Caprine humoral response to Burkholderia pseudomallei antigens during acute melioidosis from aerosol exposure

Abstract

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.

Shotgun Immunoproteomic Approach for the Discovery of Linear B Cell Epitopes in Biothreat Agents Francisella tularensis and Burkholderia pseudomallei

“…The immune response to B. pseudomallei has not been studied in as much depth as for Francisella . So even though Bp with 6203 protein coding genes has a genome that is more than three times as large as that of Ft, we found only 61 known antigens identified in previous studies (20,21) (∼1% of the entire proteome). Our list of 47 top Bp peptides in Table 1 includes one known antigen, which does not qualify as a statistically significant enrichment primarily because of the much smaller total number of known antigens for Bp.…”

“…We leveraged a merged dataset of 164 previously identified antigens, corresponding to ∼10% of Ft proteome. The Bp immunoproteome is not as well characterized compared to that of Ft: our reference dataset contained only 61 previously identified seroreactive proteins, corresponding to ∼1% of the Bp proteome (20,21). Consequently, the dataset resulting from the Bp screen has revealed many proteins that have not been previously categorized as antigens.…”

The mycoplasma surface proteins MIB and MIP promote the dissociation of the antibody-antigen interaction

“…S13), suggesting that IgG may need to bind Mmc cell surface to be cleaved by MIB and MIP. This hypothesis was reinforced by the fact that goat serum was shown to contain substantial amounts of IgG recognizing antigens from bacteria that the animals had never been exposed to, owing to cross-reactivity or similar antigenic determinants ( 15 ). To test this hypothesis, we used Mmc cells that express a specific epitope at their surface and assessed the cleavage of the corresponding goat IgG.…”

Melioidosis DS rapid test: A standardized serological dipstick assay with increased sensitivity and reliability due to multiplex detection

“…Some studies even report a lower diagnostic performance for IgM detection [39,40,42]. This might be attributed to a strong and fast occurring IgG response, as described by Yi and colleagues in the caprine melioidosis model [43].…”