were also used to screen for TT-specific antibodies. After coating, the plates were washed in ELISA wash buffer (PBS, 0.5% Tween-20). A PBS solution containing 4% of milk was used as a blocking agent, before adding serial dilution of HIS mouse plasma (starting at a dilution of 1:5) or cell culture supernatants (starting at a dilution of 1:2). Enzyme-conjugated detection antibodies were added at a dilution of 1:2500 for HRP-conjugated anti-IgG and a dilution of 1:5000 for HRP-conjugated anti-IgM (both from Jackson ImmunoResearch). Then, TMB substrate/stop solution (Biosource) was used for the development of the ELISA assay.