Research Note: Anti-inflammatory effects and antiviral activities of baicalein and chlorogenic acid against infectious bursal disease virus in embryonic eggs.

The purpose of this study was to investigate if baicalein and chlorogenic acid could inhibit the inflammatory responses induced by and protect against infectious bursal disease virus (IBDV) in chicken embryonic eggs. Nine-day-old embryonated chicken eggs were randomly divided into 3 groups of 50 eggs per group: 1) treatment with varying concentrations of baicalein, 2) treatment with varying concentrations of chlorogenic acid, or 3) left untreated as a control. Forty-eight hours after hatching, each group was inoculated with a very virulent IBDV isolate, and the survival of the embryo was monitored daily until the embryonic livers were collected 72 h after inoculation. After IBDV infection, the viral loads in the embryonic livers were evaluated using qRT-PCR, and the hepatic content of inflammatory mediators, such as histamine, interleukin 1ß (IL-1ß), tumor necrosis factor alpha (TNF-α), and nuclear factor-kappa B (NF-κB), were examined. Significant antiviral potential was demonstrated at concentrations of 108 and 215 µg/egg of baicalein and chlorogenic acid, respectively. We observed a concentration-dependent response in the antiviral properties of these chemicals. Treating the embryos with baicalein and chlorogenic acid significantly reduced histamine production. Moreover, pretreatment with baicalein and chlorogenic acid significantly inhibited NF-κB activation, and this inhibited the subsequent production of the proinflammatory cytokines TNF-α and IL-1ß in the context of IBDV infection. These findings suggest that baicalein and chlorogenic acid have anti-IBDV properties, and they may be useful in the prevention of inflammation-related diseases.

Histamine levels in embryonic chicken livers infected with very virulent infectious bursal disease virus.

Histamine is an endogenous nitrogenous compound with extensive effects on immunologic cells and involved in many physiological functions. The current aim was to determine histamine levels in embryonic liver and its association with the pathogenicity of a very virulent infectious bursal disease virus (vvIBDV) isolate serially passaged in chicken embryos. A vvIBDV isolate and the passaged viruses were inoculated into SPF embryonated chicken eggs (0.2 ml per egg) via the chorioallantoic membrane. Embryonic livers were collected at 24, 48, 72, 96, and 120 h post-inoculation and histamine contents were quantified by fluorescence spectrophotometry analyses. Results showed that the histamine content in embryonic livers infected with the original vvIBDV isolate and the early passaged viruses significantly increased 48 h post-inoculation, as compared with the adapted IBDV isolate (p<0.01) and controls (p<0.01), with the concentration peaking from 72 h to 96 h. Most of the infected chicken embryos died from 48 h to 96 h post-inoculation. Moreover, the histamine content in dead embryos was markedly increased compared with live embryos (p<0.05), peaking at 72 h post-inoculation (p<0.01). There was an association between histamine content in embryonic livers and an elevation in histidine decarboxylase activity. Taken together, our results suggest that an excess of histamine correlates with inflammatory responses during vvIBDV infection. This study provides an incremental step in the understanding of the pathogenesis of vvIBDV.