GP (33-41)

We have shown that PLG nanoparticles loaded with peptide antigen can reduce disease in animal models of autoimmunity and in a phase 1/2a clinical trial in celiac patients. Clarifying the mechanisms by which antigen-loaded nanoparticles establish tolerance is key to further adapting them to clinical use. The mechanisms underlying tolerance induction include the expansion of antigen-specific CD4+regulatory T cells and sequestration of autoreactive cells in the spleen. In this study, we employed nanoparticles loaded with two model peptides, GP33-41(a CD8 T cell epitope derived from lymphocytic choriomeningitis virus) and OVA323-339(a CD4 T cell epitope derived from ovalbumin), to modulate the CD8+and CD4+T cells from two transgenic mouse strains, P14 and DO11.10, respectively. Firstly, it was found that the injection of P14 mice with particles bearing the MHC I-restricted GP33-41peptide resulted in the expansion of CD8+T cells with a regulatory cell phenotype. This correlated with reduced CD4+T cell viability in ex vivo co-cultures. Secondly, both nanoparticle types were able to sequester transgenic T cells in secondary lymphoid tissue. Flow cytometric analyses showed a reduction in the surface expression of chemokine receptors. Such an effect was more prominently observed in the CD4+cells rather than the CD8+cells.

Microorganisms contain PAMPs that can interact with different TLR-Ls. Cooperative signals from these receptors may modify innate and adaptive immune responses to invading pathogens. Therefore, a better understanding of the role TLRs play in initiating host defense during infections requires assessing the influence of multiple TLR engagement on pAPC activation and antigen presentation. In this study, we investigated the effects of combined TLR2, TLR3, or TLR4 engagement on DC activation and the presentation of LCMV antigens focusing on the major epitopes derived from NP and GP proteins encoded by the virus. Our results demonstrate that combined TLR ligation affected antigen presentation of NP(205-212), GP(33-41), and GP(276-286), but not NP(396-404). The altered antigen presentation was associated with changes in proteasomal activities and NO production as a result of TLR engagement. Taken together, the data demonstrate that combined TLR ligation could result in changes of innate effectors that may directly influence the adaptive immune response.

Chronic virus infection leads to the functional impairment of dendritic cells (DCs) as well as T cells, limiting the clinical usefulness of DC-based therapeutic vaccine against chronic virus infection. Meanwhile, B cells have been known to maintain the ability to differentiate plasma cells producing antibodies even during chronic virus infection. Previously, α-galactosylceramide (αGC) and cognate peptide-loaded B cells were comparable to DCs in priming peptide-specific CD8(+) T cells as antigen presenting cells (APCs). Here, we investigated whether B cells activated by αGC can improve virus-specific T cell immune responses instead of DCs during chronic virus infection. We found that comparable to B cells isolated from naïve mice, chronic B cells isolated from chronically infected mice with lymphocytic choriomeningitis virus (LCMV) clone 13 (CL13) after αGC-loading could activate CD1d-restricted invariant natural killer T (iNKT) cells to produce effector cytokines and upregulate co-stimulatory molecules in both naïve and chronically infected mice. Similar to naïve B cells, chronic B cells efficiently primed LCMV glycoprotein (GP) 33-41-specific P14 CD8(+) T cells in vivo, thereby allowing the proliferation of functional CD8(+) T cells. Importantly, when αGC and cognate epitope-loaded chronic B cells were transferred into chronically infected mice, the mice showed a significant increase in the population of epitope-specific CD8(+) T cells and the accelerated control of viremia. Therefore, our studies demonstrate that reciprocal activation between αGC-loaded chronic B cells and iNKT cells can strengthen virus-specific T cell immune responses, providing an effective regimen of autologous B cell-based therapeutic vaccine to treat chronic virus infection.