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China CDC Weekly May 2024Over the last 12 years, there has been a consistent decline in the cases of typhoid/paratyphoid fever in China. Studying the epidemiological patterns of these diseases...
INTRODUCTION
Over the last 12 years, there has been a consistent decline in the cases of typhoid/paratyphoid fever in China. Studying the epidemiological patterns of these diseases in various provincial-level administrative divisions (PLADs) and examining potential influencing factors can provide crucial information for implementing successful control strategies.
METHODS
In this study, we analyzed the cases and incidence rates of typhoid/paratyphoid fever reported in various PLADs of China from 2011 to 2022, along with exploring potential influencing factors. We initially studied spatial shifts in the incidence rates through centroid shift analysis. Seasonal variations in typhoid/paratyphoid fever onset were examined using heatmaps. Spatial autocorrelation analysis was utilized to understand the spatial correlations among different PLADs. To assess potential factors, we utilized a generalized estimating equations model that integrated spatial lag effects and sequence comparison analysis.
RESULTS
The study identified significant geographical clustering of typhoid/paratyphoid fever cases in southwestern China. A decrease in incidence rates in the west resulted in a movement of the disease center towards the east. Higher incidence occurred during warmer seasons, highlighting the seasonal pattern of the diseases. Factors such as meteorological conditions and socioeconomic status were probable influencers of typhoid/paratyphoid fever.
CONCLUSIONS
The geographical and temporal spread of typhoid/paratyphoid fever can be impacted by meteorological and socioeconomic factors. Enhancing economic conditions, particularly in regions with high disease prevalence, could aid in the prevention and management of these fevers.
PubMed: 38854465
DOI: 10.46234/ccdcw2024.095 -
Frontiers in Immunology 2024None of the typhoid Vi Polysaccharide (ViPS) subunit vaccines incorporate adjuvants, and the immunogenicity of ViPS vaccines (e.g. Typbar TCV and Typhim Vi) is in part...
None of the typhoid Vi Polysaccharide (ViPS) subunit vaccines incorporate adjuvants, and the immunogenicity of ViPS vaccines (e.g. Typbar TCV and Typhim Vi) is in part due to associated TLR4 ligands such as endotoxin present in these vaccines. Since endotoxin content in vaccines is variable and kept very low due to inherent toxicity, it was hypothesized that incorporating a defined amount of a non-toxic TLR4-ligand such as monophosphoryl lipid A in ViPS vaccines would improve their immunogenicity. To test this hypothesis, a monophosphoryl lipid A-based adjuvant formulation named Turbo was developed. Admixing Turbo with Typbar TCV (ViPS-conjugated to tetanus toxoid) increased the levels of anti-ViPS IgM, IgG1, IgG2b, IgG2a/c, and IgG3 in inbred and outbred mice. In infant mice, a single immunization with Turbo adjuvanted Typbar TCV resulted in a significantly increased and durable IgG response and improved the control of bacterial burden compared to mice immunized without Turbo. Similarly, when adjuvanted with Turbo, the antibody response and control of bacteremia were also improved in mice immunized with Typhim Vi, an unconjugated vaccine. The immunogenicity of unconjugated ViPS is inefficient in young mice and is lost in adult mice when immunostimulatory ligands in ViPS are removed. Nevertheless, when adjuvanted with Turbo, poorly immunogenic ViPS induced a robust IgG response in young and adult mice, and this was observed even under antigen-limiting conditions. These data suggest that incorporation of Turbo as an adjuvant will make typhoid vaccines more immunogenic regardless of their intrinsic immunogenicity or conjugation status and maximize the efficacy across all ages.
Topics: Animals; Typhoid-Paratyphoid Vaccines; Mice; Toll-Like Receptor 4; Vaccines, Subunit; Antibodies, Bacterial; Adjuvants, Immunologic; Lipid A; Typhoid Fever; Immunoglobulin G; Female; Ligands; Polysaccharides, Bacterial; Immunogenicity, Vaccine; Adjuvants, Vaccine; Salmonella typhi; Mice, Inbred BALB C
PubMed: 38799439
DOI: 10.3389/fimmu.2024.1383476 -
PLoS Neglected Tropical Diseases May 2024
Topics: Salmonella paratyphi A; Paratyphoid Fever; Vaccines, Attenuated; Typhoid-Paratyphoid Vaccines; Flagella; Animals; Humans; Mice; Antibodies, Bacterial
PubMed: 38709719
DOI: 10.1371/journal.pntd.0012160 -
MBio May 2024serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars are exclusively...
UNLABELLED
serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars are exclusively adapted to the human host, where they can cause life-long persistent infection. A distinct feature of these serovars is the presence of a relatively high number of degraded coding sequences coding for metabolic pathways, most likely a consequence of their adaptation to a single host. As a result of convergent evolution, these serovars shared many of the degraded coding sequences although often affecting different genes in the same metabolic pathway. However, there are several coding sequences that appear intact in one serovar while clearly degraded in the other, suggesting differences in their metabolic capabilities. Here, we examined the functionality of metabolic pathways that appear intact in . Typhi but that show clear signs of degradation in . Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in . Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. Thus, the inability of . Typhi to metabolize Glucose-6-Phosphate or 3-phosphoglyceric acid is due to the silencing of the expression of the genes encoding the transporters for these compounds due to point mutations in the transcriptional regulatory proteins. In contrast, its inability to utilize glucarate or galactarate is due to the presence of point mutations in the transporter and enzymes necessary for the metabolism of these sugars. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted serovars and highlight a limitation of bioinformatic approaches to predict metabolic capabilities.
IMPORTANCE
serovar Typhi and Paratyphi A are the cause of typhoid and paratyphoid fever in humans, which are systemic life-threatening illnesses. Both serovars can only infect the human host, where they can cause life-long persistent infection. Because of their adaptation to the human host, these bacterial pathogens have changed their metabolism, leading to the loss of their ability to utilize certain nutrients. In this study we examined the functionality of metabolic pathways that appear intact in . Typhi but that show clear signs of degradation in . Paratyphi A. We found that, in all cases, the existence of single amino acid substitutions in . Typhi metabolic enzymes, transporters, or transcription regulators resulted in the inactivation of these metabolic pathways. These studies provide additional support for the concept of adaptive convergent evolution of these two human-adapted serovars.
Topics: Metabolic Networks and Pathways; Salmonella typhi; Humans; Genome, Bacterial; Salmonella paratyphi A; Loss of Function Mutation; Bacterial Proteins; Typhoid Fever; Serogroup
PubMed: 38572992
DOI: 10.1128/mbio.00607-24 -
Vaccine Apr 2024Typhoid fever causes substantial morbidity and mortality in Bangladesh. The government of Bangladesh plans to introduce typhoid conjugate vaccines (TCV) in its expanded...
PURPOSE
Typhoid fever causes substantial morbidity and mortality in Bangladesh. The government of Bangladesh plans to introduce typhoid conjugate vaccines (TCV) in its expanded program on immunization (EPI) schedule. However, the optimal introduction strategy in addition to the costs and benefits of such a program are unclear.
METHODS
We extended an existing mathematical model of typhoid transmission to integrate cost data, clinical incidence data, and recently conducted serosurveys in urban, semi-urban, and rural areas. In our primary analysis, we evaluated the status quo (i.e., no vaccination) and eight vaccine introduction strategies including routine and 1-time campaign strategies, which differed by age groups targeted and geographic focus. Model outcomes included clinical incidence, seroincidence, deaths, costs, disability-adjusted life years (DALYs), and incremental cost-effectiveness ratios (ICERs) for each strategy. We adopted a societal perspective, 10-year model time horizon, and 3 % annual discount rate. We performed probabilistic, one-way, and scenario sensitivity analyses including adopting a healthcare perspective and alternate model time horizons.
RESULTS
We projected that all TCV strategies would be cost saving compared to the status quo. The preferred strategy was a nationwide introduction of TCV at 9-12 months of age with a single catch-up campaign for children ages 1-15, which was cost saving compared to all other strategies and the status quo. In the 10 years following implementation, we projected this strategy would avert 3.77 million cases (95 % CrI: 2.60 - 5.18), 11.31 thousand deaths (95 % CrI: 3.77 - 23.60), and save $172.35 million (95 % CrI: -14.29 - 460.59) compared to the status quo. Our findings were broadly robust to changes in parameter values and willingness-to-pay thresholds.
CONCLUSIONS
We projected that nationwide TCV introduction with a catch-up campaign would substantially reduce typhoid incidence and very likely be cost saving in Bangladesh.
Topics: Child; Humans; Typhoid Fever; Cost-Benefit Analysis; Vaccines, Conjugate; Public Health; Typhoid-Paratyphoid Vaccines; Bangladesh
PubMed: 38531727
DOI: 10.1016/j.vaccine.2024.03.035 -
MBio Apr 2024serovars Typhi and Paratyphi cause a prolonged illness known as enteric fever, whereas other serovars cause acute gastroenteritis. Mechanisms responsible for the...
UNLABELLED
serovars Typhi and Paratyphi cause a prolonged illness known as enteric fever, whereas other serovars cause acute gastroenteritis. Mechanisms responsible for the divergent clinical manifestations of nontyphoidal and enteric fever infections have remained elusive. Here, we show that . Typhi and . Paratyphi A can persist within human macrophages, whereas . Typhimurium rapidly induces apoptotic macrophage cell death that is dependent on pathogenicity island 2 (SPI2). . Typhi and . Paratyphi A lack 12 specific SPI2 effectors with pro-apoptotic functions, including nine that target nuclear factor κB (NF-κB). Pharmacologic inhibition of NF-κB or heterologous expression of the SPI2 effectors GogA or GtgA restores apoptosis of . Typhi-infected macrophages. In addition, the absence of the SPI2 effector SarA results in deficient signal transducer and activator of transcription 1 (STAT1) activation and interleukin 12 production, leading to impaired T1 responses in macrophages and humanized mice. The absence of specific nontyphoidal SPI2 effectors may allow . Typhi and . Paratyphi A to cause chronic infections.
IMPORTANCE
Salmonella enterica is a common cause of gastrointestinal infections worldwide. The serovars Typhi and Paratyphi A cause a distinctive systemic illness called enteric fever, whose pathogenesis is incompletely understood. Here, we show that enteric fever serovars lack 12 specific virulence factors possessed by nontyphoidal serovars, which allow the enteric fever serovars to persist within human macrophages. We propose that this fundamental difference in the interaction of with human macrophages is responsible for the chronicity of typhoid and paratyphoid fever, suggesting that targeting the nuclear factor κB (NF-κB) complex responsible for macrophage survival could facilitate the clearance of persistent bacterial infections.
Topics: Humans; Animals; Mice; Salmonella typhi; Typhoid Fever; NF-kappa B; Macrophages; Salmonella
PubMed: 38497655
DOI: 10.1128/mbio.00454-24 -
Frontiers in Cellular and Infection... 2024Different serovars of Salmonella enterica cause systemic diseases in humans including enteric fever, caused by S. Typhi and S. Paratyphi A, and invasive nontyphoidal...
INTRODUCTION
Different serovars of Salmonella enterica cause systemic diseases in humans including enteric fever, caused by S. Typhi and S. Paratyphi A, and invasive nontyphoidal salmonellosis (iNTS), caused mainly by S. Typhimurium and S. Enteritidis. No vaccines are yet available against paratyphoid fever and iNTS but different strategies, based on the immunodominant O-Antigen component of the lipopolysaccharide, are currently being tested. The O-Antigens of S. enterica serovars share structural features including the backbone comprising mannose, rhamnose and galactose as well as further modifications such as O-acetylation and glucosylation. The importance of these O-Antigen decorations for the induced immunogenicity and cross-reactivity has been poorly characterized.
METHODS
These immunological aspects were investigated in this study using Generalized Modules for Membrane Antigens (GMMA) as delivery systems for the different O-Antigen variants. This platform allowed the rapid generation and in vivo testing of defined and controlled polysaccharide structures through genetic manipulation of the O-Antigen biosynthetic genes.
RESULTS
Results from mice and rabbit immunization experiments highlighted the important role played by secondary O-Antigen decorations in the induced immunogenicity. Moreover, molecular modeling of O-Antigen conformations corroborated the likelihood of cross-protection between S. enterica serovars.
DISCUSSION
Such results, if confirmed in humans, could have a great impact on the design of a simplified vaccine composition able to maximize functional immune responses against clinically relevant Salmonella enterica serovars.
Topics: Humans; Animals; Mice; Rabbits; O Antigens; Salmonella enterica; Salmonella typhimurium; Serogroup; Salmonella Infections; Immunity; Models, Animal; Salmonella Vaccines
PubMed: 38487353
DOI: 10.3389/fcimb.2024.1347813 -
The Lancet. Global Health Apr 2024Typhoid is a serious public health threat in many low-income and middle-income countries. Several vaccines for typhoid have been recommended by WHO for typhoid... (Meta-Analysis)
Meta-Analysis
BACKGROUND
Typhoid is a serious public health threat in many low-income and middle-income countries. Several vaccines for typhoid have been recommended by WHO for typhoid prevention in endemic countries. This study aimed to review the efficacy of typhoid vaccines against culture-confirmed Salmonella enterica serovar Typhi.
METHODS
We searched the Cochrane Central Register of Controlled Trials, MEDLINE, and Embase for studies published in English between Jan 1, 1986 and Nov 2, 2023. We included randomised controlled trials (RCTs) comparing typhoid vaccines with a placebo or another vaccine. This meta-analysis evaluated the efficacy and safety of several typhoid vaccines, including live attenuated oral Ty21a vaccine, Vi capsular polysaccharide (Vi-PS), Vi polysaccharide conjugated to recombinant Pseudomonas aeruginosa exotoxin A vaccine (Vi-rEPA), and Vi-tetanus toxoid conjugate vaccine (TCV). The certainty of evidence for key outcomes was evaluated using Grading of Recommendations, Assessment, Development, and Evaluations methodology. The outcome of interest was typhoid fever confirmed by the isolation of Salmonella enterica serovar Typhi in blood and adverse events following immunisation. This study is registered with PROSPERO (CRD42021241043).
FINDINGS
We included 14 RCTs assessing four different vaccines (Ty21a: four trials; Vi-PS: five trials; Vi-rEPA: one trial; TCV: four trials) involving 585 253 participants. All trials were conducted in typhoid endemic countries and the age of participants ranged from 6 months to 50 years. The pooled efficacy against typhoid fever was 45% (95% CI 33-55%; four trials; 247 649 participants; I 59%; moderate certainty) for Ty21a and 58% (44-69%; five trials; 214 456 participants; I 34%; moderate certainty) for polysaccharide Vi-PS. The cumulative efficacy of two doses of Vi-rEPA vaccine at 2 years was 91% (88-96%; one trial; 12 008 participants; moderate certainty). The pooled efficacy of a single shot of TCV at 2 years post-immunisation was 83% (77-87%; four trials; 111 130 participants; I 0%; moderate certainty). All vaccines were safe, with no serious adverse effects reported in the trials.
INTERPRETATION
The existing data from included trials provide promising results regarding the efficacy and safety of the four recommended typhoid vaccines. TCV and Vi-rEPA were found to have the highest efficacy at 2 years post-immunisation. However, follow-up data for Vi-rEPA are scarce and only TCV is pre-qualified by WHO. Therefore, roll-out of TCV into routine immunisation programmes in typhoid endemic settings is highly recommended.
FUNDING
There was no funding source for this study.
Topics: Humans; Infant; Salmonella typhi; Typhoid Fever; Typhoid-Paratyphoid Vaccines; Pseudomonas aeruginosa Exotoxin A; Vaccines, Attenuated; Vaccines, Conjugate; Tetanus Toxoid; Polysaccharides
PubMed: 38485426
DOI: 10.1016/S2214-109X(23)00606-X -
The Lancet. Global Health Apr 2024
Topics: Humans; Typhoid Fever; Typhoid-Paratyphoid Vaccines; Vaccines, Conjugate; Africa South of the Sahara
PubMed: 38485416
DOI: 10.1016/S2214-109X(24)00079-2