Complex Subunit and Glycoconjugate Vaccines and Their Potential to Elicit Cross-Protection to Complex

are a group of Gram-negative bacteria that can cause a variety of diseases in at-risk populations. and , the etiological agents of melioidosis and glanders, respectively, are the two clinically relevant members of the complex (Bpc). The development of vaccines against Bpc species has been accelerated in recent years, resulting in numerous promising subunits and glycoconjugate vaccines incorporating a variety of antigens. However, a second group of pathogenic species exists known as the complex (Bcc), a group of opportunistic bacteria which tend to affect individuals with weakened immunity or cystic fibrosis. To date, there have been few attempts to develop vaccines to Bcc species. Therefore, the primary goal of this review is to provide a broad overview of the various subunit antigens that have been tested in Bpc species, their protective efficacy, study limitations, and known or suspected mechanisms of protection. Then, we assess the reviewed Bpc antigens for their amino acid sequence conservation to homologous proteins found in Bcc species. We propose that protective Bpc antigens with a high degree of Bpc-to-Bcc sequence conservation could serve as components of a pan- vaccine capable of protecting against both disease-causing groups.