Haemophilus ducreyi is the etiologic agent of chancroid, a sexually transmitted genital ulcer disease. Very little Is known about how this unencapsulated. Gram-negative bacterium evades host defenses and causes demrial lesion development. However, it has been shown that H. ducreyi has the ability to prevent phagocytosis of both itself and secondary targets by macrophages in vitro. We identified two extremely large H. ducreyi proteins, designated LspA1 and LspA2, that are released into H. ducreyi culture supernatant fluid and which are necessary for the observed inhibition of phagocytic activity. That these proteins are relevant to disease production was proven by the finding that a H. ducreyi mutant unable to express either LspA1 or LspA2 had drastically reduced virulence in both animal and human models of experimental chancroid. Little is known, however, about how the LspA proteins inhibit phagocytic activity. The proposed research project in this MERIT extension application will investigate the stoicture, function, and expression of the LspA proteins. In the first Specific Aim, we will capitalize on our recent successful cloning of the H. ducreyi IspAl gene to purify a functional recombinant LspAl protein and then determine the composition of the active form of this protein. In the second Specific Aim, we will elucidate the mechanism of action involved in the inhibition of phagocytic activity by the LspA proteins. We already have data which indicate that the LspA proteins can affect signaling pathways that control phagocytosis in macrophages, and our research efforts will be focused on the most proximal elements, and especially the Src family protein tyrosine kinases, in the phagocytic signaling cascade. In the third Specific Aim, we will characterize the H. ducreyi CpxRA two-component signal transduction system that is responsible for control of expression of both the LspA proteins as well as other co-regulated gene products of this bacterium.

Public Health Relevance

The relevance of this research to public health involves the new infomnation that will be gained about H. ducreyi inhibits phagocytosis, one of the primary defense mechanisms of the human body. The ability of phagocytes to engulf and kill bacteria is essential to preventing or curing infectious diseases. Infomnation gained from this study will help us understand how phagocytes control this protective activity.

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Method to Extend Research in Time (MERIT) Award (R37)
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No Study Section (in-house review) (NSS)
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Hiltke, Thomas J
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University of Texas Sw Medical Center Dallas
Schools of Medicine
United States
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Dodd, Dana A; Worth, Randall G; Rosen, Michael K et al. (2014) The Haemophilus ducreyi LspA1 protein inhibits phagocytosis by using a new mechanism involving activation of C-terminal Src kinase. MBio 5:e01178-14
Gangaiah, Dharanesh; Labandeira-Rey, Maria; Zhang, Xinjun et al. (2014) Haemophilus ducreyi Hfq contributes to virulence gene regulation as cells enter stationary phase. MBio 5:e01081-13
Labandeira-Rey, Maria; Dodd, Dana A; Brautigam, Chad A et al. (2013) The Haemophilus ducreyi Fis protein is involved in controlling expression of the lspB-lspA2 operon and other virulence factors. Infect Immun 81:4160-70
Labandeira-Rey, Maria; Dodd, Dana; Fortney, Kate R et al. (2011) A Haemophilus ducreyi CpxR deletion mutant is virulent in human volunteers. J Infect Dis 203:1859-65
Labandeira-Rey, Maria; Brautigam, Chad A; Hansen, Eric J (2010) Characterization of the CpxRA regulon in Haemophilus ducreyi. Infect Immun 78:4779-91
Labandeira-Rey, Maria; Janowicz, Diane M; Blick, Robert J et al. (2009) Inactivation of the Haemophilus ducreyi luxS gene affects the virulence of this pathogen in human subjects. J Infect Dis 200:409-16
Labandeira-Rey, Maria; Mock, Jason R; Hansen, Eric J (2009) Regulation of expression of the Haemophilus ducreyi LspB and LspA2 proteins by CpxR. Infect Immun 77:3402-11