Banca de QUALIFICAÇÃO: JÉSSICA FIOROTTI DE PAULO

Uma banca de QUALIFICAÇÃO de DOUTORADO foi cadastrada pelo programa.
STUDENT : JÉSSICA FIOROTTI DE PAULO
DATE: 05/02/2021
TIME: 09:00
LOCAL: Internet - Zoom
TITLE:

Effect of Metarhizium spp. on hemocytes and the role of phagocytosis in tick immune response

KEY WORDS:

entomopathogenic fungi, biological control, tolerance, immunity

PAGES: 136
BIG AREA: Ciências Agrárias
AREA: Medicina Veterinária
SUBÁREA: Medicina Veterinária Preventiva
SPECIALTY: Doenças Parasitárias de Animais
SUMMARY:

Metarhizium is an entomopathogenic fungus widely used in the biological control of arthropods.  The effectiveness of these fungi in colonizing a wide range of hosts is apparently linked to the insufficiency of the arthropods' immune system to eliminate pathogens and resolve infection.  Despite this, knowledge about the role of hemocytes in responding to fungal infection remains scarce.  At the tick interface, proteins from the complement system, especially those containing thio-ester clusters (TEPs), including α2-macroglobulins (A2M), molecules related to the complement component C3 (C3), complement-related macroglobulin (Mcr) and a  type of insect protein (Tep) are essential for immune responses.  At the pathogen interface, alteration of the fungal cell wall may be a way to escape the tick's immune system.  In this context, the present study aimed to analyze the hemocytes of Rhipicephalus microplus females after infection by Metarhizium robertsii, using light microscopy and transmission electron microscopy approaches, as well as the evaluation of cytotoxicity.  It also aimed to assess the role of TEPs in tick immunity against entomopathogenic fungi (FEP), through a quantitative analysis of the real-time PCR expression of Ixodes ricinus TEPs in different periods.  It has been shown that Tween 80 detergent does not influence cell morphology and can be used as a control for entomopathogen infections. Twenty-four hours after fungal infection, only granulocytes and plasmatocytes were detected in the analysis by transmission electron microscopy and these cells  of infected females presented a very heterogeneous cytoplasm, with several vacuoles of different electrondensities, as well as the formation of autophagosomes and subcellular material in different stages of degradation.  The propagules of M. robertsii were more toxic to the tick's hemocytes in the highest concentration tested (1.0 × 108 conidia / mL).  Interestingly, the lower concentration of fungi did not significantly affect cell viability.  In addition, granulocyte microanalysis demonstrated that granules of infected and non-fungal tick cells had a similar composition.  Regarding the gene expression profile, a positive regulation was observed in the expression of 6 genes in relation to the control group, 2 hours after infection by FEP.  After gene silencing, hemocytes showed significant reductions in phagocytosis rates when compared to the control group.  The IrC3-3 gene was the most representative, whose silencing resulted in a 60% reduction in the phagocytosis index.  In addition, the tick's survival time was longer when lower fungal concentrations were used, in contrast to when we decreased the phagocytosis action and the average survival time decreased considerably.  The present study demonstrated for the first time an assessment of the phagocytosis process in hemocytes challenged by Metarhizium robertsii, demonstrating that ticks react differently to fungal infection when compared to insects and that possibly fungi can also use the phagocytosis process to escape from  subsequent immune response of the tick.

BANKING MEMBERS:
Interno - 3701492 - HUARRISSON AZEVEDO SANTOS
Interna - 2860277 - ISABELE DA COSTA ANGELO
Interna - 387922 - VANIA RITA ELIAS PINHEIRO BITTENCOURT
Externo à Instituição - RUBEM FIGUEIREDO SADOK MENNA BARRETO - FIOCRUZ