Fundamental Molecular Biology Drift in Influenza Virus

Question: Discuss about the Fundamental Molecular Biology? Answer: Technology has advanced by leaps and bounds and made the great revolution in the field of biotechnology. In the present world, the DNA-based recombinant technology has gained massive popularity. With this tool scientists can make some interesting gene manipulations. The standard sequence includes gene isolation from desired source, cleaving and introducing them into the target organism's genome to transfer required characteristics. Talking about Recombinant DNA Technology (RDT) one word that none can stop recalling is the wonderful "Superbug." It was an important product of RDT to play a prominent role in bioremediation. RDT has been applied in medical field. In this paper, the author tries to emphasize the role of RDT in vaccination. The essay will take us to the details of the preparation of the DNA vaccines and how it is introduced into the host and its clinical efficacy. It will further throw light on the outcome of DNA vaccines and the research conducted in this area. A vaccine may be an antigen of bacterial or viral origin exposed to an individual to evoke an immune response of that individual by the formation of antibodies. The process of generating the systemic immune response is called as vaccination. However, the antigenic material is prepared in a manner such that it is non-toxic, but it can trigger humoral and cell-mediated immune response against the pathogen (Kowalczyk et al., 1997), figure 1. The immune system responses to proteins and peptides on the bacterial surface. Several vaccines are commercially prepared by using recombinant hosts. During preparation of vaccines only surface features of bacteria are considered (Kindt et al., 2007). DNA vaccines are the modern types of vaccines prepared by RDT. There is ongoing research on development of vector vaccines for various diseases like HIV, Malaria, etc. In these genetic vaccines, the genome of a pathogen is fragmented, and the genes encoding proteins are directly introduced into say muscle cells of the host by in vivo transfection. So that the gene can integrate into the chromosomal DNA. Inside the host, the foreign proteins are expressed. Dendritic cells also present these antigens. This triggers the production of ctyotoxic T lymphocytes which recognise peptides associated with Major Histocompatibility Complex (Kindt et al., 2007). In the case of DNA vector vaccines, genes encoding the bacterial proteins are initially introduced into non-virulent bacteria that serve as vector or carrier. The genes and the vector are cleaved by same restriction endonuclease and are ligated using DNA ligase (as shown in figure 2). The vector is introduced in the host where it replicates and expresses the gene product of the pathogen. The vectors contain an origin of replication, antibiotic resistant markers like ampicillin that helps selection of only transformed bacteria in the ampicillin containing media, a restriction site and extra non-essential DNA (Kowalczyk et al., 1997). The antibiotic resistance gene is called as selectable markers as this helps to select only those bacteria in the media that contains vector which imparts resistance property to the bacteria. The non-transformed bacteria do not grow on media due to antibiotic sensitivity. Inside the bacteria vector replicates to express the protein encoded by the pathogen . Plasmids are introduced into host by intradermal or intramuscular injection along with diluents such as saline or sucrose and sometimes gene gun method is used. Yellow fever vaccine developed can express the product of West Nile Virus. This was the first vaccine developed for horses that showed enhanced immune response. Various micro-organisms used for DNA vaccine is vaccinia virus, adenovirus, etc. (Donnelly et al., 1995). Figure 2 describes the production of recombinant vaccinia vector vaccine. When DNA vaccine containing malarial gene was administered to human subjects, there was enhanced CTL and antibody response. However the response was low as compared to that observed in mice (Sedar et al., 2013). Therefore, there is need for more research to recommend DNA vaccine finally for human use in next few years (Monath, 2005) DNA vaccines are effective as they are not denatured inside the host and seem promising to protect against several diseases. In near future DNA vaccine will move from clinical trials to effective safe human use. It's a cost-effective and straightforward process as it can be delivered easily and has no special storage requirements. It has been found effective against influenza, rabies, etc. However, there are more complications to it because the delivery of polysaccharide antigen is not as easy as that of protein antigens. Figure 1: the Overview of an immune response to DNA vaccine. (Source: Kowalczyk et al., 1997) Figure 2: Production of vaccine by vaccinia vector. (Source: Kindt et al., 2007. The desired gene is introduced into vaccinia vector. Flanked by Thymidine kinase. The recombinant virus so produced contains the genome of pathogen and promoter of a virus at the nonessential site TK site. Thus, the cells are TK- and rescued in the medium containing Budr that kills TK+ cells). References Donnelly, J. J., Friedman, A., Martinez, D., Montgomery, D. L., Shiver, J. W., Motzel, S. L., ... Liu, M. A. (1995). Preclinical efficacy of a prototype DNA vaccine: enhanced protection against antigenic drift in influenza virus. Nature medicine, 1(6), 583-587. Kindt, T. J., Goldsby, R. A., Osborne, B. A., Kuby, J. (2007). Kuby immunology. Macmillan. Kowalczyk, D. W., Ertl, H. C. J. (1999). Immune responses to DNA vaccines. Cellular and Molecular Life Sciences CMLS, 55(5), 751-770. Monath, T. P. (2005). Yellow fever vaccine. Expert review of vaccines, 4(4), 553-574. Sedar, R. A.., Chang, L. J., Enama, M. E., Zephir, K. L., Sarwar, U. N., Gordon, I. J., Richman, A. (2013). Protection against malaria by intravenous immunization with a nonreplicating sporozite vaccine. Science, 341 (6152), 1359-1365.