Engineering of viral structural proteins
Our research group is currently involved in several closely related projects. The main aim of our work is design of the virus-like particles (VLPs) with defined structural and immunological properties. VLPs can be obtained by heterologous expression of a wide range of viral structural genes. VLPs exhibit morphology, antigenicity, and cell tropism similar to the native viruses but are non-infectious, due to the absence of viral nucleic acid. The repetitive antigenic structure of VLPs makes them highly immunogenic. However, per se assembly incompetent proteins of viruses and other pathogens may profit from the highly organized structure of VLPs. Therefore, different strategies have been developed to present foreign protein segments on the surface of VLPs. Such engineered VLPs can be used for a wide range of applications, e.g. for serodiagnostics, gene transfer and vaccine development.  
 
Research group
 

Andris Kazāks
Dr.Biol. Group leader.  
Leader of project “Recombinant hantavirus antigens for diagnostic purposes; isolation and comparative analysis of viral genome sequences”.  
(tel. 7808242, e-mail: andris@biomed.lu.lv)
 
Worldwide, hantaviruses cause more than 100,000 human infections annually. These infections are hemorrhagic fever with renal syndrome and hantavirus pulmonary syndrome. Rapid and accurate methods are important both in monitoring acute infections and for epidemiological studies.  
This study was initiated with an aim to test prevalence of hantavirus infection in Latvia. It is planned to evaluate immunoenzyme assays based on several hantavirus nucleocapsid proteins (N-proteins) for detection of IgG and IgM antibodies in human sera. Generation of highly pure N-proteins will be performed by affinity chromatography.  
 

Jānis Freivalds
MSc.Biol. Participates in project “Combined use of E. coli, S. cerevisiae and P. pastoris expression systems to obtain recombinant proteins in functional form” (leader of project Dr. A. Dišlers).
e-mail: janitis@biomed.lu.lv
 
To ensure high-level synthesis and formation of VLPs, the choice of proper expression system is of major importance. Bacteria Escherichia coli is one of the most commonly used host, however, a lot of structural genes from mammalian viruses do not form VLPs in bacteria and should be synthesized in eukaryotic cells. Yeast as a simpliest eukaryote represents attractive alternative system behind E. coli for several of its advantages, such as posttranslacional modifications, lack of endotoxins, and better outcome of biomass. Currently, synthesis and self-assembly of coat protein of bacterial virus in yeast Saccharomyces cerevisiae and Pichia pastoris is under investigation.
 

Reinis Balmaks
Medical student. Participates in project “Construction of recombinant melanoma vaccine candidates” (leader of project Dr. P. Pumpēns).
e-mail: reinis@biomed.lu.lv
 
Hepatitis B virus core protein (HBc) is one of the most intensively studied VLP models and has been successfully used for incorporation of more than 100 foreign sequences. A number of chimeric HBc genes with incorporated coding sequence from tumor-specific MAGE-3 antigen epitope were generated by gene engineering techniques and expressed in Escherichia coli. The chimeric particles were purified from E. coli proteins for further loading with imunostimulatory CpG oligodeoxynucleotides. Such VLPs could possibly be used as antitumor vaccines.
       
Larisa Kovaļevska
Technician. Expert in purification of hepatitis B nucleocapsid-derived recombinant proteins