Identification of Cross-Protective Surface Antigens in Burkholderia Species

PROJECT SUMMARY
Burkholderia are a group of environmental bacteria, a subset of which cause disease in at-risk populations. The
two most prominent disease-causing groups are the Burkholderia pseudomallei complex (Bpc) and the
Burkholderia cepacia complex (Bcc). The former group primarily consists of B. pseudomallei and B. mallei, both
of which are designated Tier 1 Select Agents on account of their high mortality, resistance to antibiotics, a lack
of approved vaccines, and the ability of the bacteria to infect humans by various routes. Furthermore, B.
pseudomallei is associated with significant disease incidence in areas of endemicity. As a result, the Bpc remains
the most well-studied group of pathogenic Burkholderia and numerous Bpc vaccine candidates have been
evaluated. By comparison, there have been very few attempts to develop Bcc-specific vaccines, which can be
at least partly attributed to the smaller patient population that could benefit from a prophylactic vaccine. Despite
this, cystic fibrosis (CF) patients are significantly impacted by Bcc lung colonization, which causes an accelerated
decline in lung function over their lives and can cause cepacia syndrome, a rapid onset necrotizing pneumonia
that is almost always lethal. Furthermore, antibiotics are rarely able to clear Bcc in the lungs of CF patients,
causing them to receive lower priority for lung transplants. Therefore, CF patients can clearly benefit from a
preventative Bcc vaccine. This led us to explore the following research question: could a single vaccine elicit
protective immunity to both Bpc and Bcc species, thereby leveraging the interest in Bpc vaccines to help meet
the needs of CF patients? There has been surprisingly little investigation of this strategy, though antibodies and
T cells are capable of cross-reacting to orthologous proteins of both Bpc and Bcc species. This leads us to our
central hypothesis that gold nanoparticle vaccine conjugates carrying surface-exposed proteins that are highly
conserved between Bpc and Bcc would elicit antibodies and T cells that are broadly protective against
heterologous species of Burkholderia. We first bioinformatically identified three Burkholderia surface antigens
exhibiting a high degree of interspecies sequence conservation that were previously identified as vaccine or
therapeutic targets in different contexts. Top candidates were then linked to a gold nanoparticle platform that was
previously developed by our laboratory to induce robust mucosal and cellular immune responses. In Aim 1, we
will determine the pharmacokinetic profiles and immunogenicity of our gold nanoparticle vaccine candidates in
vivo. Aim 2 will confirm that vaccine induced antibodies and/or T cells are protective against B. pseudomallei in.
murine models of infection. In Aim 3, we will examine the cross-protective efficacy of conserved Bpc antigen-
linked gold nanoparticle vaccine candidates against B. cenocepacia. Collectively, these experiments will provide
experimental data to support whether the identified highly conserved surface antigens have potential to be used
in a pan-Burkholderia vaccine and fulfill a gap in coverage to a vulnerable population affected by these
pathogens.

Grant Number: 1F31AI191684-01
NIH Institute/Center: NIH
Principal Investigator: Alexander Badten