epidemics of shigellosis, an infectious diarrheal disease, causing thousands of deaths per year. Unfortunately, there are no licensed vaccines, primarily due to low or serotype-specific immunogenicity. Thus, conserved subunit vaccines utilizing recombinant invasion plasmid antigens (Ipa) have been explored as cross-protective vaccine candidates. However, achieving cross-protection against Shigella dysenteriae 1, which caused multiple pandemics/epidemics in the recent past, has been difficult. Therefore, a rational approach to improve cross-protection in the preparation for a possible pandemic should involve conserved proteins from S. dysenteriae 1 (Sd1). IpaC is one such conserved immunogenic protein that is less explored as an independent vaccine due to its instability/aggregation. Therefore, to improve cross-protection and potential immunogenicity and to be prepared for a future epidemic/pandemic, herein, we stabilized recombinant Sd1 IpaC, expressed without its chaperone, using a previously reported stabilizing detergent (LDAO) in a modified protocol and assessed its vaccine potential without an adjuvant. The protein assembled into heterogeneous complex spherical structures in the presence of LDAO and showed improved stability at storage temperatures of -80, -20, 4, 25, and 37 °C while providing enhanced yield and concentration. The protein could also be stably lyophilized and reconstituted, increasing the convenience of transportation and storage. Upon intranasal administration in BALB/c mice, the stabilized-IpaC-immunized groups generated significant antibody response and were not only protected against a high intraperitoneal dose of homologous S. dysenteriae 1 but also showed 100% survival against heterologous Shigella flexneri 2a without an adjuvant, while the control animals showed visible diarrhea (bloody-Sd1 challenge), lethargy, and weight loss with 0% survival. Overall, this work demonstrates that stabilized IpaC can be explored as a minimalist, self-adjuvanting, cross-protective, intranasal, single-antigen Shigella vaccine.