In vitro trypanocidal effect of sera from Erythrocebus patas (Red patas monkey) and Chlorocebus tantalus (Tantalus monkey) on Trypanosoma brucei brucei Plimmer & Bradford, 1899 and Trypanosoma congolense Broden, 1894

Anti-Trypanosoma brucei brucei and anti-Trypanosoma congolense activities of sera from two species of uninfected zoo-primates, Erythrocebus patas (red patas monkey) and Chlorocebus tantalus (tantalus monkey) were investigated. The sera were screened using thick films and haematocrit centrifugation technique (HCT), to ensure that the donor primates were not infected with trypanosomes. Trypanosoma brucei brucei (Federe strain) and Trypanosoma congolense were suspended in supplemented RPMI (Rossvelt Park Memorial Institute) 1640 medium and the motility of the parasite was used as index of viability after the addition of each test serum. The selected primate sera exhibited some degree of anti-Trypanosoma brucei brucei activities in vitro. Red patas monkey serum had an inhibition index of 0.27, while that of Tantalus monkey was 0.34, against Trypanosoma brucei brucei, with mean survival times of 22.00{+/-}1.73 hours for red patas monkey serum and 19.67{+/-}0.58 hours for tantalus monkey serum, which are significantly lower (P<0.05) than that of the control (30.00{+/-}0.00 hours). The selected primate sera had pronounced inhibitory activities against Trypanosoma congolense. Sera from the two species of primate had very high anti-Trypanosoma congolense activity showing an inhibition index of 0.91 for Red patas monkey serum and 0.90 for Tantalus monkey serum, with marked and significant reduction (P<0.05) in survival time of 7.00{+/-}1.73 hours in Red patas monkey serum and 7.67{+/-}0.58 hours in Tantalus monkey serum, compared with the control (74.00{+/-}1.00 hours). The in vitro anti-trypanosomal activity of the serum samples was shown to be cidal in nature. The activity was not associated with xanthine oxidase. This study revealed that sera from red patas monkey and tantalus monkey had a moderate anti-Trypanosoma brucei brucei activity and a very high anti-Trypanosoma congolense activity in vitro suggesting the presence of some non-specific materials. Authors SummaryThe mechanisms that allow trypanosomiasis-resistant animals to control blood trypanosomes are being investigated, to identify non-specific factors that kill trypanosomes or limit their proliferation, contributing to host resistance. For instance, xanthine oxidase has been isolated and identified as the protein that kills trypanosomes in Cape buffalo. Humans and several other primates are also known to be resistant to infection by several animal-specific trypanosome species. In this study, sera from some zoo primates, red patas monkey and tantalus monkey, tested on Trypanosoma brucei brucei and Trypanosoma congolense in vitro, showed a slight anti-Trypanosoma brucei brucei activity and a very high anti-Trypanosoma congolense activity. These activities were shown to be cidal in nature and not associated with the protein xanthine oxidase. The authors suggest that non-specific factors other than the enzyme xanthine oxidase might have accounted for the sera anti-trypanosomal activities.