Inactivation Kinetics and Replication Cycle Inhibition of Coxsackievirus B5 by Free Chlorine

Abstract

The kinetics of coxsackievirus serotype B5 (CVB5) inactivation with free chlorine is characterized over a range of pH and temperature relevant to drinking water treatment with the primary goal of selecting experimental conditions used for assessing inactivation mechanisms. The inactivation kinetics identified in our study is similar to or slower than experimental data reported in the literature and thus provides a conservative representation of the kinetics of CVB5 inactivation for free chlorine that could be useful in developing future regulations for waterborne viral pathogens including adequate disinfection treatment for CVB5. Untreated and free chlorine-treated viruses, and host cells synchronized-infected with these viruses, are analyzed by a reverse transcription-quantitative polymerase chain reaction (RT-qPCR) method with the goal of quantitatively investigating the effect of free chlorine exposure on viral genome integrity, attachment to host cell, and viral genome replication. The inactivation kinetics observed results from a combination of hindering virus attachment to the host cell, inhibition of one or more subsequent steps of the replication cycle, and possibly genome damage.

Influence of Amino Acid Substitutions in Capsid Proteins of Coxsackievirus B5 on Free Chlorine and Thermal Inactivation

“…Moreover, the inactivation rate constants of the variants that we previously tested are also significantly different between the two 5′UTR-based genogroups (Wilcoxon-rank sum test: P < 0.01). Given that the genome damage induced by free chlorine also contributes to viral inactivation, , it is plausible that the mutations in the 5′UTR alter the composition and the secondary structures, thereby changing chlorine sensitivity. A total of 12 common mutations were observed among the two 5′UTR-based genogroups.…”

“…7,15,17 Free chlorine has been found to oxidize the viral capsid, 18,19 which protects the viral genome from chemical and enzymatic damage, 20,21 and has been reported to inhibit the viral attachment function, thereby partially contributing to enter-ovirus inactivation. 13,17,22,23 Sulfur-containing amino acids (cysteine (Cys) and methionine (Met)) react with free chlorine much faster than other amino acid residues. 24,25 Thus, differing abundances and solvent-accessibilities of Cys and Met in capsid proteins have been suggested as a rationale for the varying virus sensitivities to commonly used oxidants.…”

“…Free chlorine has been found to oxidize the viral capsid, , which protects the viral genome from chemical and enzymatic damage, , and has been reported to inhibit the viral attachment function, thereby partially contributing to enterovirus inactivation. ,,, Sulfur-containing amino acids (cysteine (Cys) and methionine (Met)) react with free chlorine much faster than other amino acid residues. , Thus, differing abundances and solvent-accessibilities of Cys and Met in capsid proteins have been suggested as a rationale for the varying virus sensitivities to commonly used oxidants. ,,,− This theory is consistent with the findings on the free chlorine susceptibility of 13 environmental isolates of CVB5, where isolates belonging to genogroup B, which contain fewer Met in the capsid proteins, also exhibited a 1.9-fold lower sensitivity to free chlorine compared to isolates falling within genogroup A …”

“…Most studies to date have focused on a single CVB5 variant, the Faulkner strain, to understand CVB5 inactivation kinetics ,,− and to investigate inactivation mechanism by disinfectants. It is increasingly apparent, however, that genetically diverse CVB5 environmental isolates differ in their sensitivity to chlorine and heat. , Variant-dependent sensitivity to disinfectants has also been reported for other genotypes of enterovirus. , Furthermore, variants also exhibit differing susceptibilities to other disinfectants, whereby the extent of the difference has been found to depend on the mechanism of action exerted by the disinfectant. ,, …”

Influence of amino acid substitutions in capsid proteins of coxsackievirus B5 on free chlorine and thermal inactivation

“…Most studies to date have employed only CVB5 Faulkner strain, to understand CVB5 inactivation kinetics 4,6,10–12 and to investigate its inactivation mechanism 13 by disinfectants. It is increasingly apparent, however, that genetically diverse CVB5 environmental isolates differ in their sensitivity to free chlorine and heat 7,14 .…”