Ultraviolet radiation, resistance to infectious diseases, and vaccination responses

Latitude impact on Pandemic Sars-Cov-2 2020 outbreaks and possible utility of UV indexes in predictions of regional daily infections and deaths

The importance of two related factors ^_ latitude and solar ultraviolet radiation ^_ has been insufficiently recognized as determining the spread of pandemic Sars-CoV-2 outbreaks across the globe. In this study we provide evidence of the impact of latitude and investigate how daily RT-PCR diagnosed infections and deaths are quantitively correlated with the UV component of Solar light. Here, we present regression analyses using daily national numbers from Austria and from Portugal with daily ultraviolet indexes of two selected locations in these territories, obtained from a Satellite source. These countries, have similar surfaces areas and population size but Austria's mean latitude is 9° up-north. The equations derived from regression analyses of those two variables are comparable for both countries, fit best the fall (2^nd) pandemic wave and can be a useful non-R(t) (rate of transmission) dependent predictive tool. Similar equations were derived for deaths that follow infections within a few weeks delay. Strong correlations depend on the size of the region/country from which infections are collected, the robustness of screening practices, ideally kept through weekends and holidays. Besides the forecasting usefulness of such correlations, these findings also suggest that covid-19 transmission co-exists with a Sars-Cov-2 specific UV-induced immunosuppression response. While in 2020, intensity of pandemic spring and fall waves reflect a Solar UV-light modulation, we relate exceptional low temperature and humidity with additional waves, as the winter 2020/2021 3^rd wave, felt in the western European countries. This work may help understanding this Pandemic phenomenon and dealing with similar catastrophes in the future.

The microclimatic impacts of urban spaces on the behaviour of pandemics between propagation and containment: Case study historic Cairo

Although previous researches proved that frequent visits to urban spaces enhance the physical and mental health of people, most governments adopted lockdown policies after the outbreak of COVID-19. This decision has negatively impacted the wellbeing of communities and the livability of urban spaces. In this context the research questions how far the microclimatic conditions of urban space would influence its performance during respiratory pandemics? The study investigated this question through a dense literature survey including 47 scientific journal articles and governmental reports. The outputs were synthesized through a quantitative assessment framework. It detected the spatio-environmental parameters influencing the behaviour of respiratory pandemics in urban settings. To validate the framework's outputs, the research applied case study sampling for 3 urban spaces in historic Cairo. It generated digital simulations and computations addressing solar radiation, natural ventilation, air temperature, and humidity, besides space dimension and number of users. The results illustrated the areas of adequate and poor microclimatic performance during pandemics. They are demonstrated through numerical tables, digital simulations, and graphs. Eventually, a concluding assessment framework selected the optimum urban space performance to be engaged in the public life of historic Cairo during lockdown periods.

Effect of A Sun Protection Intervention on the Immune Response to Measles Booster Vaccination in Infants in Rural South Africa

The incidence of many serious childhood infections can be reduced by vaccination. High sun exposure at the time of vaccination has been associated with a reduced antigen-specific immune response. We hypothesized that providing sun protection advice and equipment to mothers of children who were waiting to be vaccinated would result in a more robust immunization response. We conducted a pilot study in 2015/2016 (data analyzed in 2017-2018) among 98 Black African children (~18 months of age) receiving the booster measles vaccination at two clinics in South Africa. Clinics were randomized to receive (or not) sun protection advice and equipment. We recorded demographic information on children and mothers and data on the child's usual sun exposure. At approximately 4 weeks' postmeasles vaccination, we measured measles immunoglobulin G levels in children. All children with blood results (n = 87, 89%) across both groups had antibody titers higher than 200 mIU mL^-1 which was considered the protective antibody concentration. There was no statistically significant difference in titers between groups: geometric difference in mean titers 1.13 mIU mL^-1 (95% CI 0.85, 1.51; P = 0.39) and 1.38 mIU mL^-1 (95% CI 0.90, 2.11, P = 0.14) for unadjusted and adjusted analyses, respectively. This study demonstrated that a sun protection intervention study could be performed in a developing-world pediatric vaccination setting. Although the sun protection intervention around the time of vaccination was not associated with a higher antibody level, given the potential importance of such an effect, a larger study should be considered.

The role of UV radiation and vitamin D in the seasonality and outcomes of infectious disease

The seasonality of infectious disease outbreaks suggests that environmental conditions have a significant effect on disease risk. One of the major environmental factors that can affect this is solar radiation, primarily acting through ultraviolet radiation (UVR), and its subsequent control of vitamin D production. Here we show how UVR and vitamin D, which are modified by latitude and season, can affect host and pathogen fitness and relate them to the outcomes of bacterial, viral and vector-borne infections. We conducted a thorough comparison of the molecular and cellular mechanisms of action of UVR and vitamin D on pathogen fitness and host immunity and related these to the effects observed in animal models and clinical trials to understand their independent and complementary effects on infectious disease outcome. UVR and vitamin D share common pathways of innate immune activation primarily via antimicrobial peptide production, and adaptive immune suppression. Whilst UVR can induce vitamin D-independent effects in the skin, such as the generation of photoproducts activating interferon signaling, vitamin D has a larger systemic effect due to its autocrine and paracrine modulation of cellular responses in a range of tissues. However, the seasonal patterns in infectious disease prevalence are not solely driven by variation in UVR and vitamin D levels across latitudes. Vector-borne pathogens show a strong seasonality of infection correlated to climatic conditions favoring their replication. Conversely, pathogens, such as influenza A virus, Mycobacterium tuberculosis and human immunodeficiency virus type 1, have strong evidence to support their interaction with vitamin D. Thus, UVR has both vitamin D-dependent and independent effects on infectious diseases; these effects vary depending on the pathogen of interest and the effects can be complementary or antagonistic.

Geographic variation in pneumococcal vaccine efficacy estimated from dynamic modeling of epidemiological data post-PCV7

Although mean efficacy of multivalent pneumococcus vaccines has been intensively studied, variance in vaccine efficacy (VE) has been overlooked. Different net individual protection across settings can be driven by environmental conditions, local serotype and clonal composition, as well as by socio-demographic and genetic host factors. Understanding efficacy variation has implications for population-level effectiveness and other eco-evolutionary feedbacks. Here I show that realized VE can vary across epidemiological settings, by applying a multi-site-one-model approach to data post-vaccination. I analyse serotype prevalence dynamics following PCV7, in asymptomatic carriage in children attending day care in Portugal, Norway, France, Greece, Hungary and Hong-Kong. Model fitting to each dataset provides site-specific estimates for vaccine efficacy against acquisition, and pneumococcal transmission parameters. According to this model, variable serotype replacement across sites can be explained through variable PCV7 efficacy, ranging from 40% in Norway to 10% in Hong-Kong. While the details of how this effect is achieved remain to be determined, here I report three factors negatively associated with the VE readout, including initial prevalence of serotype 19F, daily mean temperature, and the Gini index. The study warrants more attention on local modulators of vaccine performance and calls for predictive frameworks within and across populations.

Sun protection to improve vaccine effectiveness in children in a high ambient ultraviolet radiation and rural environment: an intervention study

BACKGROUND

Vaccination is a mainstay of preventive healthcare, reducing the incidence of serious childhood infections. Ecological studies have demonstrated an inverse association between markers of high ambient ultraviolet (UV) radiation exposure (e.g., sunny season, low latitude of residence) and reduction in the vaccination-associated immune response. Higher sun exposure on the day prior to and spanning the day of vaccination has been associated with a reduced antigen-specific immune response independent of skin pigmentation. The South African Department of Health's Expanded Programme on Immunisation provides free vaccinations in government primary health care clinics. In some areas, these clinics may have only a small waiting room and patients wait outside in full sun conditions. In rural areas, patients may walk several kilometres to and from the clinic. We hypothesised that providing sun protection advice and equipment to mothers of children (from 18 months) who were waiting to be vaccinated would result in a more robust immune response for those vaccinated.

METHODS

We conducted an intervention study among 100 children receiving the booster measles vaccination. We randomised clinics to receive (or not) sun protection advice and equipment. At each clinic we recorded basic demographic data on the child and mother/carer participants, their sun exposure patterns, and the acceptability and uptake of the provided sun protection. At 3-4 weeks post-vaccination, we measured measles IgG levels in all children.

DISCUSSION

This is the first intervention study to assess the effect of sun protection measures on vaccine effectiveness in a rural, real-world setting. The novel design and rural setting of the study can contribute much needed evidence to better understand sun exposure and protection, as well as factors determining vaccine effectiveness in rural Africa, and inform the design of immunisation programmes. (TRN PACTCR201611001881114, 24 November 2016, retrospective registration).

Will Global Climate Change Alter Fundamental Human Immune Reactivity: Implications for Child Health?

The human immune system is an interface across which many climate change sensitive exposures can affect health outcomes. Gaining an understanding of the range of potential effects that climate change could have on immune function will be of considerable importance, particularly for child health, but has, as yet, received minimal research attention. We postulate several mechanisms whereby climate change sensitive exposures and conditions will subtly impair aspects of the human immune response, thereby altering the distribution of vulnerability within populations-particularly for children-to infection and disease. Key climate change-sensitive pathways include under-nutrition, psychological stress and exposure to ambient ultraviolet radiation, with effects on susceptibility to infection, allergy and autoimmune diseases. Other climate change sensitive exposures may also be important and interact, either additively or synergistically, to alter health risks. Conducting directed research in this area is imperative as the potential public health implications of climate change-induced weakening of the immune system at both individual and population levels are profound. This is particularly relevant for the already vulnerable children of the developing world, who will bear a disproportionate burden of future adverse environmental and geopolitical consequences of climate change.

The Use of In Vitro Systems for Evaluating Immunotoxicity: The Report and Recommendations of an ECVAM Workshop

This is the report of a workshop organised by the European Centre for the Validation of Alternative Methods (ECVAM). ECVAM's main goal, as defined in 1993 by its Scientific Advisory Committee, is to promote the scientific and regulatory acceptance of alternative methods that are of importance to the biosciences and which replace, reduce or refine the use of laboratory animals. One of the first priorities set by ECVAM was the implementation of procedures that would enable it to become well informed about the state-of-the-art of non-animal test development and validation, and the potential for the possible incorporation of alternative tests into regulatory procedures. It was decided that this would be best achieved by the organization of ECVAM workshops on specific topics, at which small groups of invited experts would review the current status of various types of in vitro tests and their potential uses, and make recommendations about the best ways forward (Anonymous, 1994). The workshop on "The use of in vitro systems for evaluating Immunotoxicity" was held at ECVAM (Ispra), Italy, on 24th-26th November 2003. The participants represented academia, national organizations, international regulatory bodies and industry. The aim of the workshop was to review the state-of-the-art in the field of in vitro immunotoxicology, and to develop strategies towards the replacement of in vivo testing. At the end of this report are listed the recommendations that should be considered for prevalidation and validation of relevant and reliable procedures, that could replace the use of animals in chemical and cosmetics toxicity testing.

The challenges of UV-induced immunomodulation for children's health

Exposure to solar ultraviolet radiation (UVR) is recognised to have both beneficial and harmful effects on human health. With regard to immune responses, it can lead to suppression of immunity and to the synthesis of vitamin D, a hormone that can alter both innate and adaptive immunity. The consequences in children of such UV-induced changes are considerable: first there are positive outcomes including protection against some photoallergic (for example polymorphic light eruption) and T cell-mediated autoimmune diseases (for example multiple sclerosis) and asthma, and secondly there are negative outcomes including an increased risk of skin cancer (squamous cell carcinoma, basal cell carcinoma and cutaneous malignant melanoma) and less effective control of several infectious diseases. Many uncertainties remain regarding the amount of sun exposure that would provide children with the most effective responses against the variety of immunological challenges that they are likely to experience.

Modulation of the immune system by UV radiation: more than just the effects of vitamin D?

Humans obtain most of their vitamin D through the exposure of skin to sunlight. The immunoregulatory properties of vitamin D have been demonstrated in studies showing that vitamin D deficiency is associated with poor immune function and increased disease susceptibility. The benefits of moderate ultraviolet (UV) radiation exposure and the positive latitude gradients observed for some immune-mediated diseases may therefore reflect the activities of UV-induced vitamin D. Alternatively, other mediators that are induced by UV radiation may be more important for UV-mediated immunomodulation. Here, we compare and contrast the effects of UV radiation and vitamin D on immune function in immunopathological diseases, such as psoriasis, multiple sclerosis and asthma, and during infection.

Effect of season of inoculation on immune response to rubella vaccine in children

The yearly seasons are marked by changes in the amount of sunlight. Ultraviolet radiation (UVR) is known to adversely affect the course of viral infections, immunologic memory and cellular and humoral immune responses. Our objectives were to investigate potential differences in the immune response of the rubella vaccine after 3-4 years by season of inoculation. Children aged 4-5 years attending four kindergartens in villages in northern Israel, all of whom had been vaccinated at 1 year of age, were enrolled in the study. Participants were divided into three groups by season of the year in which the inoculation was performed: summer (N = 63), winter (N = 36) and intermediate (N = 104). Main outcome measures were mean geometrical titer of rubella antibodies and complete, partial or no immunity to rubella by season of inoculation. Of the 203 children tested, 186 (91.6%) had adequate antibody levels, 7 (3.4%) had equivocal levels and 10 (4.9%) had inadequate levels. Significantly higher mean geometrical titers were found in the winter-inoculated compared with the summer-inoculated group (73.0 ± 2.6 vs 47.6 ± 2.8; p < 0.05). The same tendency was noted in the percent of infants properly immunized. This preliminary study shows a strong correlation between the immune response to rubella vaccine and the season of vaccination. Immunogenicity may be improved by inoculating children during seasons of less sunlight or by reducing the children's exposure to sunlight following inoculation. This practice is especially important in areas with extreme seasonal variability in solar radiation and tropical areas. Further studies are needed to corroborate and expand these findings.

UV-induced immunosuppression and the efficacy of vaccination

Exposure to ultraviolet radiation (UVR) suppresses immunity by complex pathways, initiated by chromophores located in the skin and ending with the generation of specific subsets of T and B regulatory cells. The primary and memory (recall) immune response to a wide variety of antigens, including microorganisms, can be reduced by UVR, leading to the possibility that the efficacy of vaccination could be similarly reduced. A limited number of animal models of vaccination demonstrate that this may indeed be the case. The situation in human subjects has not been rigorously assessed but there are indications from a variety of sources that UVR adversely affects the immune responses to several vaccines. These studies are reviewed and the implications for vaccine administration discussed. As vaccination represents a major public health measure world-wide for the control of an increasing number of common infections, it is important to maximise its efficacy; therefore further evaluation of UVR in the context of vaccination is required and warranted.

UV irradiation of immunized mice induces type 1 regulatory T cells that suppress tumor antigen specific cytotoxic T lymphocyte responses

We previously showed that exposure to UV radiation after immunization suppresses Th1 and Th2 immune responses, leading to impaired Ab and allo-immune responses, but the impact of UV radiation after immunization on anti-tumor immune responses mediated by tumor-specific CD8(+) T cell responses remains less clear. Furthermore, the exact phenotypic and functional characteristics of regulatory T cell population responsible for the UV-induced immunosuppression still remain elusive. Using the MBL-2 lymphoma cell line engineered to express OVA as a surrogate tumor Ag, here we demonstrate that UV irradiation after tumor Ag-immunization suppresses the anti-tumor immune response in a manner dependent on the immunizing Ag. This suppression was mediated by interleukin (IL)-10 released from CD4(+) CD25(+) T cells, by which impaired the induction of cytotoxic T lymphocytes (CTL) able to kill Ag-expressing tumor cells. In addition, we generated a panel of T cell clones from UV-irradiated and non-irradiated mice, and all of the clones derived from UV-irradiated mice had a Tr1-type regulatory T cell phenotype with expression of IL-10 and c-Maf, but not Foxp3. These Tr1-type regulatory T cell clones suppressed tumor rejection in vivo as well as Th cell activation in vitro in an IL-10 dependent manner. Given that suppression of Ag-specific CTL responses can be induced in Ag-sensitized mice by UV irradiation, our results may imply that exposure to UV radiation during premalignant stage induces tumor-Ag specific Tr1 cells that mediate tumor-Ag specific immune suppression resulting in the promotion of tumor progression.

Skin exposure to chronic but not acute UV radiation affects peripheral T-cell function

Ultraviolet (UV) radiation (UVR) produces deleterious effects that may finally lead to carcinogenesis. These adverse effects include tissue inflammation, free radical formation with consequent oxidation of proteins and lipids, DNA damage, and immune function suppression. The aim of this study was to evaluate the effects of UVR at the local and systemic levels following acute (4 consecutive days with 0.5 minimal erythema dose [MED]) or chronic (20 consecutive days with 0.25 MED) exposure. Locally, histological alterations and epidermal T-cell populations were studied. Systemically, inguinal lymph-node and spleen T cells were analyzed with respect to proliferative response and cytokine production against a nonspecific mitogen. Lymph-node T-cell populations were also characterized. Our results indicated that while both acute and chronic UVR produced epidermal hyperplasia and a decrease in epidermal T-cell density, acute UVR increased T-cell proliferative response, while chronic UVR produced the opposite effect, shifting the cytokine production toward a Th2/Treg profile. Therefore, even though acute irradiation produced a direct effect on skin, it did not correlate with a marked modification of overall T-cell response, which is in contrast to marked effects in chronically irradiated animals. These findings may contribute to understanding the clinical relevance of occupational UVR exposure, typically related to outdoor activities, which is associated with nonmelanoma skin carcinogenesis.

Genome-wide identification of susceptibility alleles for viral infections through a population genetics approach

Viruses have exerted a constant and potent selective pressure on human genes throughout evolution. We utilized the marks left by selection on allele frequency to identify viral infection-associated allelic variants. Virus diversity (the number of different viruses in a geographic region) was used to measure virus-driven selective pressure. Results showed an excess of variants correlated with virus diversity in genes involved in immune response and in the biosynthesis of glycan structures functioning as viral receptors; a significantly higher than expected number of variants was also seen in genes encoding proteins that directly interact with viral components. Genome-wide analyses identified 441 variants significantly associated with virus-diversity; these are more frequently located within gene regions than expected, and they map to 139 human genes. Analysis of functional relationships among genes subjected to virus-driven selective pressure identified a complex network enriched in viral products-interacting proteins. The novel approach to the study of infectious disease epidemiology presented herein may represent an alternative to classic genome-wide association studies and provides a large set of candidate susceptibility variants for viral infections.

Viruses have represented a constant threat to human communities throughout their history, therefore, human genes involved in anti-viral response can be thought of as targets of virus-driven selective pressure. Here we utilized the marks left by selection to identify viral infection-associated allelic variants. We analyzed more than 660,000 single nucleotide polymorphisms (SNPs) genotyped in 52 human populations, and we used virus diversity (the number of different viruses in a geographic region) to measure virus-driven selective pressure. Results showed that genes involved in immune response and in the biosynthesis of glycan structures functioning as viral receptors display more variants associated with virus diversity than expected by chance. The same holds true for genes encoding proteins that directly interact with viral components. Genome-wide analysis identified 441 variants, mapping to 139 human genes, significantly associated with virus-diversity. We analyzed the functional relationships among genes subjected to virus-driven selective pressure and identified a complex interaction network enriched in viral products-interacting proteins. Therefore, we describe a novel approach for the identification of gene variants that may be involved in the susceptibility to viral infections.

Immunotoxicology: Opportunities for Non-animal Test Development

At present, several animal-based assays are used to assess immunotoxic effects such as immunosuppression and sensitisation. The use of whole animals, however, presents several secondary issues, including expense, ethical concerns and relevance to human risk assessment. There is a growing belief that non-animal approaches can eliminate these issues without impairing human safety, provided that biological markers are available to identify the immunotoxic potentials of new chemicals to which humans may be exposed. Driven by the 7th Amendment to the EU Cosmetics Directive, the new EU policy on chemicals (the REACH system), proposals to update the European legislation on the protection of animals used in research, and emerging visions and strategies for predicting toxicity, such in vitro methods are likely to play a major role in the near future. The realisation that the immune system can be the target of many chemicals, resulting in a range of adverse effects on the host's health, has raised serious concerns from the public and within the regulatory agencies. Hypersensitivity and immunosuppression are considered the primary focus for developing in vitro methods in immunotoxicology. However, in vitro assays to detect immunostimulation and autoimmunity are also needed. This review of the state-of-the-art in the field of in vitro immunotoxicity, reveals a lack of cell-based immunotoxicity assays for predicting the toxicity of xenobiotics toward the immune system in a simple, fast, economical and reliable way.

Alloantigen-specific prolongation of allograft survival in recipient mice treated by alloantigen immunization following ultraviolet-B irradiation

It is well documented that ultraviolet (UV) radiation present in sunlight suppresses immune responses. However, the majority of studies documenting the immunosuppressive effects of UV irradiation have been carried out in animals exposed to UV irradiation before immunization. Here, we report that recipient mice exposed to UV irradiation 7 days after immunization with a donor alloantigen exhibited prolongation of allograft survival in an alloantigen-specific manner. Recipient mice (H-2(b)) intravenously immunized with 2 x 10(7) allogeneic spleen cells (H-2(b/d)) 7 days before UV irradiation (40 kJ/m(2)) showed prolonged survival of allografts presenting the alloantigen used for sensitization (H-2(b/d)), but not third-party allografts (H-2(b/k)). Adoptive transfer experiments revealed that CD4(+) T cells in UV-irradiated recipients were responsible for this prolongation. CD4(+) T cells that could transfer the suppression produced large amounts of interleukin (IL)-10, but not IL-4. The effect of UV irradiation on alloantigen-specific immunosuppression was cancelled by administration of an anti-IL-10 monoclonal antibody. These results indicate that UV irradiation given after alloantigen immunization induces alloantigen-specific type 1 regulatory T cell-like regulatory T cells that prolong allograft survival and imply that the difficulties associated with predicting donor-related organ availability in transplantation can be dealt with, given the effectiveness of UV irradiation after immunization.

Post-immune UV irradiation induces Tr1-like regulatory T cells that suppress humoral immune responses

It is well documented that UV radiation present in sunlight suppresses immune responses, especially T(h)1-driven cellular immune responses, resulting in the exacerbation of skin cancer and infectious diseases. However, the effects of UV irradiation on humoral immune responses remain less clearly defined. In addition, the majority of studies documenting immunosuppressive effects of UV irradiation has been demonstrated in animals exposed to UV radiation before immunization. In the present study, therefore, we examined the effects of UV irradiation on humoral immune responses in mice that had been immunized before UV irradiation. Both T(h)1- and T(h)2-associated Ig responses were significantly suppressed by UV irradiation given 7 days after immunization in an antigen-specific manner. Adoptive transfer experiments revealed that CD4(+) T cells from UV-irradiated mice are responsible for the UV-induced suppression of antibody responses. These CD4(+) regulatory T cells suppressed proliferation of conventional CD4(+) T cells in vivo and in vitro and contained IL-10-producing cells that did not express Foxp3. Mice depleted of CD25(+) cells also exhibited reduced antibody responses by UV irradiation. Finally, we showed that CD4(+) T cells from UV-irradiated mice treated with anti-IL-10 mAb failed to suppress antibody responses upon transfer. These results indicate that UV irradiation after immunization suppresses T(h)1- and T(h)2-mediated humoral immunity via the generation of Tr1-like regulatory T cells, in the process of which IL-10 appears to be important. Possible detrimental effects of UV irradiation after vaccination are also discussed.

Ultraviolet B Irradiation Affects Resistance of Rainbow Trout (Oncorhynchus mykiss) Against Bacterium Yersinia ruckeri and Trematode Diplostomum spathaceum

Ultraviolet B (UVB) radiation is known to have various effects on the immune system of fish, but the effect on the actual disease resistance has remained largely unknown. Here we studied the effect of UVB on the resistance of rainbow trout (Oncorhynchus mykiss) against a bacterium Yersinia ruckeri, the causative agent of enteric red mouth disease, and a trematode parasite Diplostomum spathaceum, which causes cataracts in fish. The fish were exposed to UVB irradiation seven times in 14 days, and inoculated intraperitoneally with Y. ruckeri on day 5 after the first irradiation. On day 2 postinfection (p.i.), the number of viable bacteria in the kidney was lower in UVB-exposed than in unexposed fish. However, on day 8 p.i., UVB-irradiated fish had not been able to clear remaining Y. ruckeri effectively, and had a slightly higher bacterial load than controls. A similar, although not significant, effect was seen in the bacterial numbers in spleen. In the other experiment, fish were exposed to UVB for six consecutive days and then exposed to D. spathaceum. A significantly higher number of parasites was detected in the eyes of irradiated fish, indicating reduced resistance against the pathogen. Furthermore, UVB-irradiation altered the immunological and hematological parameters of fish, which also verified the immunomodulatory potential of UVB in the present study.

Arctic stratospheric ozone depletion and increased UVB radiation: potential impacts to human health

Contrary to popular belief, stratospheric ozone depletion, and the resultant increase in solar UV-B (280-320 nm), are unlikely to fully recover soon. Notwithstanding the success of the Montreal Protocol in reducing the amount of ozone destroying chemicals into the stratosphere, the life-times of these compounds are such that even with full compliance with the Protocol by all countries, it will be decades before stratospheric ozone could return to pre-1980 levels. This raises the question, therefore, of what will happen to biological processes essential to the maintenance of life on earth which are sensitive to damage by increased UV-B radiation, particularly those involved with human health? The polar regions, because of the vagaries of climate and weather, are the bellwether for stratospheric ozone depletion and will, therefore, be the first to experience impacts due to increases in solar UV-B radiation. The impacts of these are incompletely understood and cannot be predicted with certainty. While some UV-B impacts on human health are recognized, much is unknown, unclear and uncertain. Thus, this paper attempts, as a first approximation, to point out potential impacts to the health and welfare of human inhabitants of the Arctic due to increased solar UV-B radiation associated with stratospheric ozone depletion. As will be seen, much more data is critically needed before adequate risk assessment can occur.

Ultraviolet Irradiation Suppresses T Cell Activation via Blocking TCR-Mediated ERK and NF-κB Signaling Pathways

UV irradiation is carcinogenic and immunosuppressive. Previous studies indicate that UV-mediated alteration of APCs and induction of suppressor T cells play a critical role in UV-induced immune suppression. In this study, we show that UV irradiation can directly (independently of APCs and suppressor T cells) inhibit T cell activation by blocking TCR-mediated phosphorylation of ERK and IkappaB via overactivation of the p38 and JNK pathways. These events lead to the down-modulation of c-Jun, c-Fos, Egr-1, and NF-kappaB transcription factors and thereby inhibit production of cytokines, e.g., IL-2, IL-4, IFN-gamma, and TNF-alpha, upon TCR stimulation. We also show that UV irradiation can suppress preactivated T cells, indicating that UV irradiation does not only impair T cell function in response to T cell activation, but can also have systemic effects that influence ongoing immune responses. Thus, our data provide an additional mechanism by which UV irradiation directly suppresses immune responses.

Comparisons of Estimated Economic Burdens due to Insufficient Solar Ultraviolet Irradiance and Vitamin D and Excess Solar UV Irradiance for the United States

Vitamin D sufficiency is required for optimal health, and solar ultraviolet B (UVB) irradiance is an important source of vitamin D. UVB and/or vitamin D have been found in observational studies to be associated with reduced risk for over a dozen forms of cancer, multiple sclerosis, osteoporotic fractures, and several other diseases. On the other hand, excess UV irradiance is associated with adverse health outcomes such as cataracts, melanoma, and nonmelanoma skin cancer. Ecologic analyses are used to estimate the fraction of cancer mortality, multiple sclerosis prevalence, and cataract formation that can be prevented or delayed. Estimates from the literature are used for other diseases attributed to excess UV irradiation, additional cancer estimates, and osteoporotic fractures. These results are used to estimate the economic burdens of insufficient UVB irradiation and vitamin D insufficiency as well as excess UV irradiation in the United States for these diseases and conditions. We estimate that 50,000-63,000 individuals in the United States and 19,000-25,000 in the UK die prematurely from cancer annually due to insufficient vitamin D. The U.S. economic burden due to vitamin D insufficiency from inadequate exposure to solar UVB irradiance, diet, and supplements was estimated at $40-56 billion in 2004, whereas the economic burden for excess UV irradiance was estimated at $6-7 billion. These results suggest that increased vitamin D through UVB irradiance, fortification of food, and supplementation could reduce the health care burden in the United States, UK, and elsewhere. Further research is required to confirm these estimates.

Sunlight exposure and (sero)prevalence of epidermodysplasia verruciformis-associated human papillomavirus

Ultraviolet radiation (UVR) is associated with an increased risk of squamous cell carcinoma (SCC), which is in part due to immunomodulation. In addition, human papilloma virus (HPV), especially the epidermodysplasia verruciformis (EV)-associated types, may be involved. In view of the capacity of UVR to impair host resistance to infections, we investigated the relationship between solar exposure and the prevalence of cutaneous HPV. In a case-control study on skin cancer (320 controls and 156 patients) a lifetime-retrospective questionnaire on sun exposure was administered. The presence of DNA of HPV types 5, 8, 15, 20, 24, and 38 in plucked eyebrow hair and type-specific seroreactivity were assessed and analyzed in relation to estimated exposure. Sunburn episodes in the past, especially at age 13-20 y, appeared to be associated with an enhanced risk of EV-HPV DNA positivity. In contrast, a higher lifetime sun exposure was associated with a lower risk of HPV infection. These results indicate that UVR at erythematogenic doses increases the risk of EV-HPV infection, possibly due to impaired host resistance to HPV and/or a direct effect of UVR on viral replication. The favorable association between lifetime sun exposure and HPV prevalence, however, underscores the enigmatic role of HPV in skin carcinogenesis.