INSECT CELL

AND VIRAL PROTEINS

IDENTIFICATION AND USE: Insect cells (IC) and particularly lepidopteran cells are an attractive alternative to mammalian cells for biomanufacturing. Insect cell culture, coupled with the lytic expression capacity of baculovirus expression vector systems (BEVS), constitutes a powerful platform, IC-BEVS, for the abundant and versatile formation of heterologous gene products, including proteins, vaccines and vectors for gene therapy. Such products can be manufactured on a large scale thanks to the development of efficient and scalable production processes involving the integration of a cell growth stage and a stage of cell infection with the recombinant baculovirus vector.

Insect cells can produce multimeric proteins functionally equivalent to the natural ones and engineered vectors can be used for efficient expression. Insect cells can be cultivated easily in serum- and protein-free media. Insect cell culture is a common choice for heterologous protein expression. For large scale production or basic research, insect cells are able to express large quantities of protein with complex post-translational modifications. Sf9 (Cat. no. B825-01) and Sf21 (Cat. no. B821-01) cell lines are the traditional cell lines used with baculovirus and originated at the USDA Insect Pathology Laboratory. The cell lines are also suitable for use in the InsectSelect™ System. These two cell lines originated from the IPLBSF-21 cell line, derived from the pupal ovarian tissue of the fall armyworm, Spodoptera frugiperda (O’Reilly et al., 1992; Vaughn et al., 1977). When working with recombinant or wild-type viral stocks (e.g.,infecting cells), always maintain separate media bottles for cell culture and for virus work. Baculovirus particles can survive and be maintained in media at 4°C, and will contaminate your stock cultures if introduced to culture plates or flasks during passaging

COMMON PROBLEMS ASSOCIATED WITH INSECT CELL CULTURE: morphological changes in the cells or changes in the growth rate can indicate an underlying problem with the culture. Baculoviruses are arthropod‐specific, enveloped viruses with circular, supercoiled double‐stranded DNA genomes. They infect Lepidoptera (butterflies and moths), Hymenoptera (sawflies) and Diptera (mosquitoes). While many viruses are studied because of their damaging effects, the study of baculoviruses was stimulated by their potential utility to control insect pests. Later, the utility of baculovirus as gene expression vectors was evidenced and a new research area emerged. A major step forward was the development of bacmid technology (the construction of bacterial artificial chromosomes containing the genome of the baculovirus) which allows the manipulation of the baculovirus genome in bacteria. With this technology, foreign genes can be introduced into the bacmid by site‐directed recombination or by transposition.

HUMAN STUDIES: Baculoviruses have been used to explore fundamental questions in molecular biology such as the nature of programmed cell‐death. Moreover, the ability of baculoviruses to transduce mammalian cells led to the consideration of their use as gene therapy and vaccine vectors. Strategies for genetic engineering of baculoviruses have been developed to meet the requirements of new application areas, and the establishment of new genetic modification systems is still necessary when an unexplored experimental system is to be addressed.

A new vaccine for influenza has hit the market, and it is the first ever to contain genetically-modified (GM) proteins derived from insect cells. According to reports, the U.S. Food and Drug Administration (FDA) recently approved the vaccine, known as Flublok, which contains recombinant DNA technology and an insect virus known as baculovirus that is purported to help facilitate the more rapid production of vaccines.

According to Flublok’s package insert, the vaccine is trivalent, which means it contains GM proteins from three different flu strains. The vaccine’s manufacturer, Protein Sciences Corporation (PSC), explains that Flublok is produced by extracting cells from the fall armyworm, a type of caterpillar, and genetically altering them to produce large amounts of hemagglutinin, a flu virus protein that enables the flu virus itself to enter the body quickly. So rather than have to produce vaccines the “traditional” way using egg cultures, vaccine manufacturers will now have the ability to rapidly produce large batches of flu virus protein using GMOs, which is sure to increase profits for the vaccine industry.

ADVERSE EFFECTS: serious side effects, including the deadly nerve disease Guillain-Barre Syndrome (GSB), which is listed on the shot as a potential side effect. If Guillain-Barre Syndrome (GBS) has occurred within six weeks of receipt of a prior influenza vaccine, the decision to give Flublock should be based on careful consideration of the potential benefits and risks,” explains a section of the vaccine’s literature entitled “Warnings and Precautions.” Other potential side effects include allergic reactions, respiratory infections, headaches, fatigue, altered immunocompetence, rhinorrhea, and myalgia. According to clinical data provided by PSC in Flublok’s package insert, two study participants actually died during trials of the vaccine, but the company still insists Flublok is safe and effective, and that it is about 45 percent effective against all strains of influenza in circulation, rather than just one or two strains.

FOUND IN THE FOLLOWING VACCINES: HPV (CERVARIX) AND INFLUENZA (FLUBLOCK)