Histological Observation and Expression Patterns of antimicrobial peptides during Fungal Infection in Musca domestica (Diptera: Muscidae) Larvae

Abstract

Housefly, Musca domestica, has a complicated immune system. However, its underlying operating mechanism remains elusive. Candida albicans is a major pathogen affecting humans by causing deep infection fungous disease, but it is non-symbiotic in houseflies. To investigate the C. albicans infection process in housefly, the changes in morphological and histological and expression patterns of antimicrobial peptide were monitored to indicate the insect's response to fungal infection. The results showed that scattered brown spots were comprising melanized encapsulation and encapsulated fungal cells were initially observed at the inner side of larvae's body wall 3 h postinfection (PI). Between 6 and 36 h PI, the whole body of larvae was densely covered with the brown spots, which then gradually disappeared. The majority had disappeared at 48 h PI. Some fungi colonized in the gaps between the body wall and the muscle layer, as well as among muscle fibers of the muscle layer at 12 h PI and hyphal was observed at 18 h PI. These fungi colonized distribution changed from a continuous line to scattered spots at 24 h PI and virtually disappeared at 48 h. The results of quantitative PCR analysis revealed that in coordination with the variation during the infection, the expression levels of four antimicrobial peptides were up-regulated. In conclusion, C. albicans infection in M. domestica larvae involved the following stages: injection, infection, immune response and elimination of the pathogen. The rapid response of antimicrobial peptides, melanized encapsulation and agglutination played a vital role against the pathogenic invasion.

Ultrastructural and Immunohistochemical Alterations in Hemocytes and Fat Body of the Flesh Fly (Sarcophaga Argyrostoma) Larvae Upon Cancer Cell Line Inoculation

“…Also, increase in number of hemocytes was in Anopheles gambiae upon infection with Escherichia coli (King, 2013). These reports suggested that, insect hemocells were constantly regenerated and kept a dynamic change during insect infection (Jiangfan et al, 2016;Mishra et al, 2015). The hemocytes formed multicellular aggregates, i.e., nodules, at the first period post injection that aided to entrap the invading cancer cells.…”

“…Knowledge on how the insect innate immune response to fight foreign body aided to understand the first step in human diseases interaction (Wang et al, 2013;Singh et al, 2014;Wu et al, 2014;Khalil et al, 2015). Injury, rolling and ingestion methods are techniques of insect infection that have been successfully established (Jiangfan et al, 2016). The injury method mainly used needles to deliver foreign bodies by piercing the somatic layer or directly injects foreign cell into the insect coelom to cause acute infection and rapidly activate immune response (Matsumoto et al, 2012).…”

“…So, difference in hemocyte between normal and stressed larvae showed that the host defense system was activated (Nappi, 1981;Brehélin, 1982). Larvae of flesh fly like some other insects have humoral hemocytes concentrated in the last segments and scattered around tissues and organs (Jiangfan et al, 2016). Some of invaders were able to persist between the inner side of the body wall and muscle tissue layers because of the low concentration of hemocytes in these spaces, so they stayed in these locations and were not eliminated immediately (Chen et al, 1997).…”

“…Many pathogens or foreign bodies are able to overcome the first line of host defense and get into the body. Foreign cells in the hemocel activated systemic immune mechanisms, which consisted of cellular and humoral immunity (Lemaitre and Hoffmann, 2007;Jiangfan et al, 2016). Hemocytes being precursor of innate immunity in insects, a strong correlation between hemocyte number and immune response (Mishra et al, 2015).…”

Antimicrobial peptide AMP-17 exerts anti-Candida albicans effects through ROS-mediated apoptosis and necrosis

“…AMP-17 (Musca domestica antimicrobial peptide-17) is encoded by a speci c high-expression gene selected from M. domestica transcriptome database constructed after microbial infection 12 hours. In the previous study, our research team successfully produced the recombinant protein AMP-17 with excellent antifungal activity in a prokaryotic expression system [14][15]. Further research has found that it can reduce the cell wall integrity of C. albicans, destroy the cell membrane structure, and increase cell membrane permeability [16].…”