- Bovine leukocyte antigen major histocompatibility complex class II DRB3*2703 and DRB3*1501 alleles are associated with variation in levels of protection against Theileria parva challenge following immunization with the sporozoite p67 antigen. Ballingall, K.T., Luyai, A., Rowlands, G.J., Sales, J., Musoke, A.J., Morzaria, S.P., McKeever, D.J. Infect. Immun. (2004)