Haemagglutination inhibition (HI) and virus neutralization (VN) titers in hen sera and egg yolks.

ND: Not done.
NA: Not available.
* A/PR/8/34 (PR8).
** A/Vietnam/1203/2004 (VN/1203 – H1N1).
*** A/Aquatic bird/Korea/W81/2005 (H5N2).
▴Mean and SEM of log2 titers.
Two hens were immunized with heat inactivated PR8 (as described in Materials and Methods) and IgY was pooled from 15 collected eggs. Sera of hens raised in Vietnam farms were tested individually (10 samples in each batch) and IgY was pooled from 10 eggs in each batch. If not otherwise indicated A/ck/Scotland/59 (H5N1) was used for H5 virus-specific HI titration. Sera from two unimmunized hens and IgY pooled from 10 eggs obtained in Korea were used as negative control. Titers of VN antibody were determined as the reciprocal of the highest dilution of specimens that neutralized 100 pfu or TCID50 of virus in MDCK cell cultures.