CD8 + T cells (TCD8) confer protective immunity against many infectious diseases, suggesting that microbial TCD8 determinants are promising vaccine targets. Nevertheless, current T cell antigen identification approaches do not discern which epitopes drive protective immunity during active infection -information that is critical for the rational design of TCD8-targeted vaccines. We employed a proteomics-based approach for large-scale discovery of naturally processed determinants derived from a complex pathogen, vaccinia virus (VACV), that are presented by the most frequent representatives of four major HLA class I supertypes. Immunologic characterization revealed that many previously unidentified VACV determinants were recognized by smallpox-vaccinated human peripheral blood cells in a variegated manner. Many such determinants were recognized by HLA class I-transgenic mouse immune TCD8 too and elicited protective TCD8 immunity against lethal intranasal VACV infection. Notably, efficient processing and stable presentation of immune determinants as well as the availability of naive TCD8 precursors were sufficient to drive a multifunctional, protective TCD8 response. Our approach uses fundamental insights into T cell epitope processing and presentation to define targets of protective TCD8 immunity within human pathogens that have complex proteomes, suggesting that this approach has general applicability in vaccine sciences.

It has been reported recently that the bacterial respiratory pathogen Chlamydia pneumoniae is present in the cerebrospinal fluid of a subset of multiple sclerosis (MS) patients. However, it is not known whether this organism is a causative agent of MS, or merely an opportunistic pathogen that takes advantage of a disease process initiated by some other means. We report identification of a 20-mer peptide from a protein specific to C. pneumoniae which shares a 7-aa motif with a critical epitope of myelin basic protein, a major CNS Ag targeted by the autoimmune response in MS. This bacterial peptide induces a Th1 response accompanied by severe clinical and histological experimental autoimmune encephalomyelitis in Lewis rats, a condition closely reflective of many aspects of MS. Studies with peptide analogues suggest that different populations of encephalitogenic T cells are activated by the C. pneumoniae and myelin basic protein Ags. Mild experimental autoimmune encephalomyelitis was also observed when rats were immunized with sonicated C. pneumoniae in CFA.

Background: Inflammatory processes are increased in the Parkinson's disease (PD) brain. The long-term use of nonsteroidal anti-inflammatory drugs has been associated, in retrospective studies, with decreased risk for PD, suggesting that inflammation may contribute to development of this disorder. The objective of this study was to determine the extent of complement activation, a major inflammatory mechanism, in PD.

Purpose MHC class I presentation of peptides allows T cells to survey the cytoplasmic protein milieu of host cells. During infection, presentation of self peptides is, in part, replaced by presentation of microbial peptides. However, little is known about the self peptides presented during infection, despite the fact that microbial infections alter host cell gene expression patterns and protein metabolism. Experimental design The self peptide repertoire presented by HLA-A*01;01, -A*02;01, -B*07;02, -B*35;01 and -B*45;01 was determined by mass spectrometry before and after vaccinia virus infection. Results We observed a profound alteration in the self peptide repertoire with hundreds of self peptides uniquely presented after infection for which we have coined the term ‘self peptidome shift’. The fraction of novel self peptides presented following infection varied for different HLA class I molecules. A large part (~40%) of the self peptidome shift was composed of peptides derived from type I interferon-inducible genes, consistent with cellular responses to viral infection. Interestingly, ~12% of self peptides presented after infection showed allelic variation when searched against ~300 human genomes. Conclusion and clinical relevance Self peptidome shift in a clinical transplant setting could result in alloreactivity by presenting new self peptides in context of infection-induced inflammation.

Lewis rats can be rendered unresponsive to experimental autoimmune encephalomyelitis by immunization with myelin basic protein (MBP), or MBP68–86, the dominant encephalitogenic MBP epitope for this strain, administered in IFA. However, protected rats harbor potentially encephalitogenic T cells, which are maintained in an inactive state. We investigated whether these quiescent effector cells could be activated in vitro. Although these T cells respond poorly to MBP68–86, they proliferate vigorously whether cocultured with MBP68–86 and either IL-2 or IL-12, suggesting that the T cells are in a state of anergy. Moreover, we could activate these anergic T cells with peptide and cytosine-guanine dinucleotide (CpG) oligonucleotide, but not control oligonucleotide, suggesting that products of the innate immune response are capable of activating anergic autoreactive T cells. The activated T cells produced the proinflammatory cytokine, IFN-γ in response to IL-12, and IL-6 was secreted in response to CpG oligonucleotide. IL-6 has been reported to play a role in T cell activation by blocking T regulatory/suppressor (Treg) cell-mediated suppression through a Toll-like receptor-dependent pathway. However, anti-IL-6 mAb did not block CpG activation of the anergized cells. In contrast, anti-TGF-β1 Ab released the unresponsive T cells from the anergic state in the presence of MBP68–86, whereas TGF-β1 inhibited proliferation of MBP68–86- plus CpG-activated T cells. Because TGF-β1 has previously been implicated in Treg activity, this finding is consistent with a role for Treg cells in maintaining autoreactive T cells in the anergic state.

Seven mycobacteriophages from distinct geographical locations were isolated, using Mycobacterium smegmatis mc2155 as the host, and then purified and sequenced. All of the genomes are related to cluster A mycobacteriophages, BobSwaget and Lokk in subcluster A2; Fred313, KADY, Stagni, and StepMih in subcluster A3; and MyraDee in subcluster A18, the first phage to be assigned to that subcluster.

It is generally assumed that the MHC class I antigen (Ag)-processing (CAP) machinery —which supplies peptides for presentation by class I molecules— plays no role in class II-restricted presentation of cytoplasmic Ags. In striking contrast to this assumption, we previously reported that proteasome inhibition or TAP- or ERAAP-deficiency led to dramatically altered T helper (Th) cell responses to allograft (HY) and microbial (Listeria monocytogenes) Ags. Herein, we tested whether altered Ag processing and presentation, altered CD4+ T cell repertoire, or both underlay the above finding. We found that TAP- and ERAAP-deficiency dramatically altered the quality of class II-associated self peptides suggesting that the CAP machinery impacts class II-restricted Ag processing and presentation. Consistent with altered self peptidomes, the CD4+ T cell receptor repertoire of mice deficient in the CAP machinery substantially differed from that of wildtype animals resulting in altered CD4+ T cell Ag recognition patterns. These data suggest that TAP and ERAAP sculpt the class II-restricted peptidome, impacting the CD4+ T cell repertoire, and ultimately altering Th cell responses. Together with our previous findings, these data suggest multiple CAP machinery components sequester or degrade MHC class II-restricted epitopes that would otherwise be capable of eliciting functional Th cell responses.

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