TY - JOUR

T1 - In vivo antigen expression regulates cd4 t cell differentiation and vaccine efficacy against mycobacterium tuberculosis infection

AU - Clemmensen, Helena Strand

AU - Dube, Jean Yves

AU - McIntosh, Fiona

AU - Rosenkrands, Ida

AU - Jungersen, Gregers

AU - Aagaard, Claus

AU - Andersen, Peter

AU - Behr, Marcel A.

AU - Mortensen, Rasmus

PY - 2021

Y1 - 2021

N2 - New vaccines are urgently needed against Mycobacterium tuberculosis (Mtb), which kills more than 1.4 million people each year. CD4 T cell differentiation is a key determinant of protective immunity against Mtb, but it is not fully understood how host-pathogen interactions shape individual antigen-specific T cell populations and their protective capacity. Here, we investigated the immunodominant Mtb anti-gen, MPT70, which is upregulated in response to gamma interferon (IFN-γ) or nutrient/ oxygen deprivation of in vitro-infected macrophages. Using a murine aerosol infection model, we compared the in vivo expression kinetics of MPT70 to a constitutively expressed antigen, ESAT-6, and analyzed their corresponding CD4 T cell phenotype and vaccine protection. For wild-type Mtb, we found that in vivo expression of MPT70 was delayed compared to ESAT-6. This delayed expression was associated with induction of less differentiated MPT70-specific CD4 T cells but, compared to ESAT-6, also reduced protection after vaccination. In contrast, infection with an MPT70-overexpress-ing Mtb strain promoted highly differentiated KLRG1+CX3CR1+ CD4 T cells with lim-ited lung-homing capacity. Importantly, this differentiated phenotype could be pre-vented by vaccination, and against the overexpressing strain, vaccination with MPT70 conferred protection similar to vaccination with ESAT-6. Together, our data indicate that high in vivo antigen expression drives T cells toward terminal differentiation and that targeted vaccination with adjuvanted protein can counteract this phenomenon by maintaining T cells in a protective less differentiated state. These observations shed new light on host-pathogen interactions and provide guidance on how future Mtb vaccines can be designed to tip the immune balance in favor of the host. IMPORTANCE Tuberculosis, caused by Mtb, constitutes a global health crisis of mas-sive proportions and the impact of the current coronavirus disease 2019 (COVID-19) pandemic is expected to cause a rise in tuberculosis-related deaths. Improved vaccines are therefore needed more than ever, but a lack of knowledge on protective immunity hampers their development. The present study shows that constitutively expressed antigens with high availability drive highly differentiated CD4 T cells with diminished protective capacity, which could be a survival strategy by Mtb to evade T cell immunity against key antigens. We demonstrate that immunization with such antigens can counteract this phenomenon by maintaining antigen-specific T cells in a state of low differentiation. Future vaccine strategies should therefore explore combinations of multiple highly expressed antigens and we suggest that T cell differentiation could be used as a readily measurable parameter to identify these in both preclinical and clinical studies.

AB - New vaccines are urgently needed against Mycobacterium tuberculosis (Mtb), which kills more than 1.4 million people each year. CD4 T cell differentiation is a key determinant of protective immunity against Mtb, but it is not fully understood how host-pathogen interactions shape individual antigen-specific T cell populations and their protective capacity. Here, we investigated the immunodominant Mtb anti-gen, MPT70, which is upregulated in response to gamma interferon (IFN-γ) or nutrient/ oxygen deprivation of in vitro-infected macrophages. Using a murine aerosol infection model, we compared the in vivo expression kinetics of MPT70 to a constitutively expressed antigen, ESAT-6, and analyzed their corresponding CD4 T cell phenotype and vaccine protection. For wild-type Mtb, we found that in vivo expression of MPT70 was delayed compared to ESAT-6. This delayed expression was associated with induction of less differentiated MPT70-specific CD4 T cells but, compared to ESAT-6, also reduced protection after vaccination. In contrast, infection with an MPT70-overexpress-ing Mtb strain promoted highly differentiated KLRG1+CX3CR1+ CD4 T cells with lim-ited lung-homing capacity. Importantly, this differentiated phenotype could be pre-vented by vaccination, and against the overexpressing strain, vaccination with MPT70 conferred protection similar to vaccination with ESAT-6. Together, our data indicate that high in vivo antigen expression drives T cells toward terminal differentiation and that targeted vaccination with adjuvanted protein can counteract this phenomenon by maintaining T cells in a protective less differentiated state. These observations shed new light on host-pathogen interactions and provide guidance on how future Mtb vaccines can be designed to tip the immune balance in favor of the host. IMPORTANCE Tuberculosis, caused by Mtb, constitutes a global health crisis of mas-sive proportions and the impact of the current coronavirus disease 2019 (COVID-19) pandemic is expected to cause a rise in tuberculosis-related deaths. Improved vaccines are therefore needed more than ever, but a lack of knowledge on protective immunity hampers their development. The present study shows that constitutively expressed antigens with high availability drive highly differentiated CD4 T cells with diminished protective capacity, which could be a survival strategy by Mtb to evade T cell immunity against key antigens. We demonstrate that immunization with such antigens can counteract this phenomenon by maintaining antigen-specific T cells in a state of low differentiation. Future vaccine strategies should therefore explore combinations of multiple highly expressed antigens and we suggest that T cell differentiation could be used as a readily measurable parameter to identify these in both preclinical and clinical studies.

KW - ESAT-6

KW - Immunization

KW - In vivo expression

KW - MPT70

KW - Mycobacterium tuberculosis

KW - T cell differentiation

KW - Vaccination

U2 - 10.1128/mBio.00226-21

DO - 10.1128/mBio.00226-21

M3 - Journal article

C2 - 33879592

AN - SCOPUS:85104422303

VL - 12

JO - mBio

JF - mBio

SN - 2161-2129

IS - 2

M1 - e00226-21

ER -