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Acting Head: Jongsik Chun, Ph.D.

Understanding biological nature of microbial pathogens is one of the prerequisites for successful vaccine development. After the first pathogenic bacterium, namely Haemophilus influenzae, was sequenced by the researchers at TIGR in 1995, there has been a flood of genome sequences of most major killers such as vibrios, salmonellas and shigellas. It is evident that vaccine development should take advantage of this wealth of genomic information. Molecular Microbiology Department has been established in 2004 to tackle the problems of vaccine development using the state-of-art molecular biological techniques and bioinformatics. The department is currently divided into three sections: Molecular Genetics, Molecular Vaccinology and Bioinformatics.

 


1) Section : Bioinformatics
Person in charge: Jongsik Chun, Ph.D.
 
Message
Bioinformatics has become an essential part in biological researches and vaccine development is not an exception. The goal of this laboratory to establish an integrated database management system for the Laboratory Sciences Division. Multi-user, intranet-based computer servers are generated to deal with the following functions.
- Storage of information on biological resources at the IVI bio-bank (Strains, DNA, sera, blood etc.).
- User-friendly interface
- Sophisticated bio-data analysis
 
Research interests
- Development of novel typing methods for bacterial pathogens
- Development of software tools in comparative genomics
- Comparative genomic analysis of bacterial pathogens
- Establishment of integrated typing system for bacterial pathogens
 


2) Section: Molecular Vaccinology
Person in charge: Manki Song, Ph.D.
 
Introduction
 
We started Molecular Vaccinology Laboratory from Jul. 1st, 2004 in the IVI. Our research will focus on the molecular and immunological study to develop new generation vaccines and to evaluate and characterize the immune responses induced by conventional vaccines. Research at the IVI focuses on infectious diseases that afflict people in less-developed countries. Our research concerned with the characterization, establishment, and use of animal models to assess the immunogenicity of vaccine candidates developed at the IVI or other institutes, to determine their potentials for further evaluation in human clinical trials. Anyone who has interested in the vaccine studies don't hesitate to contact us.
 
Research Interest
 
DNA Vaccines
In 1990, a novel and powerful method for vaccine research, known as DNA vaccines has been introduced. The gene for an antigenic determinant of a pathogenic organism is inserted into a plasmid. This genetically engineered plasmid comprises the DNA vaccine which is then injected into the host. Within the host cells, the foreign gene can be expressed from the plasmid DNA, and they elicit an immune response. DNA vaccines have several distinct advantages, which include ease of manipulation, use of a generic technology, simplicity of manufacture, and chemical and biological stability. In addition, DNA vaccines induce long-lasting, antigen specific Th1 and CTL responses which are important for the protection from intracellular pathogens like virus and some bacteria. DNA vaccines are at present experimental, but hold promise for future therapy since they can induce both humoral and cell-mediated immunity, without the dangers associated with live virus vaccines. Our study will focus on the new generation DNA vaccines to enhance the antigen expression and delivery to the host.
 
 
Oral delivery of DNA vaccines
This research focuses on the evaluation and characterization of immune responses induced by Shigella and Salmonella live vector vaccines expressing bacterial and viral antigens or as delivery vehicles for DNA vaccines. This strategy is intended to prime the immune system through the mucosal route to elicit protective immune responses. One of the main limitations of DNA vaccines has been the lack of an induced mucosal response, i.e., IgA isotype immunoglobulins produced on mucosal surfaces and in exocrine gland secretions. Secreted IgA represents the most efficient and effective immune barrier against a number of pathogens, such as virus and enteric bacterial pathogens which use the intestinal mucosal surface to gain access to the mammalian host. We will study the combination of this recombinant bacterial vaccine with naked-DNA vaccine using prime-boost strategy to achive optimal immune responses.
 
 
Our Mission
 
Development of TB Vaccine
To be an effective prophylactic and therapeutic tuberculosis (TB) vaccine, the induction of Th1 type immune responses are essential. Among the vaccination strategies, DNA vaccines have been known to induce strong Th1 type immune responses. To develop a new generation DNA vaccine to TB, we will use Sindbis virus replicon system as a naked DNA vaccine. It was previously reported that pSINCP-85A shows enhanced immunogenicity and long-term protection against TB compared with the conventional DNA vaccine vector. In this study, we will compare the immune responses induced by conventional vector and pSINCP encoding several TB Ags either codon-optimized or not. Recently, we observed that attenuated Salmonella typhi which has DNA vaccine plasmid encoding measles virus (MV) H could induce three times higher IFN- immune responses than naked DNA vaccine. Hence, we will try these attenuated bacteria as a delivery system of DNA vaccine.
Tuberculosis (TB) remains a significant worldwide health problem killing more than 2 millions annually. Attempts over the years to vaccinate with the attenuated BCG strain of Mycobacterium bovis have proved disappointing; in various studies, its efficacy has varied from 0 to 80%. About 30% of the world's population has latent M. tuberculosis infection and 5-10% of those with latent infection are expected to develop clinical tuberculosis at a later stage. Clearly, there remains an urgent need for a new prophylactic and therapeutic TB vaccine. Recently, there have been many studies about DNA vaccination to prevent and cure infectious diseases that require cell-mediated immune responses, including TB. The reports about DNA vaccination against TB have been accumulating. Various target antigens (Ags) for TB DNA vaccination have been reported, including the Ag85 complex molecules, Hsp65, Hsp70, the 38-kDa Ag, ESAT-6 and so on.
 
DNA vaccines have many advantages over other methods of immunization: they have a relatively easy of production, safety, a strong induction of cellular immunity, and so on. For successful results with DNA vaccination, however, intramuscular immunization (i.m.) with large amounts of plasmid DNA was reported to be necessary and the induction of immunity with i.m. of plasmid DNA is poor in terms of reproducibility. Recently, many investigators tried attenuated intracellular bacteria as the carriers of DNA vaccines. These bacterial carrier systems have several special features, like direct delivery of the plasmid DNA to professional antigen-presenting cells, low cost of production and the possibility of mucosal administration where is the major route of infection. Bacteria used as this type of vaccine carrier include Salmonella, Shigella and Listeria.
 
While DNA vaccination has been shown to induce strong humoral and cellular immune responses in mice, it is far less immunogenic in humans. Incorporation of Sindbis virus replicons into plasmid DNA vectors for the amplification of RNA expressing the gene of interest has been an exciting approach toward improving DNA vaccination. Vectors encoding the replicons have been shown to be immunogenic in mouse models at doses up to 1,000-fold lower than those used for conventional plasmid vectors and are effective when used as vaccines against viral infections in monkey experiments. Recently, one research showed that pSINCP vector expressing Ag85 has enhanced immunogenicity against TB compared with the conventional DNA vaccine vector.
 
 
Development of SARS Vaccine and Building International Network for SARS Research
Due to the sudden outbreak of Severe Acute Respiratory Syndrome (SARS) worldwide, the needs for effective vaccines are very high. Recently, I applied research grant for SARS DNA vaccine and building international networks to collaborate for SARS research. Recently, KCDC accepted our proposal. They will apply 8.5 million dollars per year for 9 years to the National Assembly of Korea to expand this project. KCDC and many Korean scientists asked us to make international networks especially with China to get information and materials needed for SARS research, like patient sera, inactivated virus particle, genes and so on.
Studies of the immune responses to corona viruses imply that both cell-mediated and humoral immunity contribute for the long-term protection. Based on this result, we will apply DNA vaccine priming and recombinant adenovirus boosting approach to develop efficient SARS vaccine.
The spike protein (S) of SARS-CoV is a ~180-kDa glycoprotein and has been shown to be an important component of candidate vaccines. Recently, it has been shown that the neutralization antibody (nAb) to S is more important for the protection of mice against SARS-CoV infection than T-cell immunity induced by DNA vaccination. Similar results were observed with the highly attenuated modified vaccinia virus Ankara (MVA) containing the gene encoding full-length SARS-CoV S. Based on these results, the induction of nAb to S protein is essential to generate efficient SARS-CoV vaccine. However, these experiments were done in mice. Clinical observations in SARS patients imply both humoral and cell-mediated immune responses may be needed to prevent SARS-CoV infection. Apparent depletion of T cells occurred in the early infection and a gradual increase to normal level was observed as the patients recovered. Therefore, to be an effective vaccine for SARS-CoV, both nAb and T-cell immunities are might be important.
 


3) Section: Molecular genetics
Person in charge : Dong Wook Kim
 
Introduction
 
We are currently establishing the molecular genetics laboratory in IVI. Scientists in the molecular genetics section are involved in studying the molecular, cellular basis of the inflammatory destruction of the intestinal barrier by invasive bacteria Shigella species. Shigella is a gram-negative bacillus responsible for bacillary dysentery, an acute recto-colitis that causes about 160 million cases every year, with 600,000 to 1 million deaths, mostly young children in the developing areas of the world. The research aims of the molecular genetics section have been (i) to identify the repertoire of Shigella genes encoding the invasive phenotype, their regulation and the functional organization, (ii) to decipher the molecular cross talks occurring between the bacterium and the mammalian cell targets that lead to its internalization, escape into the cytoplasm; (iii) to establish in vitro and in vivo models to study how bacteria invade, disrupt and cause the inflammatory destruction of the intestinal epithelium; and (iv) to identify the inductive and effective mechanisms of the innate and adaptive immune responses against Shigella. From this study, we can understand detailed mechanisms of bacterial infection and this can be applied to develop more efficient live-vaccine strains.
We have a wonderful opportunity in IVI to access to various pathogens such as Salmonella Typhi, S.Paratyphi A, B, C, and Vibrio cholera from the epidemic regions. The molecular genetics section will develop molecular epidemiological analysis methods of these pathogens using various molecular biological techniques.

 
Our Mission
 
Virulence factors analysis
Type III secretion (TTS) pathway is used by numerous Gram-negative pathogenic bacteria to deliver virulence factors (proteins) to the membrane or directly to the cytoplasm of host cells, where they interfere with cellular signaling pathways. Shigella, Yersinia, Salmonella, enteropathogenic E.coli, and some plant pathogens use the type III secretion. The TTS system consists of
1) secretion apparatus
2) translocators that are inserted into the host cell membrane and effectors that are translocated into the host cell cytoplasm
3) Specific cytoplasmic chaperones that associate with the translocators and effectors within the bacterial cytoplasm
4) Transcriptional regulators required for the expression of TTS components
The functions of the effector molecules are to invade the host, avoid or resist the innate immune response, damage the cell etc. We focus on effector molecules that facilitate the bacteria to escape from the host immune response. For this study, we apply a multidisciplinary approach that encompasses molecular genetics, biochemistry, functional genomics, and cell biology.
 
Development of genetically-attenuated vaccine strain of Shigella flexneri
In collaboration with unit PMM (Molecular Microbiology of Pathogen) of Pasteur Institute in France, we are developing genetically attenuated Shigella vaccine strains. Using the knowledge acquired from the study of virulence factors we will construct genetically modified strains and characterize these strains by a number of routine tests (infectivity, dissemination, and other physiological tests). One difficulty in Shigella vaccine development is that there is no adequate animal model. Unit PMM is developing a 'humanized mouse' model for Shigella infection, and upon the construction of this humanized mouse model, we will test our candidate strains.
 
Genotypic characterization of pathogens.
We are now planning a collection of pathogens from all over the world. The purpose of this study is to identify the bacteria responsible for infectious diseases, their biological relationships and global distribution of the bacteria and drug-resistance. With various techniques including plasmid analysis, ribotyping, pulsed-field electrophoresis, and multi locus sequence typing, we will build a pathogen collection for establishing a reference laboratory.