Furthermore, available studies report that fat-soluble and water-soluble vitamins are necessary for correct functioning of the Immune System, and that in patients with different chronic infections, including HBV, HCV and HIV infections, vitamin A, D, E and C deficiency is associated with higher levels of viral replication and with higher titers of inflammatory cytokines, like IL-6 and TNF-α. Here, TNF is linked to HIV infectious disease.