TRYPANOSOMA-BRUCEI-RHODESIENSE - USE OF AN ANTIGEN-DETECTION ENZYME-IMMUNOASSAY FOR EVALUATION OF RESPONSE TO CHEMOTHERAPY IN INFECTED VERVET MONKEYS (CERCOPITHECUS-AETHIOPS)
Cw. Gichuki et al., TRYPANOSOMA-BRUCEI-RHODESIENSE - USE OF AN ANTIGEN-DETECTION ENZYME-IMMUNOASSAY FOR EVALUATION OF RESPONSE TO CHEMOTHERAPY IN INFECTED VERVET MONKEYS (CERCOPITHECUS-AETHIOPS), Tropical medicine and parasitology, 45(3), 1994, pp. 237-242
Thirty eight Trypanosoma brucei rhodesiense-infected vervet monkeys (C
ercopithecus aethiops) in the late (meningoencephalitic) stage of dise
ase, treated with various trypanocidal drugs, were monitored for a per
iod of more than 600 days to assess the rate of clearance of trypanoso
me antigens from serum and cerebrospinal fluid (CSF). There was a comp
lete but gradual reduction in antigen titres, as assessed by ELISA, in
animals treated intravenously with melarsoprol, the standard drug for
the late stage disease. In 8 of the 9 monkeys treated with melarsopro
l, the antigen titres, as assessed by optical density values, dropped
by 50% within 252 days (mean value 68 days for antigens in CSF and 116
for serum) following treatment. The remaining animal in this group, t
hat displayed persistent antigenaemia, had been treated with a sub-cur
ative drug dosage level. Thus, if time to 50% reduction in antigen lev
els were to be taken as an index to predict cure, the follow-up period
after melarsoprol treatment could have been reduced from 600 to 252 d
ays for 8 of the 9 animals, leaving only one animal for further follow
up. The animals treated with experimental drug combinations displayed
a variable picture: Five monkeys showed a persistence of antigens in
both serum and CSF throughout the observation period, suggesting failu
re of the drugs to cure the infection. Parasitologically confirmed rel
apse of the infection was indeed observed in all the five monkeys. In
some monkeys, the parasite antigens eventually cleared from serum and
CSF completely, but this took a longer time duration than in the melar
soprol treated animals; others showed persistence of parasite antigens
in serum, but the parasites were not detected in blood or CSF through
out the entire follow-up period. These results suggest that the experi
mental drug combinations used were not effective in clearing the paras
ites from cryptic foci and hence the persistence of antigens in serum
and/or CSF. Antigen ELISA would, thus, appear to be a useful tool for
evaluation of response to chemotherapy.