Ioannis Gryllos, PhD

Department	Infectious Diseases
Hospital Title:	Research Associate
Academic Title:	Instructor in Pediatrics
Phone:	617-919-2908
Fax:	617-730-0254
Email:	Ioannis Gryllos
Location:	300 Longwood Avenue, Enders 7 Boston, MA 02115

Research Overview

Research in Dr. Gryllos' laboratory seeks to understand the pathogenesis mechanisms of group A Streptococcus (GAS, or Streptococcus pyogenes). GAS is the leading cause of bacterial pharyngitis in humans, but it is also associated with skin and soft tissue infections that may progress to invasive life-threatening disease. GAS infections are usually treated successfully with antibiotics, however, a GAS vaccine is lacking.

Our goal is to improve our understanding of the GAS adaptation and survival strategies taking place in the human host, which may lead to the identification of target molecules or pathways for new antimicrobial treatments or vaccine development. GAS survival in the host is the result of tightly regulated gene expression that leads to the timely production of products required in the human pharynx or deeper tissues during invasive infection. The identification of gene regulatory networks operating during infection and the characterization of the environmental stimuli/ligands that signal through those networks is the focus of our current efforts. Recent studies have shown the role of the peroxide response regulator (PerR) in GAS resistance to killing by host phagocytes and its contribution to adaptation and survival in the pharynx. Additional studies report the paradoxical finding that at sub-inhibitory concentrations the human antimicrobial peptide cathelicidin, LL37, is an inducer of bacterial virulence leading to increased GAS killing resistance by human phagocytes.

About Ioannis Gryllos

Ioannis Gryllos received his PhD from University of Sheffield, England. He then completed a postdoctoral research fellowship at Brigham and Women's Hospital, Boston.

Key Publications

• Gryllos I, Levin JC, Wessels MR. (2003) The CsrR/CsrS two-component system of group A Streptococcus responds to environmental Mg2+. Proc. Natl. Acad Sci. USA 100: 4227-32.
   
• Gryllos I, Grifantini R, Colaprico A, Jiang S, DeForce E, Hakansson A, Telford JL, Grandi G, Wessels MR. (2007) Mg2+ signaling defines the group A streptococcal CsrRS regulon. Mol. Microbiol. 65: 671-683.
   
• Gryllos I, Grifantini R, Colaprico A, Cary ME, Hakansson A, Carey DW, Suarez-Chavez M, Kalish LA, Mitchell PD, White GL, Wessels MR. (2008) PerR confers phagocytic killing resistance and allows pharyngeal colonization by group A Streptococcus. PLoS Pathogens 4: e1000145.
   
• Gryllos I, Tran-Winkler HJ, Cheng M-F, Chung H, Bolcome R, Lu W, Lehrer RI, Wessels MR. (2008) Induction of group A Streptococcus virulence by a human antimicrobial peptide. Proc. Natl. Acad. Sci. USA 105: 16755-16760.