Insights into Acinetobacter baumannii protective immunity

Abstract

Acinetobacter baumannii is a nosocomic opportunistic Gram-negative bacteria known for its extensive drug-resistant phenotype. A. baumannii hospital-acquired infections are major contributors to increased costs and mortality observed during the COVID-19 pandemic. With few effective antimicrobials available for treatment of this pathogen, immune-based therapy becomes an attractive strategy to combat multi-drug resistant Acinetobacter infection. Immunotherapeutics is a field of growing interest with advances in vaccines and monoclonal antibodies providing insight into the protective immune response required to successfully combat this pathogen. This review focuses on current knowledge describing the adaptive immune response to A. baumannii, the importance of antibody-mediated protection, developments in cell-mediated protection, and their respective therapeutic application going forward. With A. baumannii’s increasing resistance to most current antimicrobials, elucidating an effective host adaptive immune response is paramount in the guidance of future immunotherapeutic development.

Epitope mapping of Acinetobacter baumannii outer membrane protein W (OmpW) and laboratory study of an OmpW-derivative peptide

“…In addition to humoral responses that are effective in protecting against A. baumannii infection, cellular responses can also play a significant role in protecting against this pathogen, although there are conflicting opinions in this regard [ 24 ]. In any case, these responses usually fight the infectious agent by inducing cytokines in addition to increased proliferation.…”

“…A. baumannii infections can be protected against through antibody-mediated immunity, as evidenced by successful passive immunization with monoclonal antibodies and the correlation of specific antibody titers with survival rates [ 19 , [21] , [22] , [23] ]. Vaccine development has largely focused on antibody-mediated protection, with less emphasis on cell-mediated protection [ 24 ]. The IgG isotype ratio has been used to assess Th1 or Th2-driven immunity, but few studies have investigated T cell responses [ 24 ].…”

“…Vaccine development has largely focused on antibody-mediated protection, with less emphasis on cell-mediated protection [ 24 ]. The IgG isotype ratio has been used to assess Th1 or Th2-driven immunity, but few studies have investigated T cell responses [ 24 ]. Research has shown that inactivated or attenuated strains of A. baumannii can elicit both Th1 and Th2 responses, indicated by strong IgG1 and IgG2a (or IgG2c) antibody responses [ 21 , 25 , 26 ].…”

“…While the role of T cells in vaccine-induced protection remains unclear, some studies have examined T cell cytokine profiles and the impact of A. baumannii on antigen-presenting cells [ 27 ]. Further research is needed to determine the preferred T cell cytokine response for protection and the role of Th2 cells in providing B cell assistance [ 24 ].…”

Effectors of the Type VI Secretion System Have the Potential to Be Modified into Antimicrobial Peptides

“…To combat the serious challenge posed by MDR, new antibacterial approaches are being sought. These approaches include (i) the synthesis and design of new antibacterial materials ( 6 – 10 ), (ii) the discovery of new uses for old drugs ( 11 – 14 ), (iii) the construction of new drug delivery vehicles ( 9 , 15 , 16 ), and (iv) vaccine development ( 17 – 19 ). AMPs have attracted considerable attention as antimicrobials.…”