Anti-Viral Properties: Proteins, peptides and polysaccharopeptides from mushrooms have been reported to be capable of inhibiting human immunodeficiency virus type 1 (HIV-1) reverse transcriptase and protease, the two enzymes of paramount importance to the life cycle of the HIV. Inhibitory effects on hepatitis B and herpes simplex virus type I have also been reported.

Antiviral mushrooms

Lectins from Agaricus bisporus, Phaseolus vulgaris, Momordica charantia, Ricinus communis and its constituent chains have been shown to inhibit human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (Wang and Ng, 2001). A ubiquitin-like protein from Pleurotus ostreatus has also been shown to have inhibitory activity toward HIV-1 reverse transcriptase, which could be enhanced by succinylation  (Wang and Ng, 2000).

A polysaccharopeptide from the Turkey Tail fungus Trametes (Coriolus) versicolor has been reported to be capable of inhibiting human immunodeficiency virus type 1 (HIV-1) reverse transcriptase and protease, the two enzymes of paramount importance to the life cycle of the HIV. The polysaccharopeptide inhibited other proteases including trypsin, chymotrypsin, proteinase K, subtilisin, and elastase to a lesser extent. The anti-HIV enzyme and immuno-stimulatory activities of the mushroom polysaccharopeptide make it an interesting potential candidate for the therapeutic treatment of AIDS (Tzi et al., 2006), although clearly further studies are required to confirm such effects. Anti-HIV-1 protease activity has also been reported of lanostane triterpenes from Ganoderma colossum(El Dine et al., 2008) and from Ganoderma sinense(Sato et al., 2009), while nebrodeolysin from Pleurotus nebrodensis has also been shown to possess anti-HIV-1 activity in vitro(Lv et al., 2009). Lanostane triterpenoids from Phellinus igniarius have been reported to mediate their effects via inhibitory effects of inducible nitric oxide synthase (Wang et al., 2009).

A fraction extracted from Grifola frondosa (Maitake, GF-D) and its combination with human interferon alpha-2b (IFN) has been investigated for an inhibitory effect on hepatitis B virus (HBV) in HepG2 2.2.15 cells (2.2.15 cells). In combination with GF-D, the anti-viral activity for IFN was increased 9-fold suggesting that the Grifola frondosa extract, in combination with human interferon alpha-2b, might provide a potentially effective therapy against chronic hepatitis B virus infections (Gu et al., 2006).

A further study by the same group has reported the purification of an anti-viral protein from an extract of Grifola frondosa (Maitake) fruiting bodies. The protein inhibited herpes simplex virus type 1 (HSV-1) replication in vitro with an IC50 value of 4.1mg/ml. Topical administration of the protein to the mouse cornea resulted in a significant decrease in virus production. It was reported that the protein directly inactivated HSV-1 while simultaneously inhibiting HSV-1 penetration into Vero cells. The N (amino)-terminal sequence of the protein consisted of an 11 amino acid peptide, NH2-REQDNAPCGLN-COOH that did not match any known amino acid sequences, indicating that the protein is likely to be a novel anti-viral protein (Gu et al., 2007).

Anti-tubercular activity and an inhibitory effect on Epstein-Barr virus activation of sterols and polyisoprenepolyols from an edible mushroom, Hypsizigus marmoreus (Buna-shimeji) have been reported. Seven sterols and eight polyisoprenepolyols, isolated from the non-saponifiable lipid fraction of the dichloromethane extract of Hypsizigus marmoreus, have been tested for their anti­tubercular activity against Mycobacterium tuberculosis strain H37Rv using the Microplate Alamar Blue Assay (MABA). Six of the sterols and two of the polyisoprenepolyols showed a minimum inhibitory concentration (MIC) in the range of 1-51mg/ml, while the others were inactive. The seven sterols and three polyisoprenepolyols were further evaluated for their inhibitory effects on Epstein-Barr virus early antigen (EBV-EA) activation induced by the tumour promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) in Raji cells. Two of the sterols showed a potent inhibitory effects while preserving the high viability of the Raji cells (Akihisa et al., 2005).

Isolated polysaccharides (PLS) from the fruiting body of Agaricus brasiliensis (previously named Agaricus blazei ss Heinem), also known as the sun mushroom, have been shown to have anti-viral activity and were more effective when added during poliovirus infection. The extracts had little effect on reducing viral adsorption and did not show any virucidal effect, suggesting that they may act at the initial stage of the replication of poliovirus (Faccin et al., 2007).

Anti-viral activities of Agaricus blazei Murill have been demonstrated against cytopathic effects induced by western equine encephalitis (WEE) virus by the mycelial fractions but not those of fruiting bodies (Sorimachi et al., 2001).

The effects of a mushroom-derived active hexose correlated compound (AHCC) on the immune response to influenza A virus (H1N1, PR8) infection have been shown to be dose dependent and low-dose AHCC supplementation improved the response to influenza infection despite no effect on total NK cell cytotoxicity (Nogusa et al., 2009).

An inhibitory effect of conditioned medium (CM) from P338D1 (D1) cells, a murine macrophage cell line, stimulated for 10 h with extracts from the fruiting bodies of Grifola frondosa (ME) or its ultrafiltration fractions (MFs), has been reported on the growth of influenza A/Aichi/2/68 virus in Madin-Darby canine kidney cells. Direct addition of ME and 3 fractions of MFs to the infected cells had no obvious inhibitory effect. However, virus yields were reduced in the presence of CMs, with. RT-PCR and ELISA assays showing that the CMs could induce the expression of TNF-a mRNA in D1 cells leading to production of TNF-a, known as an anti-viral cytokine. These findings suggest that ME and MFs might induce the production of certain factors, including TNF-a , which are responsible for the inhibition of viral growth in vitro(Obi et al., 2008).

Extracts of mycelia derived from Phellinus linteus have recently been tested as adjuvants for intranasal influenza vaccine. The adjuvant effects of extracts of mycelia were examined by intranasal co-administration of the extracts and inactivated A/PR8 (H1N1) influenza virus hemagglutinin (HA) vaccine in BALB/c mice. The mycelial extract-adjuvanted vaccines were shown to confer cross-protection against variant H5N1 influenza viruses (Ichinohe et al., 2010).