Highlights of the advances in basic immunology in 2011

In this review, we summarize the major fundamental advances in immunological research reported in 2011. The highlights focus on the improved understanding of key questions in basic immunology, including the initiation and activation of innate responses as well as mechanisms for the development and function of various T-cell subsets. The research includes the identification of novel cytosolic RNA and DNA sensors as well as the identification of the novel regulators of the Toll-like receptor （TLR） and retinoic acid-inducible gene I （RIG-I）-Iike receptor （RLR） signaling pathway. Moreover, remarkable advances have been made in the developmental and functional properties of innate lymphoid cells （I LCs）. Helper T cells and regulatory T （Treg） cells play indispensable roles in orchestrating adaptive immunity. There have been exciting discoveries regarding the regulatory mechanisms of the development of distinct T-cell subsets, particularly Th17 cells and Treg cells. The emerging roles of microRNAs （miRNAs） in T cell immunity are discussed, as is the recent identification of a novel T-cell subset referred to as follicular regulatory T （TFR） cells.

A modified HLA-A^(*)0201-restricted CTL epitope from human oncoprotein (hPEBP4) induces more efficient antitumor responses

We previously identified human phosphatidylethanolamine-binding protein 4(hPEBP4)as an antiapoptotic protein with increased expression levels in breast,ovarian and prostate cancer cells,but low expression levels in normal tissues,which makes hPEBP4 an attractive target for immunotherapy.Here,we developed hPEBP4-derived immunogenic peptides for inducing antigen-specific cytotoxic T lymphocytes(CTLs)targeting breast cancer.A panel of hPEBP4-derived peptides predicted by peptide-MHC-binding algorithms was evaluated to characterize their HLAA2.1 affinity and immunogenicity.We identified a novel immunogenic peptide,P40–48(TLFCQGLEV),that was capable of eliciting specific CTL responses in HLA-A2.1/K^(b) transgenic mice,as well as in peripheral blood lymphocytes from breast cancer patients.Furthermore,amino-acid substitutions in the P40–48 sequence improved its immunogenicity against hPEBP4,a self-antigen,thus circumventing tolerance.We designed peptide analogs by preferred auxiliary HLA-A^(*)0201 anchor residue replacement,which induced CTLs that were crossreactive to the native peptide.Several analogs were able to stably bind to HLA-A^(*)0201 and elicit specific CTL responses better than the native sequence.Importantly,adoptive transfer of CTLs induced by vaccination with two analogs more effectively inhibited tumor growth than the native peptide.These data indicate that peptide analogs with high immunogenicity represent promising candidates for peptide-mediated therapeutic cancer vaccines.

HSP70L1-mediated intracellular priming of dendritic cell vaccination induces more potent CTL response against cancer

Heat-shock protein(HSP)-based immunotherapy is established on its adjuvant effects when applied via an extracellular approach to pulse and activate dendritic cells(DCs).Our previous studies indicate that DCs pulsed with recombinant fusion proteins of antigenic fragment and HSP70-like protein 1(HSP70L1)are potent in stimulating antigen-specific Th1 responses.We herein evaluated the cytotoxic T cell(CTL)response by an intracellular approach of priming DCs with transfection of recombinant adenovirus-expressing the fusion gene of the 576–699 fragment of carcinoembryonic antigen(CEA)and HSP70L1.As compared with DCs pulsed with extracellular fusion protein,the DCs transfected with recombinant adenovirus expressing the fusion gene displayed equivalent mature phenotypes but less inflammatory appearance.However,the transfected DCs were superior to the pulsed DCs in inducing CEA-specific CTLs.Consistently,immunization of HLA-A2.1/H-2Kb transgene mice with the transfected DCs could induce more quantities of HLA-A2.1-restricted CEA-specific CTLs,protecting nude mice more significantly from human CEA-expressing colon tumor challenge when adoptively transferred.Mechanistic investigation indicated that intracellular expression of the fusion protein empowered the transfected DCs by activation of STAT1 possibly via inducing IFN-βand ERK pathways.Therefore,the more potent ability to induce anti-CEA CTL responses enables the DCs,which transfected with recombinant adenovirus expressing the fusion gene of antigenic CEA fragment and Th1 adjuvant,as an alternative promising approach for the immunotherapy of CEA-positive tumors.

Intracellular HSP70L1 inhibits human dendritic cell maturation by promoting suppressive H3K27me3 and H2AK119Ub1 histone modifications

Epigenetic regulation has been attracting increasing attention due to its role in cell differentiation and behaviors.However,the epigenetic mechanisms that regulate human dendritic cell(DC)differentiation and development remain poorly understood.Our previous studies show that extracellular heat shock protein 70-like protein(HSP70L1)is a potent adjuvant of Th1 responses via stimulating DCs when released from cells;however,the role of intracellular HSP70L1 in DC differentiation and maturation remains unknown.Herein,we demonstrate that intracellular HSP70L1 inhibits human DC maturation by suppressing MHC and costimulatory molecule expression,in contrast to the adjuvant activity of extracellular HSP70L1.The stability of intracellular HSP70L1 is dependent on DNAJC2,a known epigenetic regulator.Mechanistically,intracellular HSP70L1 inhibits the recruitment of Ash1l to and maintains the repressive H3K27me3 and H2AK119Ub1 modifications on the promoter regions of costimulatory,MHC and STAT3 genes.Thus,intracellular HSP70L1 is an inhibitor of human DC maturation.Our results provide new insights into the epigenetic regulation of cell development by intracellular HSP70L1.

Cloning and Characterization of DULP,a Novel Ubiquitin-Like Molecule from Human Dendritic Cells

We identified a novel ubiquitin-like molecule DULP from human dendritic cells. DULP contains a domain that shares 26% identity and 34% similarity with ubiquitin, and it possesses the corresponding Ile-44 hydrophobic patch used by mono- or poly-ubiquitin to interact with a ubiquitin-interaction motif （UIM） or ubiquitin-associated domain （UBA）. Lysine residue corresponding to 6 of ubiquitin, which is involved in the formation of a multi-ubiquitin chain that can bind proteasomal subunit Rpn10/S5a, is also conserved in its ubiquitin-homology domain. However, DULP does not possess the highly conserved C-terminus Gly-Gly required for ubiquitin conjugation or the Lys-48 required for the formation of polyubiquitin chain to target substrates for degradation, suggesting it might be a novel ubiquitin-domain protein （UDP）. DULP was found widely expressed in many cells and the ubiquitin-homology domain was not cleaved. We also confirmed that DULP expression was enriched in the nucleus and much weaker in the cytosol. Besides, we found that overexpression of DULP in 293T cells induced apoptosis, which might not be associated with the mitochondrial or proteasome pathway, with the specific mechanism remain unclear. Further investigations are needed to identify the precise biological functions of DULP. Cellular ＆ Molecular Immunology.

Correction: HSP70L1-mediated intracellular priming of dendritic cell vaccination induces more potent CTL response against cancer

In the published version of Fig.3D,the data of the CH and AdCtrl groups in the CFSE-Lovo/Medium panel were mistakenly presented with incorrected images.Figure 3D has now been corrected.The corrected version of Figure 3 is shown below.Although we regret our mistake during figure assembly and would like to apologize for any inconvenience it may have caused,we did not manipulate our data in any way.This unintentional error also has no bearing on the workʼs scientific conclusions.

Innate immune imprints in SARS-CoV-2 Omicron variant infection convalescents

SARS-CoV-2 Omicron variant infection generally gives rise to asymptomatic to moderate COVID-19 in vaccinated people.The immune cells can be reprogrammed or“imprinted”by vaccination and infections to generate protective immunity against subsequent challenges.Considering the immune imprint in Omicron infection is unclear,here we delineate the innate immune landscape of human Omicron infection via single-cell RNA sequencing,surface proteome profiling,and plasma cytokine quantification.We found that monocyte responses predominated in immune imprints of Omicron convalescents,with IL-1β-associated and interferon(IFN)-responsive signatures with mild and moderate symptoms,respectively.Low-density neutrophils increased and exhibited IL-1β-associated and IFN-responsive signatures similarly.Mild convalescents had increased blood IL-1β,CCL4,IL-9 levels and PI3+neutrophils,indicating a bias to IL-1βresponsiveness,while moderate convalescents had increased blood CXCL10 and IFN-responsive monocytes,suggesting durative IFN responses.Therefore,IL-1β-or IFN-responsiveness of myeloid cells may indicate the disease severity of Omicron infection and mediate post-COVID conditions.