Figure 9: ELISA detection of SARS-CoV – 2 like antibodies in animal samples using modified human Diagnostics Commercial Kit. The assay is a modification of the ELISA test described by Amanat et al, (2020) by replacing the anti-human IgG conjugate antibody with (anti-Llama IgG ). D0 – samples collected before COVID-19 outbreak announcement in Kenya while D8 samples were collected 8 days after the COVID-19 outbreak announcement in the country. The 10% PP cut off: 83 % exposed / cross reacting, 20% PP cut off: 57% exposed
The mean OD absorbance values generated in Figure 9 above were used to calculate the percent positivity scores relative to the absorbance values for the positive control serum. On the basis of the stringent pp threshold of 20%, we found evidence of SARS COV-2 like antibodies in all the three species studied.
The plot in figure 10 enables clearer visual comparisons to be drawn between the results of the analysis of SARS COV-2 like antibody titers based on the crude lysate ELISA and the commercial kit based on the Spike specific RBD antigen. In the figure, the individual camel antibody titers are shown as small white lines in a one-dimensional scatter plot. The estimated density of the distributions of the percent positivity values is visible as a polygon and the average is also shown as a black line. It is clear that the results based on the crude lysate are corroborated by commercial kit ELISA and as already mentioned, the higher pp scores in the crude lysate ELISA relative to the commercial kit could be due to the additional antigens present in the crude lysate.