Synthetic TLR4 agonist as a potential immunotherapy for melioidosis

Abstract

Melioidosis, an infection caused by Gram-negative Burkholderia pseudomallei (Bp), has high clinical recurrence and mortality rates associated with pneumonia and sepsis. With the limitations in current therapeutic options and the lack of available human vaccines, development of novel countermeasures against Bp infection is vital. In this study, we evaluated the efficacy of an aminoalkyl glucosaminide 4-phosphate (AGP), a synthetic toll like receptor 4 agonist (CRX-527), in conferring protection against melioidosis in a murine model. Survival data showed 66% of mice treated with AGP prior to lethal intranasal Bp challenge survived and presented no signs of illness over a 3 months period. In contrast, all control mice succumbed to infection within 4 days. Kinetic study on organ bacterial burden demonstrated mice treated with AGP had dramatically reduced bacterial loads in both the lungs and spleens as compared to control mice. Notably, all but one AGP-treated mouse had no Bp growth in the blood as compared to overwhelming bacteraemia found in all control mice. The protective effect of CRX-527 was associated with a transient increase in pulmonary cytokine/ chemokine levels, which boosted the host’s innate immunity. This enabled rapid clearance of the pulmonary and systemic bacterial burden and prevented the development of sepsis. This study demonstrated the potential use of TLR4 agonist as a prophylactic immunotherapy in preventing melioidosis.