The Heat Inactivation of Vaccinia Virus

Abstract

SUMMARY: Heat inactivation curves of vaccinia virus between 50' and 60' indicate that the virus is heterogeneous in its heat sensitivity. The proportion of heatresistant particles varies inversely with the temperature of exposure. The inactivation of heat-sensitive virus is temperature dependent and seems to be a first-order reaction, while the heat-resistant fraction is inactivated at a constant slow rate unrelated to temperature over the range 5Oo-6O0.The work reported here is part of a larger investigation of virus inactivation by physical agents including ultraviolet and ionizing radiations, under conditions that do not destroy antigenicity (McClean, 1945;Collier, McClean & Vallet, 1956). The heat inactivation of vaccinia virus was determined as a preliminary to testing the protective antigenicity of heat inactivated vaccines. METHODS Virus.Most of the experiments were done with the Lister Institute strain of vaccinia virus adapted to the chick embryo; two experiments were done with the WR mouse neuro-adapted strain of virus. Infected chorioallantoic membranes were extracted in dilute McIlvaine buffer by grinding with sterile powdered neutral glass, Extracts were centrifuged at l O O O g for 15 min. to clear them of debris, titrated and stored at 4". For inactivation, extracts were diluted to a titre between about lo7 and lo8 infective units/ml. Experimental procedure. One ml. samples of virus were heated in small, thin-walled test tubes in a water bath accurate to +0-2'. Samples were removed from the bath at intervals and immediately cooled in a melting ice bath. They were stored at 4" until infectivity titrations were made: this was generally within a few hours, but on a few occasions there was an interval of 2 or 8 days.Infectivity titrations were made by pock counts on the chorioallantoic membranes of 12-or 13-day chick embryos. The refinements of membrane handling technique described by Westwood, Phipps & Boulter (1957) were used. In titrations of WR strain 3-day instead of the usual 2-day incubation was used, because after 2 days the pocks were pale and poorly developed.Diluent. All extractions and dilutions were made in McIlvaine's phosphate + citrate buffer, pH 7.2, 0-004 M-phosphate.In graphs of the results each point is the arithmetic mean of at least four experiments unless otherwise stated. The results are plotted as log Vo/V against time, where Vo is the original concentration and V the concentration at any time t. This enables all the inactivation curves to be given a common

Intra-Family and Inter-Family Comparisons for Viral Susceptibility to Heat Inactivation

“…Retrieving the various publications cited herein was one of the most difficult aspects of this survey. The literature obtained includes reports of the inactivation of a variety of non-enveloped [3][4][5][7][8][9][10][11]19,[23][24][25][26][27][28]39] and enveloped [1,6,12,[14][15][16][17][18]21,22,26,[29][30][31]33] viruses. As might be expected, those viruses considered a threat to food safety are somewhat more highly represented in the heat inactivation literature.…”

“…Heat inactivation of viruses represents an important approach for mitigating the risk of viral contamination for food and drinking water protection [1][2][3][4][5][6][7][8][9][10], inactivation of vaccine viruses [11][12][13][14][15], inactivation of viruses of importance to agriculture and animal husbandry [16][17][18][19][20][21][22][23][24][25][26][27][28][29][30], and inactivation of viruses in blood products [31][32][33]. More recently, heat inactivation and more particularly high-temperature short-time (HTST) treatment have been evaluated as a barrier technology for mitigating the risk of introducing adventitious viral contaminants into biologics manufacturing processes through contaminated cell culture reagents [34][35][36].…”

Studies of the Suitability of Fowlpox as a Decontamination and Thermal Stability Simulant for Variola Major

“…Hahon and Kozikowski [8] determined the Δ H and Δ S of variola major virus in various buffers at temperatures from 40°C to 55°C. Previous studies with vaccinia virus demonstrated that vaccinia virus has a range of Δ H values from 20,000 to 90,000 calories per mole [12]. Variola major virus has a Δ H values in the range described by Kaplan [12].…”

Review of Vaccinia Virus and Baculovirus Viability Versus Virucides

“…Studies on VACV have traditionally focused on virus viability and potency of stored vaccine preparations, while baculovirus research is agriculturally based with a centralized focus on the improvement of formulation and insecticide performance (Falcon, 1969;Kaplan, 1958;Roberts and Hope, 2003). These divergent research topics and wide variety of experimental conditions have resulted in many datasets that are difficult to compare with one another.…”

“…Kaplan (1958) investigated the persistence of VACV and determined inactivation curves at temperature ranges between 50-60 °C. The results from this study demonstrated a rapid fall of infectivity followed by a complete inactivation at a much slower rate.…”