Serotype-specific antibodies to pneumococcal capsular polysaccharide (PPS) are a critical component of vaccine-mediated immunity to Streptococcus pneumoniae. In this study, we investigated the in vitro opsonophagocytic activities of three PPS-specific mouse immunoglobulin G1 monoclonal antibodies (MAbs), 1E2, 5F6, and 7A9, and determined their in vivo efficacies against intranasal challenge with WU2, a serotype 3 pneumococcal strain, in normal and immunodeficient mice. The MAbs had different in vitro activities in a pneumococcal killing assay: 7A9 enhanced killing by mouse neutrophils and J774 cells in the presence of a complement source, whereas 5F6 promoted killing in the absence, but not the presence, of complement, and 1E2 did not promote killing under any conditions. Nonetheless, all three MAbs protected normal and complement component 3-deficient mice from a lethal intranasal challenge with WU2 in passive-immunization experiments in which 10 g of the MAbs were administered intraperitoneally before intranasal challenge. In contrast, only 1E2 protected Fc␥ receptor IIB knockout (Fc␥RIIB KO) mice and mice that were depleted of neutrophils with the MAb RB6, whereas 7A9 and 5F6 required neutrophils and Fc␥RIIB to mediate protection. Conversely, 7A9 and 5F6 protected Fc␥R KO mice, but 1E2 did not. Hence, the efficacy of 1E2 required an activating Fc␥R(s), whereas 5F6 and 7A9 required the inhibitory Fc␥R (Fc␥RIIB). Taken together, our data demonstrate that both MAbs that do and do not promote pneumococcal killing in vitro can mediate protection in vivo, although their efficacies depend on different host receptors and/or components.

Pyroptosis is a type of programmed cell death, which has been associated with multiple inflammatory diseases including diabetic atherosclerosis (DA). This study aims to explore the role of sinapic acid (SA) in the pyroptosis of macrophages in DA. Our results from the in vivo experiments showed that low-dose (≤50 mg/kg) chronic SA administration suppressed serum endothelin 1 (ET-1) and interleukin-1β (IL-1β) contents, pyroptotic death of bone marrow-derived macrophages, and the expression of pyroptotic proteins ASC, NRLP3, and caspase-1. Besides, lncRNA-metastasis associated lung adenocarcinoma transcript 1 (MALAT1) was robustly upregulated in the macrophages of rats with DA and could be lowered by low-dose SA administration. Gene overexpression and knockdown experiments showed that MALAT1 had a modestly positive effect on the pyroptosis of normal macrophages. Moreover, in macrophages incubated with high-glucose and Ox-LDL, 1-μM SA treatment displayed a suppressive effect on the cell pyroptosis similar to that of MALAT1 knockdown. Transfection of the pcDNA-MALAT1 expression vector counteracted the decrease in MALAT1 expression and macrophage pyroptosis caused by SA. In conclusion, low-dose SA can abate the pyroptosis of macrophages by downregulation of lncRNA-MALAT1 in rats with DA.

Four groups of juvenile Megalobrama amblycephala were fed three times daily with six semi-purified diets containing 3.39 (PA unsupplied diet), 10.54, 19.28, 31.04, 48.38 and 59.72 mg kg-1 calcium D-pantothenate. The results showed that survival rate, final weight, specific growth rate, protein efficiency ratio and nitrogen retention efficiency all increased significantly (P<0.01) as dietary PA levels increased from 3.39 to 19.28 mg kg-1, whereas the opposite was true for feed conversion ratio. Whole-body crude protein increased as dietary PA levels increased, while the opposite pattern was found for the crude lipid content. Intestinal α-amylase, lipase, protease, Na+-K+-ATPase, alkaline phosphatase and gamma-glutamyl transferase activities were all elevated in fish fed PA-supplemented diets. Hepatic catalase activities improved with increases in dietary PA, while the opposite was true for malondialdehyde contents. The liver PA concentration and coenzyme A content rose significantly (P<0.01), up to 31.04 mg kg-1, with increasing dietary PA levels and then plateaued. The percentage of hepatic saturated fatty acids increased significantly (P<0.01) as dietary PA levels increased, while the percentages of monounsaturated fatty acids and polyunsaturated fatty acid (PUFA) decreased as dietary PA increased. Fish fed diets containing 19.28 and 31.04 mg kg-1 PA exhibited higher (P<0.01) docosahexaenoic acid and PUFA percentages in muscle than those fed with other diets. The expression of the gene encoding pantothenate kinase was significantly up-regulated (P<0.01) in fish fed PA-supplemented diets. Hepatic Acetyl-CoA carboxylase α, fatty acid synthetase, stearoyl regulatory element-binding protein 1 and X receptor α genes all increased significantly (P<0.01) as dietary PA levels increased from 3.39 to 31.04 mg kg-1. Based on broken-line regression analyses of weight gain, liver CoA concentrations and PA contents against dietary PA levels, the optimal dietary PA requirements of juvenile blunt snout bream were estimated to be 24.08 mg kg-1.

Despite the success of the pneumococcal conjugate vaccine, pneumococcal pneumonia remains a significant clinical problem, and there is still much to learn about natural resistance and cellular immunity to pneumococcus. We investigated the role of T lymphocytes in resistance to serotype (ST) 3 Streptococcus pneumoniae in an intranasal infection model in C57BL/6 (wild-type [Wt]) and CD8+ (CD8−/−)- and CD4+ (MHC class II−/−)-deficient mice. CD8−/− mice exhibited significantly more bacterial dissemination and lung inflammation and a significantly more lethal phenotype than Wt mice. However, there was no difference in the bacterial dissemination, lung inflammation, or survival of Wt and MHC class II−/− mice. Perforin (Pfn)−/− and IFN-γ−/− mice, which were used to dissect the role of CD8+ T cells in our model, also exhibited a more lethal survival phenotype than Wt mice. Comparison of lung chemokine/cytokine levels by Luminex and cellular recruitment by FACS in Wt mice and knockout strains revealed that CD8−/− and IFN-γ−/− mice, which had the most lethal survival phenotype, had more CD4+IL-17+ T (Th17) cells, IL-17, neutrophil chemoattractants, and lung neutrophils, and fewer regulatory T cells than Wt mice. CD4+ T cell depletion improved the survival of ST-infected CD8−/− mice, and survival studies in Th17-deficient mice revealed that the Th17 response was dispensable for ST3 resistance in our model. Taken together, these findings demonstrate that CD8+ cells are required, but CD4+ T cells are dispensable for resistance to ST3 pneumonia in mice and suggest a previously unsuspected role for CD8+ cells in modulating the inflammatory response to ST3.