Austin B. Shannon

Melioidosis is an emerging infectious disease caused by the intracellular bacterial pathogen, Burkholderia pseudomallei. Infection of humans and animals can occur through multiple routes of bacterial entry resulting in life-threatening pneumonia and/or bacteremia. B. pseudomallei is inherently resistant to multiple antibiotics and mortality rates are high despite therapeutic intervention. Development of an effective vaccine could protect at-risk individuals, such as those who reside in highly endemic areas, military personnel, diabetics, and travelers. Despite decades of pursuit, no candidate vaccine for melioidosis has advanced beyond pre-clinical testing in rodent models. Here, we demonstrate that an outer membrane vesicle (OMV) vaccine prevents pulmonary disease in non human primates (NHP) using survivability, biotelemetry, and clinical pathology assessments. Using two independent serologic assays, we demonstrate that vaccination in rhesus macaques is associated with systemic and mucosal IgG and IgA to OMV surface proteins and polysaccharides. We also show that NHP immune sera promotes opsonophagocytosis by macrophages and that human sera responses to several key OMV antigens are associated with survival in melioidosis. Collectively, these results attest to the potential efficacy of the OMV vaccine and lay the groundwork for its advancement to human phase 1 clinical trials.

Burkholderia pseudomallei causes melioidosis, a common source of pneumonia and sepsis in Southeast Asia and Northern Australia that results in high mortality rates. A caprine melioidosis model of aerosol infection that leads to a systemic infection has the potential to characterize the humoral immune response. This could help identify immunogenic proteins for new diagnostics and vaccine candidates. Outbred goats may more accurately mimic human infection, in contrast to the inbred mouse models used to date. B. pseudomallei infection was delivered as an intratracheal aerosol. Antigenic protein profiling was generated from the infecting strain MSHR511. Humoral immune responses were analyzed by ELISA and western blot, and the antigenic proteins were identified by mass spectrometry. Throughout the course of the infection the assay results demonstrated a much greater humoral response with IgG antibodies, in both breadth and quantity, compared to IgM antibodies. Pre-infection sera showed multiple immunogenic proteins already reactive for IgG (7–20) and IgM (0–12) in most of the goats despite no previous exposure to B. pseudomallei. After infection, the number of IgG reactive proteins showed a marked increase as the disease progressed. Early stage infection (day 7) showed immune reaction to chaperone proteins (GroEL, EF-Tu, and DnaK). These three proteins were detected in all serum samples after infection, with GroEL immunogenically dominant. Seven common reactive antigens were selected for further analysis using ELISA. The heat shock protein GroEL1 elicited the strongest goat antibody immune response compared to the other six antigens. Most of the six antigens showed the peak IgM reactivity at day 14, whereas the IgG reactivity increased further as the disease progressed. An overall MSHR511 proteomic comparison between the goat model and human sera showed that many immune reactive proteins are common between humans and goats with melioidosis. B. pseudomallei infection, the causative agent of melioidosis, results in severe disseminated or localized infections. A systemic study of the humoral immune response to B. pseudomallei infection using the B. pseudomallei aerosol caprine model would help understand the detectable antigenic proteins as the infection progresses. To study the immune response, IgG and IgM antibody responses to whole cell lysate proteins were identified and analyzed. Antigenic carbohydrates were also studied. From the results, this study suggests that the caprine humoral immune response to aerosolized B. pseudomallei has similarities to human melioidosis and may facilitate the analysis of the temporal antibody responses. In addition, commonly detected immunogenic proteins may be used as biomarkers for the future point of care (POC) diagnostics.

Burkholderia pseudomallei causes melioidosis, a common source of pneumonia and sepsis in Southeast Asia and Northern Australia, that results in high mortality rates. A caprine melioidosis model of aerosol infection that leads to a systemic infection has the potential to characterize the humoral immune response. This could help identify immunogenic proteins for new diagnostics and vaccine candidates. Outbred goats may more accurately mimic human infection, in contrast to the inbred mouse models used to date. B. pseudomallei infection was delivered as an intratracheal aerosol. Antigenic protein profiling was generated from the infecting strain MSHR511. Humoral immune responses were analyzed by ELISA and western blot, and the antigenic proteins were identified by mass spectrometry. Throughout the course of the infection the assay results demonstrated a much greater humoral response with IgG antibodies, in both breadth and quantity, compared to IgM antibodies. Pre-infection sera showed multiple immunogenic proteins already reactive for IgG (7-20) and IgM (0-12) in most of the goats despite no previous exposure to B. pseudomallei . After infection, the number of IgG reactive proteins showed a marked increase as the disease progressed. Early stage infection (day 7) showed immune reaction to chaperone proteins (GroEL, EF-Tu, and DnaK). These three proteins were detected in all serum samples after infection, with GroEL immunogenically dominant. Seven common reactive antigens were selected for further analysis using ELISA. The heat shock protein GroEL1 elicited the strongest goat antibody immune response compared to the other six antigens. Most of the six antigens showed the peak IgM reactivity at day 14, whereas the IgG reactivity increased further as the disease progressed. An overall MSHR511 proteomic comparison between the goat model and human sera showed that many immune reactive proteins are common between humans and goats with melioidosis. Author Summary: B. pseudomallei infection, the causative agent of melioidosis, results in severe disseminated or localized infections. A systemic study of the humoral immune response to B. pseudomallei infection using the B. pseudomallei aerosol caprine model would help understand the detectable antigenic proteins as the infection progresses. To study the immune response, IgG and IgM antibody responses to whole cell lysate proteins were identified and analyzed. Antigenic carbohydrates were also studied. From the results, this study suggests that the caprine humoral immune response to aerosolized B. pseudomallei has similarities to human melioidosis and may facilitate the analysis of the temporal antibody responses. In addition, commonly detected immunogenic proteins may be used as biomarkers for the future point of care (POC) diagnostics.