Margiotta, Marina (2015) IMMUNOMODULAZIONE DELL'APE E INTERAZIONI SIMBIOTICHE FRA VARROA E DWV (Deformed Wing Virus). [Tesi di dottorato]


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Item Type: Tesi di dottorato
Lingua: Italiano
Date: 30 March 2015
Number of Pages: 100
Institution: Università degli Studi di Napoli Federico II
Department: Agraria
Scuola di dottorato: Biotecnologie
Dottorato: Insect science and biotechnology
Ciclo di dottorato: 27
Coordinatore del Corso di dottorato:
Pennacchio, FrancescoUNSPECIFIED
Date: 30 March 2015
Number of Pages: 100
Uncontrolled Keywords: honeybee, immunocompetence
Settori scientifico-disciplinari del MIUR: Area 07 - Scienze agrarie e veterinarie > AGR/11 - Entomologia generale e applicata
Aree tematiche (7° programma Quadro): BIOTECNOLOGIE, PRODOTTI ALIMENTARI E AGRICOLTURA > Scienze della vita, biotecnologia e biochimica per prodotti e processi non-alimentari sostenibili
Date Deposited: 07 Apr 2015 09:08
Last Modified: 19 May 2018 01:00
DOI: 10.6093/UNINA/FEDOA/10308


The honeybee colony losses, often denoted as colony collapse disorder (CCD), have been widely reported throughout the Northern hemisphere in the last few years. There is a large consensus that this is a multifactorial syndrome, with many stress agents involved in its induction. Among these, the parasitic mite Varroa destructor associated with Deformed Wing Virus (DWV) plays a key-role. The delicate balance of the silent DWV infections is disrupted by the Varroa feeding, which further depletes the limited pool of an important transcription factor (NF-kB) activating and regulating a number of stress, both biotic and abiotic, and immune responses. Therefore, any stress factor triggering a response NF-kB dependent may lower the immune barriers and promote the proliferation of silent viral infections. This PhD program aims to further analyze the complex interplay between the Varroa-DWV interaction and the bee immune system. Initially, interest was pointed on a honeybee immune gene (Amel\102), that in other insects is involved in cellular immune response. It resulted that the transcription level of Amel\102 was negatively influenced by combined exposure to Varroa and DWV. This negative effectwas largely due to DWV infection, and was depended on the virus load. In fact when a critical threshold of viral infection was exceeded, very high viral loads resulted in a marked transcriptional down-regulation of Amel\102. Moreover, the encapsulation and melanization response, induced with an implantation of a nylon "pseudoparasite" were negatively correlated with DWV infection.Finally, to test if the viral pathogen could have a positive influence on mite feeding and, as a consequence, on its reproduction,the reproductive success of isolated mites placed on host individuals with different levels of DWV infection were monitored. The results indicated that high viral loads of DWV were associated with an increase of mite reproduction. The results of this study represent an attempt to measure honeybee immune-suppression at phenotypic level, rather than inferring a reduced immune competence on the basis of transcriptional data. Here we show that honeybees with increasing DWV loads have a lower reaction to immune challenges, both at humoral and cellular level. Indeed, the expression of an immune gene, controlling the encapsulation and melanization reactions is negatively associated with DWV loads and is under NF-kB control. The study also shows that there is a positive effect of DWV infection on mite reproduction. The basal level of infertility in Varroa mite populations can be quite high and may vary for reasons not completely understood, but apparently related to undefined host factors. We suggest that the presence and the level of infection by DWV might account for part of this variation as a consequence of different levels of honeybee immunosuppression.


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