Microbiological Assessment and Evaluation of Yellow Fever Virus Vaccine Strain 17D Yield in Germ-Free Chicken Eggs

Abstract Internal microbial contamination of specific pathogen-free (SPF) eggs results in batches of vaccines being rejected and negatively impacts vaccine yield. Thus, increasing viral yield will have major implications for vaccine manufacturers. In this context, we analysed the microbiological contents of Germ-Free (GF) eggs and evaluated the yield of Yellow Fever virus vaccine strain 17D (YFV-17D) in GF eggs when compared with SPF eggs from 2 different suppliers. Chick Embryo Fibroblast (CEF) cells were generated from GF and SPF eggs and infected with YFV-17D to quantify the interferon beta (IFN-β) antiviral response.The batch viral yield from GF eggs was 18 fold and 1350 fold higher than that from SPF supplier #1 and SPF supplier #2 respectively. The IFN-β antiviral response of GF-derived CEF cells was 1.6–4.7 fold lower than SPF supplier 1-derived and 1.9–5.1 fold lower than SPF supplier 2-derived CEF cells.In conclusion, the contents of the GF eggs were sterile, the yield of YFV-17D was significantly higher in GF eggs than in SPF eggs, and the higher yield was associated with a significant reduction in IFN-β levels.