Advax4 delta inulin combination adjuvant together with ECMX, a fusion construct of four protective mTB antigens, induces a potent Th1 immune response and protects mice against Mycobacterium tuberculosis infection

ABSTRACT

Tuberculosis (TB) remains a main public health concern and 10.4 million new cases occurred in 2015 around the world. BCG is the only approved vaccine against TB, but has variable efficacy and new vaccines are needed. We developed two new mTB vaccine candidates based on the recombinant fusion proteins, rCMX and rECMX formulated with Advax4, a new combination adjuvant combining delta inulin, CpG oligonucleotide and murabutide. BALB/c mice were immunized three times intramuscularly with these vaccine formulations. Injection of Advax4 alone increased the percentage of lymphatic endothelial cells and activated macrophages (F480/CD11b⁺) in the draining lymph nodes consistent with a chemotactic adjuvant effect. Advax4+CMX and Advax4+ECMX induced the highest levels of IgG1 and IgG2a antibodies against rCMX and rECMX, respectively. Immunized mice challenged with Mycobacterium tuberculosis (Mtb) had increased vaccine-specific Th1 responses in the lungs together with reduced Mtb – associated alveolar damage, although only the Advax4+ECMX vaccine demonstrated significant reduction of lung bacterial load. This study confirmed Advax4+ECMX as a potential TB vaccine candidate, with potential for further optimization and clinical development.

KEYWORDS:

• tuberculosis
• vaccine
• adjuvant
• TB
• ECMX
• advax
• delta inulin

Disclosure of potential conflicts of interest

The authors declare no conflict of interest in this study.

Acknowledgments

Vaxine Pty Ltd, Adelaide Australia provided the Advax4 adjuvant. Development of Advax adjuvants was supported by the National Institute of Allergy and Infectious Diseases of the National Institutes of Health through Contracts AI061142, HHSN272200800039C and HHSN272201400053C. Conselho Nacional de Ciência e Tecnologia (CNPq) of Ministry of Science and Technology of Brazil supported the CMX and ECMX development and the animal testing contract: 303675/2015-2. This publication's contents are solely the responsibility of the authors and do not necessarily represent the official views of the National Institutes of Health or CNPq/Brazil. BPOS, MMT and RBM received fellowship from CNPq. This publication is part of BPOS dissertation of their Master degree.

Authors’ contributions

BPOS developed the experiments and wrote the draft. MRNC carried out the histopathological analyses. NP provided the Advax4. APJK, AK and NP designed the experiments and wrote the manuscript. All authors read and critically revised the manuscript.