A human model of Buruli ulcer: Provisional protocol for a Mycobacterium ulcerans controlled human infection study.

Critical knowledge gaps have impeded progress towards reducing the global burden of disease due to Mycobacterium ulcerans, the cause of the neglected tropical disease Buruli ulcer (BU). Development of a controlled human infection model of BU has been proposed as an experimental platform to explore host-pathogen interactions and evaluate tools for prevention, diagnosis, and treatment. We have previously introduced the use case for a new human model and identified M. ulcerans JKD8049 as a suitable challenge strain. Here, we present a provisional protocol for an initial study, for transparent peer review during the earliest stages of protocol development. Following simultaneous scientific peer review and community/stakeholder consultation of this provisional protocol, we aim to present a refined protocol for institutional review board (IRB) evaluation.

This paper describes a provisional clinical protocol for the pilot human challenge model of Mycobacterium ulcerans infection, which causes the skin disease 'Buruli ulcer' (BU). BU is typically painless and begins as a small area of redness or swelling, and is curable with antibiotics. If the diagnosis is delayed, it can result in large ulceration and disability. Side effects from antibiotics are common but rarely severe; nevertheless, preventative strategies, such as vaccination, are urgently needed. The overarching project, known as 'MuCHIM', aims to establish a safe and acceptable controlled human challenge model (CHIM) of this disease in healthy volunteers in Melbourne, Australia. This pilot protocol primarily aims to establish that it is safe and acceptable to participants, and secondarily to confirm successful establishment of infection and the infection rate amongst participants. We also aim to test less invasive diagnostic tests, assess immune responses to infection, to understand changes in the human microbiome during the trial, and explore microbiological characteristics of M. ulcerans infection. If this pilot is successful, we hope to test vaccines and other therapeutics using this model, which could blunt or reduce the rising incidence of this disease in Australia, while further informing vaccine development research.

Tick-borne viruses: Epidemiology, pathogenesis, and animal models.

Tick-borne viruses, capable of infecting animals and humans, are expanding geographically and increasing in prevalence, posing significant global public health threats. This review explores the current epidemiology of human pathogenic tick-borne viruses, emphasizing their diversity and the spectrum of symptomatic manifestations in humans, which range from mild to severe. We highlight how the infrequent and unpredictable nature of viral outbreaks complicates the precise identification and understanding of these viruses in human infections. Furthermore, we describe the utility of animal models that accurately mimic human clinical symptoms, facilitating the development of effective control strategies. Our comprehensive analysis provides crucial insights into disease progression and emphasizes the urgent need for continued research. This work aims to provide insight into knowledge gaps to mitigate the health burden of tick-borne infections and open an avenue for further study to enhance our understanding of these emerging infectious diseases.

Clinical and epidemiological investigation of human infection with zoonotic parasite Trypanosoma dionisii in China.

BACKGROUND: Trypanosomiasis continues to pose a global threat to human health, with human infection mainly caused by Trypanosoma brucei and Trypanosoma cruzi. METHODS: We present a 30-year-old pregnant woman with persistent high fever from Shandong Province, China. High-throughput sequencing revealed the presence of Trypanosoma dionisii in blood. We conducted an analysis of the patient's clinical, epidemiological, and virological data. RESULTS: The patients exhibited fever, shortness of breath, chest tightness, accompanied by change in liver function and inflammatory response. She made a full recovery without any long-term effects. T. dionisii was detected in blood collected 23 days after onset of illness. The 18S rRNA gene sequence showed close similarity to T. dionisii found in bats from Japan, while the gGAPDH gene was closely related to T. dionisii from bats in Mengyin County, Shandong Province. Phylogenetic analysis demonstrated the current T. dionisii belongs to clade B within its species group. Positive anti-Trypanosoma IgG antibody was detected from the patient on Day 23, 66 and 122 after disease onset, as well as the cord blood and serum from the newborn. Retrospective screening of wild small mammals captured from Shandong Province revealed a prevalence rate of 0.54% (7/1304) for T. dionisii; specifically among 0.81% (5/620) of Apodemus agrarius, and 0.46% (2/438) of Mus musculus. CONCLUSIONS: The confirmation of human infection with T. dionisii underscores its potential as a zoonotic pathogen, while the widespread presence of this parasite in rodent and bat species emphasizes the emerging threat it poses to human health.

INTRA- AND INTER-HOST EVOLUTION OF HUMAN NOROVIRUS IN HEALTHY ADULTS.

Background: Human noroviruses are a leading cause of acute and sporadic gastroenteritis worldwide. The evolution of human noroviruses in immunocompromised persons has been evaluated in many studies. Much less is known about the evolutionary dynamics of human norovirus in healthy adults. Methods: We used sequential samples collected from a controlled human infection study with GI.1/Norwalk/US/68 virus to evaluate intra- and inter-host evolution of a human norovirus in healthy adults. Up to 12 samples from day 1 to day 56 post-challenge were sequenced using a norovirus-specific capture probe method. Results: Complete genomes were assembled, even in samples that were below the limit of detection of standard RT-qPCR assays, up to 28 days post-challenge. Analysis of 123 complete genomes showed changes in the GI.1 genome in all persons, but there were no conserved changes across all persons. Single nucleotide variants resulting in non-synonymous amino acid changes were observed in all proteins, with the capsid VP1 and nonstructural protein NS3 having the largest numbers of changes. Conclusions: These data highlight the potential of a new capture-based sequencing approach to assemble human norovirus genomes with high sensitivity and demonstrate limited conserved immune pressure-driven evolution of GI.1 virus in healthy adults.

Role of cellular effectors in the induction and maintenance of IgA responses leading to protective immunity against enteric bacterial pathogens.

The mucosal immune system is a critical first line of defense to infectious diseases, as many pathogens enter the body through mucosal surfaces, disrupting the balanced interactions between mucosal cells, secretory molecules, and microbiota in this challenging microenvironment. The mucosal immune system comprises of a complex and integrated network that includes the gut-associated lymphoid tissues (GALT). One of its primary responses to microbes is the secretion of IgA, whose role in the mucosa is vital for preventing pathogen colonization, invasion and spread. The mechanisms involved in these key responses include neutralization of pathogens, immune exclusion, immune modulation, and cross-protection. The generation and maintenance of high affinity IgA responses require a delicate balance of multiple components, including B and T cell interactions, innate cells, the cytokine milieu (e.g., IL-21, IL-10, TGF-ß), and other factors essential for intestinal homeostasis, including the gut microbiota. In this review, we will discuss the main cellular components (e.g., T cells, innate lymphoid cells, dendritic cells) in the gut microenvironment as mediators of important effector responses and as critical players in supporting B cells in eliciting and maintaining IgA production, particularly in the context of enteric infections and vaccination in humans. Understanding the mechanisms of humoral and cellular components in protection could guide and accelerate the development of more effective mucosal vaccines and therapeutic interventions to efficiently combat mucosal infections.

Transmission potential of Streptococcus pyogenes during a controlled human infection trial of pharyngitis.

Controlled human infection (CHI) models can provide insights into transmission of pathogens such as Streptococcus pyogenes (Strep A). As part of the Controlled Human Infection with Penicillin for Streptococcus pyogenes (CHIPS) trial, we explored the potential for transmission among participants deliberately infected with the Strep A emm75 strain. Three approaches to understanding transmission were employed: the use of agar settle plates to capture possible droplet or airborne spread of Strep A; measurement of distance droplets could spread during conversation; and environmental swabbing of high-touch items to detect Strep A on surfaces. Of the 60 (27%) CHIPS trial participants across five cohorts, 16 were enrolled in this sub-study; availability of study staff was the primary reason for selection. In total, 189 plates and 260 swabs were collected. Strep A was grown on one settle plate from a participant on the second day, using plates placed 30 cm away. This participant received the placebo dose of penicillin and had met the primary endpoint of pharyngitis. Whole-genome sequencing identified this to be the challenge strain. Strep A was not detected on any swabs. In this small sample of CHI participants, we did not find evidence of Strep A transmission by the airborne route or fomites, and just one instance of droplet spread while acutely symptomatic with streptococcal pharyngitis. Although these experiments provide evidence of minimal transmission within controlled clinical settings, greater efforts are required to explore Strep A transmission in naturalistic settings.IMPORTANCEStreptococcus pyogenes remains a significant driver of morbidity and mortality, particularly in under-resourced settings. Understanding the transmission modalities of this pathogen is essential to ensuring the success of prevention methods. This proposed paper presents a nascent attempt to determine the transmission potential of Streptococcus pyogenes nested within a larger controlled human infection model.

The use of controlled human infection models to identify correlates of protection for invasive Salmonella vaccines.

Controlled human infection model (CHIM) studies, which involve deliberate exposure of healthy human volunteers to an infectious agent, are recognised as important tools to advance vaccine development. These studies not only facilitate estimates of vaccine efficacy, but also offer an experimental approach to study disease pathogenesis and profile vaccine immunogenicity in a controlled environment, allowing correlation with clinical outcomes. Consequently, the data from CHIMs can be used to identify immunological correlates of protection (CoP), which can help accelerate vaccine development. In the case of invasive Salmonella infections, vaccination offers a potential instrument to prevent disease. Invasive Salmonella disease, caused by the enteric fever pathogens Salmonella enterica serovar Typhi (S. Typhi) and S. Paratyphi A, B and C, and nontyphoidal Salmonella (iNTS), remains a significant cause of mortality and morbidity in low- and middle-income countries, resulting in over 200,000 deaths and the loss of 15 million DALYs annually. CHIM studies have contributed to the understanding of S. Typhi infection and provided invaluable insight into the development of vaccines and CoP following vaccination against S. Typhi. However, CoP are less well understood for S. Paratyphi A and iNTS. This brief review focuses on the contribution of vaccine-CHIM trials to our understanding of the immune mechanisms associated with protection following vaccines against invasive Salmonella pathogens, particularly in relation to CoP.

Human infection with IsrRAPXV, a novel zoonotic bat-derived poxvirus.

BACKGROUND: Bats are recognized as the natural reservoir of several zoonotic viruses that pose a threat to public health worldwide. In our recent reports we describe the identification of a novel poxvirus, IsrRAPXV, in Egyptian fruit bats. This poxvirus is associated with high morbidity and mortality in bats. METHODS: Herein, we describe the identification of poxvirus in a female patient hospitalized with systemic symptoms and severe painful skin lesions on her hands. We performed qPCR, whole genome sequencing and phylogenetic analysis to identify and characterize this poxvirus as the etiologic agent. RESULTS: The patient interacted with wounded and sick bats as a volunteer in a bat shelter run by the Israel bat sanctuary organization. Samples collected from the patient's skin lesions were positive for the presence of IsrRAPXV by PCR. Additionally, phylogenetic analysis showed that this virus is identical to IsrRAPXV originally described by us as the causative agent of skin lesions in fruit bats. CONCLUSIONS: Our finding suggest that IsrRAPXV is zoonotic and therefore veterinarians and volunteers working in bats shelter should meticulously follow the guidelines of working with bats and use required personal protective equipment.

Is it possible to eliminate or eradicate human fish-borne parasitic diseases? A sweet dream or a nightmare?

Human fish-borne parasitic diseases may be caused by at least 111 taxa of both freshwater and marine fish parasites. It is estimated that they occur in many hundreds of millions of people all over the world, and many more are at risk, sometimes with serious consequences including the death of the host. Therefore, all efforts must be made to minimize and prevent the infection. In this paper we present an overview detailing the several types of parasites infecting humans, the reasons for the occurrence of the disease, the ways of infection, the preventive measures and difficulties encountered when combating such infections. Finally, we discuss the possibility of eliminating or eradicating fish-borne diseases. It is concluded that elimination is difficult to achieve but it is possible in some places under favourable circumstances, and that eradication will probably never be fully achieved.

Complete genome of a rare Salmonella enterica subsp. enterica serovar Hessarek from human stool.

We present a complete genome of Salmonella enterica subsp. enterica serovar Hessarek isolated from a human stool from an outbreak linked to egg consumption in South Australia. Orientation of the rrn operon and characteristics of the Salmonella virulence plasmid indicates that this serovar is virulent toward humans and birds.

Vibrio mimicus Lineage Carrying Cholera Toxin and Vibrio Pathogenicity Island, United States and China.

Vibrio mimicus bacteria have caused sporadic cases and outbreaks of cholera-like diarrhea throughout the world, but the association of lineages with such events is unexplored. Genomic analyses revealed V. mimicus lineages carrying the virulence factors cholera toxin and toxin coregulated pilus, one of which has persisted for decades in China and the United States.

Phylogenetic and mutational analysis of H10N3 avian influenza A virus in China: potential threats to human health.

In recent years, the avian influenza virus has emerged as a significant threat to both human and public health. This study focuses on a patient infected with the H10N3 subtype of avian influenza virus, admitted to the Third People's Hospital of Kunming City on March 6, 2024. Metagenomic RNA sequencing and polymerase chain reaction (PCR) analysis were conducted on the patient's sputum, confirming the H10N3 infection. The patient presented severe pneumonia symptoms such as fever, expectoration, chest tightness, shortness of breath, and cough. Phylogenetic analysis of the Haemagglutinin (HA) and neuraminidase (NA) genes of the virus showed that the virus was most closely related to a case of human infection with the H10N3 subtype of avian influenza virus found in Zhejiang Province, China. Analysis of amino acid mutation sites identified four mutations potentially hazardous to human health. Consequently, this underscores the importance of continuous and vigilant monitoring of the dynamics surrounding the H10N3 subtype of avian influenza virus, utilizing advanced genomic surveillance techniques.

Human fascioliasis emergence in southern Asia: Complete nuclear rDNA spacer and mtDNA gene sequences prove Indian patient infection related to fluke hybridization in northeastern India and Bangladesh.

Fascioliasis is a snail-borne zoonotic disease with impact on the development of human subjects and communities. It is caused by two liver-infecting fasciolid trematode species, the globally-distributed Fasciola hepatica and the Africa/Asia-restricted but more pathogenic, larger F. gigantica. Fasciola gigantica is the cause of endemicity in livestock throughout the warm lowlands from Pakistan to southeastern Asia since old times. Human fascioliasis is emerging in this region at present, with an increase of patient reports. Complete sequences of rDNA ITS-1 and ITS-2 spacers and mtDNA nad1 and cox1 genes were obtained from fasciolid eggs found in the endoscopic bile aspirate from a patient of Arunachal Pradesh, northeastern India. Egg measurements, pronounced ITS heterozygosity, and pure F. gigantica mtDNA haplotypes demonstrate an infection by a recent F. gigantica-like hybrid. Sequence identities and similarities with the same DNA markers found in livestock from Bangladesh prove the human-infecting fasciolid to present identical ITSs and nad1 haplotypes and only one silent transversion in cox1 when compared to a widely-spread combined haplotype in animals. In northeastern India and Bangladesh, human fascioliasis emergence appears linked to increasing livestock prevalences due to: ruminant importation from other countries because of the increasing demand of rapidly growing human populations; numerous livestock movements, including transborder corridors, due to the uncontrolled small-scale household farming practices; and man-made introduction of F. hepatica with imported livestock into an area originally endemic for F. gigantica leading to frequent hybridization. Sequences, phylogenetic trees, and networks indicate that the origins of intermediate/hybrid fasciolids and factors underlying human infection risk differ in eastern and western South Asia. The emergence scenario in southern China and Vietnam resembles the aforementioned of northeastern India and Bangladesh, whereas in Pakistan it is linked to increasing monsoon rainfall within climate change combined with an impact of an extensive irrigation system. Past human-guided movements of pack animals along the western Grand Trunk Road and the eastern Tea-Horse Road explain the F. gigantica mtDNA results obtained. Physicians should be aware about these emerging scenarios, clinical pictures, diagnostic techniques and treatment. Government authorities must appropriately warn health professionals, ensure drug availability and improve livestock control.

Binary Enterotoxin Producing Clostridium perfringens Isolated in Blood Cultures: Case Report and Review of the Literature.

Clostridium perfringens (C. perfringens) is an anaerobic, spore-forming Gram-positive rod responsible for necrotizing gangrene, bacteremia in patients with cancer or gastrointestinal tract infection. C. perfringens virulence is due in large part to toxin production. In 2014, a new enterotoxin, BEC (binary enterotoxin of Clostridium perfringens) encoded by becA and becB genes, distinct from enterotoxin (CPE) encoded by the cpe gene, has been described. BEC-producing strains can be causative agents of acute gastroenteritis in humans. We present herein the case of a 64-year-old man who presented to the emergency department of Toulouse University Hospital with pneumonia and septic shock, without digestive symptoms. Blood cultures showed C. perfringens bacteremia and despite appropriate antibiotic treatment the patient passed away 7 h after admission. The characterization of the strain by whole genome sequencing revealed the presence of typical genes of C. perfringens: plc gene (alpha-toxin, phospholipase C) and pfoA (theta-toxin, perfringolysine). Surprisingly, this strain also harbored becA and becB genes encoding the recently described BEC toxin. Interestingly, alpha-toxin typing of our isolate and other published BEC isolates showed that they belonged to different PLC subtypes, confirming the high genetic diversity of these strains. To our knowledge, it is the first clinical case reporting bacteremia due to a BEC-producing C. perfringens isolate.

Rickettsia asembonensis Isolated from Four Human Cases with Acute Undifferentiated Febrile Illness in Peru.

Rickettsioses, often underreported, pose public health challenges. Rickettsia asembonensis is a potential emerging pathogen that was previously detected in humans, animals, and a variety of arthropods. While its pathogenicity in humans remains unclear, it poses a potential public health threat. Here, we present an extended epidemiological, diagnostic, and genetic analysis of the information provided in a preliminary report on the investigation of rickettsiae in Peru. In particular, we report the detection of R. asembonensis in blood specimens collected from four human patients with an acute undifferentiated fever of a seven- to nine-day duration, all of whom tested negative for other vector-borne pathogens. Additionally, we describe the replicative capacity of the R. asembonensis isolates in cell cultures.

Review of Current Tuberculosis Human Infection Studies for Use in Accelerating Tuberculosis Vaccine Development: A Meeting Report.

Tools to evaluate and accelerate tuberculosis (TB) vaccine development are needed to advance global TB control strategies. Validated human infection studies for TB have the potential to facilitate breakthroughs in understanding disease pathogenesis, identify correlates of protection, develop diagnostic tools, and accelerate and de-risk vaccine and drug development. However, key challenges remain for realizing the clinical utility of these models, which require further discussion and alignment among key stakeholders. In March 2023, the Wellcome Trust and the International AIDS Vaccine Initiative convened international experts involved in developing both TB and bacillus Calmette-Guérin (BCG) human infection studies (including mucosal and intradermal challenge routes) to discuss the status of each of the models and the key enablers to move the field forward. This report provides a summary of the presentations and discussion from the meeting. Discussions identified key issues, including demonstrating model validity, to provide confidence for vaccine developers, which may be addressed through demonstration of known vaccine effects (eg, BCG vaccination in specific populations), and by comparing results from field efficacy and human infection studies. The workshop underscored the importance of establishing safe and acceptable studies in high-burden settings, and the need to validate >1 model to allow for different scientific questions to be addressed as well as to provide confidence to vaccine developers and regulators around use of human infection study data in vaccine development and licensure pathways.

A rare case of an endobronchial mass due to Neurospora intermedia.

The ascomycete filamentous fungus Neurospora intermedia is commonly used in the food industry and considered nonpathogenic to humans. This study characterizes four N. intermedia isolates recovered from three patients. The first patient had a mediastinal germ cell tumor with multiple metastases. N. intermedia was recovered from his endotracheal aspirate and from the endobronchial mass obtained by bronchoscopic forceps biopsy. Histopathology of the biopsy tissue revealed necrotic tissue mixed with septate fungal hyphae with right-angle branching. An endobronchial mass caused by N. intermedia was thus diagnosed. Another two N. intermedia isolates were recovered from the endotracheal aspirates of two critically ill patients. In vitro, N. intermedia grows rapidly and forms orange, conidiating colonies composed of septate hyphae. Two isolates from the first patient belong to mating type a; the other two isolates belong to mating type A. Coculture of isolates of opposite mating types yielded dark ascomata containing ascospores, supporting that N. intermedia is a heterothallic fungus. N. intermedia isolates cross-reacted with the Aspergillus galactomannan antigen assay and were susceptible to amphotericin B and voriconazole. In conclusion, this report describes the first human infection (endobronchial mass) caused by N. intermedia, highlighting its potential to invade the human respiratory tract.

A Haemophilus ducreyi strain lacking the yfeABCD iron transport system is virulent in human volunteers.

Haemophilus ducreyi causes the genital ulcer disease chancroid and painful cutaneous ulcers in children who live in the tropics. To acquire heme from the host, H. ducreyi expresses a TonB-dependent hemoglobin receptor, HgbA, which is necessary and sufficient for H. ducreyi to progress to the pustular stage of disease in a controlled human infection model. HgbA transports hemoglobin across the outer membrane; how heme is transported across the cytoplasmic membrane is unclear. In previous studies, transcripts encoding the YfeABCD heme transporter were upregulated in experimental lesions caused by H. ducreyi in human volunteers, suggesting the latter may have a role in virulence. Here we constructed a double deletion mutant, 35000HPΔyfeABΔyfeCD, which exhibited growth defects relative to its parent 35000HP in media containing human hemoglobin as an iron source. Five human volunteers were inoculated at three sites on the skin overlying the deltoid with each strain. The results of the trial showed that papules formed at 100% (95% CI, 71.5, 100) at both 35000HP and 35000HPΔyfeABΔyfeCD-inoculated sites (P = 1.0). Pustules formed at 60% (95% CI, 25.9, 94.1) at parent-inoculated sites and 53% (95% CI, 18.3, 88.4) at mutant-inoculated sites (P = 0.79). Thus, the ABC transporter encoded by yfeAB and yfeCD was dispensable for H. ducreyi virulence in humans. In the absence of YfeABCD, H. ducreyi likely utilizes other periplasmic binding proteins and ABC-transporters such as HbpA, SapABCDF, and DppBCDF to shuttle heme from the periplasm into the cytoplasm, underscoring the importance of redundancy of such systems in gram-negative pathogens.

A highly sensitive 3base™ assay for detecting Streptococcus pyogenes in saliva during controlled human pharyngitis.

Streptococcus pyogenes (Group A Streptococcus; GAS) is a Gram-positive bacterium responsible for substantial human mortality and morbidity. Conventional diagnosis of GAS pharyngitis relies on throat swab culture, a low-throughput, slow, and relatively invasive 'gold standard'. While molecular approaches are becoming increasingly utilized, the potential of saliva as a diagnostic fluid for GAS infection remains largely unexplored. Here, we present a novel, high-throughput, sensitive, and robust speB qPCR assay that reliably detects GAS in saliva using innovative 3base™ technology (Genetic Signatures Limited, Sydney, Australia). The assay has been validated on baseline, acute, and convalescent saliva samples generated from the Controlled Human Infection for Vaccination Against Streptococcus (CHIVAS-M75) trial, in which healthy adult participants were challenged with emm75 GAS. In these well-defined samples, our high-throughput assay outperforms throat culture and conventional qPCR in saliva respectively, affirming the utility of the 3base™ platform, demonstrating the feasibility of saliva as a diagnostic biofluid, and paving the way for the development of novel non-invasive approaches for the detection of GAS and other oropharyngeal pathogens.