Trypanosoma rangeli: Effects of physalin B on the immune reactions of the infected larvae of Rhodnius prolixus

• Published in: Experimental parasitology 2006, Vol.112 (1), p.37-43
• Main Authors: Garcia, Eloi S., Castro, Daniele P., Ribeiro, Ivone M., Tomassini, Therezinha C.B., Azambuja, Patrícia
• Format: Article
• Language: English
• Subjects: Animals; Biological and medical sciences; Catechol Oxidase - metabolism; Cell Aggregation - drug effects; Cell Count; dose response; Enzyme Activation - drug effects; enzyme activity; Enzyme Precursors - metabolism; Fundamental and applied biological sciences. Psychology; hemocyte microaggregation; Hemocytes; Hemocytes - cytology; Hemocytes - drug effects; immune response; immunomodulators; insect vectors; Lactones - chemistry; Lactones - pharmacology; Larva - drug effects; Larva - immunology; Larva - parasitology; Life cycle. Host-agent relationship. Pathogenesis; Microaggregation; mortality; Nitrates - metabolism; Nitric Oxide; Nitrites - metabolism; Physalin; Physalis angulata; Physalis angulata L; Prophenoloxidase; Protozoa; Rhodnius - drug effects; Rhodnius - immunology; Rhodnius - parasitology; Rhodnius prolixus; Seco-steroids; Secosteroids; Solanaceae; steroids; Steroids - chemistry; Steroids - pharmacology; Trypanosoma - immunology; Trypanosoma rangeli
• ISSN: 0014-4894; 1090-2449
• DOI: 10.1016/j.exppara.2005.09.003

Physalins are seco-steroids obtained from plants of the family Solanaceae. Herein, we tested Physalis angulata L purified physalin B as an immunomodulatory compound in 5th-instar larvae of Rhodnius prolixus, which were systemically infected with the H14 Trypanosoma rangeli strain protozoan. In uninfected insects, the effective concentration of physalin B, which inhibited 50% of the blood ingested (ED 50) volume, was 15.2 ± 1.6 μg/ml of the meal. Ecdysis processes and mortality in uninfected larvae, treated orally with physalin B in concentrations ranging from 1 to 10 μg/ml, was similar to that observed in insects not treated with physalin B. However, R. prolixus larvae previously fed on blood containing 1.0, 0.1, and 0.01 μg of physalin B/ml exhibited mortality rates of 78.1, 54.3, and 12.7%, respectively, 6 days after inoculation of T. rangeli (1 × 10 3 parasites/insect), whereas only 7.2% mortality was observed in the control group, injected with sterile culture medium. The insects treated with physalin B (0.1 μg/ml) and inoculated with T. rangeli did not modify the phenoloxidase (PO) activity and total hemocyte count in the hemolymph. However, physalin B treatment caused a reduction in hemocyte microaggregation and nitric oxide production and enhanced the parasitemia in the hemolymph. These results demonstrate that physalin B from P. angulata is a potent immunomodulatory substance for the bloodsucking insect, R. prolixus.