Experimental evidence that immune trypanolysis using the LiTat 1.3 and LiTat 1.5 variant antigen types is not specific to Trypanosoma brucei gambiense in pigs

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Résumé

In the context of the human African trypanosomiasis elimination process, reliable and accurate diagnostic
tools are crucial for exploring the role of a potential animal reservoir of Trypanosoma brucei gambiense. The immune
trypanolysis test (TL) using the variant antigen types (VAT) LiTat 1.3 and LiTat 1.5, described as a specific serological
method to detect people infected by T. b. gambiense, seems to be a promising tool. However, its specificity was recently
questioned during field animal surveys. The present study evaluates the performance of TL during experimental
T. b. brucei infection in pigs. Eight infected pigs and four uninfected pigs were followed up with blood and plasma
collection. Blood was used for parasitological investigation. TL was performed on the plasma with the LiTat 1.3, LiTat
1.5 and LiTat 1.6 VATs. All control pigs remained negative to parasitological investigation and TL. Trypanosomes
were detected in all the infected pigs and the first detection was between 10 and 14 days post infection (dpi). TL results
showed that infected pigs developed antibodies against the three VATs. The first antibody detections by TL occurred
between 14 and 21 dpi for antibodies directed against LiTat 1.6, 21 and 168 dpi for antibodies directed against LiTat
1.5 and 70, and 182 dpi for antibodies directed against LiTat 1.3. This study highlights for the first time that TL using
LiTat 1.3 and LiTat 1.5 VATs is not specific to T. b. gambiense. Development of specific diagnostic tools for the detection
of T. b. gambiense infections in animals, especially in pigs, is still needed.

Mots-clés

Trypanosoma brucei, Human African trypanosomiasis, Trypanolysis, Diagnosis, Experimental infection, Pig.