PfRH1 has been shown to bind erythrocytes in a sialic acid dependent, trypsin resistant, chymotrypsin resistant manner [11], [21], [22].
However, in addition a 65 kDa processed fragment of EBA-175 has also been reported to bind erythrocytes in a sialic acid independent manner [39].
On the other hand, the smaller 80 kDa processed fragment of PfRH2a/b was observed to bind erythrocytes in a sialic acid dependent, trypsin resistant, chymotrypsin sensitive manner.
Interestingly, we found that the smaller 80 kDa PfRH2a/2b fragment is processed from the larger 220 kDa fragment and binds erythrocytes in a sialic acid dependent, trypsin resistant and chymotrypsin sensitive manner.
The PfRH1 protein of the RH family has been shown to bind erythrocytes in a sialic-acid-dependent manner [7].
These include interactions mediated by three erythrocyte-binding antigen proteins of the parasite, which bind to erythrocytes in a sialic acid-dependent manner.
Our observations are similar to the case of erythrocyte binding of EBA-175 which has been shown to bind Glycophorin A in a sialic acid dependent manner [8], [31].
PfRh1 binds to erythrocytes in a sialic acid-dependent manner as this interaction is sensitive to neuraminidase-treatment of the host cell and the properties of the receptor have been defined although it has yet to be identified and is currently called 'Y' (Rayner et al., 2001; Gao et al., 2008).
Thus, PfRH5 binds to RBCs in a sialic-acid-independent fashion, similar to PfRH4 but unlike PfRH1.
The PfRH4 recombinant protein, rPfRH430, has been reported earlier to bind erythrocytes in sialic acid independent (neuraminidase resistant), trypsin and chymotrypsin sensitive manner [23], [24].
