Viruses, Vaccines, Bacteria and Yeasts

All substances of this chapter can only be dried in the present of CPAs, if their natural qualities are to be protected. 

Greiff [3.24] studied the stability of purified influenza virus of the strain PR 8 in physiological NaCl solution with calcium lactobionate and human serum albumin (each 1 % in the solution). The freezing rate was approx. 1 °C/min down to -30 °C. During the freeze drying, the product temperature was raised in 12 to 16 h from -30 °C to 0 °C and the product was dried at this temperature. After 24 h, the first 145 vials were removed, and additional vials after intervals of 24 h each. The residual moisture content was 3.0,2.0,1.5, 1.0 and 0.5 %. The stability of the freeze dried virus (expressed in days during which the titer of the infectivity decreased by a factor of 10 was most unfavorable at 0.4 % and 3.2 % RM, (4 and 7 days respectively at +10 °C) and best at 1.7 % RM 145 days or more than 1000 days at -10 °C. 

Overdrying (0.4 % RM) and to high RM (3,2 %) results in unstable dry products. Overdrying removes bond water, which is essential to keep the protein structure furthermore the hydrophilic locations of the protein are exposed to gases, e. g. 02. At too high an RM, free water remains in the dry product and induces reactions which change the protein molecule. 

Greiff [3.25] classified the virus into five categories 1, Nucleic acid type (either DNA-core or RNA-core) 2, sensitivity against lipid solvents 3, envelope about the nucleocapsid or not (naked) 4, pH sensitivity, exposure to pH 3 for 30 min differentiates between those viruses, which lose more than a decade in titer and those which lose no titer or less than one decade 5, heat-sensitive virus cannot be exposed to +50 °C for 30 min. 

During the freeze drying tests the virus suspensions are either basic salt medium (BSM) or BSM plus calcium lactobionate (CL) plus serum albumin (SA) frozen at -76 °C and dried either at 0 °C or at -40 °C. The activity has been evaluated after 30 days storage at -4 °C or -65 °C. Rehydratation was done with distilled water at 0 °C. The results with the freeze dried viruses indicate  

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