PLOD1 and diphtheria: In a later attempt, the β-subunit of hCG was paired with the α-subunit of ovine LH to produce a heterospecies dimer, which was then linked to tetanus toxoid or to diphtheria toxoid and adsorbed on alum with the sodium pthalyl derivative of lipopolysacaride (SPLPS) as an adjuvant [22].