Increased susceptibility of mice to malarial infection following UV-B irradiation.
Using a mouse model, we examined whether UV-B was a risk factor for malarial infection. Two mouse strains, susceptible (BALB/c) and resistant (C57BL/10) to murine malaria (Plasmodium chabaudi), were UV-preirradiated and infected with a sub-lethal dose of malaria parasite (104 and 105, respectively). Parasite growth was assayed with tail-blood smears counting parasitized red blood cells. Mice resistant to malaria were bled by heart puncture and the plasma cytokines were determined. Our results showed that UV-B irradiation worsened the malarial infection and 100% of the malaria-resistant mice strains died due to a usual infection at sub-lethal dose following UV-B irradiation. In the resistant mice strain infected with the parasite, the plasma IFN-gamma production was inhibited by UV-B irradiation and the maximum titer was about one-fifth of the non-irradiated mice. Furthermore, activation of macrophages from UV-irradiated mice also decreased compared with that of non-irradiated mice. IFN-gamma administration prevented the death of UV-B irradiated resistant mice and the cure ratio was 60%. In conclusion, UV-B increased the susceptibility of both strains of mice and impaired IFN-gamma production in the malaria-resistant mice strain.
Yamamoto
K
K
Department of Virology I, National Institute of Infectious Diseases, Tokyo, Japan.
Ito
R
R
Koura
M
M
Kamiyama
T
T
D000818:Animals; D004195:Disease Models, Animal; D004198:Disease Susceptibility / Q000276:immunology; D004912:Erythrocytes / Q000469:parasitology; D005260:Female; D015994:Incidence; D007371:Interferon-gamma / Q000008:administration & dosage / Q000096:biosynthesis; D016753:Interleukin-10 / Q000096:biosynthesis; D008288:Malaria / Q000276:immunology* / Q000517:prevention & control; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D016788:Plasmodium chabaudi; D011829:Radiation Dosage; D018570:Risk Assessment; D014466:Ultraviolet Rays / Q000009:adverse effects*
D016753:Interleukin-10; D007371:Interferon-gamma