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.