AimsTo make a comparative evaluation of the effects of different stabilizers and freezing rates on structurally different viruses during lyophilization and storage. Methods and ResultsTwo virus strains from each of six animal virus families, including both enveloped and nonenveloped viruses, were lyophilized in (i) culture medium, (ii) with the addition of gelatine-sucrose and (iii) skim milk-sodium glutamate. All the virus suspensions were frozen (i) at -80 degrees C or (ii) in liquid nitrogen before lyophilization. Virus titre assay after lyophilization and after 8months storage at 4 degrees C revealed that the efficacy of stabilizers depended on virus structure. Generally, the best protective quality for enveloped viruses was achieved with gelatine-sucrose, which best maintained their infectivity and envelope morphology. Even additive-free culture medium proved adequate for nonenveloped viruses. Differences in stabilizer efficacy were also found between virus families and were expressed immediately after lyophilization; the activity of stabilizers in the course of storage was very similar. Freezing in liquid nitrogen proved beneficial for picornaviruses. ConclusionsThe choice of an appropriate stabilizer with respect to virus type is crucial for effective lyophilization. Significance and Impact of the StudyThis study contributes to the establishment of general guidelines for animal virus lyophilization, with particular respect to differences in virus structure.