Therefore, in absence of dietary zinc supplementation, S-HBsAg and M-HBsAg proteins, but not L-HBsAg envelope protein, are expressed, resulting in high serum levels of HBsAg (based on HBsAg ELISA, data not shown) with very low hepatocellular retention, similar to the human infection. This evidence concerns the gene ERVW-1 and infection.