BACKGROUND
trachoma continues to be the most common cause of preventable blindness worldwide.
it has been estimated to visually impair between two and nine million people globally, although this may be an underestimate due to the lack of screening programs in endemic areas  <cit> .
one of the etiologic agents is the obligate intracellular bacterium chlamydia trachomatis <cit> , which is also the leading bacterial cause of sexually transmitted infections  worldwide.
these reproductive infections can lead to clinical symptoms such as urethritis, cervicitis, and pelvic inflammatory disease  <cit> .
the ability of c. trachomatis to evade the immune system  results in 70-90% of infected women and 30-50% of infected men being asymptomatic  <cit> .
due to repeated or persistent infections, or an absence of antibiotic treatment, ocular and reproductive tract sequelae can develop, resulting in corneal pacification and salpingitis respectively  <cit> .
c. trachomatis has a unique biphasic life cycle involving both elementary and reticulate bodies.
elementary bodies  represent a metabolically inactive infectious phenotype capable of attaching to epithelial cells with subsequent internalization resulting in the formation of an inclusion body.
once inside the inclusion, the eb differentiates into a metabolically active reticulate body  that multiplies via binary fission.
as the inclusion grows, the rbs reorganize into ebs that are released from the host cell and can infect adjacent cells.
these varying bioforms make treatment of chlamydial infections difficult.
furthermore, antibiotic therapies, exposure to ifnγ, or nutrient deprivation can lead to an atypical, persistent, non-cultivable, and morphologically aberrant intracellular state .
chlamydial infections in the conjunctiva and genitalia can incite an intense inflammatory response that, if chronic, can lead to scarring and fibrosis.
numerous pro-inflammatory cytokines, including tnfα, il-1α, il- <dig> and il- <dig>  <cit> , as well as a group of chemokines  <cit>  responsible for the recruitment of leukocytes have been shown to be secreted from c. trachomatis-infected epithelial cells.
this arsenal of cytokines and chemokines with incoming leukocytes results in the stimulation of both cellular- and humoral-mediated immune defenses.
the type of host inflammatory response that is initiated with the infection determines the outcome of the infection.
the current hypothesis is that resolution is mediated primarily by a dominant cell-mediated th <dig> response, whereas chronic inflammation with subsequent scarring ensues if either the humoral th <dig> response or regulatory t cells predominate .
development of chronic chlamydial infections is believed to arise as a result of immunopathology.
this has been demonstrated by persistent elevation of pro-inflammatory cytokines like il- <dig> among infertile women  <cit>  and in tear fluid from post-scarring trachoma populations  <cit> .
one study identified il- <dig> secretion via the tlr <dig> signaling pathway after c. trachomatis infections  <cit> .
this tlr <dig> pathway has been shown to be associated with fallopian-tube pathology, potentially contributing to the immunopathogenesis associated with c. trachomatis infection  <cit> .
the chemokine monocyte chemoattractant protein- <dig>  has also been identified in chronic chlamydial infections demonstrating elevated levels in post-scarring trachoma populations  <cit> .
due to the high prevalence of worldwide trachoma, the world health organization  established and supports the use of the safe  strategy to reduce disease transmission in endemic areas.
mass antibiotic therapy has been a mainstay in this program resulting in diminished prevalence of active chlamydial infections  <cit> .
however, heightened recurrence rates of infection 6-24 months after termination of antibiotic therapy were evident in multiple studies  <cit> .
additionally, burnham et al.
saw an increase in chlamydia-associated sti reinfection after a control program with antibiotic treatment was established  <cit> .
the mass administration of antibiotics may lead to the development of antibiotic resistance in chlamydial species as well as other pathogenic bacteria.
it is apparent that research into alternative treatments is warranted, and the use of phototherapy may be an attractive option.
phototherapy utilizing low power lasers or light emitting diodes  has been shown to reduce pain and chronic inflammation, and to promote tissue regeneration via a photochemical mechanisms .
additionally, anti-bacterial effects due to the increased production of reactive oxygen species resulting in membrane instability and dna damage have been evident with phototherapy  <cit> .
its use with several discrete wavelengths exhibits anti-bacterial activity requiring short treatment times without inducing anti-bacterial resistance subsequent to multiple treatment sessions  <cit> .
in this study, we analyzed the effect of low-level 405 nm and 670 nm led irradiation on the growth of c. trachomatis and the ensuing secretion of pro-inflammatory cytokines il- <dig> and ccl <dig> from c. trachomatis-infected epithelial cells.
RESULTS
inhibition of chlamydial growth post - 405 nm irradiation
this study assessed the use of 405 nm and 670 nm leds as an alternative treatment against chlamydial infections.
in figure 1a, hela cells were infected with c. trachomatis at a multiplicity of infection  of  <dig>  irradiation treatment with violet 405 nm leds demonstrated chlamydial growth inhibition at energy densities as low as 5 j/cm <dig> .
anti-chlamydial properties were dose dependent with the strongest effect visible at 20 j/cm <dig> .
fluorescent staining  for chlamydial antigens supported an impairment of chlamydial growth and inclusion body expansion after 405 nm exposure  compared to c. trachomatis infected cells alone .
we also analyzed the effect of irradiation application time post-infection to determine if it was growth phase specific.
at 24 h post-infection, irradiation with 405 nm  leds still demonstrated a significant growth inhibition .
c. trachomatis-infected cells treated with red 670 nm leds at similar energy densities  showed no significant effect on growth .
considering many chronic chlamydial infections are in a persistent stage of growth, we tested the effect of 405 nm on chlamydial growth after penicillin-induced persistence.
as shown in figure 1c, 405 nm retarded chlamydial growth during a persistent state  at 20 j/cm <dig>  though the result was not as pronounced as it was in the active state.
once again, no effect was seen with 670 nm treatment .
the effect of 405 nm irradiation on il- <dig> production in c. trachomatis-infected hela cells
previous studies have identified il- <dig> as a pro-inflammatory cytokine associated with immunopathologic effects in chronic c. trachomatis infections  <cit> .
in this study, we demonstrated elevated il- <dig> levels post-chlamydial infection compared to uninfected cells .
c. trachomatis infected hela cells were treated with varying 405 nm energy densities  promptly after infection.
irradiation with 405 nm at energy densities of  <dig>   <dig>  and 20 j/cm <dig> diminished il- <dig> secretion in a dose-dependent manner 48 h post-c. trachomatis infection when compared to c. trachomatis infection alone .
considering the potential for clinical therapies, we tested whether the effect of this phototherapy was dependent upon the 405 nm application time post-chlamydial infection.
if applied 24 h post-infection rather than two hours, the significant 405 nm effect on il- <dig> was lost .
due to the elevated levels of il- <dig> with chlamydia-induced chronic grades of disease, we determined whether penicillin-induced persistence of a c. trachomatis infection in vitro would mimic the above clinical inflammatory signs.
we demonstrated that persistence induction by penicillin significantly increased il- <dig> production compared to c. trachomatis infection alone .
the absence of il- <dig> production above mock-infected levels from hela cells stimulated with  <dig> u/ml of penicillin alone indicates this effect was not cumulative .
no significant effects were evident on il- <dig> production after 405 nm  or 670 nm  irradiation in this penicillin-induced persistent state.
the effect of 405 nm irradiation on ccl <dig> production in c. trachomatis infected hela cells
due to the involvement of ccl <dig> with acute and chronic grades of chlamydial infections  <cit>  and its association with a th2-mediated response  <cit> , we evaluated the effect of 405 nm photo treatment on its production.
in figure 4c.
trachomatis infection increased production of ccl <dig> in hela cells relative to uninfected cells .
though a diminishing pattern was evident for ccl <dig> production with increasing 405 nm energy densities , 405 nm treatment failed to demonstrate any significant difference in ccl <dig> production compared to c. trachomatis infection alone.
unlike il- <dig>  penicillin-induced c. trachomatis persistence did not significantly influence ccl <dig> levels  in vitro.
discussion
multiple studies have demonstrated inadequate long-term protection of azithromycin for treating trachomatous trichiasis  <cit> .
suboptimal efficacy of antibiotics was also evident amongst a chlamydia-associated reactive arthritis population where persistent chlamydial bodies were identified in fibroblasts and macrophages one month after doxycycline treatment  <cit> .
further support for the poor antibiotic efficacy against chronic c. trachomatis infections was demonstrated in a population of women with post-infectious tubal infertility who remained infected despite antibiotic treatment  <cit> .
urogenital chlamydial re-infections have been identified as probable treatment failure with azithromycin or doxycycline using ompa genotyping in approximately  <dig> and  <dig> % of cases  <cit> .
together the suboptimal efficacy of therapeutic antibiotics in the treatment of active and persistent chlamydial infections indicates the need for alternative treatments.
one potential alternative treatment utilizing 405 nm irradiation was evaluated in this study and demonstrated photo inactivation of c. trachomatis during active and persistent states.
small dosages starting at 5 j/cm <dig> had a significant growth inhibiting effect, with increasing energy densities positively correlating with growth inhibition.
therapeutic utility and clinical safety have been described using led phototherapy at 405 nm against acne vulgaris  <cit>  and gastric helicobacter pylori infections, with the latter applied to the gastrointestinal mucosa via a light wand  <cit> .
in vitro anti-bacterial activity of 405 nm irradiation has been demonstrated against multiple medically relevant gram-positive and gram-negative extracellular pathogens like staphylococcus aureus , streptococcus pyogenes, pseudomonas aeruginosa, clostridium perfringens, campylobacter jejuni, salmonella enteritidis and escherichia coli <cit> .
overall gram-negative bacteria appear more resistant to 405 nm irradiation than gram-positive, with the exception of enterococcus faecalis.
the majority of gram-positive bacteria appeared to require less than 11 j/cm <dig> for a log <dig> reduction in colony forming units, whereas gram-negative bacteriocidal effects were apparent between  <dig> and 96 j/cm <dig> <cit> .
the portable leds used in this study were battery operated with 88 second dosing times, therefore making it difficult to obtain higher energy densities.
comparing the log <dig> reduction levels of other gram negative bacteria with c. trachomatis is difficult due to its intracellular nature and considering it may exist as two-uncultivable life cycle forms: rbs and aberrant persistent forms.
after irradiation with an energy density of 20 j/cm <dig> we demonstrated a nearly 70% reduction in chlamydial growth, reflecting levels similar to other gram-negative bacteria.
to our knowledge, this is the first data demonstrating chlamydial growth inhibition caused by 405 nm irradiation.
photo inactivation by 405 nm irradiation is believed to be caused by excitation of androgenic porphyrins, resulting in oxygen free radical production and subsequent bacterial membrane disruption  <cit> .
endogenously produced porphyrins, like coproporphyrin, uroporphyrins, and protoporphyrin ix, have been shown to be produced by both gram positive and negative bacteria  <cit>  though, to our knowledge, porphyrin production by c. trachomatis has not yet been demonstrated.
considering the intracellular nature of c. trachomatis, a second photo inactivation mechanism might be associated with altered expression of eukaryotic proteins in response to 405 nm irradiation.
boncompain et al.
demonstrated a transient upregulation of reactive oxygen species within c. trachomatis-infected hela cells for approximately six hours after infection, with subsequent basal levels ensuing nine hours post-infection.
the regulation of reactive oxygen species appears to be mediated by c. trachomatis sequestration of the nadph oxidase subunit, rac <dig>  to the inclusion membrane  <cit> .
considering the significant growth inhibition effect when 405 nm was applied promptly two hours post-infection rather than 24 h, the irradiation might have altered chlamydial protein expression thus influencing its ability to sequester host rac <dig>  thereby increasing reactive oxygen species within the epithelial cells.
an alteration in protein expression may have also delayed the formation and secretion of bacterial type iii effector proteins, such as cpaf, that have previously been shown to be involved in binding and degrading eukaryotic proteins like cytokeratin  <dig>  adhesion protein nectin- <dig>  host transcription factor rfx <dig>  and multiple host pro-apoptotic bh <dig> proteins  <cit> .
alternatively, the lack of 405 nm photo inactivation effect on chlamydial growth at 24 h post-infection might be due to the exponentially higher bacterial burdens within the inclusion body 24 h post-infection relative to two hours post-infection, potentially causing the differences after treatment to be less pronounced.
it is also possible that multiple mechanisms co-exist and provide a cumulative anti-proliferative effect on c. trachomatis, though further studies are warranted.
the immunopathologic sequelae from conjunctival and genital chlamydial infections are likely mediated through the secretion of a group of pro-inflammatory cytokines.
in trachoma, we demonstrated elevated levels of il- <dig> during both acute and chronic grades of infection, with detectable chlamydial cases exhibiting more pronounced concentrations  <cit> .
the role of il- <dig> in immunopathologenesis was also evident in women with ectopic pregnancies  <cit>  and positively correlated with antibody titers against chlamydophila pneumoniae amongst atherosclerotic patients  <cit> .
in an attempt to mimic chronic chlamydial infections, macaca nemestrina fallopian tubes received repeated c. trachomatis infections, which resulted in fibrosis and elevated il- <dig>  il- <dig>  il- <dig>  and ifnγ levels  <cit> .
in tlr <dig> -/- ko mice infected with mouse pneumonitis , decreased fibrosis and inflammation with in oviducts and mesosalpinx correlated with abated il- <dig> concentrations  <cit> .
to determine the immunologic correlation of persistence in vitro with clinical presentation, we quantified il- <dig> in penicillin-induced c. trachomatis persistent infections in hela cells.
we demonstrated similar increases in il- <dig> production in persistent infections compared to active infections in vitro.
a previous study looked at persistent infections with c. pneumoniae in the presence of iron-depletion, ifnγ and penicillin, and demonstrated slightly diminished production of il- <dig> after 24 h and 48 h  <cit> .
however, multiple experimental differences between these studies, including the use of different chlamydial species, might provide an explanation for the differences in results.
for example, peters et al.
added penicillin 30 min after infection, followed by daily media change.
this is in contrast to our study which added penicillin 24 h post-infection without a daily media change.
wang et al.
provided more molecular details of this persistent state, demonstrating attenuated production of secreted chlamydial proteins from ampicillin-induced persistence of c. trachomatis infected hela cells  <cit> , suggesting that secreted type iii effector proteins like cpaf  <cit> , tarp  <cit> , ct <dig>  <cit> , and ct <dig>  <cit>  may be involved in regulating il- <dig> levels.
we are unaware of any other studies that examine inflammatory differences associated with penicillin-induced persistence.
the elevation of il- <dig> after penicillin-induced persistence supports the importance of this model in elucidating other inflammatory mediators that may be associated with chronic infections in vivo.
further research on molecular characterizations and their immunostimulatory properties is needed to understand this in vitro antibiotic-induced persistent model.
considering the immunopathologic response to chronic chlamydial infections, we were interested in determining the role of 405 nm irradiation on cytokines previously associated with immunopathogenesis.
in our study, irradiation with 405 nm had a dose-dependent effect on il- <dig> production with 20 j/cm <dig> causing a 64% reduction.
however, this effect was most likely associated with a decreased bacterial burden since previous studies demonstrated elevated il- <dig> from uv-a  exposed fibroblasts  <cit>  and minimal effects of uv-a  treated keratinocytes on il- <dig> production  <cit> .
interestingly, attenuation of il- <dig> after 405 nm treatment was only evident if 405 nm irradiation was applied promptly after infection; the effect was lost if applied 24 h post-infection.
we believe that at this later time point, multiple chlamydial proteins were already secreted by type iii secretory pathways into the host cytoplasm and interacted with pattern recognition receptors  resulting in il- <dig> production.
previously, we have identified ccl <dig> as a risk factor for trichiasis  <cit> , and therefore analyzed the effect of 405 nm irradiation on c. trachomatis induced ccl <dig> production.
to our knowledge, our findings are the first to demonstrate elevated levels of ccl <dig> after c. trachomatis infection in hela cells.
in vivo analysis has shown elevated mrna levels of ccl <dig> at two days post-infection with c. trachomatis mouse pneumonitis  strain  <cit> .
unlike il- <dig>  the use of 405 nm phototherapy on c. trachomatis infected hela cells did not have a significant effect on ccl <dig> production.
more studies are needed to further understand the relationship between c. trachomatis infection and ccl <dig> production resulting in these inflammatory differences.
CONCLUSIONS
with increasing evidence to support persistent infections amongst a percentage of chlamydial infections post-antibiotic treatment  <cit> , it is important to look for alternative treatments.
in this study, we have provided the first in vitro evidence for anti-bacterial effects against an intracellular bacterium, c. trachomatis, using 405 nm irradiation administered by portable leds.
the reduction in bacterial numbers and il- <dig> concentrations, and the clinical safety of 405 nm irradiation, supports further studies evaluating its use as a phototherapy against chlamydial infections within the conjunctival and reproductive tract mucosae.
the ability of photo treatment to penetrate mucosal tissue layers was demonstrated within the gastric mucosa against helicobacter pylori using 408 nm light  <cit> .
together, these data provide a plausible alternative treatment against chlamydial infections and expands the anti-bacterial properties of 405 nm irradiation to include intracellular bacteria.

 trachoma continues to be the most common cause of preventable blindness worldwide. it has been estimated to visually impair between two and nine million people globally, although this may be an underestimate due to the lack of screening programs in endemic areas. one of the etiologic agents is the obligate intracellular bacterium chlamydia trachomatis, which is also the leading bacterial cause of sexually transmitted infections worldwide. these reproductive infections can lead to clinical symptoms such as urethritis, cervicitis, and pelvic inflammatory disease. the ability of c. trachomatis to evade the immune system results in 70-90% of infected women and 30-50% of infected men being asymptomatic. due to repeated or persistent infections, or an absence of antibiotic treatment, ocular and reproductive tract sequelae can develop, resulting in corneal pacification and salpingitis respectively. c. trachomatis has a unique biphasic life cycle involving both elementary and reticulate bodies. elementary bodies represent a metabolically inactive infectious phenotype capable of attaching to epithelial cells with subsequent internalization resulting in the formation of an inclusion body. once inside the inclusion, the eb differentiates into a metabolically active reticulate body that multiplies via binary fission. as the inclusion grows, the rbs reorganize into ebs that are released from the host cell and can infect adjacent cells. these varying bioforms make treatment of chlamydial infections difficult. furthermore, antibiotic therapies, exposure to ifnγ, or nutrient deprivation can lead to an atypical, persistent, non-cultivable, and morphologically aberrant intracellular state. chlamydial infections in the conjunctiva and genitalia can incite an intense inflammatory response that, if chronic, can lead to scarring and fibrosis. numerous pro-inflammatory cytokines, including tnfα, il-1α, il- and il-, as well as a group of chemokines responsible for the recruitment of leukocytes have been shown to be secreted from c. trachomatis-infected epithelial cells. this arsenal of cytokines and chemokines with incoming leukocytes results in the stimulation of both cellular- and humoral-mediated immune defenses. the type of host inflammatory response that is initiated with the infection determines the outcome of the infection. the current hypothesis is that resolution is mediated primarily by a dominant cell-mediated th response, whereas chronic inflammation with subsequent scarring ensues if either the humoral th response or regulatory t cells predominate. development of chronic chlamydial infections is believed to arise as a result of immunopathology. this has been demonstrated by persistent elevation of pro-inflammatory cytokines like il- among infertile women and in tear fluid from post-scarring trachoma populations. one study identified il- secretion via the tlr signaling pathway after c. trachomatis infections. this tlr pathway has been shown to be associated with fallopian-tube pathology, potentially contributing to the immunopathogenesis associated with c. trachomatis infection. the chemokine monocyte chemoattractant protein- has also been identified in chronic chlamydial infections demonstrating elevated levels in post-scarring trachoma populations. due to the high prevalence of worldwide trachoma, the world health organization established and supports the use of the safe strategy to reduce disease transmission in endemic areas. mass antibiotic therapy has been a mainstay in this program resulting in diminished prevalence of active chlamydial infections. however, heightened recurrence rates of infection 6-24 months after termination of antibiotic therapy were evident in multiple studies. additionally, burnham et al. saw an increase in chlamydia-associated sti reinfection after a control program with antibiotic treatment was established. the mass administration of antibiotics may lead to the development of antibiotic resistance in chlamydial species as well as other pathogenic bacteria. it is apparent that research into alternative treatments is warranted, and the use of phototherapy may be an attractive option. phototherapy utilizing low power lasers or light emitting diodes has been shown to reduce pain and chronic inflammation, and to promote tissue regeneration via a photochemical mechanisms. additionally, anti-bacterial effects due to the increased production of reactive oxygen species resulting in membrane instability and dna damage have been evident with phototherapy. its use with several discrete wavelengths exhibits anti-bacterial activity requiring short treatment times without inducing anti-bacterial resistance subsequent to multiple treatment sessions. in this study, we analyzed the effect of low-level 405 nm and 670 nm led irradiation on the growth of c. trachomatis and the ensuing secretion of pro-inflammatory cytokines il- and ccl from c. trachomatis-infected epithelial cells.  inhibition of chlamydial growth post - 405 nm irradiation this study assessed the use of 405 nm and 670 nm leds as an alternative treatment against chlamydial infections. in figure 1a, hela cells were infected with c. trachomatis at a multiplicity of infection of irradiation treatment with violet 405 nm leds demonstrated chlamydial growth inhibition at energy densities as low as 5 j/cm. anti-chlamydial properties were dose dependent with the strongest effect visible at 20 j/cm. fluorescent staining for chlamydial antigens supported an impairment of chlamydial growth and inclusion body expansion after 405 nm exposure compared to c. trachomatis infected cells alone. we also analyzed the effect of irradiation application time post-infection to determine if it was growth phase specific. at 24 h post-infection, irradiation with 405 nm leds still demonstrated a significant growth inhibition. c. trachomatis-infected cells treated with red 670 nm leds at similar energy densities showed no significant effect on growth. considering many chronic chlamydial infections are in a persistent stage of growth, we tested the effect of 405 nm on chlamydial growth after penicillin-induced persistence. as shown in figure 1c, 405 nm retarded chlamydial growth during a persistent state at 20 j/cm though the result was not as pronounced as it was in the active state. once again, no effect was seen with 670 nm treatment. the effect of 405 nm irradiation on il- production in c. trachomatis-infected hela cells previous studies have identified il- as a pro-inflammatory cytokine associated with immunopathologic effects in chronic c. trachomatis infections. in this study, we demonstrated elevated il- levels post-chlamydial infection compared to uninfected cells. c. trachomatis infected hela cells were treated with varying 405 nm energy densities promptly after infection. irradiation with 405 nm at energy densities of and 20 j/cm diminished il- secretion in a dose-dependent manner 48 h post-c. trachomatis infection when compared to c. trachomatis infection alone. considering the potential for clinical therapies, we tested whether the effect of this phototherapy was dependent upon the 405 nm application time post-chlamydial infection. if applied 24 h post-infection rather than two hours, the significant 405 nm effect on il- was lost. due to the elevated levels of il- with chlamydia-induced chronic grades of disease, we determined whether penicillin-induced persistence of a c. trachomatis infection in vitro would mimic the above clinical inflammatory signs. we demonstrated that persistence induction by penicillin significantly increased il- production compared to c. trachomatis infection alone. the absence of il- production above mock-infected levels from hela cells stimulated with u/ml of penicillin alone indicates this effect was not cumulative. no significant effects were evident on il- production after 405 nm or 670 nm irradiation in this penicillin-induced persistent state. the effect of 405 nm irradiation on ccl production in c. trachomatis infected hela cells due to the involvement of ccl with acute and chronic grades of chlamydial infections and its association with a th2-mediated response, we evaluated the effect of 405 nm photo treatment on its production. in figure 4c. trachomatis infection increased production of ccl in hela cells relative to uninfected cells. though a diminishing pattern was evident for ccl production with increasing 405 nm energy densities, 405 nm treatment failed to demonstrate any significant difference in ccl production compared to c. trachomatis infection alone. unlike il- penicillin-induced c. trachomatis persistence did not significantly influence ccl levels in vitro. discussion multiple studies have demonstrated inadequate long-term protection of azithromycin for treating trachomatous trichiasis. suboptimal efficacy of antibiotics was also evident amongst a chlamydia-associated reactive arthritis population where persistent chlamydial bodies were identified in fibroblasts and macrophages one month after doxycycline treatment. further support for the poor antibiotic efficacy against chronic c. trachomatis infections was demonstrated in a population of women with post-infectious tubal infertility who remained infected despite antibiotic treatment. urogenital chlamydial re-infections have been identified as probable treatment failure with azithromycin or doxycycline using ompa genotyping in approximately and % of cases. together the suboptimal efficacy of therapeutic antibiotics in the treatment of active and persistent chlamydial infections indicates the need for alternative treatments. one potential alternative treatment utilizing 405 nm irradiation was evaluated in this study and demonstrated photo inactivation of c. trachomatis during active and persistent states. small dosages starting at 5 j/cm had a significant growth inhibiting effect, with increasing energy densities positively correlating with growth inhibition. therapeutic utility and clinical safety have been described using led phototherapy at 405 nm against acne vulgaris and gastric helicobacter pylori infections, with the latter applied to the gastrointestinal mucosa via a light wand. in vitro anti-bacterial activity of 405 nm irradiation has been demonstrated against multiple medically relevant gram-positive and gram-negative extracellular pathogens like staphylococcus aureus, streptococcus pyogenes, pseudomonas aeruginosa, clostridium perfringens, campylobacter jejuni, salmonella enteritidis and escherichia coli. overall gram-negative bacteria appear more resistant to 405 nm irradiation than gram-positive, with the exception of enterococcus faecalis. the majority of gram-positive bacteria appeared to require less than 11 j/cm for a log reduction in colony forming units, whereas gram-negative bacteriocidal effects were apparent between and 96 j/cm. the portable leds used in this study were battery operated with 88 second dosing times, therefore making it difficult to obtain higher energy densities. comparing the log reduction levels of other gram negative bacteria with c. trachomatis is difficult due to its intracellular nature and considering it may exist as two-uncultivable life cycle forms: rbs and aberrant persistent forms. after irradiation with an energy density of 20 j/cm we demonstrated a nearly 70% reduction in chlamydial growth, reflecting levels similar to other gram-negative bacteria. to our knowledge, this is the first data demonstrating chlamydial growth inhibition caused by 405 nm irradiation. photo inactivation by 405 nm irradiation is believed to be caused by excitation of androgenic porphyrins, resulting in oxygen free radical production and subsequent bacterial membrane disruption. endogenously produced porphyrins, like coproporphyrin, uroporphyrins, and protoporphyrin ix, have been shown to be produced by both gram positive and negative bacteria though, to our knowledge, porphyrin production by c. trachomatis has not yet been demonstrated. considering the intracellular nature of c. trachomatis, a second photo inactivation mechanism might be associated with altered expression of eukaryotic proteins in response to 405 nm irradiation. boncompain et al. demonstrated a transient upregulation of reactive oxygen species within c. trachomatis-infected hela cells for approximately six hours after infection, with subsequent basal levels ensuing nine hours post-infection. the regulation of reactive oxygen species appears to be mediated by c. trachomatis sequestration of the nadph oxidase subunit, rac to the inclusion membrane. considering the significant growth inhibition effect when 405 nm was applied promptly two hours post-infection rather than 24 h, the irradiation might have altered chlamydial protein expression thus influencing its ability to sequester host rac thereby increasing reactive oxygen species within the epithelial cells. an alteration in protein expression may have also delayed the formation and secretion of bacterial type iii effector proteins, such as cpaf, that have previously been shown to be involved in binding and degrading eukaryotic proteins like cytokeratin adhesion protein nectin- host transcription factor rfx and multiple host pro-apoptotic bh proteins. alternatively, the lack of 405 nm photo inactivation effect on chlamydial growth at 24 h post-infection might be due to the exponentially higher bacterial burdens within the inclusion body 24 h post-infection relative to two hours post-infection, potentially causing the differences after treatment to be less pronounced. it is also possible that multiple mechanisms co-exist and provide a cumulative anti-proliferative effect on c. trachomatis, though further studies are warranted. the immunopathologic sequelae from conjunctival and genital chlamydial infections are likely mediated through the secretion of a group of pro-inflammatory cytokines. in trachoma, we demonstrated elevated levels of il- during both acute and chronic grades of infection, with detectable chlamydial cases exhibiting more pronounced concentrations. the role of il- in immunopathologenesis was also evident in women with ectopic pregnancies and positively correlated with antibody titers against chlamydophila pneumoniae amongst atherosclerotic patients. in an attempt to mimic chronic chlamydial infections, macaca nemestrina fallopian tubes received repeated c. trachomatis infections, which resulted in fibrosis and elevated il- il- il- and ifnγ levels. in tlr -/- ko mice infected with mouse pneumonitis, decreased fibrosis and inflammation with in oviducts and mesosalpinx correlated with abated il- concentrations. to determine the immunologic correlation of persistence in vitro with clinical presentation, we quantified il- in penicillin-induced c. trachomatis persistent infections in hela cells. we demonstrated similar increases in il- production in persistent infections compared to active infections in vitro. a previous study looked at persistent infections with c. pneumoniae in the presence of iron-depletion, ifnγ and penicillin, and demonstrated slightly diminished production of il- after 24 h and 48 h. however, multiple experimental differences between these studies, including the use of different chlamydial species, might provide an explanation for the differences in results. for example, peters et al. added penicillin 30 min after infection, followed by daily media change. this is in contrast to our study which added penicillin 24 h post-infection without a daily media change. wang et al. provided more molecular details of this persistent state, demonstrating attenuated production of secreted chlamydial proteins from ampicillin-induced persistence of c. trachomatis infected hela cells, suggesting that secreted type iii effector proteins like cpaf, tarp, ct, and ct may be involved in regulating il- levels. we are unaware of any other studies that examine inflammatory differences associated with penicillin-induced persistence. the elevation of il- after penicillin-induced persistence supports the importance of this model in elucidating other inflammatory mediators that may be associated with chronic infections in vivo. further research on molecular characterizations and their immunostimulatory properties is needed to understand this in vitro antibiotic-induced persistent model. considering the immunopathologic response to chronic chlamydial infections, we were interested in determining the role of 405 nm irradiation on cytokines previously associated with immunopathogenesis. in our study, irradiation with 405 nm had a dose-dependent effect on il- production with 20 j/cm causing a 64% reduction. however, this effect was most likely associated with a decreased bacterial burden since previous studies demonstrated elevated il- from uv-a exposed fibroblasts and minimal effects of uv-a treated keratinocytes on il- production. interestingly, attenuation of il- after 405 nm treatment was only evident if 405 nm irradiation was applied promptly after infection; the effect was lost if applied 24 h post-infection. we believe that at this later time point, multiple chlamydial proteins were already secreted by type iii secretory pathways into the host cytoplasm and interacted with pattern recognition receptors resulting in il- production. previously, we have identified ccl as a risk factor for trichiasis, and therefore analyzed the effect of 405 nm irradiation on c. trachomatis induced ccl production. to our knowledge, our findings are the first to demonstrate elevated levels of ccl after c. trachomatis infection in hela cells. in vivo analysis has shown elevated mrna levels of ccl at two days post-infection with c. trachomatis mouse pneumonitis strain. unlike il- the use of 405 nm phototherapy on c. trachomatis infected hela cells did not have a significant effect on ccl production. more studies are needed to further understand the relationship between c. trachomatis infection and ccl production resulting in these inflammatory differences.  with increasing evidence to support persistent infections amongst a percentage of chlamydial infections post-antibiotic treatment, it is important to look for alternative treatments. in this study, we have provided the first in vitro evidence for anti-bacterial effects against an intracellular bacterium, c. trachomatis, using 405 nm irradiation administered by portable leds. the reduction in bacterial numbers and il- concentrations, and the clinical safety of 405 nm irradiation, supports further studies evaluating its use as a phototherapy against chlamydial infections within the conjunctival and reproductive tract mucosae. the ability of photo treatment to penetrate mucosal tissue layers was demonstrated within the gastric mucosa against helicobacter pylori using 408 nm light. together, these data provide a plausible alternative treatment against chlamydial infections and expands the anti-bacterial properties of 405 nm irradiation to include intracellular bacteria. 
previous studies have demonstrated anti-bacterial effects using different wavelengths of visible light at varying energy densities, though only against extracellular bacteria. c. trachomatis-infected hela cells were treated with or 670 nm irradiation at varying energy densities. chlamydia trachomatis is an intracellular bacterium that resides in the conjunctival and reproductive tract mucosae and is responsible for an array of acute and chronic diseases. we investigated the effects of visible light irradiation via light emitting diode on chlamydial growth in endocervical epithelial cells, hela, during active and penicillin-induced persistent infections. our results demonstrated a significant dose-dependent inhibitory effect on chlamydial growth during both active and persistent infections following 405 nm irradiation. in vitro modeling of a persistent c. trachomatis infection induced by penicillin demonstrated significantly elevated il- levels compared to c. trachomatis infection alone, though 405 nm irradiation had a minimal effect on this production. together these results identify novel inhibitory effects of 405 nm violet light on the bacterial growth of intracellular bacterium c. trachomatis in vitro, which also coincides with diminished levels of the pro-inflammatory cytokine il- a percentage of these infections persist even after use of antibiotics, suggesting the need for alternative treatments. furthermore, we analyzed the effect of this photo treatment on the ensuing secretion of il- and ccl two pro-inflammatory cytokines that have previously been identified as immunopathologic components associated with trichiasis in vivo.
 chlamydia trachomatis is an intracellular bacterium that resides in the conjunctival and reproductive tract mucosae and is responsible for an array of acute and chronic diseases. a percentage of these infections persist even after use of antibiotics, suggesting the need for alternative treatments. previous studies have demonstrated anti-bacterial effects using different wavelengths of visible light at varying energy densities, though only against extracellular bacteria. we investigated the effects of visible light irradiation via light emitting diode on chlamydial growth in endocervical epithelial cells, hela, during active and penicillin-induced persistent infections. furthermore, we analyzed the effect of this photo treatment on the ensuing secretion of il- and ccl two pro-inflammatory cytokines that have previously been identified as immunopathologic components associated with trichiasis in vivo.  c. trachomatis-infected hela cells were treated with or 670 nm irradiation at varying energy densities. bacterial growth was assessed by quantitative real-time pcr analyzing the 16s: gapdh ratio, while cell-free supernatants were examined for il- and monocyte chemoattractant protein- production. our results demonstrated a significant dose-dependent inhibitory effect on chlamydial growth during both active and persistent infections following 405 nm irradiation. diminished bacterial load corresponded to lower il- concentrations, but was not related to ccl levels. in vitro modeling of a persistent c. trachomatis infection induced by penicillin demonstrated significantly elevated il- levels compared to c. trachomatis infection alone, though 405 nm irradiation had a minimal effect on this production.  together these results identify novel inhibitory effects of 405 nm violet light on the bacterial growth of intracellular bacterium c. trachomatis in vitro, which also coincides with diminished levels of the pro-inflammatory cytokine il- 405 nmchlamydia trachomatisil-6ccl2phototherapy 