Progress 07/01/08 to 06/30/13
Outputs
Target Audience: Scientific Community working on vector-borne diseases. Changes/Problems:
Nothing Reported
What opportunities for training and professional development has the project provided?
Nothing Reported
How have the results been disseminated to communities of interest? Peer Reviewed Publications What do you plan to do during the next reporting period to accomplish the goals?
Nothing Reported
Impacts
What was accomplished under these goals?
Mosquitoes are insect vectors responsible for the transmission of some devastating infectious diseases, such as malaria and dengue fever. Although many of these diseases were once all but eliminated from the United States, climate change and global travel/trade has greatly increased the risk of emergence and re-emergence of mosquito-borne diseases. Pathogens taken up by a female mosquito must undergo complex developmental transitions and survive numerous attacks from the mosquito’s innate immunity system to accomplish transmission from person to person. A variety of mosquito factors have been shown to affect the development of pathogens in the mosquito. Elucidating molecular basis of the intricate pathogen-vector interactions will reveal promising targets for the control of mosquito-borne diseases. Studying the immune reaction of mosquitoes in response to the invading pathogens requires comparison of protein synthesis between the infected and uninfected mosquitoes. The production of proteins in cells is controlled by genes in a two-step process. The first step is transcription in which the genetic code of one gene is replicated in a messenger RNA molecule (mRNA). The second step is translation in which the mRNA molecule carries the genetic code from the gene to a ribosome complex to create this particular protein. Current studies of mosquito immune reactions primarily monitor alterations in the level of cellular mRNA, but never addresses the equally critical issue of whether the mRNA abundance is closely correlated with the level of the corresponding protein. In this study, we compared the rate of protein synthesis using polysome profiling, which is based on the principle that actively translated messenger RNAs usually have multiple ribosomes associated with them, forming large structures known as polysomes. We discovered a previously neglected aspect of gene regulation in the midgut of Anopheles gambiae mosquitoes after ingestion of a blood meal containing the human malaria parasites Plasmodium falciparum. The mRNA levels of 1,017 mosquito genes showed no significant difference between the Plasmodium-infected and uninfected mosquitoes, but their mRNA association with polysomes increased significantly in the infected mosquitoes, suggesting that those genes produced more proteins in response to the Plasmodium infection. Proteins encoded by those genes are predicted to have diverse molecular functions, including some genes that have been shown previously to play pivotal roles in anti-Plasmodium immunity. Caspar, a negative regulator of the NF-kappaB transcription factor Rel2, appears to be substantially activated at the translational levels during Plasmodium infection. In addition, transcripts of Dcr1, Dcr2 and Drosha, which are involved in small RNA biosynthesis, exhibited enhanced associations with polysomes after P. falciparum challenge. This observation suggests that mosquito microRNAs may play an important role in reactions against Plasmodium invasion. This study provides more molecular details in the interaction between mosquitoes and malaria parasites, and identifies some mosquito factors that might have gone unrecognized because their mRNA levelswere not altered by exposure to the parasites. Functions of genes identified in this project will be further explored in future studies to reveal new targets that can be exploited to make mosquitoes unable to transmit diseases.
Publications
- Type:
Journal Articles
Status:
Published
Year Published:
2013
Citation:
Wu, X.B., Na, R.H., Wei, S.S., Zhu, J., and Peng, H.J. (2013) Distribution of tick-borne diseases in China. Parasites & Vectors 6:119.
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Progress 10/01/11 to 09/30/12
Outputs
OUTPUTS: In December 2011, we presented a poster in the American Society of Tropical Medicine and Hygiene (ASTMH) 60th Annual Meeting. We reported our recent progress to scientists, clinicians, and program professionals who are interested in control of infectious diseases. In December 2011, I was invited to give a seminar on the mosquito-pathogen interactions in the School of Public Health and Tropical Medicine, Southern Medical University, China. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Malaria is the most deadly tropical parasitic disease faced by mankind, responsible for around 1.2 million deaths each year. The malaria parasite Plasmodium must complete a complex developmental cycle in the mosquito in order to be transmitted from person to person. Midgut invasion is a major bottleneck for Plasmodium development inside the mosquito vectors. Malaria parasites in the midgut are surrounded by a hostile environment rich in digestive enzymes, while a rapidly responding immune system recognizes Plasmodium ookinetes and recruits killing factors from the midgut and surrounding tissues, dramatically reducing the population of invading ookinetes before they can successfully traverse the midgut epithelium. Understanding molecular details of the parasite-vector interactions requires precise measurement of nascent protein synthesis in the mosquito during Plasmodium infection. Current expression profiling primarily monitors alterations in steady-state levels of mRNA, but does not address the equally critical issue of whether the proteins encoded by the mRNAs are actually synthesized. We report a previously neglected aspect of gene regulation in the midgut of Anopheles gambiae mosquitoes after ingestion of a Plasmodium-infected blood meal. A plethora of mosquito genes show no significant difference in total cellular abundance between the Plasmodium-infected and uninfected mosquitoes, but exhibit a redistribution of their mRNA transcripts between translationally inactive mono-ribosomes and translationally active poly-ribosomes. Translational regulation allows cells to respond swiftly to all types of environmental stimuli and to fine-tune protein levels in both time and space. This finding supports our hypothesis that the anti-malarial response of Anopheles gambiae occurs at both the transcriptional and translational level. We simultaneously monitor transcriptomes and nascent protein synthesis in the mosquito. This approach provides more molecular details in the interaction between mosquitoes and malaria parasites, and identifies some mosquito factors that might have gone unrecognized because their transcription is not altered by exposure to the parasites. Functions of genes identified in this project will be further explored in future studies to reveal new targets that can be employed to make mosquitoes unable to transmit diseases, and will potentially help elucidate the molecular basis of vectoring.
Publications
- Mead, E.A., Li, M., Tu, Z. and Zhu, J. (2012). Translational regulation of Anopheles gambiae mRNAs in the midgut during Plasmodium falciparum infection. BMC Genomics. 13:366.
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Progress 10/01/10 to 09/30/11
Outputs
OUTPUTS: I supervised and trained a Postdoctoral Research Associate who worked on this project. In summer 2011, I mentored an undergraduate student in the Multicultural Academic Opportunities Program (MAOP). This student conducted research on the mosquito-pathogen interaction and made impressive progress. In December 2010, I was invited to give a seminar in the Entomological Society of America 58th Annual Meeting. I presented our new discoveries regarding gene regulation in adult female mosquitoes. The meeting attracted more than 3,000 researchers, professors, extension service personnel, research technicians, consultants, graduate and undergraduate students from around the world. PARTICIPANTS: Not relevant to this project. TARGET AUDIENCES: Scientific Community. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Malaria is caused by Plasmodium parasites, which are transmitted via the bites of infected mosquitoes. The success of transmission is largely dependent on whether the pathogens can avert or suppress the innate immune responses of the mosquito vectors. Understanding molecular details of the parasite-vector interactions relies heavily on precise measurement of nascent protein synthesis in the mosquito during Plasmodium infection. Current expression profiling primarily monitors alterations in steady-state levels of messenger RNA (mRNA), but does not address the equally critical issue of whether the proteins encoded by the mRNAs are actually synthesized. We combine the profiling of total cellular mRNA with genome-wide analysis of mRNA translational states to simultaneously monitor changes in the transcriptome and nascent protein synthesis in the mosquito. This approach provides more accurate information regarding the rate of protein synthesis, and leads to identification of 355 mosquito genes that are primarily regulated at the translational level after ingestion of Plasmodium-infected blood. Some of these genes have been previously shown to play important roles in regulating mosquito innate immunity. Our study clearly demonstrates a new mechanism for boosting the immune responses in the infected mosquitoes. In addition, our results indicate that expression of several key players in the microRNA pathway is substantially activated at the translational levels during Plasmodium infection, suggesting that mosquito microRNAs are involved in defense reactions against Plasmodium invasion. Elucidating functions of the newly identified genes will undoubtedly advance our understanding of the pathogen-vector interactions, and provide novel targets for blocking transmission of the mosquito-borne diseases.
Publications
- No publications reported this period
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Progress 10/01/09 to 09/30/10
Outputs
OUTPUTS: From August, 2009 to July, 2010, I supervised a VT-PREP scholar who worked on this project in my laboratory. VT-PREP is a 12 to 24-month mentored research experiential work and educational program supported by National Institute of Health. It aims to prepare post-baccalaureate scholars from underrepresented ethnic groups for the successful pursuit of a PhD and a research career in the biomedical and behavioral sciences. After the training, the scholar was admitted to a graduate program in the University of Porto Rico, and is currently studying vector-borne infectious disease. We have also launched collaboration with Dr. Luiz Shozo Ozaki at the Virginia Commonwealth University to test the feasibility of using bacterial viruses as genetic tool for blocking transmission of the malaria parasite. A proposal has been submitted to the Bill & Melinda Gates Foundation to seek financial support for innovative solutions to improve global health. PARTICIPANTS: Dr. Jinsong Zhu, PI; Dr. Edward Mead, Postdoctoral Associate; Yashira M. Afanador, VT-PREP Scholar. Collaborator: Luiz Shozo Ozaki, Ph.D., Associate Professor, Virginia Commonwealth University, Department of Microbiology and Immunology; Center for the Study of Biological Complexity TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Approximately 243 million malaria cases and 863,000 attributed deaths were reported globally in 2009 (World Health Organization, 2009). The malaria parasite Plasmodium must undergo complex developmental transitions and survive numerous attacks from the mosquito's innate immunity system to accomplish transmission from person to person. Elucidating the molecular basis of the parasite-vector interactions is of utmost interest for the development of vector-based malaria control strategies. MicroRNAs (miRNA) are small endogenous regulatory molecules that suppress gene expression either through inhibition of translation or through mRNA degradation. We hypothesize that regulation of protein synthesis by miRNAs forms another layer of regulatory control in the mosquito defense against malaria parasites. To test this hypothesis, we assessed the effects of Plasmodium infection on the miRNA abundance in the mosquito midgut. A cage of Anopheles gambiae G3 mosquitoes were fed on a mouse infected with rodent malaria. As a control, a replicate cage of G3 mosquitoes was fed on a mouse of the same cohort that was uninfected. Midguts were dissected from the mosquitoes at 24 hours after blood feeding for RNA extraction. miRNAs were analyzed by using next generation sequencing technology. miRNA expression levels were compared based on the number of reads obtained after normalization. We have obtained 20,055,530 reads and 19,512,521 reads from mosquitoes that were fed on Plasmodium-infected or uninfected blood respectively. 50 miRNAs were found to have at least 100 reads in one of the two samples. Substantial changes in miRNA abundance were observed for some miRNAs. For example, levels of aga-miR-X1 increase over 7 times in mosquitoes fed on the infected blood as compared to the control group, while the amount of aga-miR-989 in the infected mosquitoes was about 25 percent of that in the control group. Although it is not clear whether these miRNAs play a direct role in defense against the parasites, this study undoubtedly establishes a close link between Plasmodium infection and the changes in the miRNA expression, providing a solid basis for further study.
Publications
- No publications reported this period
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Progress 10/01/08 to 09/30/09
Outputs
OUTPUTS: A poster was presented by my laboratory in the American Society of Tropical Health and Hygiene (ASTMH) 2008 annual meeting in New Orleans. We reported our recent progress to scientists, clinicians, and program professionals who are interested in control of infectious diseases. In July 2009, I was invited to give a seminar on the mosquito-pathogen interactions in Shanghai Institute of Plant Physiology & Ecology (Chinese Academy of Sciences). While in Shanghai, I discussed and shared ideas with many European and American insect scientists who were attending the 2009 International Symposium on Insect Physiology, Biochemistry and Molecular Biology. As a continuous effort to seek collaborators, I gave a talk on the potential implications of our current study in the School of Life Science and Biotechnology, Shanghai JiaoTong University. In the graduate student recruiting weekend hosted by the Fralin Life Science Institute at Virginia Tech, I also gave an introduction to the students who are interested in research on infectious diseases. PARTICIPANTS: Nothing significant to report during this reporting period. TARGET AUDIENCES: Nothing significant to report during this reporting period. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Pathogens transmitted by mosquitoes, such as malaria parasites and Dengue viruses, have to undergo sophisticated development and multiplication inside the mosquito vectors before they are passed on and infect the next victim. The success of transmission is largely dependent on whether the pathogens can avert or suppress the innate immune responses of the mosquito vectors. Therefore, it is important to understand how the pathogens affect mosquito gene expression upon feeding of a pathogen-infected blood meal. While most other studies focus only on transcriptional regulation of mosquito genes, our laboratory is combining deep sequencing-based whole transcriptome analysis with polysomal profiling, to identify both transcriptional and translational regulation of mosquito genes in the interactions between pathogens and vectors. This new approach has revealed novel genes that were not contained in the current genome annotation. We are discovering mosquito genes that are primarily regulated by translational mechanisms in response to the pathogen infection. Elucidating functions of the newly discovered or previously overlooked genes will undoubtedly advance our understanding of the pathogen-vector interactions, and provide novel targets for blocking transmission of the mosquito-borne diseases.
Publications
- No publications reported this period
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Progress 07/01/08 to 09/30/08
Outputs
OUTPUTS: A poster presentation was given in the Dean's Forum on Infectious Diseases at Virginia Tech on September 29, 2008. The goal and experimental procedures of this project were illustrated. The principal investigator exchanged ideas and shared information with scientists from Virginia, several other states, and from federal government. PARTICIPANTS: Jinsong Zhu, Ph.D., Principal Investigator. Xing Zhang, Ph.D., Postdoctoral Associate. Jeff Busche, Graduate Student. TARGET AUDIENCES: Not relevant to this project. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
An active area of investigation has been the molecular basis of mosquito defense against infection by malaria parasites and dengue virus. While most studies focus on transcriptional regulation of mosquito genes, we have relatively little understanding of protein changes. It is plausible that some defenses might have gone unrecognized because they are regulated at translation rather than at transcription. We are performing a comprehensive study of translation regulation of mosquito genes after adult mosquitoes ingest vertebrate blood infected with malaria parasites or dengue viruses. Nascent protein synthesis will be monitored by microarray analysis of mRNA associated with polyribosomes. We demonstrate that the subcellular distribution of mRNAs accurately reflects their translational status. This result was shared with many scientists in the field of vector biology. They show a high level of enthusiasm for this innovative approach, and want to be kept informed about the progress. They believe that this project will shed light on an under-studied area and advance the understanding of mosquito-parasite interactions.
Publications
- Bian, G., Raikhel, A. S., and Zhu, J. (2008) Characterization of a juvenile hormone-regulated chymotrypsin-like serine protease gene in Aedes aegypti mosquito. Insect Biochemistry and Molecular Biology. 38: 190-200.
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