Mycobacterium tuberculosis stimulates IL-1β production by macrophages in an ESAT-6 dependent manner with the involvement of serum amyloid A3

Abstract

To explore interleukin (IL)-1{beta} production in tuberculosis, we infected mouse bone marrow-derived macrophages (BMDM) with Mycobacterium tuberculosis (Mtb) H37Rv, its early secreted antigenic target protein of 6 kDa (ESAT-6) gene deletion (H37Rv:{Delta}3875) or complemented strain (H37Rv:{Delta}3875C) and evaluated IL-1{beta} production. H37Rv induced significantly increased IL-1{beta} production by BMDMs compared to non-infected BMDMs. In contrast, H37Rv:{Delta}3875 induced significantly less mature IL-1{beta} production despite eliciting comparable levels of pro-IL-1{beta} and IL-8 from BMDMs compared to H37Rv and H37Rv:{Delta}3875C. Blocking either NLRP3 or K+ efflux diminished H37Rv-induced IL-1{beta} production by BMDMs. Infection of mice intranasally with H37Rv:{Delta}3875 induced less IL-1{beta} production in the lungs compared with H37Rv.Intranasal delivery of ESAT-6 but not CFP10 induced production of IL-1{beta} in mouse lungs and RNA-Seq analysis identified serum amyloid A (SAA) 3 as one of the highly expressed genes in mouse lungs. Infection of mice with H37Rv but not H37Rv:{Delta}3875 induced expression of lung SAA3 mRNA and protein, consistent with the effect of intranasal delivery of ESAT-6. Silencing SAA3 reduced Mtb-induced IL-1{beta} production by BMDMs. We conclude that the production of SAA3 is required for Mtb stimulated IL-1{beta} production by macrophages in tuberculosis infection.