Bacteroides-derived isovaleric acid enhances mucosal immunity by facilitating intestinal IgA response in broilers

Background:The interaction between nutrition and immunity plays a vital role in nutrient digestion,absorption,and metabolism during poultry production.Recent studies showed that the gut microbiota contributes to the development of intestinal mucosal immunity.However,the mechanisms by which gut microbes regulate this process remain unclear.Methods:We compared the intestinal mucosal immunity and gut microbiota of Arbor Acre broilers AA(lower mucosal immunity)and Chinese native Wuliang Mountain Black-bone chickens(WLMB)(higher mucosal immunity)using 16S rDNA sequencing,transcriptomic analysis,and immunoglobulin A(IgA)antibody repertoire sequencing.We then combined 16S rDNA sequencing with transcriptomics to identify the key microbes and found that they were positively correlated with IgA production.Next,we transplanted candidate microbes into 1-day-old broiler to explore their role in intestinal mucosal immunity.Finally,we verified the function of candidate microbial metabolites in regulating the immune function of macrophages and the intestinal-epithelial cells(IECs)using in vitro experiments.Results:WLMB performs stronger mucosal immunity than AA,including higher IgA levels,more diverse IgA antibody repertoire,and higher bacterial affinity.Bacteroides was identified as the key microbes related to the intestinal IgA response.Bacteroides transplantation could increase IgA concentration in the duodenal contents by enhancing the expression of IgA,polymeric immunoglobin receptor(PIgR),B cell-activating factor of the TNF family(BAFF),and activation-induced cytidine deaminase(AID)in the duodenum.Additionally,Bacteroides-derived isovaleric acid promoted M2 macrophage polarization of macrophage via mTOR/PPAR-γ/STAT3 signaling pathways and regulated the immunologic function of IECs to produce cytokines,including interleukin(IL)-10,IL-4,BAFF,and transforming growth factor-beta(TGF-β),thus promoting IgA production in B cells by facilitating AID expression.Conclusion:Our study revealed that Bacteroides modulate the intestinal IgA response and maintain gut health in broilers.Bacteroides may be a promising alternative as an immunomodulatory microbial agent for developing nextgeneration probiotics for broiler production.

Neonatal isovaleric acidemia in China: A case report and review of literature

BACKGROUND Isovaleric acidemia(IVA)is a rare autosomal recessive inherited organic acidemia caused by a genetic deficiency of isovaleryl-CoA dehydrogenase(IVD).Its morbidity is low,but mortality is high.There is no effective cure for this disease.Early identification of IVA using clinical features can significantly slow disease progression and reduce mortality.Here we report a Chinese neonate with two mutations of IVD and share valuable information on this disease.CASE SUMMARY A 12-day-old male neonate with“poor response for 1 d and repeated convulsions accompanied by high muscle tension for 6 h”was hospitalized.The patient was the first child of nonconsanguineous ethnic Chinese parents.He was delivered by cesarean section due to breech position at 39+1 wk of gestation with a birth weight of 3.27 kg.Initially,he suffered from dyspnea and rhinobyon,and at 10 d after birth the patient suddenly developed poor feeding,low response,lethargy and seizures.Organic acid analysis of blood and urine by tandem mass spectrometry and gas chromatography mass spectrometry showed extremely high concentrations of isovaleryl glycine.The patient had an acute episode of IVA causing severe metabolic stress and eventually died.CONCLUSION A new case of an IVA patient carrying c.1193G>A(p.Arg398Gln)and c.1208A>G(p.Try403Cys)mutations is reported in China.