Another study showed a similar relative bias towards anti-NA seroconversion when mice were primed to N2 with infection with A/Hong Kong/1/68 (an H3N2 strain) and then boosted with purified HA or NA from A/Turkey/Mass/75-A/Aichi/2/68 (an HA-heterotypic H6N2 reassortant strain) [72]. The gene discussed is XK; the disease is infection.