The same well-characterized T cell epitope SIINFEKL expressed in the context of a cytoplasmic or secreted protein in BCG induces different CD8+ T cell responses

Abstract

SummaryMycobacterium bovis BCG is still the most widely used vaccine against tuberculosis and CD8 + T cells play important roles in fighting infection. We investigated how well antigen is processed and presented to CD8 + T cells using the same well-characterized CD8 + T cell epitope SIINFEKL expressed in either a cytoplasmic (GFP-OVA) or secreted (85B-OVA) context from BCG. We report that secreted SIINFEKL from 85B-OVA BCG is presented better than cytoplasmic SIINFEKL expressed by GFP-OVA BCG. IntroductionBCG is the most widely used human vaccine and has been administered to more than 3 billion people to protect against tuberculosis (TB) [1]. There are currently over 2 billion people infected with latent TB, and over 9 million incident cases of TB were reported in 2007 [2]. There is a great need to improve the efficacy of BCG since its protection is limited and variable against active pulmonary disease. While BCG is an excellent inducer of Th1 CD4 + T cell responses, it is less effective at inducing CD8 + T cell responses, in contrast to Mtb, which induces strong responses from both. Because CD8 + T cells provide additional mechanisms to combat mycobacteria, efforts were aimed at increasing CD8 + responses induced by BCG antigens, such as creating recombinant BCG (rBCG) that secretes listeriolysin, which perforates the phagosome allowing antigens greater access to the cytosol for classical MHC I processing and presentation [3,4]. The difference between CD8 + T cell activation by cytoplasmic or secreted BCG antigens is poorly understood. rBCG expressing the well-

CC Chemokine Receptor 4 Contributes to Innate NK and Chronic Stage T Helper Cell Recall Responses during Mycobacterium bovis Infection

“…14 Ovalbumin peptides recognized by the OT-I and OT-II TCR-transgenic T cells were cloned by PCR into the C-terminal end of the GFP molecule using extended primers. The altered construct was checked by sequencing, then BCG-Pasteur was transfected with the OVA peptide construct and selected in kanamycin-containing media.…”

Mycobacterium tuberculosisDirects Immunofocusing of CD8+ T Cell Responses Despite Vaccination

“…Technical improvements in the ability to quantify the naive T cell repertoire indicate that precursor frequency can affect immunodominance to microbial Ags (8). Microbial factors including whether proteins are secreted (9, 10), their abundance (11), and their elaboration of pathogen-associated molecular patterns (12) all affect immunogenicity of microbial proteins.…”

BrucellaPeptide Cross-Reactive MHC I Presentation Activates SIINFEKL-Specific TCR Expressing T Cells

“…This included proteomes of Listeria monocytogenes , Salmonella enterica , and Mycobacteria bovis BCG. Listeria , Salmonella , and BCG have all been engineered to express OVA similar to the approach shown here with Brucella (13, 32, 33). However, no cross-reactivity of native bacterial peptides to OVA specific TCR was reported.…”