[Background]Aflatoxin B1(AFB1)is a secondary metabolite produced by Aspergillus parasiticus,which is widely found in contaminated food and feed all over the world and is considered one of the major risk factors affecting human and animal health.The swine influenza virus(SIV)is currently one of the most widespread viruses in the world,and its replication is susceptible to environmental and nutritional factors.However,the relationship between AFB1 contamination in feed and SIV infection is not clear.[Objective]The objective of this study was to investigate the effects of AFB1 exposure on SIV replication,organs damage and intestinal microbiota,so as to lay a foundation for the study on the mechanism of mycotoxin poisoning,and also provide a reference for exploring the reasons for the increase in susceptibility to other infectious diseases.[Method]In this study,thirty-two male piglets were randomly divided into 4 groups(8 piglets in each group),the low-pathogenic SIV virus dilution was inoculated on the first and fourth day of the trial,and established a piglet model of SIV infection(the natural host of SIV).AFB1 was freshly diluted daily and and given 0,10,20 and 40 μg·kg-1(feed)AFB1 to piglets for 21 days.The piglets were weighed before feeding at 7,14 and 21 days,respectively,and used a variety of technologies to assess the effects of dietary AFB1 exposure on the weight gain,SIV replication,organs index,autopsy changes,and pathological characteristics,On this basis,the expression of nucleoprotein(NP)of SIV in the lungs were further analyzed by Western blotting and the changes of intestinal microbiota were detected by 16S rRNA,thereby elucidate the effect of AFB1 exposure on SIV infection,organ damage,and intestinal microbiota.[Result]The results showed that piglets exposed to 40 μg·kg-1AFB1 had significantly lower weight gain(P＜0.01),the expression of NP and lung index of SIV were significantly higher(P＜0.01),and the spleen index was significantly lower than those exposed to 0 μg·kg-1AFB1(P＜0.01);The results of autopsy showed severe spleen,liver and lung damage in piglets exposed to 40 μg·kg-1 AFB1;HE-stained also showed similar results,compared with the SIV control group,40 μg·kg-1 AFB1 treatment group showed congestion in the spleen,the red and white pulp were not clear;the liver tissue was hemorrhage,inflammatory cells were infiltrated;the small alveoli of the lungs fused into large alveoli with irregular morphology,the alveolar interstitium was thickened,and the inflammatory cell infiltration was increased;in addition,the intestinal villi were irregularly shaped,the connective tissue was loose,and there was lymphocytic infiltration.The results from 16S rRNA sequencing showed that the exposure to 40 μg·kg-1 AFB1 significantly increased the relative abundance of Actinomycetota and Clostridium in the intestinal tract of piglets,and decreased the abundance of Lactobacillus and Bacteroidetes.[Conclusion]Taken together,our results suggest that AFB1 exposure can reduce the body weight gain,promote SIV replication,aggravated the damage of lung tissue and other organs,and cause intestinal microbiota disorders,which provided a theoretical reference for the study of the toxic mechanism of AFB1.
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