3.8. Cytokine secretion
The cytokine secretion was important for a vaccine to direct the immune
response. IFN-γ, IFN-β, and TNF-α belonged to Th1-type cytokines, while
IL-5 was considered as a Th2-type cytokine. These cytokines in the cell
supernatants after stimulation with ORF8 were measured by ELISA. As
shown in Fig. 4, the levels of the four cytokines in the ORF8-CRM,
ORF8-PEG and ORF8/AL groups were all higher than the ORF8 group
(P<0.05). The IFN-γ level of the ORF8-PEG group (2675.1 pg/mL)
were higher than that of the ORF8-CRM group (443.8 pg/mL) and comparable
to that of the ORF8/AL group (2649.0 pg/mL). The TNF-α (3221.4 pg/mL)
and IL-5 (17.0 pg/mL) levels of the ORF8-PEG group were higher than
those of the ORF8-CRM and ORF8/AL groups. The IFN-β level of the
ORF8-PEG group (47.9 pg/mL) were higher than that of the ORF8/AL group
(38.2 pg/mL) and comparable to that of the ORF8-CRM group (49.6 pg/mL).
Thus, ORF8-PEG showed high ability to increase the Th1- and Th2-type
immune responses.