Infectivity of RNA from Inactivated Poliovirus

Abstract

During inactivation of poliovirus type 1 (PV-1) by exposure to UV, hypochlorite, and heat (72°C), the infectivity of the virus was compared with that of its RNA. DEAE-dextran (1-mg/ml concentration in Dulbecco's modified Eagle medium buffered with 0.05 M Tris, pH 7.4) was used to facilitate transfecting PV-1 RNA into FRhK-4 host cells. After interaction of PV-1 RNA with cell monolayer at room temperature (21 to 22°C) for 20 min, the monolayers were washed with 5 ml of Hanks balanced salt solution. The remainder of the procedure was the same as that for the conventional plaque technique, which was also used for quantifying the PV-1 whole-particle infectivity. Plaque formation by extracted RNA was approximately 100,000-fold less efficient than that by whole virions. The slopes of best-fit regression lines of inactivation curves for virion infectivity and RNA infectivity were compared to determine the target of inactivation. For UV and hypochlorite inactivation the slopes of inactivation curves of virion infectivity and RNA infectivity were not statistically different. However, the difference of slopes of inactivation curves of virion infectivity and RNA infectivity was statistically significant for thermal inactivation. The results of these experiments indicate that viral RNA is a primary target of UV and hypochlorite inactivations but that the sole target of thermal inactivation is the viral capsid.Leading causes of food-borne, and probably water-borne, disease in the United States are the Norwalk-like viruses (NLVs) of the family Caliciviridae and the hepatitis A virus (HAV) of the family Picornaviridae (11). Poliovirus (PV) is the type species of the genus Enterovirus in the Picornaviridae family (19). PV has the same genomic structure and gene organization as that of HAV and has a close phylogenetic relationship with the NLVs (26). We have studied the inactivation of PV, HAV, and feline calicivirus (FCV, which is often used as a surrogate for NLVs because NLVs have no laboratory host cell line). Inactivating agents used in these studies were UV, hypochlorite, and heat (72°C), all of which are commonly used in food processing or preparation and in water disinfection.These simple viruses comprise only a single strand of RNA coated with protein. The RNA contains the genetic information by which intracellular infection results in production of progeny virus, so infectivity ultimately resides in the RNA. The coat protein (capsid) performs three functions: (i) protection of the RNA against environmental degradation and in transit down the digestive tract until susceptible cells are reached; (ii) attachment to the receptor of a susceptible cell, whereby the viral particle is engulfed and the capsid removed, to initiate the infection; and (iii) antigenic activity that evokes an immune response by the host and reacts with the antibody that has been produced. We have shown that capsids of HAV, vaccine PV type 1 (PV-1), and FCV inactivated (from an initial titer of ϳ1,000 PFU/ml) by UV, hypochlorite, or high temperature ...

Mechanisms of Methods for Hepatitis C Virus Inactivation

“…Even though we did not see an influence of either treatment method on the viral capsid, we cannot exclude that the viral capsid itself might also be damaged since the core ELISA is based on the detection of only a small part of the capsid (27). It has been shown for other viruses that heat inactivation induces structural changes in viral proteins, which might cause the loss of infectivity (29,30) and degrades the viral RNA (31,32). Whether heat inactivation influences only the viral proteins or also the RNA might depend on the applied temperature, as well as on the duration of heat administration.…”

“…The same holds true for UV irradiation. UV irradiation, typically at a wavelength of 254 nm, is known to target nucleic acids, while leaving proteins largely preserved (29,33). However, both viral genome and protein damage have been reported previously due to UV irradiation (30,34,35).…”

Inactivation of Virus-Containing Aerosols by Ultraviolet Germicidal Irradiation

“…To reduce infection risk from virus infection, control techniques for inactivating such viruses have been extensively researched (Jensen 1964;Gerba et al 2002;Shin et al 2003;Thurston-Enriquez et al 2003). Among these control techniques, ultraviolet germicidal irradiation (UVGI) was demonstrated to be extremely efficient for virus inactivation (Jensen 1964 ;Galasso et al 1965;Gerba et al 2002;Nuanualsuwan et al 2003;Thurston-Enriquez et al 2003).…”

Thermal Inactivation of Foot-and-Mouth Disease Viruses in Suspension

“…Engulfment, or endocytosis, follows in PV and is believed to happen similarly in FMDV, given their similarities in capsid symmetry and their phylogeny (20). If infectious RNA can get inside an otherwise-insusceptible host cell, the replicative cycle can be completed without a capsid, so the capsid integrity essentially mediates virus and tissue interactions (37). The capsid integrity and immunological properties of 37°C-inactivated human picornaviruses and FMDV serotype O (7) were intact, while the capsid protein of human picornaviruses was unfolded at 72°C and readily hydrolyzed by protease (36).…”