The malignant potential of papillomavirus

Exposure to ultraviolet radiation enhances mortality and pathology associated with influenza virus infection in mice

Ultraviolet radiation (UVR) causes systemic immune suppression, decreasing the delayed type and contact hypersensitivity responses in animals and humans and enhancing certain mycobacterial, parasitic and viral infections in mice. This study tests the hypothesis that prior exposure to UVR enhances influenza infections in mice. BALB/c female mice were exposed to 0-8.2 kJ/m2 of UVR. Exposed and unexposed mice were infected intranasally three days later with 150-300 plaque-forming units/mouse (lethal dose (LD)20-LD40) of mouse-adapted Hong Kong Influenza A/68 (H3N2) virus or sham infected with 50 microL Hanks' balanced salt solution/mouse. Mortality from viral infection ranged from 25-50%. UVR exposure increased virus-associated mortality in a dose-dependent manner (up to a two-fold increase at 8.2 kJ/m2). The increased mortality was not associated with bacterial pneumonia. The highest dose of UVR also accelerated the body weight loss and increased the severity and incidence of thymic atrophy associated with influenza infection. However, UVR treatment had little effect on the increase in lung wet weight seen with viral infection, and, to our surprise, did not cause an increase in virus titers in the lung or dissemination of virus. The mice died 5-6 days after infection, too early for adaptive immune responses to have much impact. Also, UVR did not interfere with the development of protective immunity to influenza, as measured by reinfection with a lethal challenge of virus. Also, cells adoptively transferred from UVR or untreated mice were equally protective of recipient mice challenged with a lethal dose of virus. The mice resemble mice succumbing to endotoxin, and influenza infection increased the levels of tumor necrosis factor alpha (TNF-alpha) in bronchoalveolar lavage fluid and serum cortisol levels; however, UVR preexposure did not increase either of these responses to the virus. The results show that UVR increased the morbidity, mortality and pathogenesis of influenza virus in mice without affecting protective immunity to the virus, as measured by resistance to reinfection. The mechanism of enhanced mortality is uncertain, but the data raises concerns that UVR may exacerbate early responses that contribute to the pathogenesis of a primary viral infection.

The epidemiology of non-melanoma skin cancer: who, why and what can we do about it

Non-melanoma skin cancer (NMSC) comprised of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) are the most common cancers in humans in many countries. Sunlight plays a major part in the development of these tumours which appear predominantly on areas of the most frequently exposed skin. The site distribution for BCC and SCC is not the same, with SCC being most common on the sites of very heavy exposure and BCC becoming more common on areas of only moderate exposure, e.g. upper trunk in men and women and lower leg in women. Incidence rates of NMSC, where they are being recorded, show rises over time. Mortality rates, on the other hand, have been dropping most of this century until they have been levelling out recently. The case fatality rate due to SCC appears to be between 1-2%. The malignant transformation rate of actinic keratoses to SCC appears to be very low. Studies on similar populations at different latitudes allow estimates to be made of increases which might occur with increasing exposure to ultraviolet radiation (UVR) over a life time. These have been used to estimate the possible increases in NMSC due to stratospheric ozone depletion. Finally, recent studies on the reduction of existing actinic keratoses and prevention of new ones with regular use of sunscreen augurs well for prevention of NMSC in the future.

Effects of ultraviolet B irradiation on cutaneous leishmaniasis

Protection against many infectious diseases is mediated by cellular immunity in the competent host. Ultraviolet (UV) radiation, a component of sunlight, is a potent suppressor of cell-mediated immune responses. Suzanne Holmes Giannini discusses the possible relevance of ambient levels of UVB to pathogenesis and immunity in infectious diseases, with special reference to cutaneous leishmaniasis.