Physical and chemical properties of MB strain of infectious bursal disease virus used as commercial vaccine

Subrat Kumar
Department of Virology, PGI, MER
Chandigarh - 16

The "MB" strain of IBD vaccine strain was successfully harvested in chick embryo fibroblast monolayer cells and its physiochemical properties are studied in details. The fifth passaged seed virus having a TCID50 of 10-5.2/0.1ml was subjected to temperature treatment at 41 , 50 and 56 C for 30min in a water bath and transferred to ice bath immediately. All the heat-treated inoculums was subjected to titration, TCID50 of the reference IBDV both exposures to heat at 41 and 50 C were found to be 10-5 and 10-4.9 respectively. It is further noted that exposure to 56 C showed the titer of 10-4.7. This clearly indicated no significant difference of IBDV in exposure to varying temperatures and proved its stability. The above virus was treated with 10% v/v chloroform and titration of TCID50 remained to be 10-5.2 /0.1ml. This clearly indicated the IBDV is resistant to the treatment of chloroform and did not posses any lipid and thus confirming it to be a naked virus. Similarly, 3% formalin treatment did not show any difference of CPE but completely inactivated the virus. This virus was found to be stable at PH 2 to 7.4 but completely inactivated at alkaline PH of 10-12. It is concluded that physicochemical characterization revealed no effect and this vaccine virus remains unaffected in the presence of RNA and confirming it to be lack lipid and so envelope as chloroform did not have any effect on it.

Source : IPSACON-2005

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