Up Regulated During Skeletal Muscle Growth Protein 5 (USMG5)

The hepatitis C virus (HCV) F protein is a recently described, frameshift product of HCV core encoding sequence of genotype 1a. Its function and antigenic properties are unknown. To exclude a potential cross-reaction of anti-F antibodies with anti-core antibodies, a specific enzyme-linked immunosorbent assay was performed for anti-core antibodies.  The prevalence of anti-F antibodies did not correlate with HCV RNA serum level, genotype, or stage of liver disease. Sequence analysis from 8 anti-F-positive and 5 anti-F-negative serum samples did not reveal any particular difference potentially accounting for their respective anti-F responses. In conclusion, the F protein elicits specific antibodies in 62% of individuals chronically infected with HCV; such anti-F response does not seem to be affected by the F sequence heterogeneity.