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Dengue is endemic in tropical countries worldwide and the four dengue virus serotypes often co-circulate. Infection with one serotype results in high titers of cross-reactive antibodies produced by plasmablasts, protecting temporarily against all serotypes, but impairing protective immunity in subsequent infections. To understand the development of these plasmablasts, we analyzed virus-specific B cell properties in patients during acute disease and at convalescence. Plasmablasts were unrelated to classical memory cells expanding in the blood during early recovery. We propose that only a small subset of memory B cells is activated as plasmablasts during repeat infection and that plasmablast responses are not representative of the memory B cell repertoire after dengue infection.

16Prior genome-wide association studies have identified a melanoma-associated locus on 17 chr1q42.1 that encompasses a ~100 kb region spanning the PARP1 gene. eQTL analysis in 18 multiple cell types of melanocytic lineage consistently demonstrated that the 1q42.1 melanoma 19 risk allele (rs3219090, G) is correlated with higher PARP1 levels. In silico fine-mapping and 20 functional validation identified a common intronic indel, rs144361550 (-/GGGCCC, r 2 =0.947 21 with rs3219090) as displaying allele-specific transcriptional activity. A proteomic screen 22 identified RECQL as binding to rs144361550 in an allele-preferential manner. In human primary 23 melanocytes, PARP1 promotes cell proliferation and rescues BRAF V600E -induced senescence 24 phenotypes in a PARylation-independent manner. PARP1 also transforms TERT-immortalized 25 melanocytes expressing BRAF V600E . PARP1-mediated senescence rescue is accompanied by 26 transcriptional activation of melanocyte lineage survival oncogene, MITF, highlighting a new role 27 of PARP1 in melanomagenesis. 28 29To date, genome-wide association studies (GWAS) have identified twenty common, 30 genome-wide significant melanoma susceptibility loci [1][2][3][4][5][6][7][8][9] , most of which do not appear to be 31 explained by protein-coding variants. A subset of these loci harbor known pigmentation genes 32 that mediate melanoma-associated phenotypes such as eye, hair, and skin color. While several 33 loci harbor genes implicated in cancer, evidence directly linking common risk variants within 34 most of these loci to altered function of specific genes is lacking. 35MacGregor and colleagues initially identified a melanoma risk locus tagged by 36 rs3219090 on chromosome band 1q42.1 in an Australian case-control study at a near genome-37 wide level of significance (P = 9.3 x 10 -8 , OR = 0.87, protective allele A) 8 . The association has 38 since been replicated by multiple other studies 3,10 , including most recently by a meta-analysis of 39 12,874 melanoma cases (rs1858550, P = 1.7 x 10 -13 ) 7 . Notably, the locus at 1q42.1 has also 40 been associated with melanoma survival 11 , where the melanoma risk allele correlates with 41 increased survival, an association that has since been replicated 12 . The region of association 42 spans from 226.52 Mb to 226.63 Mb (hg19) of chromosome 1, encompassing the entirety of the 43 poly(ADP-ribose) (PAR) polymerase-1 (PARP1) (OMIM: 173870) gene, and fine-mapping 44 suggests that the association is best explained by a single-SNP model 3 . 45While a number of other genes are located in the vicinity of the association peak, PARP1 46 has the most well-established role in cancer. PARP1 is best known for its role as a DNA repair 47 enzyme and genotoxic sensor that functions in base excision repair (BER), single-strand break 48 repair, and double-strand break repair , and appear to play a role in oncogene-induced senescence (OIS) 20,21 . 56Aside from DNA repair, PARP1 functions in regulating gene expression by modif...

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CD4+CD25high regulatory T cells (Treg) protect the host from autoimmune diseases but are also obstacles against cancer therapies. An ideal cancer vaccine would stimulate specific cytotoxic responses and reduce/suppress Treg function. In this study, we showed that Escherichia coli expressing listeriolysin O and OVA (E. coli LLO/OVA) demonstrated remarkable levels of protection against OVA-expressing tumor cells. By contrast, E. coli expressing OVA only (E. coli OVA) showed poor protection. High-avidity OVA-specific CTL were induced in E. coli LLO/OVA-vaccinated mice, and CD8+ depletion—but not NK cell depletion, abolished the antitumor activity of the E. coli LLO/OVA vaccine. Phenotypic analysis of T cells following vaccination with either vaccine revealed preferential generation of CD44highCD62Llow CD8+ effector memory T cells over CD44highCD62Lhigh central memory T cells. Unexpectedly, CD4+ depletion turned E. coli OVA into a vaccine as effective as E. coli LLO/OVA suggesting that a subset of CD4+ cells suppressed the CD8+ T cell-mediated antitumor response. Further depletion experiments demonstrated that these suppressive cells consisted of CD4+CD25high regulatory T cells. We therefore assessed these vaccines for Treg function and found that although CD4+CD25high expansion and Foxp3 expression within this population was similar in all groups of mice, Treg cells from E. coli LLO/OVA-vaccinated animals were unable to suppress conventional T cells proliferation. These findings provide the first evidence that LLO expression affects Treg cell function and may have important implications for enhancing antitumor vaccination strategies in humans.

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Recent studies suggested that the histidine residues at 118 and 122 play an important role for the toxicity of staphylococcal enterotoxin C subtype 2 (SEC2), and the substitutions of both histidines with alanine can severely impair the fever activity of SEC2. We hypothesized that promising SEC2 antitumor agent with low toxicity and enhanced superantigen activity can be constructed by introducing related mutations at protein functional sites of SEC2. We showed that the SEC2 mutants H122A and H118A/H122A exhibited improved superantigen activity after introducing the point mutations at Thr20 and Gly22. A resultant mutant, named as SAM-3, has considerable abilities to inhibit the growth of H22 and Hepa1-6 tumor cells in vitro and colon 26 solid tumor in vivo. Furthermore, SAM-3 also exhibits significantly reduced toxicity compared with native SEC2. The study provides a novel strategy for designing promising superantigen immunotherapeutic agent. The constructed SEC2 mutant SAM-3 can be used as a powerful candidate for cancer immunotherapy and could compensate the deficiency caused by toxicity of native SEC2 in clinic.

Edited by Luke O'Neill SEC2, a major histocompatibility complex class II (MHC II)dependent T-cell mitogen, binds MHC II and T-cell receptor (TCR) V␤s to induce effective co-stimulating signals for clonal T-cell expansion. We previously characterized a SEC2 mutant with increased recognition of TCR V␤s, ST-4, which could intensify NF-B signaling transduction, leading to IL-2 production and T-cell activation. In this study, we found that in contrast to SEC2, ST-4 could induce murine CD4 ؉ T-cell proliferation in a V␤8.2and V␤8.3-specific manner in the absence of MHC II ؉ antigenpresenting cells (APCs). Furthermore, although IL-2 secretion in response to either SEC2 or ST-4 stimulation was accompanied by up-regulation of protein kinase C (PKC), inhibitor of B (IB), ␣ and ␤ IB kinase (IKK␣/␤), IB␣, and NF-B in mouse splenocytes, only ST-4 could activate CD4 ؉ T cells in the absence of MHC II ؉ APCs through the PKC/NF-B signaling pathway. The PKC inhibitor AEB071 significantly suppressed SEC2/ST-4-induced T-cell proliferation, CD69 and CD25 expression, and IL-2 secretion with or without MHC II ؉ APCs. Further, SEC2/ST-4-induced changes in PKC/NF-B signaling were significantly relieved by AEB071 in a dose-dependent manner. Using Lck siRNA, we found that Lck controlled SEC2/ST-4-induced phosphorylation of PKC. We also demonstrated that the IL-2R/STAT5 pathway is essential for SEC2/ST-4-induced T-cell activation. Collectively, our data demonstrate that an enhanced ST-4-TCR interaction can compensate for lack of MHC II and stimulate MHC II-free CD4 ؉ T-cell proliferation via PKC/NF-B and IL-2R/STAT5 signaling pathways. Compared with SEC2, intensified PKC/NF-B and IL-2R/STAT5 signals induced by ST-4 lead to enhanced T-cell activation. The results of this study will facilitate better understanding of TCR-based immunotherapies for cancer.