Indresh K. Srivastava, PhD

Associate Director, Novartis Vaccines and Diagnostics, Emeryville, CA

Our focus is to develop effective vaccines against different diseases caused by pathogens such as HIV, HCV, Flu, Men, SARS and others. Once the structural and conformational integrity of a potential vaccine is established (based on biochemical and biophysical characterization), and after in vivo evaluation in animal models, an important step is to establish the stability and optimal formulation conditions of the vaccine. Several state of the art analytical tools are available such as Circular Dichroism (CD) Spectral Analysis, Tryptophanyl Fluorescence Emission, Differential Scanning Calorimetric (DSC) Analysis, Carbohydrate Profiling and Sequencing Analysis, and high resolution Mass Spectrometric Analysis. CD spectral analysis measures structural

asymmetries indicative of both protein secondary structural elements (alpha- helices, beta-sheets, random coils) in the far ultraviolet range and tertiary structure in the near UV range, while dispersed tryptophanyl fluorescence emission is sensitive to the conformation and oxidation state around Tryptophan residues. Differential Scanning calorimetric Analysis is used to determine the melting temperature (Tm) of the target protein that is dependent upon secondary and tertiary structure. Generally a higher Tm for a target vaccine is indicative of greater stability. Using the same principle, optimal formulation conditions can also be screened for a given protein. We have used DSC for determining the stability of flu and HIV vaccines, and it has potential to be used routinely for assessment of vaccine candidates.