الفهرس 
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Abstract
The present study was carried out to declare availability and valuation of in-vitro potency assay (relative potency) of commercial inactivated Newcastle Disease Virus (NDV) oil–adjuvant vaccines throughout quantification of NDV antigen in aqueous phases extracted with isopropyl myristate from samples of 47 batches of 20 different manufacturers by validated Haemagglutination (HA) test and developed Indirect Liquid Phase Blocking (LPB)-ELISA. The obtained results demonstrated that the viral antigen was retrieved successfully from 12 out of the 27 test vaccines (44 %) as measured by HA test and indirect LPB-ELISA; the NDV antigen-HA units per dose ranged between >4128 and 716, and its correlative indirect LPB-ELISA units per dose ranged between >356 and 30 were recorded by the 12 vaccines.
There was an absolute correlation between HA titers and indirect LPB-ELISA titers in log2 scored by the 47 batches (R2= 0.924). Therefore, the estimated protective NDV antigen ELISA cut-off value was 28 units per dose.
To verify the efficiency of the used extraction method in the 15 test batches which given HAUs scores below the cut-off value. In-vivo potency assays results revealed that only one batch of the 13 batches was impotent; chickens vaccinated with that batches developed GMT of HI antibodies of 4.9, no correlation at all between HA titer exhibited by the aqueous extracts of the 11 batches and its in-vivo potency assay results.
In conclusion, in-vitro potency assay by quantification of NDV antigen in aqueous extracts of at least three containers of the test vaccine with a validated HA test or indirect LPB-ELISA and requirement of mean NDV antigen HAUs/dose not less than 500 or its equivalent NDV antigen ELISA units, and if HA or ELISA units per dose is not satisfactory, in-vivo potency assay must be performed.