Research

CURRENT RESEARCH

The Lewinsohn laboratory studies cellular immunity against Mycobacterium tuberculosis (Mtb), a leading cause of infectious disease mortality worldwide. We believe that improved vaccines and diagnostics will require an understanding of the mechanisms by which T cells recognize cells infected with the bacterium Mtb. Because Mtb is a facultative intracellular pathogen, cytotoxic T cells may be important in the recognition and elimination of infected cells.

Mtb resides in the phagosome, an intracellular compartment traditionally thought to be a component of the MHC-II antigen processing pathway. As a result, the laboratory has focused on understanding the mechanisms by which CD8 T cells recognize those cells infected with Mtb.

Topics under active investigation include: 

  • What are the immunodominant antigens recognized by humans infected with Mtb? Using a combination of genomic and proteomic approaches, we have begun to elucidate the antigen repertoire. Interestingly, HLA-B appears to play a dominant role in the presentation of Mtb-derived peptides.

 

  • What are the molecular requirements for the activation of Mtb-reactive T cells? We have found that Mtb-reactive T cells are both classically (HLA-A,B,C) and non-classically restricted. We have found that the molecules HLA-E and MR1 are capable of displaying Mtb-derived antigens. MR1 restricted cells are also termed Mucosa Associated Invariant T Cells.

 

  • How do antigens derived from Mtb gain access to the MHC-I antigen processing pathway? We are exploring the hypothesis that the Mtb-phagosome can process and present antigens, in effect allowing the immune system to focus on pathogens found within this organelle.

 

  • What is the role of the lung epithelium in controlling the growth of Mtb? We have found that the non-classically restricted cells recognize Mtb infected lung epithelial cells. We are exploring the mechanisms of antigen processing and presentation, and the ability of these cells to control Mtb growth.

 

  • What is the function and phenotype of lung-resident Mtb-reactive CD8+ T cells? What is the relationship of these cells to pulmonary diseases such as TB, sarcoidosis, and non-TB infection?
Preliminary Data:

As part of the T-Cell Epitope Discovery NIH contract (HHSN272200900053C), a peptide library was made that is comprised of peptide pools representing 80% of the Mtb genome. Peptide pools in this library represent regions of Mtb proteins predicted by HLA binding algorithms to encode a high density of peptides that bind strongly to HLA supertypes. CD8+ T cells from Mtb-infected individuals revealed strong and broad recognition of the Mtb proteome. Peptide pools that were strongly recognized by at least one Mtb-infected individual, represent all or parts of Mtb proteins that we define as immunodominant CD8 antigens or antigenic regions of proteins, respectively. Immunodominant peptide pools were selected for deconvolution, using CD8+ T cells derived from an Mtb-infected individual whose CD8+ T cells recognize the peptide pool, to identify the specific 15-mer within the peptide pool that is responsible for the CD8+ T cell response. A list of these 15-mer peptides identified to date is below. The genomic peptide library was made using the HN878 Mtb strain, so both the HN878 and H37Rv identifiers are included.

Peptide

Protein

H37Rv Homolog

Rv position #

Gene Name

RPAATRVLYVSPLKG

HN3284

Rv3296

870-884

lhr

VLRPAAQRLGRPLRIG

HN2371c

Rv2379c

646-660

mbtF

AHIPQLIASHTAFAA

HN3006c

Rv3020c

6-20

esxS

LRPNTIRLPAWPDKV

HN1440

Rv1431

121-135

Rv1431

LAYPRVVWIAGGLLK

HN2149

Rv2155c

343-357

murD

IQPQTRWEAFANQSL

HN1577

Rv1565c

117-131

Rv1565c

LTLASFIYAIVAHHA

HN1577

Rv1565c

179-193

Rv1565c

RPELPVRNYIRIPAL

HN0217

Rv0219

92-106

Rv0219

FVGDYVTAGGLLGWC

HN1298

Rv1290c

295-309

Rv1290c

FIIDPTISAI

HN3609

Rv3616c

5-14

Rv3616c

NGFQLRRPLFPPLPG

HN0195

Rv0197

440-454

Rv0197

LLPAFVAPSVTVPVS

HN2546

Rv2556c

82-96

Rv2556c

HHLPVDQVFTLEAGR

HN3511

Rv3519

102-116

Rv3519

VDQVFTLEAGRTIWG

HN3511

Rv3519

106-120

Rv3519

VTAAILVFIFAWNDL

HN1245

Rv1237

192-206

sugB

ILVFIFAWNDLLLAL

HN1245

Rv1237

196-110

sugB

GATSRPSALALDDVV

HN0643

Rv0639

134-148

nusG

IYLRNTENPLHPAFA

HN0921

Rv0913c

52-66

 

RIYEKLEAFANFGFP

HN3361

Rv3370c

760-774

dnaE2

LLLANPGLPLWPYLV

HN0260

Rv0261c

113-127

narK3

LVIAYCLGLGIPFVL

HN0527

Rv0527

184-198

ccdA