Comparison of three non-human primate aerosol models for glanders, caused by Burkholderia mallei

Antibody isotyping and cytokine profiling in natural cases of Burkholderia mallei infection (glanders) in equines

OBJECTIVES

Immunological aspects of B. mallei infection were rarely studied in natural cases of equines. The present study was conducted to determine IgG, IgM, IgA and IgG (T) titre against recombinant Hcp1, TssA and TssB proteins and PilA-Hcp1-TssN-BipD and BpaB-BpaC- BMAA0553 chimeras and cytokine responses in glanders affected equine serum.

METHODS

The study was conducted on serum samples collected from 151 glanders positive equines which include horses (n = 134), mules (n = 16), and donkeys (n = 01). The IgM, IgG, IgA and IgG (T) titre were determined against recombinant antigens by indirect ELISA and interleukin(IL)-1β, IL-17, IL-6, tumor necrosis factor alpha(TNF-α), monocyte chemoattractant protein 1 (MCP-1) and interferon gamma (IFN-γ) responses were measured by commercial ELISA kits.

RESULTS

The study showed that glanders affected equines elicited strong antibody response against Hcp1, moderate responses against TssA and TssB, and weak responses against two chimeras. Among the cytokines, IL-1β, MCP-1, IL-17 and IL-6 concentration were significantly higher in glanders affected equine serum.

CONCLUSION

We found that IgG antibody titre was higher than IgM, IgG (T) and IgA isotypes and Hcp1 was most predominant antibody inducers in comparison to TssA, TssB, PilA-Hcp1-TssN-BipD and BpaB-BpaC-T2SS proteins. The elevated level of IL-1β, MCP-1, IL-17, IL-6, IFN-γ and TNF-α observed in this study support the important role of this cytokines for augmenting cellular defence by recruitment of macrophages, neutrophil and dendritic cells against B. mallei infection. Further studies should be conducted to determine memory cell responses in natural cases of equine glanders using recombinant B. mallei proteins for identifying well-characterized immuno-protective vaccine candidates.

Clinical and Molecular Characterization of Human Burkholderia mallei Infection, Brazil

We report a case of Burkholderia mallei causing glanders in a 73-year-old patient from the Northeast Region of Brazil. The patient was hospitalized with severe pneumonia. PCR and genomic sequencing confirmed B. mallei in pleural drainage. Genotyping revealed a novel genotype, emphasizing the need for genetic surveillance in zoonotic infections.

Marmosets as models of infectious diseases

Animal models of infectious disease often serve a crucial purpose in obtaining licensure of therapeutics and medical countermeasures, particularly in situations where human trials are not feasible, i.e., for those diseases that occur infrequently in the human population. The common marmoset (Callithrix jacchus), a Neotropical new-world (platyrrhines) non-human primate, has gained increasing attention as an animal model for a number of diseases given its small size, availability and evolutionary proximity to humans. This review aims to (i) discuss the pros and cons of the common marmoset as an animal model by providing a brief snapshot of how marmosets are currently utilized in biomedical research, (ii) summarize and evaluate relevant aspects of the marmoset immune system to the study of infectious diseases, (iii) provide a historical backdrop, outlining the significance of infectious diseases and the importance of developing reliable animal models to test novel therapeutics, and (iv) provide a summary of infectious diseases for which a marmoset model exists, followed by an in-depth discussion of the marmoset models of two studied bacterial infectious diseases (tularemia and melioidosis) and one viral infectious disease (viral hepatitis C).

Glanders Diagnosis in an Asymptomatic Mare from Brazil: Insights from Serology, Microbiological Culture, Mass Spectrometry, and Genome Sequencing

This manuscript elucidates the occurrence of glanders in an asymptomatic mare from Brazil presenting positive Burkholderia mallei antibody titers. The diagnosis was established through a multi-pronged approach encompassing microbiological culture, mass spectrometry, and genome sequencing. The outbreak occurred in 2019 in Tatuí, São Paulo, Brazil, and the infected mare, despite displaying no clinical symptoms, had multiple miliary lesions in the liver, as well as intense catarrhal discharge in the trachea. Samples were collected from various organs and subjected to bacterial isolation, molecular detection, and identification. The strain was identified as B. mallei using PCR and confirmed by MALDI-TOF mass spectrometry. Whole-genome sequencing revealed a genome size of 5.51 Mb with a GC content of 65.8%, 5871 genes (including 4 rRNA and 53 tRNA genes), and 5583 coding DNA sequences (CDSs). Additionally, 227 predicted pseudogenes were detected. In silico analysis of different genomic loci that allow for differentiation with Burkholderia pseudomallei confirmed the identity of the isolate as B. mallei, in addition to the characteristic genome size. The BAC 86/19 strain was identified as lineage 3, sublineage 2, which includes other strains from Brazil, India, and Iran. The genome sequencing of this strain provides valuable information that can be used to better understand the pathogen and its epidemiology, as well as to develop diagnostic tools for glanders.

A Case Report of Burkholderia mallei Infection Leading to Pneumonia

BACKGROUND

Glanders is a rare zoonotic disease caused by Burkholderia mallei. Humans can be infected by B. mallei, which causes cutaneous lymphadenitis and pneumonia, leading to sepsis and death in severe cases.

CASE PRESENTATION

We report a case of a 60-year-old male who was diagnosed with glanders. The patient who had a history of diabetes presented with cough, expectoration, and fever. Computed tomography (CT) imaging showed B. mallei infection in the right upper lobe of the lung with mediastinal lymph node involvement and the lingual segment of the left lung. Moreover, the posterior basal segment of the lower lobe of both lungs had inflammation. Subsequently, B. mallei infection was confirmed by lymph node biopsy and bronchoalveolar lavage multiplex PCR-based targeted gene sequencing. After meropenem treatment, the patient was discharged, and CT imaging showed reduced absorption of pulmonary inflammatory lesions.

CONCLUSIONS

Glanders is a rare disease that can cause skin infection, lymphadenitis, and pneumonia, and in severe cases, it can be life-threatening. The diagnosis of this disease mainly relies on microbiological culture and pathological biopsy. Diagnosis is also facilitated by multiplex PCRbased targeted gene sequencing. Glanders is treated with cephalosporins, carbapenems, and other sensitive antibiotics.

Characterization of immunoglobulin and cytokine responses in Burkholderia mallei infected equids

Burkholderia mallei causes a highly fatal infectious disease in equines known as glanders. It is one of the OIE listed notifiable diseases, which entails strict control policy measures once B. mallei infection is confirmed in the susceptible hosts. Humans, especially equine handlers, veterinary professionals and laboratory workers are at greater risk to acquire the B. mallei infection directly through prolonged contact with glanderous equines, and indirectly through unprotected handling of B. mallei contaminated materials. Further, natural resistance of B. mallei to multiple antibiotics, aerosol transmission, lack of effective vaccine and treatment make this organism a potential agent of biological warfare. Results of experimental B. mallei infection in mouse and non-human primates and immunization with live attenuated B. mallei strains demonstrated that activation of early innate and adaptive immune responses play a critical role in controlling B. mallei infection. However, the immune response elicited by the primary hosts (equids) B. mallei infection is poorly understood. Therefore, we aimed to investigate immune responses in glanders affected horses (n = 23) and mules (n = 1). In this study, chronically infected equids showed strong humoral responses (IgM, IgG and IgA) specific to B. mallei type 6 secretory proteins such as Hcp1, TssA and TssB. The infected equids also elicited robust cellular responses characterized by significantly elevated levels of IFN-γ, TNF-α, IL-12, IL-17 and IL-6 in PBMCs. In addition, stimulation of equine PBMCs by Hcp1 resulted in the further elevation of these cytokines. Thus, the present study indicated that antibody response and T helper cell (Th) type 1-associated cytokines were the salient features of chronic B. mallei infection in horses. The immune responses also suggest further evaluation of these proteins as potential vaccine candidates.