Immunoreactivity of Sera From Low to Moderate Malaria-Endemic Areas Against r48/45 Proteins Produced in and Chinese Hamster Ovary Systems.

P48/45 is a conserved gametocyte antigen involved in parasite fertilization. A recombinant P48/45 (48/45) protein expressed in () was highly antigenic and immunogenic in experimental animals and elicited specific transmission-blocking (TB) antibodies in a previous pilot study. Here, a similar 48/45 gene was expressed in Chinese Hamster Ovary (CHO) cells and we compared its immunoreactivity with the product. Specific antibody titers were determined using plasma from Colombian individuals (n=227) living in endemic areas where both and are prevalent and from Guatemala (n=54) where is highly prevalent. In Colombia, plasma seroprevalence to CHO-48/45 protein was 46.3%, while for -48/45 protein was 36.1% (0.001). In Guatemala, the sero prevalence was 24.1% and 14.8% (0.001), respectively. Reactivity index (RI) against both proteins showed an age-dependent increase. IgG2 was the predominant subclass and the antibody avidity index evaluated by ELISA ranged between 4-6 mol/L. mosquito direct membrane feeding assays (DMFA) performed in presence of study plasmas, displayed significant parasite transmission-blocking (TB), however, there was no direct correlation between antibody titers and oocysts transmission reduction activity (%TRA). Nevertheless, DMFA with CHO 48/45 affinity purified IgG showed a dose response; 90.2% TRA at 100 μg/mL and 71.8% inhibition at 10 μg/mL. In conclusion, the CHO-r48/45 protein was more immunoreactive in most of the malaria endemic places studied, and CHO-r48/45 specific IgG showed functional activity, supporting further testing of the protein vaccine potential.