Submitted to: Developmental and Comparative Immunology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/9/2009
Publication Date: 6/30/2009
Publication URL: http://dx.doi.org/10.1016/j.dci.2009.06.009
Citation: Terenius, O., Popham, H.J., Shelby, K. 2009. Bacterial, but not Baculoviral Infections Stimulate Hemolin Expression in Noctuid Moths. Developmental and Comparative Immunology. 33:1176-1185. Interpretive Summary: How an insect responds to a bacterial, fungal or viral infection and ultimately survives the infection are questions that need to be answered to develop insect control measures that ultimately outwit an insect’s defense mechanism. A protein called Hemolin has been found to be produced in response to bacteria and virus in several crustaceans and insects and is believed to have a role in protecting these organisms from infection. In this study, Hemolin was identified and sequenced from the budworm, Heliothis virescens as well as the corn earworm, Helicoverpa zea. Larvae from both species of insect were found to produce more Hemolin when infected with bacteria but not when challenged with virus. These findings will impact scientists working on how an insect resists infection because it demonstrates that the same protein can have a different response in different species which is important information when studying why some infections are fatal while others are not and how the defense machinery of insects can be overcome in the field.
Technical Abstract: Lepidopteran larvae are regularly infected by baculoviruses during feeding on infected plants. The differences in sensitivity to these infections can be substantial, even among closely related species. For example, the noctuids Cotton bollworm (Helicoverpa zea) and Tobacco budworm (Heliothis virescens), which a couple of decades ago were considered to belong to the same genus, have a 1000-fold difference in sensitivity to Autographa californica multiple nucleopolyhedrovirus (AcMNPV) infection. Recent data were interpreted to indicate that the lepidopteran immunoglobulin protein, Hemolin, is activated upon viral injection and therefore to participate in anti-viral responses. To investigate whether Hemolin is activated after a natural virus infection specific transcription in fat bodies and hemocytes of H. zea and H. virescens larvae was monitored following per os infection with the baculovirus HzSNPV (H. zea single nucleopolyhedrovirus). Both moths showed strong Hemolin expression at 24 and 48 hours, which are time points that correspond to viral entry into hemocytes. However, the same expression pattern was seen in uninfected animals and coincided with ecdysone responses, previously known to induce Hemolin expression. In contrast, injection of lyophilized Micrococcus luteus resulted in increased Hemolin expression supporting a role for Hemolin as an immunoresponsive protein in these species. The combined data are consistent with the suggestion that while Hemolin seems to participate in the response to virus infection in the superfamily Bombycoidea, this is not true in the Noctuoidea.