Development of a droplet digital PCR for pertussis toxin locus copy number determination in a genetically-modified Bordetella pertussis strain.

To improve pertussis toxin (PT) yield in B. pertussis strains for vaccine production a genetically-engineered strain (gdPT 191-134 strain) with a second copy of the genetically detoxified PT (gdPT) locus was developed. The consistency of the production and genetic stability of the strain when used for vaccine production must be established.

Phenotypic and genetic characterization of a next generation live-attenuated yellow fever vaccine candidate.

We assessed the genetic and phenotypic characteristics of a yellow fever vaccine candidate, which was cloned from a YF-VAX substrain selected for growth in Vero cells (vYF-247), during the manufacturing process from the master seed lot (MSL) and working seed lot (WSL) through to the drug substance (DS) stage. There were nine minor nucleotide variants observed from the MSL to the DS stage, of which five led to amino acid changes. The variant positions were, however, not known risks for any virulence modification.

Development of a highly sensitive PCR/DNA chip method to detect mycoplasmas in a veterinary modified live vaccine.

Mycoplasmas are potential contaminants that introduce undesirable changes in mammalian cell cultures. They frequently contaminate cell substrates and other starting materials used for manufacturing cell-derived biologics, such as vaccines and pharmaceutical products. Mycoplasma purity testing of live vaccines, active ingredients, raw material, and seed lots is required during vaccine production.

Comparison of reverse-transcriptase qPCR and droplet digital PCR for the quantification of dengue virus nucleic acid.

Polymerase chain reaction (PCR) is an important molecular biology technique for in vitro amplification of nucleic acids. Reverse transcriptase quantitative PCR (RT-qPCR) and more recently reverse transcriptase digital droplet PCR (RT-ddPCR) have been developed for the quantification of nucleic acids. We developed an RT-ddPCR assay for the quantification of attenuated dengue virus serotype 2 nucleic acid and compared it with a routine RT-qPCR assay.

Validation of a PCR coupled to a microarray method for detection of mycoplasma in vaccines.

The revised section of the European, United States, and Japan Pharmacopeias on mycoplasma testing provided guidance for the set up and validation of a nucleic acid amplification technique (NAT) as an alternative method to agar culture and indicator cell culture compendial methods. The CytoInspect™ method, based on Polymerase Chain Reaction (PCR) coupled to microarray analysis, has been selected for detection and identification of mycoplasma in vaccines. To replace compendial methods, the alternative method must demonstrate equivalence in both limit of detection (LOD) and specificity compared with compendial methods.