The licensing of recombinant vaccines produced using the baculovirus expression vector system (BEVS) has cleared the way for the production of a variety of biopharmaceuticals produced using this technology. Obtaining accurate estimates of both total and infectious baculovirus titer in upstream and downstream bioprocess fluids is one of many process controls that will need to be addressed during the development phase of a product’s lifecycle. Traditional plaque-titer methods require 5–7 days of incubation in order to reveal plaques that may be enumerated, and is further complicated by plaques created by multiple viruses that may be scored as a single plaque, thereby lowering the titer estimate. Titer assays based on polymerase chain reaction (PCR) have been developed, but they measure the presence of baculovirus genes, not virus particles. This often results in titers one or two logs higher than the actual titer. Immunoassays correlate with host cell infection and virus replication, but they too can be time-consuming and difficult to interpret. Our goal was to identify a method that would provide estimates of both total and infectious virus particles in as close to real-time as possible. We have evaluated the ViroCyt Virus Counter over the course of three years and have found it to provide accurate and reproducible estimates of both titer types in as little as 30 minutes. We have created an algorithm that converts total virus particle counts into estimates of infectious titer and tested these values in virus amplifications. The Virus Counter method of titer determination has also been used to track the quantity of virus particles in the culture supernatant of stirred-tank bioreactors infected with standard baculovirus stocks and with baculovirus-infected insect cells (BIIC)…
Tag: <span>insect cell culture</span>
The developing biotechnology community may offer solutions and hope for recent world events that have focused attention on the vulnerability of the world’s population. Concerns about new pandemics have been raised by the emergence of new influenza strains and the re-emergence of older and even more highly virulent strains. In addition, there are fears that bioterrorism could involve agents such as anthrax or smallpox, and these threats become even more of a concern when you consider the increased mobility of such organisms via today’s commercial aviation. The ability of the biomedical community to respond rapidly to these shifting threats is more important than ever…
Parvoviruses are one of the most prevalent infectious agents in the laboratory rodent. Their effect on research can range from immune dysfunction that may mislead researchers when interpreting results to lethal effects on animals. Until recently parvovirus infection in mice was thought to be caused by minute mouse virus (MMV) and in rats by rat viral agents in the KRV or H-1 serogroups. Relatively newly discovered viruses in these groups are mouse (MPV) and rat parvoviruses (RPV-1 and 2). Parvoviruses are 15–20 nm in diameter and are single-stranded DNA viruses of about 5,000 nucleotides, which replicate through a double-stranded DNA intermediate. The protein composition consists of three structural or capsid proteins providing the viral coat (VP-1, VP-2, and VP-3) and two non-structural proteins involved in viral replication (NS-1 and NS-2). Among the capsid proteins,VP-2 is the major protein…