The Sinnis Laboratory is part of the Johns Hopkins Malaria Research Institute, committed to the pursuit of basic science research that translates into solutions targeting one of the most important infectious diseases in the world. Malaria, caused by protozoan parasites of the genus Plasmodium, is transmitted to humans by infected Anopheles mosquitoes. The evolution of drug resistance by the parasite, and insecticide resistance by the mosquito, have created an urgent need for new strategies to control and ultimately eliminate malaria.

We focus on the transmission of sporozoites from mosquito to mammalian host and how these parasites overcome physical and immunological obstacles to establishing infection. Sporozoites, the infective stage of the malaria parasite, make an impressive journey from the midgut wall of the mosquito where they emerge from oocysts, to their final destination in the mammalian liver (see picture below). Using biochemical, cell biological and genetic approaches, as well as intravital imaging, we aim to understand the molecular interactions between sporozoites and their mosquito and mammalian hosts that enable the parasite to initiate infection.

The Skin Phase of Infection

Mosquitoes inoculate sporozoites into the dermis of the mammalian host as they probe for blood. Once inoculated, sporozoites actively move through the dermis to fine a blood vessel, which they penetrate to enter the circulation and go to the liver. Using a rodent malaria model we have determined the sporozoite inoculum (Medica & Sinnis 2005), the kinetics with which sporozoites exit the dermis (Yamauchi et al. 2007), and the probability of infection after a single infectious bite (Aleshnick et al., unpublished data). Our work suggests that this is a significant bottleneck for the parasite. Intra-vital imaging of sporozoites in the skin, has led to the demonstration that sporozoites recognize blood vessels and alter their speed and trajectories when in the vicinity of a vessel (Hopp et al. 2015). Current work focuses on the host innate and adaptive immune response to sporozoites at the inoculation site and understanding the mechanism(s) by which sporozoites recognize and penetrate blood vessels.

Time lapse video: Mosquito inoculation of Plasmodium yoelli
sporozoites into a mouse. Video by Christine Hopp.

Plasmodium berghei sporozoites moving in the dermis after
their inoculation into a mouse. Video by Christine Hopp.

Structure-function studies of the circumsporozoite protein (CSP)

CSP is the major surface protein of the sporozoite, forming a dense coat on the surface of the parasite. CSP is also the basis of RTS,S, the only malaria vaccine candidate to show efficacy in Phase III clinical trials. Despite its importance, our understanding of CSP structure and function is limited and we believe that elucidating how this protein functions will inform future malaria vaccine design.

Our previous studies demonstrate that CSP has two conformational states, an adhesive conformation in which the TSR domain is exposed and a nonadhesive conformation in which the N-terminus masks this domain. As sporozoites travel from mosquito midgut to mammalian liver, the cell-adhesion domain is masked, maintaining sporozoites in a migratory state (Coppi et al., 2011). Upon arrival in the liver, the N-terminal domain is proteolytically cleaved and the cell-adhesion domain is exposed (Coppi et al., 2005; Coppi et al., 2011). Processing is triggered by the highly sulfated heparan sulfate proteoglycans of the liver, which serves as a signal for the sporozoite to switch from a migratory to an invasive state (Coppi et al 2007). We are currently focused on determining the structure of the N-terminus of CSP, the function of the central repeat region and the identity of the parasite protease that cleaves CSP.

The role of parasite proteases in the establishment of malaria infection.

Our work on CSP and another sporozoite adhesin, TRAP (Ejigiri et al 2012), demonstrates the vital role that parasite proteases play in sporozoite motility and infectivity. We are actively working to identify the CSP protease and have expanded our work to dissect the function of other Plasmodium serine and cysteine proteases expressed by pre-erythrocytic stages. Ultimately the goal of this work is to screen inhibitors of critical proteases and validate them as drug targets.

Selected Papers

Click on the publication title to read it.

Flores-Garcia Y*, Nasir G*, Hopp CS, Munoz C, Balaban AE, Zavala F, & Sinnis P. Antibody-Mediated Protection against Plasmodium Sporozoites Begins at the Dermal Inoculation Site. mBio, 9(6), e02194-18, 2018 Publication selected for commentary “Shedding Light on the Role of the Skin in Vaccine-Induced Protection against the Malaria Sporozoite” by J.P. Daily, mBio.02555-18

Hopp CS, Bennett BL, Mishra S, Lehmann C, Hanson KK, Lin JW, Rousseau K, Carvalho FA, van der Linden WA, Santos NC, Bogyo M, Khan SM, Heussler V, Sinnis P. Deletion of the rodent malaria ortholog for falcipain-1 highlights differences between hepatic and blood stage merozoites. PLoS Pathog 13:e1006586, 2017.

Swearingen KE, Lindner SE, Shi L, Shears MJ, Harupa A, Hopp CS, Vaughan AM, Springer TA, Moritz RL, Kappe SH, Sinnis P. Interrogating the Plasmodium Sporozoite Surface: Identification of Surface-Exposed Proteins and Demonstration of Glycosylation on CSP and TRAP by Mass Spectrometry-Based Proteomics. PLoS Pathog 12:e1005606, 2016.

Hopp CS, Chiou K, Ragheb DR, Salman A, Khan SM, Liu AJ, Sinnis P. Longitudinal analysis of Plasmodium sporozoite motility in the dermis reveals component of blood vessel recognition. Elife 4:doi:10.7554/eLife.07789, 2015. Publication selected for commentary “Looking for Blood” by P. Formaglio and R. Amino, Elife 4:2015.

Espinosa DA, Gutierrez GM, Rojas-López M, Noe AR, Shi L, Tse SW, Sinnis P, Zavala F. Proteolytic cleavage of the Plasmodium falciparum circumsporozoite protein is a target of protective antibodies. J Infect Dis, 212:1111-9, 2015.

Ejigiri I, Ragheb DRT, Pino P, Coppi A, Bennett BL, Soldati-Favre D and Sinnis P. Shedding of TRAP by a rhomboid protease from the malaria sporozoite surface is essential for gliding motility and sporozoite infectivity. PLoS Pathogens 8:e1002725, 2012.

Coppi A, Natarajan R, Pradel G, Bennett BL, James ER, Roggero MA, Corradin G, Persson C, Tewari R and Sinnis P. The malaria circumsporozoite protein has two functional domains each with distinct roles as sporozoites journey from mosquito to mammalian host. J Exp Med 208:341-36, 2011.

Hobbs CV, Voza T, Coppi A, Marsh K, Borkowsky W and Sinnis P. HIV protease inhibitors affect development of pre-erythrocytic stage Plasmodium. J Infect Dis 199: 134-141, 2009. Publication selected for cover image.

Li-Min T, Gissot M, Coppi A, Sinnis P and Kim K. Attenuated Plasmodium yoelii lacking purine nucleoside phosphorylase confer protective immunity. Nature Med. 14: 954-58, 2008. Publication selected for commentary by C. Engwerda and M. Good, Nature Med. 14:912-913.

Coppi A, Tewari R, Bishop JR, Bennett BL, Lawrence R, Esko J, Billker O and Sinnis P. Heparan sulfate proteoglycans provide a signal to Plasmodium sporozoites to stop migrating and productively invade cells. Cell Host Microbe 2:316-327, 2007. Publication selected for cover image and commentary by M. Mota, Cell Host Microbe 2:286-288.

Yamauchi LM, Coppi A, Snounou G and Sinnis P. Plasmodium Sporozoites Trickle Out of the Injection Site. Cell. Microbiol. 9:1215-1222, 2007.

Medica D and Sinnis P. Quantitative dynamics of Plasmodium yoelii sporozoite transmission by infected Anopheline mosquitoes feeding on vertebrate hosts. Infect Immun 73:4363-4369, 2005.

Coppi A, Pinzon-Ortiz C, Hutter C and Sinnis P. The Plasmodium circumsporozoite protein is proteolytically processed during cell invasion. J Exp Med 201:27-33, 2005.Comment by S.M. Hurtley in “Editors Choice”, Science 307:319.

Pinzon-Ortiz C, Friedman J, Esko J and Sinnis P. The binding of the circumsporozoite protein to cell surface heparan sulfate proteoglycans is required for Plasmodium sporozoite attachment to target cells. J Biol Chem 276:26784-26791, 2001.


Hover over the person's picture to see what they are working on!

The Boss. Investigating the secrets of grant writing

Photini Sinnis, MD

Principal Investigator,
Download CV

Sporozoite blood vessel interactions

Sachie Kanatani, PhD

Postdoctoral Fellow,

Trafficking of circumsporozoite protein

Sharon Patray

PhD Student

Plasmodium cysteine proteases

Ritwik Singhal

Master's Student,

Antibody-mediated immunity against sporozoites in the skin

Gibbs Nasir, ScM

Laboratory Research Manager,

Sporozoite transmission dynamics

Charisma Burrowes

Undergraduate Student

Sinnis Lab Veterans

Amanda Balaban
Graduate Student 2012-2018

Probing the function of Plasmodium CSP Repeats

Postdoctoral Fellow,
Johns Hopkins School of Medicine, MD

Jason Gregory
Laboratory Tech 2016-2018

Testing antibodies that inhibit CSP cleavage

Graduate Student,
Rutgers University, NJ

Melanie Shears
Postdoctoral Fellow 2015-2018

Proteomics of merosomes & Plasmodium glycobiology

Scientist, University of Washington Center for Emerging Infectious Diseases

Ariadne Sinnis-Bourozikas
Undergraduate Student 2016

Imaging gliding motility of CSP mutant sporozoites

Undergraduate Student,
Bard College, NY

Enoch Chan,
Masters Student 2015-2017

Investigating neutrophil infiltration at the mosquito bite site

Technician, New York City, NY

Maya Aleshnick,
Masters Student 2014-2015

The probability that a single infected mosquito bite will lead to malaria infection

National Institutes of Health

Jianyang Wang,
Postdoctoral Fellow 2013-2015

Generation and testing of transgenic parasites for evaluation of immune sera

Staff Scientist, Naval Medical Research Center

Lirong Shi,
Research Technician 2013-2015

Characterization of the surface proteome of Plasmodium falciparum

Retired; Relaxing & spending time with family in China

Christine Hopp,
Postdoctoral Fellow 2012-2016

Intravital imaging and quantitative analysis of Plasmodium sporozoite motility at the inoculation site

Visiting Fellow, National Institutes of Health

Daniel Ragheb,
Postdoctoral Fellow 2011-2015

Studies on the amino terminus of the
circumsporozoite protein

Scientist, Novavax

Satish Mishra,
Postdoctoral Fellow 2012-2013

Characterization of Plasmodium merosomes

Senior Scientist, CSIR-Central Drug Research Institute, India

Brandy Lee Bennet,
Graduate Student 2007-2011

Generation and characterization of parasites lacking the cysteine protease bergheipain-1

Director of Program Management, Regeneron Pharmaceuticals

Mariana Justino Almeida,
Visiting Student 2010-2011

Role of subtilisin 3 in the malaria lifecycle

Graduate student, Columbia University

Alida Coppi,
Postdoctoral Fellow 2003-2008, Instructor 2008-2010

Conformational changes and proteolytic processing of the circumsporozoite protein & the use of cysteine protease inhibitors as anti-malarials

Senior Staff Scientist, Regeneron Pharmaceuticals

Ijeoma Ejigiri,
Graduate Student 2005-2009

Proteolytic processing of the thrombospondin related anonymous protein (TRAP) and the role of cleavage in sporozoite motility and infectivity

Resident in Internal Medicine, Emory University School of Medicine

Charlotte Hobbs,
Postdoctoral Fellow 2005-2008

Effect of HIV protease inhibitors on the pre-erythrocytic stages of Plasmodium

Assistant Professor, Pediatric Infectious Diseases, University of Mississippi Medical Center

Joana Santos,
Visiting Student 2005-2006

Generation of berghepain deletion mutants

Postdoctoral fellow,
Penn State University

Tatiana Voza,
Postdoctoral Fellow 2005-2007

Development of preerthrocytic stages of Plasmodium at the dermal inoculation site

Associate Professor, Biological Sciences Department, City University of New York

Lucy Lioni Yamauchi,
Postdoctoral Fellow 2003-2005

The kinetics with which Plasmodium sporozoites exit the inoculation site

Professor, Universidade Estadual de Londrina, Parana, Brasil

Darcy Medica,
Postdoctoral Fellow 2002-2004

Transmission dynamics of Plasmodium sporozoites during mosquito probing

Professor, Department of Biology, Pennsylvania State University

Ramya Natarajan,
Graduate Student 2002-2005

Generation of sporozoites with mutations in the circumsporozoite protein

Program Officer, National Institutes of Health

Consuelo Pinzon-Ortiz,
Research Technician 1999-2001

Studies on sporozoite adhesion to hepatocytes under flow conditions

Scientist, AstraZenica Pharmaceuticals


September 2018: Amanda Balaban gave a great talk at the Molecular Parasitology meeting in Woods Hole.

May 2018: Congratulations to Dr. Amanda Balaban for successfully defending her doctoral dissertation!

March 2018: Photini, together with Peter Crompton, talk about "The Challenge of Malaria: The World's Number One Killer" in the NIH's Demystifying Medicine course

October 2017: Sinnis Lab awarded Honorable Mention in the 2017 Nikon Small World in Motion Competition

September 2017: Gibbs Nasir was featured in a short video about the day in the life of a Hopkins Bloomberg Public Health Student

September 2017: Melanie Shears received a Best Poster Award at the 2017 Molecular Parasitology Meeting in Woods Hole

June 2017: Photini was elected as a Fellow of the American Society of Microbiology

Summer 2017: Photini is co-directing the Biology of Parasitism Course at the Marine Biological Laboratory in Woods Hole, Massachusetts

May 2017: Congratulations to our Graduates! Gibbs Nasir, Natasha Vartak, and Enoch Chan received their Master of Science degrees

April 2017: Sinnis lab research featured in a video about the Johns Hopkins Malaria Research Institute Click Here to Watch!

January 2017: Melanie Shears received a Johns Hopkins University Provost's Postdoctoral Fellowship and was recognized at the Annual Honors and Awards Ceremony. Congratulations Melanie!

Lab Photos

Good times from years past...

The Sinnis lab at the baseball game

Team building exercise

Post-lab meeting

Lab lunch

Lirong's farewell party

Getting filmed by the Bloomberg Foundation

Whitewater rafting

Photini's tenure celebration

Amanda's graduation party

Departmental Halloween Party

Lirong and Photini

Master's graduates!

Lab Lunch

Christmas Party at Photini's

Satish and Photini

Contact Us

We welcome e-mails from prospective students, post-docs, and collaborators

The Sinnis Lab is located on the 4th floor of the Johns Hopkins Bloomberg School of Public Health building on 615 N. Wolfe Street, in Room E4209.

Mailing Address

Johns Hopkins Bloomberg School of Public Health
Dept. Molecular Microbiology & Immunology
615 N. Wolfe St.
Baltimore, Maryland 21205,
United States

Office Phone: +1(410) 502-6918
Lab Phone: +1(443) 287-0129

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