Immune depression in Rhodnius prolixus by seco-steroids, physalins

Area of Science:

• Pharmacology
• Immunology
• Entomology

Background:

• Physalis angulata is a plant known for its medicinal properties.
• Physalins are seco-steroidal compounds isolated from Physalis species.
• Rhodnius prolixus (kissing bug) is a vector of Chagas disease.

Purpose of the Study:

• To investigate the immunomodulatory effects of physalins B, D, F, and G on the immune reactions of R. prolixus.
• To determine if physalins affect insect mortality, lysozyme activity, antibacterial activity, and cellular immune responses.

Main Methods:

• R. prolixus larvae were fed blood meals containing varying concentrations of physalins.
• Insects were challenged with Enterobacter cloacae beta12.
• Immune parameters measured included mortality rates, lysozyme activity, antibacterial activity, hemocyte counts, yeast cell-hemocyte binding, and microaggregate formation.

Main Results:

• Physalins did not affect ecdysis or general mortality but increased mortality when insects were challenged with E. cloacae.
• Physalins B and F altered lysozyme activity, while physalin D reduced antibacterial activity.
• Physalins significantly reduced yeast cell-hemocyte binding and internalization, and microaggregate formation (except physalin D).
• Physalins B and F also decreased total hemocyte counts.

Conclusions:

• Physalin B, D, F, and G act as immunomodulatory substances in R. prolixus.
• The observed effects vary depending on the specific physalin, likely due to differences in chemical structure.
• These findings highlight the potential of physalins in modulating insect immunity.