Immune depression in Rhodnius prolixus by seco-steroids, physalins.
A comparative study of the effects of physalins, seco-steroidal substances of Physalis angulata (Solanaceae), on the immune reactions of R. prolixus was carried out. Ecdysis and mortality were not affected by treatment with physalins B, D, F or G (1-10 microg/ml of blood meal). R. prolixus larvae fed with blood containing physalins and inoculated with 1 microl of Enterobacter cloacae beta12 (5 x 10(3)/insect) exhibited mortality rates three times higher than controls. The insects treated with physalin B, and F (1 microg/ml) and inoculated with E. cloacae beta12 showed significant differences on lysozyme activity in the hemolymph compared to untreated insects. Furthermore, physalin D (1 microg/ml) significantly reduced the antibacterial activity. Concerning cellular immune reactions, all insects treated with physalins (1 microg/ml), exhibited drastic reductions in the quantity of yeast cell-hemocyte binding and subsequent internalization. Insects inoculated with bacteria and treated with physalins B, F and G showed reductions of microaggregate formation but physalin D did not. Physalins B and F also reduced total hemocyte count in the hemolymph. These results suggest that, in different ways, probably due to their different chemical structures, physalin B, D, F and G are immunomodulatory substances for the bloodsucking insect, R. prolixus.
Castro
D P
DP
Laboratório de Bioquímica e Fisiologia de Insetos, Instituto Oswaldo Cruz , Fundação Oswaldo Cruz, Av. Brasil 4365, Rio de Janeiro, RJ 21045900, Brazil.
Figueiredo
M B
MB
Ribeiro
I M
IM
Tomassini
T C B
TC
Azambuja
P
P
Garcia
E S
ES
D000818:Animals; D004754:Enterobacter / Q000276:immunology; D004756:Enterobacteriaceae Infections / Q000276:immunology; D006434:Hemocytes / Q000187:drug effects*; D054884:Host-Pathogen Interactions / Q000187:drug effects / Q000276:immunology; D009113:Muramidase / Q000378:metabolism*; D010587:Phagocytosis / Q000187:drug effects*; D012239:Rhodnius / Q000187:drug effects* / Q000382:microbiology / Q000502:physiology; D012632:Secosteroids / Q000494:pharmacology*
D012632:Secosteroids; D009113:Muramidase