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BACKGROUND Obesity has been associated with attenuated vaccine responses and an increased risk of contracting pneumococcal pneumonia, but no study to our knowledge has assessed the impact of obesity and genetics on 23-valent pneumococcal vaccine (PPSV23) efficacy. We assessed the relationship of obesity (primary analysis) and stimulator of interferon genes (STING1) genotype (secondary analysis) on PPSV23 efficacy. METHODS Nonobese (BMI 22–25 kg/m2) and obese participants (BMI ≥30 kg/m2) were given a single dose of PPSV23. Blood was drawn immediately prior to and 4–6 weeks after vaccination. Serum samples were used to assess PPSV23-specific antibodies. STING1 genotypes were identified using PCR on DNA extracted from peripheral blood samples. RESULTS Forty-six participants were categorized as nonobese (n = 23; 56.5% women; mean BMI 23.3 kg/m2) or obese (n = 23; 65.2% women; mean BMI 36.3 kg/m2). Obese participants had an elevated fold change in vaccine-specific responses compared with nonobese participants (P < 0.0001). The WT STING1 group (R232/R232) had a significantly higher PPSV23 response than individuals with a single copy of HAQ-STING1 regardless of BMI (P = 0.0025). When WT was assessed alone, obese participants had a higher fold serotype-specific response compared with nonobese participants (P < 0.0001), but no difference was observed between obese and nonobese individuals with 1 HAQ allele (P = 0.693). CONCLUSIONS These observations demonstrate a positive association between obesity and PPSV23 efficacy specifically in participants with the WT STING1 genotype. TRIAL REGISTRATION ClinicalTrials.gov NCT02471014. FUNDING This research was supported by the NIH and the University of Florida MD-PhD Training Program., Obesity and a WT STING1 genotype are positively associated with efficacy of the 23-valent pneumococcal vaccine in a small cohort of subjects.

Cyclic dinucleotides (CDNs), including cyclic di-GMP (CDG), are promising vaccine adjuvants in preclinical/clinical trials. The in vivo mechanisms of CDNs are not clear. Here we investigated the roles of lung DC subsets in promoting CDG mucosal adjuvant responses in vivo. Using genetically modified mice and adoptive cell transfer, we identified lung conventional DC 2 (cDC2) as the central player in CDG mucosal responses. We further identified two functionally distinct lung cDC2 subpopulations: TNFR2+pRelB+ and TNFR2−pRelB− cDC2. The TNFR2+ cDC2 were mature and migratory upon intranasal CDG administration while the TNFR2− cDC2 were activated but not mature. Adoptive cell transfer showed that TNFR2− cDC2 mediate the antibody responses of CDG, while the TNFR2+ cDC2 generate Th1/17 responses. Mechanistically, immature TNFR2− cDC2 activate monocyte-derived DCs (moDCs), which do not take up intranasally administered CDG. moDCs promote CDG-induced generation of T follicular helper- and germinal center B cells in the lungs. Our data revealed a previously undescribed in vivo mode of DCs action, whereby an immature lung TNFR2− cDC2 subpopulation directs the non-migratory moDCs to generate CDG mucosal responses in the lung.

MHC class II regulates B cell activation, proliferation, and differentiation during cognate B cell-T cell interaction. This is, in part, due to the MHC class II signaling in B cells. Activation of MHC Class II in human B cells or "primed" murine B cells leads to tyrosine phosphorylation, calcium mobilization, AKT, ERK, JNK activation. In addition, crosslinking MHC class II with monoclonal Abs kill malignant human B cells. Several humanized anti-HLA-DR/MHC class II monoclonal Abs entered clinical trials for lymphoma/leukemia and MHC class II-expressing melanomas. Mechanistically, MHC class II is associated with a wealth of transmembrane proteins including the B cell-specific signaling proteins CD79a/b, CD19 and a group of four-transmembrane proteins including tetraspanins and the apoptotic protein MPYS/STING. Furthermore, MHC class II signals are compartmentalized in the tetraspanin-enriched microdomains. In this review, we discuss our current understanding of MHC class II signaling in B cells focusing on its physiological significance and the therapeutic potential.

Hepatitis C virus (HCV) assembles its replication complex on cytosolic membrane vesicles often clustered in a membranous web (MW). During infection, HCV NS5A protein activates PI4KIIIα enzyme, causing massive production and redistribution of phosphatidylinositol 4-phosphate (PI4P) lipid to the replication complex. However, the role of PI4P in the HCV life cycle is not well understood. We postulated that PI4P recruits host effectors to modulate HCV genome replication or virus particle production. To test this hypothesis, we generated cell lines for doxycycline-inducible expression of short hairpin RNAs (shRNAs) targeting the PI4P effector, four-phosphate adaptor protein 2 (FAPP2). FAPP2 depletion attenuated HCV infectivity and impeded HCV RNA synthesis. Indeed, FAPP2 has two functional lipid-binding domains specific for PI4P and glycosphingolipids. While expression of the PI4P-binding mutant protein was expected to inhibit HCV replication, a marked drop in replication efficiency was observed unexpectedly with the glycosphingolipid-binding mutant protein. These data suggest that both domains are crucial for the role of FAPP2 in HCV genome replication. We also found that HCV significantly increases the level of some glycosphingolipids, whereas adding these lipids to FAPP2-depleted cells partially rescued replication, further arguing for the importance of glycosphingolipids in HCV RNA synthesis. Interestingly, FAPP2 is redistributed to the replication complex (RC) characterized by HCV NS5A, NS4B, or double-stranded RNA (dsRNA) foci. Additionally, FAPP2 depletion disrupts the RC and alters the colocalization of HCV replicase proteins. Altogether, our study implies that HCV coopts FAPP2 for virus genome replication via PI4P binding and glycosphingolipid transport to the HCV RC. IMPORTANCE Like most viruses with a positive-sense RNA genome, HCV replicates its RNA on remodeled host membranes composed of lipids hijacked from various internal membrane compartments. During infection, HCV induces massive production and retargeting of the PI4P lipid to its replication complex. However, the role of PI4P in HCV replication is not well understood. In this study, we have shown that FAPP2, a PI4P effector and glycosphingolipid-binding protein, is recruited to the HCV replication complex and is required for HCV genome replication and replication complex formation. More importantly, this study demonstrates, for the first time, the crucial role of glycosphingolipids in the HCV life cycle and suggests a link between PI4P and glycosphingolipids in HCV genome replication.