Effect of Host Cells on Low- and Medium-Pressure UV Inactivation of Adenoviruses

Abstract

UV disinfection is highly effective against most pathogens, with the exception of the adenoviruses (AD).UV disinfection has increasingly been adopted as a favorable technology for disinfection worldwide. It does not involve any disinfection by-product (DBP) formation and is highly effective against protozoan, bacterial, and most viral pathogens at low doses (40 to 60 mJ/cm 2 ) commonly rendered in water treatment plants. Despite numerous advantages over other disinfectants, a major concern pertaining to low-pressure (LP) UV disinfection is the low germicidal effect on adenoviruses (AD).AD are present in various environments, such as rivers, coastal waters, swimming pool waters, tap waters, and treated drinking waters worldwide (11,19,32,34,35). There are 52 different human serotypes (enteric or nonenteric) which are responsible for respiratory illnesses, conjunctivitis, and death in persons with compromised immune systems (15). AD are categorized into 6 subcategories, from species A to F. Of these, species F is known to be enteric (AD serotype 40 [AD40] and AD41). Recent studies have shown that enteric AD are not limited to causing only gastrointestinal problems. There is a possibility for all AD serotypes to be waterborne, regardless of whether they exist as enteric or nonenteric strains (37). Similarly, some nonenteric AD which are known to cause respiratory diseases (e.g., AD2 and -5) can also infect the gastrointestinal tract, leading to diarrhea (37). This emphasizes the importance of targeting both enteric and nonenteric AD serotypes during drinking water disinfection. The UV disinfection guidance manual (UVDGM) has also listed AD as a benchmark for UV reactor validation. UV reactors must be capable of delivering UV doses of 186 mJ/cm 2 for 4-log virus inactivation (33). Such a high UV dose requirement is more than 4 times that provided in most drinking water treatment plants.To date, many studies have been conducted to investigate the effect of low-pressure (LP) UV light on AD inactivation (12,18,23,25,30), but only five such studies have been published on medium-pressure (MP) UV inactivation (10,20,21,22,27). Despite numerous studies on LP UV inactivation, the UV dose requirements obtained from different studies were highly variable. Based on a review of results from the literature, it was observed that in order to achieve 4-log inactivation of AD40, LP UV dose requirements ranged from 124 to 226 mJ/cm 2 (21, 23, 30). Likewise, LP UV dose requirements for 4-log inactivation of AD41 ranged from 112 to 222 mJ/cm 2 (4, 18, 23). These differences in LP UV dose requirements have been attributed to the use of different cell lines and culturing methods, history of the viral stocks, virus preparation methods, virus serotypes, the subjective nature of cell culture infectivity assays, cell/virus storage time, and variability in experimental conditions, such as UV exposure setups, UV dosimetry measurements, etc. (2, 10, 18). To date, it is not known which factor/methodology, if any, contributes directly to these ex...

Inactivation of Viruses by Combination Processes of UV and Chlorine

“…The fluence was higher than other studies reporting 64 mJ/cm 2 (Nwachuku et al, 2005) for 2 log inactivation of AdV5. However, a study of Guo et al (2010) showed a wide range of fluence required for 2 log inactivation, which was 26 to 76 mJ/cm 2 . The result of the study clearly explained that difference of host cells using for infectivity assay affected log inactivation of AdV5.…”

UV Disinfection of Adenovirus: Present State of the Research and Future Directions

“…This is likely because damage to DNA caused by LP UV lamps can be repaired but the more widespread damage inflicted by MP or pulsed UV cannot; such damage can be expected to prevent host cell reactivation of adenovirus as well. Indeed, recent work has shown that greater inactivation of adenovirus in cell culture is achieved by both MP and pulsed UV than by LP UV (Eischeid et al, 2009;Guo et al, 2010;Linden et al, 2007); over 4-log inactivation of adenovirus can be achieved using approximately 40 mJ/cm 2 of MP or pulsed UV, and this is in much closer agreement with the LP UV doses required to inactivate other viruses.…”

“…Furthermore, formation of pyrimidine dimers in adenoviral DNA after irradiation appears to be similar to that found in mammalian cells and bacteria (Eischeid et al, 2009;Rainbow and Mak, 1973), and reports from the medical literature in which UV-irradiated adenoviruses are assayed for infectivity in DNA repair-deficient host cells clearly indicate that adenovirus is sensitive to LP UV in these cells (Day, 1974;Rainbow, 1980;Rainbow, 1989). More recently, Guo et al (2010) have shown that adenoviruses are more susceptible to both LP and MP UV in repair-deficient cells. This effect is especially pronounced after LP UV treatment, when DNA repair is expected to make the greatest difference.…”

Sequential and Simultaneous Applications of UV and Chlorine for Adenovirus Inactivation

“…A lower required fluence of 80 mJ/cm 2 for 2 log inactivation was reported by Baxter et al (2007). This difference could be attributed to many factors, such as the use of different cell lines for the plaque assay (Guo et al 2010) or a difference in the water matrix used for the UV exposure experiments. For the Cl 2 -deCl 2 -UV process, the purpose of adding the dechlorinating agent, sodium thiosulfate, was to investigate the effect of pretreatment by chlorine before UV exposure.…”