-derived diacylated lipoprotein M161Ag (MALP404) is recognized by human/mouse toll-like receptor (TLR) 2/TLR6. Short proteolytic products including macrophage-activating lipopeptide 2 (MALP2) have ...been utilized as antitumor immune-enhancing adjuvants. We have chemically synthesized a short form of MALP2 named MALP2s (
-2,3-bis(palmitoyloxy)propyl-CGNNDE). MALP2 and MALP2s provoke natural killer (NK) cell activation
but only poorly induce tumor regression using
mouse models loading NK-sensitive tumors. Here, we identified the functional mechanism of MALP2s on dendritic cell (DC)-priming and cytotoxic T lymphocyte (CTL)-dependent tumor eradication using CTL-sensitive tumor-implant models EG7 and B16-OVA. Programmed death ligand-1 (PD-L1) blockade therapy in combination with MALP2s + ovalbumin (OVA) showed a significant additive effect on tumor growth suppression. MALP2s increased co-stimulators CD80/86 and CD40, which were totally MyD88-dependent, with no participation of toll-IL-1R homology domain-containing adaptor molecule-1 or type I interferon signaling in DC priming. MALP2s + OVA consequently augmented proliferation of OVA-specific CTLs in the spleen and at tumor sites. Chemokines and cytolytic factors were upregulated in the tumor. Strikingly, longer duration and reinvigoration of CTLs in spleen and tumors were accomplished by the addition of MALP2s + OVA to α-PD-L1 antibody (Ab) therapy compared to α-PD-L1 Ab monotherapy. Then, tumors regressed better in the MALP2s/OVA combination than in the α-PD-L1 Ab monotherapy. Hence, MALP2s/tumor-associated antigens combined with α-PD-L1 Ab is a good therapeutic strategy in some mouse models. Unfortunately, numerous patients are still resistant to PD-1/PD-L1 blockade, and good DC-priming adjuvants are desired. Cytokine toxicity by MALP2s remains to be settled, which should be improved by chemical modification in future studies.
Background Staphylococcus aureus heavily colonizes the lesions of patients with atopic dermatitis (AD) and is known to trigger a worsening of AD. However, the exact mechanism by which S aureus ...promotes AD is unknown. Thymic stromal lymphopoietin (TSLP), which is highly expressed by keratinocytes in skin lesions of patients with AD and bronchial epithelial cells in asthmatic patients, represents a critical factor linking responses at interfaces between the body and the environment to allergic type 2 immune responses. Objectives We sought to examine the ability of synthetic lipopeptides and S aureus to induce TSLP expression in human keratinocytes and identify the pathway of induction. Methods We stimulated primary human keratinocytes with lipopeptides and S aureus –derived materials. The release and gene expression of TSLP were measured by means of ELISA and quantitative PCR, respectively. Results Diacylated lipopeptide upregulated the expression of TSLP and other proinflammatory molecules. Heat-killed S aureus and the subcellular fractions of S aureus induced TSLP's release, with the membranous fraction having the greatest activity. Small interfering RNA–mediated knockdown of either Toll-like receptor (TLR) 2 or TLR6 inhibited the diacylated lipopeptide– and S aureus membrane–induced TSLP gene expression. S aureus membrane– and diacylated lipopeptide–induced release of TSLP was enhanced by TH 2/TNF-α cytokines and partially suppressed by IFN-γ and TGF-β. Conclusions The results suggest that ligands for the TLR2-TLR6 heterodimer in S aureus membranes, including diacylated lipoproteins, could promote TH 2-type inflammation through TSLP production in keratinocytes, providing an overall picture of the vicious cycles between colonization by S aureus and AD in the TH 2-skewed sensitization process, exacerbation of the disease, or both.
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