Development of Subunit Vaccines that Provide High Level Protection and Sterilizing Immunity Against Acute Inhalational Melioidosis.

ABSTRACT: Burkholderia pseudomallei, the etiologic agent of melioidosis, causes severe disease in humans and animals. Diagnosis and treatment of melioidosis can be challenging and no licensed vaccines currently exist. Several studies have shown that this pathogen expresses a variety of structurally conserved protective antigens that include cell-surface polysaccharides and cell-associated/-secreted proteins. Based on this, such antigens have become important components of the subunit vaccine candidates that we are currently developing. In the present study, the 6-deoxyheptan capsular polysaccharide (CPS) from B. pseudomallei was purified, chemically activated and covalently linked to recombinant CRM197 diphtheria toxin mutant (CRM197) to produce CPS-CRM197. Additionally, tandem nickel-cobalt affinity chromatography was used to prepare highly purified recombinant B. pseudomallei Hcp1 and TssM proteins. Immunization of C57BL/6 mice with CPS-CRM197 produced high-titer IgG and opsonizing antibody responses against the CPS component of the glycoconjugate while immunization with Hcp1 and TssM produced high titer IgG and robust IFN-? secreting T cell responses against the proteins. Extending upon these studies, we found that when vaccinated with a combination of CPS-CRM197 plus Hcp1, 100% of the mice survived a lethal inhalational challenge of B. pseudomallei Remarkably, 70% of the survivors had no culturable bacteria in their lungs, livers or spleens indicating that the vaccine formulation had generated sterilizing immune responses. Collectively, these studies help to better establish surrogates of antigen-induced immunity against B. pseudomallei as well as provide valuable insights towards the development of a safe, affordable and effective melioidosis vaccine.

SUBMITTER: Burtnick MN 

PROVIDER: S-EPMC5736816 | biostudies-other | 2017 Nov

REPOSITORIES: biostudies-other