LAUSR

Background: High rates of breakthrough rotavirus gastroenteritis have been reported among Aboriginal children living in rural and remote Australia despite receipt of two doses of oral rotavirus vaccine. Histo-blood group antigens (HBGAs) may mediate rotavirus genotype-dependent differences in susceptibility to rotavirus infection and immune responses to rotavirus vaccination. Methods: HBGA phenotype, Lewis and secretor status, was determined by enzyme immunoassay of saliva samples obtained from Australian Aboriginal children who were enrolled at age 6 to < 12 months in a randomised clinical trial of an additional (booster) dose of oral rotavirus vaccine. Participants had received the routine two-dose schedule of oral rotavirus vaccine administered at age 6 weeks and 4 months. Non-secretor phenotype was confirmed by DNA extraction to identify FUT2 G428A mutation. Rotavirus seropositivity was defined as serum anti-rotavirus IgA > 20 AU/mL measured by ELISA on enrolment. Results: Of 156 children, 119 (76%) were secretors, 129 (83%) were Lewis antigen positive, and 105 (67%) were rotavirus IgA seropositive. Eighty-seven of 119 (73%) secretors were rotavirus seropositive, versus 4/9 (44%) weak secretors and 13/27 (48%) non-secretors. Eighty-nine of 129 (69%) Lewis antigen positive children were rotavirus seropositive versus 10 of 19 (53%) of those who were Lewis antigen negative. Conclusions: Most Australian Aboriginal children were secretor and Lewis antigen positive. Non-secretor children were less likely to be seropositive for rotavirus following vaccination, but this phenotype was less common. HBGA status is unlikely to fully explain the underperformance of rotavirus vaccine at a population level among Australian Aboriginal children.