Medicago manufactures influenza vaccine virus-like particles (VLPs) in an unusual production platform consisting of Nicotiana benthamiana plants. During the in vitro adventitious agent test (AAT) of certain Medicago B strain influenza vaccine VLP test samples, positive hemagglutination of guinea pig red blood cells was observed on day 14, but not on day 28. The positive result in the assay was surprising because the production process uses no animal-derived raw materials and contains a viral inactivation step. Plant-associated viruses would not be expected to infect the mammalian cell-based assay. No cytopathic effects or hemadsorption of red blood cells was observed in these AATs. The positive hemagglutination was observed at 2–8°C, but not at 36–38 °C, and only in a few of the six detector cell lines used in the assay. Because this is quite an unusual pattern of responses for an AAT, Medicago and the contract testing lab, Eurofins Lancaster Laboratories (ELLI) investigated the positive responses thoroughly for the presence of an adventitious agent or an alternative explanation not involving a viral contaminant. Investigation results indicated that the hemagglutinating activity associated with the vaccine test sample itself was responsible for the positive hemagglutination response. The positive hemagglutination on day 14 of these AATs was deemed an assay artifact, and preventive actions were taken to prevent recurrence of this type of false positive response…
Tag: <span>virus-like particles</span>
As human immunodeficiency virus type-1 (HIV-1) continues to spread around the world, scientists are actively pursuing effective vaccines against the infectious disease that results in AIDS. A number of vaccine designs have been developed, including plasmid DNA constructs encoding HIV proteins. One advantage of DNA vaccination is that after the uptake of the plasmid by the host cells, the encoded antigens are expressed in the native conformation and allow authentic immunological processing of the antigen. Another advantage of DNA vaccines is that they can be repeatedly administered without vector-directed immunity limiting the efficacy of the boost. DNA vaccines alone can induce both humoral and cellular immune responses and provide modest protection against disease progression in the preclinical, nonhuman primate model when challenged with simian immunodeficiency virus (SIV)…
The Baculovirus Expression Vector System (BEVS) is widely used for the production of a broad variety of heterologous proteins that are often secreted into the culture medium as soluble, biologically active, properly glycosylated, and correctly folded. Downstream purification of a secreted protein is considerably easier due to the absence of many contaminating cellular proteins and nucleic acids in the culture supernatant. The BEVS system has also successfully been used for the production of virus-like particles (VLPs) for a broad variety of proteins derived from many different viruses…
Globally, an estimated 36 million people are living with HIV, and some 20 million people have already died of AIDS. Today, there is still no HIV vaccine available. HIV virus-like particles are an attractive vaccine candidate due to their ability to induce both antibody and cytotoxic T-lymphocyte responses. In this article, we describe the development of a production process for an HIV particle vaccine, HIV-1 p55 (gag). The gag precursor protein (p55) is sufficient for assembly and cellular release of retrovirus-like particles. We expressed the p55 gag protein using the BEVS technology in Spodoptera frugiperda expresSF+ cells…