Thesis Defense Announcement
To: the George Mason Community

*Lilian S. Amer
Master of Science in Biology
Microbiology & Infectious Diseases concentration
*
Date: Monday November 30, 2009
Time: 2:00 - 4:00 p.m.
Place: Bull Run Hall, Room 258
Prince William campus

Thesis Chair: Dr. Monique van Hoek, MMB Dept., NCBID

*Title:* Human and Snake Cathelicidins Activity Against /Francisella 
/and Induction of LL-37 in A549 Cells _//_
*Abstract:*

/Francisella (F.) tularensis/ is a gram-negative, zoonotic, facultative 
intracellular pathogen that causes tularemia.  The disease of tularemia 
in animals and humans is characterized by infection of the macrophages, 
followed by infection of other cell types and organs including lung, 
liver and spleen. While/ Francisella/ is not normally a respiratory 
pathogen, the most severe infections by /Francisella/ species occur via 
inhalation or direct inoculation of the lungs leading to pneumonic 
tularemia. Due to its potential use as a biological weapon or 
bio-terrorist threat (via aerosol) and the probable development of 
antibiotic resistant strains of /Francisella/, new approaches to the 
treatment of pneumonic tularemia are a priority. Antimicrobial peptides 
are small (3-6 kDa), cationic peptides that exert a direct antimicrobial 
effect on microbes. Interest in antimicrobial peptides has grown due to 
increasing resistance of microorganisms to commonly used antibiotics and 
the potential therapeutic applications of these peptides. In humans, 
only one cathelicidin LL-37 has been characterized, which is derived by 
proteolysis from the C-terminal end of the human CAP18 protein. 
Recently, helical cathelicidins have been discovered in various species 
of snakes including the Chinese cobra, /Naja atra/. Two 11-residue 
peptides (NA-CATH-1 and NA-CATH-2) containing one of the two repeated 
motifs were designed from NA-CATH. We hypothesize that smaller synthetic 
peptides modeled after the reptile cathelicidin NA-CATH can be designed 
with increased antimicrobial effectiveness and decreased hemolysis 
making them better candidates for development into useful and broad 
spectrum antimicrobial compounds. We tested the susceptibility of 
/Francisella/ and /E. coli /to NA-CATH cathelicidin and four truncated 
peptides compared to the effectiveness of the human cathelicidin, LL-37. 
A killing time curve was also performed to know the activity time of the 
peptides.  Finally, we have also shown that infection of Human alveolar 
type II epithelial cells (A549) with /F. novicida/ induces an increase 
in LL-37 gene expression. Data from the antimicrobial studies shows that 
full length snake cathelicidin peptide (NA-CATH) is considerably more 
potent than LL-37 /in vitro/ against /E.coli, /but less potent against 
/Francisella./ The antimicrobial activity of the four truncated peptides 
is presented, one of which is found to be extremely potent in the nM 
range. The peptides also show no hemolytic activity even at high peptide 
concentration, indicating low cytotoxicity to host cells. These peptides 
represent a new approach to antimicrobial drug development. We also 
determined that LL-37 mRNA levels were elevated 3 fold relative to the 
levels of the corresponding LL-37 mRNAs in uninfected control cells. 
This is the first report of the induction of LL-37 expression in A549 
cells as a consequence of bacterial stimulus.


*All members of the George Mason University community are invited to 
attend.*