|KHONGPHINITBUNJONG, KITIPHONG - Chiang Mai University|
|De Guzman, Lilia|
|Chen, Yanping - Judy|
|CHANTAWANNAKUL, PANUWAN - Chiang Mai University|
Submitted to: Journal of Insect Physiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/11/2014
Publication Date: 11/29/2014
Citation: Khongphinitbunjong, K., De Guzman, L.I., Tarver, M.R., Rinderer, T.E., Chen, Y., Chantawannakul, P. 2014. Differential viral levels and immune gene expression in three stocks of Apis mellifera induced by different numbers of Varroa destructor. Journal of Insect Physiology. 72:28-34.
Interpretive Summary: Different stocks of honey bees vary in their ability to resist Varroa mites, which are vectors of the pathogenic Deformed wing virus in honey bees. However, differences in the immunosuppression among honey bee stocks have not been studied. We compared the viral levels and immune responses of Italian honey bees (IHB), Russian honey bees (RHB) and an outcross of Varroa Sensitive Hygienic bees (POL) deliberately infested with one or two foundress Varroa. We found a significant increase in the viral load of POL as compared to RHB and IHB. Also, pupae infested with two foundress Varroa mites had higher virus levels than those with only one foundress. The presence of nymphs did not increase viral levels in the honey bee hosts. Sixteen out of the 24 immunity related genes evaluated showed significant differential expression among stocks. Regardless of honey bee stocks, only Defensin, Dscam, PPOact and Spaetzle were altered by the number of feeding foundress Varroa and levels of DWV. This is the first report on the immune response profiles of different honey bee stocks parasitized by Varroa mites.
Technical Abstract: The viral levels and immune responses of Italian honey bees (IHB), Russian honey bees (RHB) and an outcross of Varroa Sensitive Hygienic bees (POL) deliberately infested with one or two foundress Varroa were compared. We found that the viral load in POL inoculated with one or two foundress Varroa increased to about 5- or 7-fold the levels of their uninfested brood. In contrast, RHB (2- or 4-fold) and IHB (3- or 5-fold) supported a lower increase in viral loads. The feeding of different stages of Varroa nymphs did not increase DWV levels of their pupal hosts. Analyses of their corresponding Varroa mites showed the same trends: two foundress Varroa yielded higher DWV levels than one foundress, and the addition of nymphs did not increase viral levels. Using the same pupae examined for the presence of viruses, 16 out of 24 genes evaluated showed significant differential mRNA expression levels among the three honey bee stocks. However, only four genes (Defensin, Dscam, PPOact and Spaetzle), which were expressed at similar levels in uninfested pupae, were altered by the number of feeding foundress Varroa and levels of DWV regardless of stocks. This research provides the first evidence that immune response profiles of different honey bee stocks are induced by Varroa parasitism.