Water-Filtered Infrared A Irradiation in Combination with Visible Light Inhibits Acute Chlamydial Infection

Abstract

New therapeutic strategies are needed to overcome drawbacks in treatment of infections with intracellular bacteria. Chlamydiaceae are Gram-negative bacteria implicated in acute and chronic diseases such as abortion in animals and trachoma in humans. Water-filtered infrared A (wIRA) is short wavelength infrared radiation with a spectrum ranging from 780 to 1400 nm. In clinical settings, wIRA alone and in combination with visible light (VIS) has proven its efficacy in acute and chronic wound healing processes. This is the first study to demonstrate that wIRA irradiation combined with VIS (wIRA/VIS) diminishes recovery of infectious elementary bodies (EBs) of both intra- and extracellular Chlamydia (C.) in two different cell lines (Vero, HeLa) regardless of the chlamydial strain (C. pecorum, C. trachomatis serovar E) as shown by indirect immunofluorescence and titration by subpassage. Moreover, a single exposure to wIRA/VIS at 40 hours post infection (hpi) led to a significant reduction of C. pecorum inclusion frequency in Vero cells and C. trachomatis in HeLa cells, respectively. A triple dose of irradiation (24, 36, 40 hpi) during the course of C. trachomatis infection further reduced chlamydial inclusion frequency in HeLa cells without inducing the chlamydial persistence/stress response, as ascertained by electron microscopy. Irradiation of host cells (HeLa, Vero) neither affected cell viability nor induced any molecular markers of cytotoxicity as investigated by Alamar blue assay and Western blot analysis. Chlamydial infection, irradiation, and the combination of both showed a similar release pattern of a subset of pro-inflammatory cytokines (MIF/GIF, Serpin E1, RANTES, IL-6, IL-8) and chemokines (IL-16, IP-10, ENA-78, MIG, MIP-1α/β) from host cells. Initial investigation into the mechanism indicated possible thermal effects on Chlamydia due to irradiation. In summary, we demonstrate a non-chemical reduction of chlamydial infection using the combination of water-filtered infrared A and visible light.

Water-filtered infrared A reduces chlamydial infectivity in vitro without causing ex vivo eye damage in pig and mouse models

“…Intra-well temperature was checked every 5 min during 30 min of irradiation with a Voltcraft thermometer (Type 2ABAc, Philips, Kassel, Germany) as previously described (20).…”

“…Afterwards, inocula were aspirated and replaced by 1 mL incubation medium without gentamycin for further incubation of plates at 37°C and 5% CO 2 . At 40 hpi, infected monolayers were irradiated with wIRA alone or wIRA/VIS, as described in 2.6, and incubated for 3 h before they were fixed in methanol for immunofluorescence or collected for titration by sub-passage as previously described (20) (Figure 2A). Non-irradiated cultures were used as controls.…”

“…For this experiment, HCjE were seeded and incubated for 48 h. During incubation, cell monolayers were irradiated four times 8 h, 6 h, 3 h and immediately before infection with EBs, which had been exposed to irradiation by transferring 1 mL of EB-containing medium to a cell-free 24-well plate for treatment as previously established (20,21). Irradiation was performed with either wIRA alone or wIRA/VIS for 30 min as shown in 2.6.…”

“…Indirect immunofluorescence assays (IFA) were performed with a primary Chlamydiaceae family-specific mouse monoclonal antibody (1:200, LPS, Clone ACI-P, Progen, Heidelberg, Germany), detecting the chlamydial lipopolysaccharide and a secondary Alexa Fluor 488-goat anti-mouse antibody (1:500, Molecular Probes, Eugene, OR, USA), as previously described (20). DNA was stained with DAPI…”

“…In our previous studies, we demonstrated that wIRA or wIRA/VIS treatment reduced chlamydial infectivity in permanent cell lines such as HeLa and Vero cells (20,21). Here, our goal was to study the effect of wIRA with and without visible light on an established in vitro ocular infection model to investigate the possibility of wIRA as a potential treatment for trachoma.…”