Today, many thousands of recombinant proteins, ranging from cytosolic enzymes to membranebound proteins, have been successfully produced in baculovirus-infected insect cells. Yet, in addition to its value in producing recombinant proteins in insect cells and larvae, this viral vector system continues to evolve in new and unexpected ways. This is exemplified by the development of engineered insect cell lines to mimic mammalian cell glycosylation of expressed proteins, baculovirus display strategies and the application of the virus as a mammalian-cell gene delivery vector. Novel vector design and cell engineering approaches will serve to further enhance the value of baculovirus technology.Over the past 20 years the baculovirus-insect cell expression system has become one of the most widely used systems for routine production of recombinant proteins [1][2][3][4][5][6] . A number of technological improvements have eliminated the original tedious procedures required to identify and isolate recombinant viruses, increasing the popularity of the system. These include development of a wide variety of transfer vectors, simplified recombinant virus isolation and quantification methods, advances in cell culture technology and the commercial availability of reagents. These enhancements have resulted in a virus-based expression system that is safe, easy to use and readily amenable to scale-up.In addition, biotechnology now uses baculoviruses in applications beyond the production of proteins in insect cells and larvae. These include the development of strategies for displaying foreign peptides and proteins on virus particles and the insertion of mammalian cell-active expression cassettes in baculoviruses to express genes efficiently into many different mammalian cell types. Baculoviruses engineered to display foreign peptides and proteins on the viral surface have proven particularly useful as immunogens and both surface display and capsid fusions may provide further opportunities for enhancing and targeting baculovirus-mediated transduction of mammalian cells.Here, we review recent advances in baculovirus-insect cell protein production, baculovirus display and the development and application of baculoviruses as mammalian-cell genedelivery vectors (Fig. 1).

ABSTRACT

The SARS-CoV-2 (COVID-19) pandemic has placed a tremendous amount of strain on resources in the health care setting. One of the most pressing issues is the rapid depletion of personal protective equipment (PPE) used in the care of patients. This is a significant concern for health care workers' health and safety. Many entities have depleted or soon will exhaust their stockpile of PPE despite adopting PPE-sparing practices as the number of COVID-19 cases in the United States increases at an almost exponential rate and manufacturers struggle to keep up with the worldwide demand. This potential shortage is particularly concerning for commonly used N95 respirators and powered-air purifying respirators (PAPRs). Recently, the US Occupational Safety and Health Administration (OSHA) 1 even temporarily suspended the requirement to perform annual fit testing of respirators to allow entities to conserve respirators and preserve them for patient care. These measures are unprecedented and highlight the urgent need for entities to develop solutions to proactively address what could be potentially a grave occupational health issue.At Duke University and Health System, we have evaluated and will begin using hydrogen peroxide vapor to decontaminate and reuse N95 respirators. In this communication, we briefly discuss the decontamination validation process and post-decontamination performance validation conducted at Duke. This validation, which is supported by previous laboratory testing, funded by the US Food and Drug Administration (FDA), demonstrated that N95 respirators still met performance requirements even after decontamination with hydrogen peroxide vapor in the laboratory setting for over 50 times. 2 While previous studies have shown the applicability of the hydrogen peroxide vapor process, we have also confirmed that the respirator still functions as designed, using our standardized human N95 fit testing methodology. We will now use this internally validated and Duke Institutional Biosafety Review Committee (IBRC)-approved laboratory decontamination process in the clinical setting to dramatically extend the life of our N95 respirators. We hope that sharing our processes through this brief communication can help other entities with access to hydrogen peroxide vapor to evaluate the potential applicability of this technology at their facility or partner with those who may already have this capability, including other private-sector life science organizations. Process/MethodWe, like others, have implemented many Centers for Disease Control and Prevention (CDC)-approved N95 reuse practices, including employees reusing their own N95s for the duration of their shifts. However, this alone may not be adequate to meet our anticipated need with various centers reporting multiplefold higher use of PPE as their caseload increases. In the interest of our workforce safety, the goal was thus to extend the life of our existing supply.

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