The use of mammalian culture systems is important for biomedical research today. This becomes important for simulating in vivo experiments such as producing biomolecules like growth factors or culturing pathogens for culturing pathogens and also mechanistic studies. Cell lines offer an advantage over animal models. The use of established cell lines, however, faces challenges as oncogenes or oncogenic viruses have been used to transform the cancer cell lines. These transforming agents can play a role in the outcome of primary cell culture experiments. For example, Adenovirus 5 derived insertions (4344 nucleotides) are seen in the HEK 293 cells that can interact with many proteins to influence the results of assays. The SV40 large T antigen is expressed by HEK 293-derived 293T cells.
Among the causes of infectious diseases, viral diseases are a huge challenge. According to IZA Discussion published in 2015, 30% of the population was targeted by the influenza virus during the 1918 pandemic. Another viral disease: gastroenteritis targets 20 and 40 percent of the US and European population. An article published in The Indian journal of medical research in 2019 reported emerging viral diseases such as pathogenic avian influenza (AI) infection (H5N1) and Nipah viral disease. According to the Integrated Disease Surveillance Programme (IDSP), viral diseases were the cause of 71% of epidemic- like outbreaks in 2017.
Thus, the study of viruses becomes an indispensable tool to understand the viral life cycle and design suitable treatments. In terms of outbreaks, the use of primary cell culture to study viruses is very useful for initial studies. According to 2011 research in The Journal of Clinical Investigation by Boeckh and Geballe, one of 8 herpes viruses that affect mainly immune-compromised patients. The seroprevalence of the disease is seen in 50% of the United States. Despite the prevalence, the disease does not cause serious symptoms in healthy individuals but can damage organs and be fatal in immunocompromised individuals and newborns.
The in vitro and in vivo study of viruses such as cytomegaloviruses can be facilitated by the use of model systems. One system for studying the pathogenesis of the virus is mouse cytomegalovirus (MCMV) that however can be replicated in specific species such as NIH/3T3. As cytomegaloviruses are highly specific, studying the effect of these viruses in humans in small animals such as rats is not meaningful. This requires the use of mice using MCMV as infection models in a native host animal to study a DNA virus. This makes the use of MCMV relevant in fundamental research in immunology.
A system to establish adherent mouse newborn cells (MNC) was reported in 2017 in PlosOne that showed the properties of mouse embryonic fibroblasts. This becomes significant given that these cells are considered the gold standard for titrating and propagating viruses. This approach of Primary Cultures can thus lower the use of animals for the purpose of experiments.
Jérôme Adda. Economic Activity and the Spread of Viral Diseases: Evidence from High-Frequency Data. IZA Discussion Paper No. 9326. September 2015.
Mourya, D. T., Yadav, P. D., Ullas, P. T., Bhardwaj, S. D., Sahay, R. R., Chadha, M. S., … Singh, S. K. (2019). Emerging/re-emerging viral diseases & new viruses on the Indian horizon. The Indian journal of medical research, 149(4), 447–467. doi:10.4103/ijmr.IJMR_1239_18
Boeckh, M., & Geballe, A. P. (2011). Cytomegalovirus: pathogen, paradigm, and puzzle. The Journal of clinical investigation, 121(5), 1673–1680. doi:10.1172/JCI45449.
Le-Trilling VTK, Trilling M (2017) Mouse newborn cells allow highly productive mouse cytomegalovirus replication, constituting a novel convenient primary cell culture system. PLoS ONE 12(3): e0174695.