Burkholderia pseudomallei and Burkholderia mallei are pathogenic bacteria causing fatal infections in animals and humans. Both organisms are classified as Tier 1 Select Agents owing to their highly fatal nature, potential/prior use as bioweapons, severity of disease via respiratory exposure, intrinsic resistance to antibiotics, and lack of a current vaccine. Disease manifestations range from acute septicemia to chronic infection, wherein the facultative intracellular lifestyle of these organisms promotes persistence within a broad range of hosts. This ability to thrive intracellularly is thought to be related to exploitation of host immune response signaling pathways. There are currently considerable gaps in our understanding of the molecular strategies employed by these pathogens to modulate these pathways and evade intracellular killing. A better understanding of the specific molecular basis for dysregulation of host immune responses by these organisms will provide a stronger platform to identify novel vaccine targets and develop effective countermeasures.

Cryptococcus gattii infection in mammals and birds has been confined historically to tropical and subtropical regions in Australia, Southeast Asia, Africa, and South America. Since the early 2000s, numerous reports describe the emergence of C. gattii on the Pacific Coast of North America. We report on a C. gattii infection in an 8-year-old male citron-crested cockatoo (Cacatua sulphurea citrinocristata) hatched on the Canadian Pacific Coast and raised in the province of Québec, Canada. The bird developed a slow growing ulcerated, fleshy, crusty, and hemorrhagic mass infiltrating the left lower rhamphotheca. Cryptococcus gattii infection was confirmed by cytologic examination of a fine needle aspirate of the mass, and results of fungal culture and sequencing. The genotype of the strain was determined to be VGIIa sequence type 20, the strongly overrepresented subgroup found on the Canadian Pacific coast. Minimum inhibitory concentrations for multiple antifungal drugs were determined. The bird received fluconazole but died acutely 55 days after initial presentation. Postmortem examination revealed a disseminated infection, with involvement of the beak, lungs, spleen, and brain.

Prior to SARS-CoV-2, M. tuberculosis was the leading infectious disease killer, with an estimated one-third of the world’s population infected and 1.7 million deaths a year. Here, we show that SARS-CoV-2 superinfection caused increased bacterial dissemination in M. tuberculosis -infected mice along with immune and pathological changes.

Background Burkholderia mallei (Bm) is a facultative intracellular bacterial pathogen causing highly-fatal glanders in solipeds and humans. The ability of Bm to thrive intracellularly is thought to be related to exploitation of host immune response-related genes and pathways. Relatively little is known of the molecular strategies employed by this pathogen to modulate these pathways and evade intracellular killing. This manuscript seeks to fill gaps in the understanding of the interface between Bm and innate immunity by examining gene expression changes during infection of host monocytes. Methods The transcriptome of Bm -infected human Mono Mac-6 (MM6) monocytes was profiled on Affymetrix Human Transcriptome GeneChips 2.0. Gene expression changes in Bm -infected monocytes were compared to those of Burkholderia thailandensis (Bt) -infected monocytes and to uninfected monocytes. The resulting dataset was normalized using Robust Multichip Average and subjected to statistical analyses employing a univariate F test with a random variance model. Differentially expressed genes significant at p < 0.001 were subjected to leave-one-out cross-validation studies and 1st and 3rd nearest neighbor prediction model. Significant probe sets were used to populate human pathways in Ingenuity Pathway Analysis, with statistical significance determined by Fisher’s exact test or z-score. Results The Pattern Recognition Receptor (PRR) pathway was represented among significantly enriched immune response-related human canonical pathways, with evidence of upregulation across both infections. Among members of this pathway, pentraxin-3 was significantly upregulated by Bm - or Bt -infected monocytes. Pentraxin-3 (PTX3) was demonstrated to bind to both Bt and Burkholderia pseudomallei (Bp) , but not Bm . Subsequent assays did not identify a role for PTX3 in potentiating complement-mediated lysis of Bt or in enhancing phagocytosis or replication of Bt in human monocytes. Conclusion We report on the novel binding of PTX3 to Bt and Bp , with lack of interaction with Bm , suggesting that a possible evasive mechanism by Bm warrants further exploration. We determined that (1) PTX3 may not play a role in activating the lytic pathway of complement in different bacterial species and that (2) the opsonophagocytic properties of PTX3 should be investigated in different primary or immortalized cell lines representing host phagocytes, given lack of binding of PTX3 to MM6 monocytes.

In collaboration with the American College of Veterinary Pathologists

No abstract

A 7-year-old female spayed Golden Retriever dog presented with fever and a 10-day history of neurological signs, including ambulatory paraparesis and pelvic limb ataxia. Neurological examination initially revealed a T3-L3 myelopathy. Thoracic radiographs revealed a diffuse miliary pulmonary pattern. Endotracheal washes and fine-needle aspirates from several organs aimed at identifying a potential infectious agent or neoplastic process were all unsuccessful. Due to worsening of the clinical signs, euthanasia was elected. Necropsy findings included multifocal, pale to dark red, firm nodules infiltrating the lungs, heart, mesentery, pancreas, small intestine, brain, and spinal cord. Cytological examination of impression smears obtained from the pulmonary nodules during necropsy revealed clusters of epithelioid cells admixed with fewer spindle cells, erythrocytes, and scattered leukocytes. Clinical signs and cytological findings initially suggested the possibility of a widespread granulomatous disease or a metastatic epithelial neoplasm as possible clinical differentials in this case. The final diagnosis was based on the gross and histological findings, with confirmation following histochemistry and immunohistochemistry. Keywords canine neoplasia, epithelioid cells, factor VIII, immunohistochemistry History, Clinical, and Pathological FindingsA 7-year-old female spayed Golden Retriever dog was referred to the University of Georgia Veterinary Teaching Hospital with fever and a 10-day history of neurological deficits. Initial neurological examination revealed a T3-L3 myelopathy characterized by progressive paraparesis and symmetrical pelvic limb ataxia, with delayed postural reaction in the pelvic limbs. Thoracic radiographs evidenced a diffuse miliary pulmonary pattern suggestive of fungal pneumonia or metastatic neoplasia. Endotracheal washes and fine-needle aspirates from lungs, liver, spleen, and peripheral lymph nodes were unsuccessful in detecting a potential infectious agent or neoplasia. A complete blood count, chemistry profile, urinalysis, and abdominal ultrasound were also performed and did not reveal any significant changes. Serology and polymerase chain reaction of blood and urine samples were also negative for potential fungal organisms. Euthanasia was elected shortly after presentation due to rapid clinical deterioration, with severe dyspnea, decompensatory hypoxemia, and worsening of neurological signs, which progressed to include a right thoracic limb nerve root signature characterized by a toe-touching lameness. Necropsy findings included multifocal, dark red, firm, 3 to 5 mm in diameter, homogeneous nodules expanding the lungs (Fig. 1), heart, mesentery, pancreas, small intestinal serosa, brain, and cervical and thoracic spinal cord. The pericardial sac contained 25 ml of serosanguineous fluid and was focally adhered to a dark red, firm, 3 cm in diameter, irregular nodule arising from the right auricle (Fig. 2). The myocardium was also infiltrated by similar masses (Fig. 2). Cytological exam...

Mycobacterium avium subspecies paratuberculosis (M. paratuberculosis) is the causative agent of Johne's disease, a chronic debilitating condition affecting ruminants causing significant economic losses to the dairy industry. Available inactivated vaccines are not effective in controlling the disease and vaccinated animals can continue to infect newly born calves. Recently, we have shown that a live-attenuated vaccine candidate (pgsN) is protective in goats and calves following challenge with virulent strains of M. paratuberculosis. To decipher the dynamics of the immune responses elicited by both live-attenuated and inactivated vaccines, we analyzed key immunological parameters of goats immunized through different routes when a marker-less pgsN vaccine was used. Within a few weeks, the inactivated vaccine triggered the formation of granulomas both at the site of inoculation and in regional lymph nodes, that increased in size over time and persisted until the end of the experiment. In contrast, granulomas induced by the pgsN vaccine were small and subsided during the study. Interestingly, in this vaccine group, histology demonstrated an initial abundance of intra-histiocytic mycobacterial bacilli at the site of inoculation, with recruitment of very minimal T lymphocytes to poorly organized granulomas. Over time, granulomas became more organized, with recruitment of greater numbers of T and B lymphocytes, which coincided with a lack of mycobacteria. For the inactivated vaccine group, mycobacterial bacilli were identified extracellularly within the center of caseating granulomas, with relatively equal proportions of B- and T-lymphocytes maintained across both early and late times. Despite the differences in granuloma-specific lymphocyte recruitment, markers for cell-mediated immunity (e.g., IFN-γ release) were robust in both injected pgsN and inactivated vaccine groups. In contrast, the intranasal live-attenuated vaccine did not elicit any reaction at site of inoculation, nor cell-mediated immune responses. Finally, 80% of animals in the inactivated vaccine group significantly reacted to purified protein derivatives from M. bovis, while reactivity was detected in only 20% of animals receiving pgsN vaccine, suggesting a higher level of cross reactivity for bovine tuberculosis when inactivated vaccine is used. Overall, these results depict the cellular recruitment strategies driving immune responses elicited by both live-attenuated and inactivated vaccines that target Johne's disease.