Identification of an antiviral principle in Spirulina platensis against Bombyx mori Nuclear Polyhedrosis Virus (BmNPV)

Virus diseases in Bombyx mori, particularly the Nuclear Polyhedrosis Virus (NPV) account for 70-80% of the total loss and thus pose a major problem in sericulture. The NPV is characterized by having distinctive inclusion bodies either polyhedral or capsular in size, in which several virus particules are embedded. Spirulina has been found to inhibit the viral replication and strengthen both the cellular and humoral arms of the immune system. In the present study, S. platensis at various concentrations. viz, 2, 4, 6, 8, 10, 12, 14, 16, 18 and 20% were given to the third instar silkworm larvae by leaf dip method, as a feed supplement along with BmNPV. A separate control (larvae fed with BmNPV alone) was maintained. The results showed that the silkworm fed with S. platensis at 10% concentration showed 90% resistance to BmNPV. This resistance was found to be due to an antiviral protein in fraction IV (60-80%) of molecular weight 29 kDa. The protein fraction was purified by HPLC and collected separately. An antibody was raised against this protein in rabbit. Western blotting, along with other serological techniques like agglutination test and precipitation test were conducted to confirm the result.