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Safety and immunogenicity testing of a melioidosis subunit vaccine candidate in cynomolgus macaques
Sineenart Sengyee1, Caitlyn E Orne1, Sarah B Weiby1
1Department of Microbiology and Immunology, University of Nevada, Reno School of Medicine, Reno, NV, USA.
Abstract:
Burkholderia pseudomallei, the etiologic agent of melioidosis, is a Gram-negative bacterial pathogen that causes severe disease in humans and animals. In this study, we evaluated the safety and immunogenicity of our lead melioidosis subunit vaccine candidate in cynomolgus macaques. To accomplish this, the 6-deoxyheptan capsular polysaccharide (CPS) from Burkholderia thailandensis E555 was purified using a phenol-free extraction process and then conjugated to CRM197 to generate CPS-CRM197. Highly purified, His-tagless B. pseudomallei Hcp1 (Hcp1-TL) was also produced. Animals immunized with CPS-CRM197 combined with Hcp1-TL and adjuvanted with Alhydrogel plus CpG DNA (ODN 2006) developed robust CPS-specific IgG and opsonizing antibody responses, alongside strong Hcp1-specific IgG and measurable IFN-γ-secreting T-cell responses. Importantly, the vaccine formulations tested were well tolerated, with no adverse events after three doses. Collectively, these studies establish good manufacturing practices-compatible processes for our vaccine antigens and demonstrate the safety and immunogenicity of the subunit vaccine in non-human primates, supporting continued advancement towards a human clinical trial.
Insights
This study shows a new melioidosis subunit vaccine candidate is safe and effective in macaques. The vaccine generated strong immune responses, supporting its advancement to human clinical trials.
Area of Science:
- Bacteriology
- Vaccinology
- Immunology
Background:
- Melioidosis is a severe disease caused by Burkholderia pseudomallei.
- Current treatments have limitations, necessitating vaccine development.
Purpose of the Study:
- To evaluate the safety and immunogenicity of a novel melioidosis subunit vaccine candidate.
- To assess the vaccine's potential for preventing melioidosis in humans.
Main Methods:
- Purification of Burkholderia thailandensis 6-deoxyheptan capsular polysaccharide (CPS) and conjugation to CRM197.
- Production of His-tagless B. pseudomallei Hcp1 (Hcp1-TL).
- Immunization of cynomolgus macaques with CPS-CRM197, Hcp1-TL, and adjuvants (Alhydrogel plus CpG DNA).
Main Results:
- Vaccine formulations induced robust CPS-specific IgG and opsonizing antibody responses.
- Strong Hcp1-specific IgG and measurable IFN-γ-secreting T-cell responses were observed.
- The vaccine was well tolerated with no adverse events after three doses.
Conclusions:
- The study established good manufacturing practices-compatible processes for vaccine antigens.
- Demonstrated the safety and immunogenicity of the subunit vaccine in non-human primates.
- Supports continued advancement of the melioidosis vaccine towards human clinical trials.
