The Martinez Lab

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The Martinez Lab’s research program is focused on the study of vector-borne rickettsial diseases and host-pathogen interactions. The Gram-negative α-proteobacteria of the genus Rickettsia are small (0.3-0.5 x 0.8-1.0 μm), obligate intracellular organisms. These bacteria are transmitted by tick bite inoculation into the skin of the human host and can ultimately damage target endothelial cells especially in the lungs and brain leading to the most severe manifestations of disease, including pulmonary edema and interstitial pneumonia. Although infections are controlled by broad-spectrum antibiotic therapies, untreated or misdiagnosed Mediterranean spotted fever (MSF), Rocky Mountain spotted fever (RMSF) and other spotted fever infections can result in severe morbidity and mortality.  Laboratory efforts are currently aimed at the following research interests: a) characterization of host cell lipid metabolic and catabolic pathways that are utilized by obligate intracellular bacteria to fulfill nutritional requirements; b) elucidation of pro-survival and anti-apoptotic pathways utilized by Rickettsia species to establish replicative intracellular niches; c) continued elucidation of the roles of conserved outer-membrane proteins spotted fever group Rickettsia species in the interaction with endothelial cells, monocytes, macrophages and other mammalian target cells; d) continued identification of mammalian receptors for pathogenic SFG Rickettsia species.

TEDXLSU 2019

What happens when bacterial infections stop responding to traditional antibiotic treatments? That scenario might sound like the plot of a blockbuster movie, but it is also the question pathobiological researcher Juan Martinez is trying to answer.

JUAN MARTINEZ TEDXLSU TALK

Select Publications

Kristof MN, Allen PE, Yutzy LD, Thibodaux B, Paddock CD and Martinez JJ, Significant Growth by Rickettsia species within Human Macrophage-Like Cells is a Phenotype Correlated with the Ability to Cause Disease in Mammals. Pathogens 2021, 10(2), 228;   

Allen PE, Martinez JJ. Modulation of Host Lipid Pathways by Pathogenic Intracellular Bacteria. Pathogens. 2020 Jul 28;9(8). doi: 10.3390/pathogens9080614. Review. PubMed PMID: 32731350; PubMed Central PMCID: PMC7460438. 

Curto P, Riley SP, Simões I, Martinez JJ. Macrophages Infected by a Pathogen and a Non-pathogen Spotted Fever Group Rickettsia Reveal Differential Reprogramming Signatures Early in Infection. Front Cell Infect Microbiol. 2019;9:97. doi: 10.3389/fcimb.2019.00097. eCollection 2019. PubMed PMID: 31024862; PubMed Central PMCID: PMC6467950. 

Curto P, Santa C, Allen P, Manadas B, Simões I, Martinez JJ. A Pathogen and a Non-pathogen Spotted Fever Group Rickettsia Trigger Differential Proteome Signatures in Macrophages. Front Cell Infect Microbiol. 2019;9:43. doi: 10.3389/fcimb.2019.00043. eCollection 2019. PubMed PMID: 30895174; PubMed Central PMCID: PMC6414445. 

Riley SP, Fish AI, Del Piero F, Martinez JJ. Immunity against the Obligate Intracellular Bacterial Pathogen Rickettsia australis Requires a Functional Complement System. Infect Immun. 2018 Jun;86(6). doi: 10.1128/IAI.00139-18. Print 2018 Jun. PubMed PMID: 29581196; PubMed Central PMCID: PMC5964522. 

McClure EE, Chávez ASO, Shaw DK, Carlyon JA, Ganta RR, Noh SM, Wood DO, Bavoil PM, Brayton KA, Martinez JJ, McBride JW, Valdivia RH, Munderloh UG, Pedra JHF. https://www.ncbi.nlm.nih.gov/pubmed/28626230/. Nat Rev Microbiol. 2017 Sep;15(9):544-558. doi: 10.1038/nrmicro.2017.59. Epub 2017 Jun 19. Review. PubMed PMID: 28626230; PubMed Central PMCID: PMC5557331. 

Riley SP, Pruneau L, Martinez JJ. Evaluation of changes to the Rickettsia rickettsii transcriptome during mammalian infection. PLoS One. 2017;12(8):e0182290. doi: 10.1371/journal.pone.0182290. eCollection 2017. PubMed PMID: 28832688; PubMed Central PMCID: PMC5568294. 

Garza DA, Riley SP, Martinez JJ. Expression of Rickettsia Adr2 protein in E. coli is sufficient to promote resistance to complement-mediated killing, but not adherence to mammalian cells. PLoS One. 2017;12(6):e0179544. doi: 10.1371/journal.pone.0179544. eCollection 2017. PubMed PMID: 28662039; PubMed Central PMCID: PMC5491016. 

Fish AI, Riley SP, Singh B, Riesbeck K, Martinez JJ. The Rickettsia conorii Adr1 Interacts with the C-Terminus of Human Vitronectin in a Salt-Sensitive Manner. Front Cell Infect Microbiol. 2017;7:61. doi: 10.3389/fcimb.2017.00061. eCollection 2017. PubMed PMID: 28299286; PubMed Central PMCID: PMC5331051. 

Curto P, Simões I, Riley SP, Martinez JJ. Differences in Intracellular Fate of Two Spotted Fever Group Rickettsia in Macrophage-Like Cells. Front Cell Infect Microbiol. 2016;6:80. doi: 10.3389/fcimb.2016.00080. eCollection 2016. PubMed PMID: 27525249; PubMed Central PMCID: PMC4965480. 

Riley SP, Fish AI, Garza DA, Banajee KH, Harris EK, del Piero F, Martinez JJ. Nonselective Persistence of a Rickettsia conorii Extrachromosomal Plasmid during Mammalian Infection. Infect Immun. 2016 Jan 11;84(3):790-7. doi: 10.1128/IAI.01205-15. PubMed PMID: 26755154; PubMed Central PMCID: PMC4771360.

Riley SP, Cardwell MM, Chan YG, Pruneau L, Del Piero F, Martinez JJ. Failure of a heterologous recombinant Sca5/OmpB protein-based vaccine to elicit effective protective immunity against Rickettsia rickettsii infections in C3H/HeN mice. Pathog Dis. 2015 Dec;73(9):ftv101. doi: 10.1093/femspd/ftv101. Epub 2015 Oct 29. PubMed PMID: 26519448; PubMed Central PMCID: PMC4732028. 

Riley SP, Macaluso KR, Martinez JJ. Electrotransformation and Clonal Isolation of Rickettsia Species. Curr Protoc Microbiol. 2015 Nov 3;39:3A.6.1-3A.6.20. doi: 10.1002/9780471729259.mc03a06s39. PubMed PMID: 26528784; PubMed Central PMCID: PMC4664152. 

Li M, Gustchina A, Cruz R, Simões M, Curto P, Martinez J, Faro C, Simões I, Wlodawer A. Structure of RC1339/APRc from Rickettsia conorii, a retropepsin-like aspartic protease. Acta Crystallogr D Biol Crystallogr. 2015 Oct;71(Pt 10):2109-18. doi: 10.1107/S1399004715013905. Epub 2015 Sep 30. PubMed PMID: 26457434; PubMed Central PMCID: PMC4601372. 

Cruz R, Huesgen P, Riley SP, Wlodawer A, Faro C, Overall CM, Martinez JJ, Simões I. RC1339/APRc from Rickettsia conorii is a novel aspartic protease with properties of retropepsin-like enzymes. PLoS Pathog. 2014 Aug;10(8):e1004324. doi: 10.1371/journal.ppat.1004324. eCollection 2014 Aug. PubMed PMID: 25144529; PubMed Central PMCID: PMC4140852. 

Riley SP, Patterson JL, Nava S, Martinez JJ. Pathogenic Rickettsia species acquire vitronectin from human serum to promote resistance to complement-mediated killing. Cell Microbiol. 2014 Jun;16(6):849-61. doi: 10.1111/cmi.12243. Epub 2013 Dec 13. PubMed PMID: 24286496; PubMed Central PMCID: PMC4028375. 

Hillman RD Jr, Baktash YM, Martinez JJ. OmpA-mediated rickettsial adherence to and invasion of human endothelial cells is dependent upon interaction with α2β1 integrin. Cell Microbiol. 2013 May;15(5):727-41. doi: 10.1111/cmi.12068. Epub 2012 Dec 6. PubMed PMID: 23145974; PubMed Central PMCID: PMC3610814. 

Cardwell MM, Martinez JJ. Identification and characterization of the mammalian association and actin-nucleating domains in the Rickettsia conorii autotransporter protein, Sca2. Cell Microbiol. 2012 Sep;14(9):1485-95. doi: 10.1111/j.1462-5822.2012.01815.x. Epub 2012 Jun 5. PubMed PMID: 22612237; PubMed Central PMCID: PMC3422371. 

Riley SP, Patterson JL, Martinez JJ. The rickettsial OmpB β-peptide of Rickettsia conorii is sufficient to facilitate factor H-mediated serum resistance. Infect Immun. 2012 Aug;80(8):2735-43. doi: 10.1128/IAI.00349-12. Epub 2012 May 21. PubMed PMID: 22615250; PubMed Central PMCID: PMC3434587. 

Chan YG, Riley SP, Chen E, Martinez JJ. Molecular basis of immunity to rickettsial infection conferred through outer membrane protein B. Infect Immun. 2011 Jun;79(6):2303-13. doi: 10.1128/IAI.01324-10. Epub 2011 Mar 28. PubMed PMID: 21444665; PubMed Central PMCID: PMC3125829. 

Chan YG, Riley SP, Martinez JJ. Adherence to and invasion of host cells by spotted Fever group rickettsia species. Front Microbiol. 2010;1:139. doi: 10.3389/fmicb.2010.00139. eCollection 2010. PubMed PMID: 21687751; PubMed Central PMCID: PMC3109342. 

Riley SP, Goh KC, Hermanas TM, Cardwell MM, Chan YG, Martinez JJ. The Rickettsia conorii autotransporter protein Sca1 promotes adherence to nonphagocytic mammalian cells. Infect Immun. 2010 May;78(5):1895-904. doi: 10.1128/IAI.01165-09. Epub 2010 Feb 22. PubMed PMID: 20176791; PubMed Central PMCID: PMC2863548. 

Cardwell MM, Martinez JJ. The Sca2 autotransporter protein from Rickettsia conorii is sufficient to mediate adherence to and invasion of cultured mammalian cells. Infect Immun. 2009 Dec;77(12):5272-80. doi: 10.1128/IAI.00201-09. Epub 2009 Oct 5. PubMed PMID: 19805531; PubMed Central PMCID: PMC2786473. 

Chan YG, Cardwell MM, Hermanas TM, Uchiyama T, Martinez JJ. Rickettsial outer-membrane protein B (rOmpB) mediates bacterial invasion through Ku70 in an actin, c-Cbl, clathrin and caveolin 2-dependent manner. Cell Microbiol. 2009 Apr;11(4):629-44. doi: 10.1111/j.1462-5822.2008.01279.x. Epub 2009 Jan 7. PubMed PMID: 19134120; PubMed Central PMCID: PMC2773465. 

Lab Alumni

Years Name
2008-2019 Sean P. Riley, Ph.D., (University of Kentucky), Post-Doctoral Scholar. Currently Assistant Professor (tenure track), University of Maryland.
2013-2018 Abigail Ines Fish, Ph.D., Department of Pathobiological Sciences. Doctoral student, Louisiana State University School of Veterinary Medicine (LSU SVM). Currently, Biosafety Officer at Louisiana State University Baton Rouge, LA.
2013-2019 Daniel Garza, Research Technician
2013-2014 Rui Cruz, Ph.D., Visiting research scholar (University of Coimbra, Portugal).
2014-2016 Pedro Thiago Curto, Ph.D. Visiting research scholar (University of Coimbra, Portugal). Currently: international graduate student at The University of Coimbra performing two years of study in the Martinez laboratory at LSU-SVM. Completed Ph.D. at the University of Coimbra in 2018.
2014-2015 Elizabeth Griggs, Ph.D., Department of Pathobiological Sciences, Doctoral student, Louisiana State University School of Veterinary Medicine (LSU SVM).  Finished her Ph.D. under the guidance of Dr. Ronald Thune (LSU SVM).
2014-2015 Ludovic Pruneau Ph.D., (University of Guadaloupe), Post-Doctoral Scholar. Currently post-doctoral scholar at Université des Antilles et de la Guyane, Pointe-à-Pitre, France.
2014-2016 Brandon Thibodeaux, B.S, Louisiana State University. Undergraduate student worker. Currently veterinary surgical resident at LSU Vet Med.
2015-2018 Isaura Simoes, Ph.D., Visiting research scholar from the University of Coimbra on a 9-month sabbatical.
2016 Kristine Frady, B.S., Summer Scholar Research Program for Veterinary Students at the LSU SVM.
2016-2019 Nathan Kristof, B.S., 2019 Louisiana State University, Undergraduate student worker.
2016-2017 Mary Joan Caldwell, Research Technician.
2018-2020 Robert Christopher Holley, Department of Pathobiological Sciences, Former Doctoral student, LSU Vet Med.