Cryptosporidium parvum proteins and peptides involved in strain differentiation and their antigenic characteristics
Sanchez Ingunza, Roxana
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The present study evaluated the differences in protein expression between three Cryptosporidium parvum isolates, and identified C. parvum antigenic proteins and peptides. The C. parvum Iowa (IO), Arizona (AZ), and Moredum (MD) isolates’ protein profiles were compared by two-dimensional difference gel electrophoresis (2D-DIGE), and proteins which were differentially expressed and characterized each isolates were annotated. C. parvum antigenic proteins were determined by one-dimensional and two-dimensional separation of soluble C. parvum proteins coupled with western blot analysis. C. parvum antigenic proteins were recognized by IgG, IgM, IgA in human sera from Cryptosporidium infected individuals. Sera reactivity was compared with that of a group of serum samples from non-infected individuals. Antigenic peptides were predicted and peptides specific for these Cryptosporidium proteins were suggested. C. parvum AZ demonstrated significant difference in the expression of a 36 kDa protein with isoelectric point (pI) of 6.6 and a 43 kDa with pI of 6.36 (p < 0.05) while C. parvum IO showed significant abundance for a 46 kDa protein with pI of 6.91with (p < 0.05) and C. parvum MD for 72 and 78 kDa proteins with pIs of 5.13 and 5.49 (p < 0.1), respectively. Six C. parvum antigenic proteins were significantly recognized by human sera from infected individuals (p < 0.05). The molecular weights for these antigens ranged from 40 to 65 kDa while their isoelectric points ranged from 5.3 to 7.2. A Cryptosporidium serine/threonine phosphatase was identified by Tandem Mass Spectrometry (MS/MS) from those antigenic proteins. This is the first report confirming the existence of a Cryptosporidium serine/threonine phosphatase which is also involved in humoral immune response against cryptosporidiosis. Two Cryptosporidium antigenic peptides predicted from this protein might be able to distinguish C. parvum and C. hominis from other apicomplexans. These antigens should be further evaluated as potential diagnostic targets to control cryptosporidiosis.