M3. Studies of the pathogenesis of fungal infections
Oral Abstract Submission
Daniel A. Powell, PhD
Research Scientist
University College of Medicine
Tucson, AZ
Disclosure: Nothing to disclose
Lisa F. Shubitz, DVM
Research Scientist
University of Arizona
Tucson, AZ
Disclosure: Nothing to disclose
Steven M. Holland, MD
Dr.
Laboratory of Clinical Immunology and Microbiology, National Institute of Allergy and Infectious Diseases, National Institutes of Health
Bethesda, Maryland
Disclosure: Nothing to disclose
Jeffrey A. Frelinger, PhD
Professor
University of Arizona
Tucson, Arizona
Disclosure: Nothing to disclose
Background :
Reported coccidioidomycosis has increased with case rates of 198/100,000 in Arizona (2012). In California alone, 2000-2011 hospitalizations were $2.2B. Dissemination occurs in 8% of reports with significant morbidity and occasional deaths. DCM was found in 3 generations: grandmother (skin), mother (skin), and son (bone). Whole exome sequencing identified a heterozygous (het) STAT4 mutation (p.E626G) in all three. This mutation alters the phosphotyrosine binding pocket and is predicted to impair STAT4 function, interfering with i) receptor binding and phosphorylation, ii) nuclear localization, and/or iii) transcription. Expression profiling of antigen stimulated peripheral blood mononuclear cells from one patient showed dampening of known STAT4 targets compared to controls.
Methods :
STAT4 p.E626G was generated and confirmed in C57BL/6NJ (WT) mice using CRISPR-Cas9. With continued breeding, neither homozygous (hom) nor het mice had gross abnormalities. There were normal spleen and lung lymphoid cell numbers. Thymus and bone marrow had normal development of lymphoid subsets. We performed intranasal infection with reduced virulence C. posadasii (Cp.) strain 1038 or with F. tularensis live vaccine- strain (LVS). Naïve or Δcps1-vaccinated mice were tested for resistance to Cp. strain Silveira.
Results :
At day 21 post Cp 1038 infection, hom, het and WT mice had similar lung fungal burdens (~104.7 cfu). All p.E626G mice died between days 31 and 39 with lung burden significantly higher (~9x106 cfu) than WT sacrificed on day 44 (7x105 cfu, p=0.015). After LVS infection, p.E626G mice had increased lung bacterial cfu and all had dissemination to the spleen compared to WT lung bacterial burden and no splenic dissemination. Immunized het, and WT mice all had significantly reduced lung cfu 14 days following Cp. infection compared to unvaccinated WT mice.
Conclusion :
The STAT4 p.E626G mutated mouse recapitulated patients’ increased susceptibility to coccidioidal infection. The decreased fungal burdens seen in Δcps1-vaccinated mice suggest that vaccination may be effective in those persons genetically susceptible to DCM. Given the increasing frequency and economic burdens of coccidioidomycosis, pursuit of vaccination strategies should continue.
