Carrier and Liquid Heat Inactivation of Poliovirus and Adenovirus

Abstract

Viral inactivation is typically studied using virus suspended in liquid (liquid inactivation) or virus deposited on surfaces (carrier inactivation). Carrier inactivation more closely mimics disinfection of virus contaminating a surface, while liquid inactivation mimics virus inactivation in process solutions. The prevailing opinion has been that viruses are more susceptible to heat inactivation when suspended in liquid than when deposited on surfaces. In part, this reflects a paucity of comparative studies performed in a side-by-side manner. In the present study, we investigated the relative susceptibilities of the enteroviruses poliovirus-1 and adenovirus type 5 to heat inactivation in liquid versus carrier studies. The results of our side-by-side studies suggest that these two viruses are more readily inactivated when heat is applied to virus deposited on carriers. Decimal reduction values (i.e., the amount of time required to reduce the virus titer by one log 10) measured at 46°C displayed the greatest difference between carrier and liquid inactivation approaches, with values ranging from 14.0 to 15.2 min (carrier) and from 47.4 to 64.1 min (liquid) for poliovirus. The corresponding values for adenovirus 5 were 18.2-29.2 min (carrier) and 20.8-38.3 min (liquid). At 65°C, the decimal reduction values were more similar (from 4 to 6 min) for the various inactivation approaches.

Thermal Inactivation of Feline Calicivirus and Herpes Simplex Virus Type 1: Side-by-Side Suspension and Carrier Studies

“…The authors reported that the parvovirus was more readily inactivated in suspension than in the lyophilized state with higher residual moisture (2%), while longer heating times were required for inactivation of the virus in lyophilized materials with lower moisture content (1%). In our own studies [8] with poliovirus type 1 and adenovirus type 5, the D values measured at 46°C displayed the greatest difference between the surface and suspension inactivation approaches, with values ranging from 14. What exactly determines the shape of the D vs. temperature curve?…”

“…Prevailing opinion is that viruses are less susceptible to heating when dried on surfaces than when suspended in solutions, and that dry heat efficacy is related to residual moisture or relative humidity [22][23][24][25][26]. As mentioned previously, there are only relatively few studies [8,25] that have actually evaluated thermal inactivation on surfaces and in suspension in a side-by-side study design. There are a number…”

“…A flattening out of the curve is typically observed at higher temperatures. From a mechanism of inactivation point of view, we have proposed previously [8] that the steep portion of the curve may represent reaching of a threshold temperature required for capsid opening. Once this threshold temperature has been reached, relatively small incremental increases in temperature result in dramatic decreases in the time required for 1 log 10 inactivation.…”

“…min) for the two inactivation approaches. The results with poliovirus and adenovirus[8] suggest that the specific virus under test is a determinant of the steepness of the D vs. temperature curve. This is supported by the results in our present study, where FeCV displayed markedly greater D values at 46°C in suspension inactivation vs. surface inactivation.…”

“…Thermal inactivation in suspensions is typically a first-order process, meaning that a plot of log 10 inactivation is linear with respect to time at temperature [6,7]. Deviations from linearity may occur as a result of experimental error or inactivation of available remaining infectious virus [8]. For a first-order process, a decimal reduction factor (D) can be calculated.…”