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Increased susceptibility of mice to malarial infection following UV-B irradiation
1Department of Virology I, National Institute of Infectious Diseases, Tokyo, Japan.
Abstract:
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.
Insights
UV-B irradiation worsens malaria infection, increasing mortality in resistant mice by impairing immune responses. Interferon-gamma (IFN-γ) administration partially protected mice, highlighting UV-B as a significant risk factor for malaria.
Area of Science:
- Immunology
- Infectious Diseases
- Photobiology
Background:
- Malaria remains a global health challenge, particularly in regions with high sun exposure.
- The impact of ultraviolet B (UV-B) radiation on malaria susceptibility is not well understood.
Purpose of the Study:
- To investigate whether UV-B radiation acts as a risk factor for malaria infection in a mouse model.
- To elucidate the immunological mechanisms underlying UV-B's effect on malaria.
Main Methods:
- Two mouse strains (susceptible BALB/c, resistant C57BL/10) were pre-irradiated with UV-B and infected with Plasmodium chabaudi.
- Parasitemia was quantified using blood smears; plasma cytokines (IFN-γ) and macrophage activation were assessed.
- Interferon-gamma (IFN-γ) was administered to UV-B irradiated, infected mice.
Main Results:
- UV-B irradiation significantly worsened malaria infection in both mouse strains.
- All UV-B irradiated, malaria-resistant mice died from a normally sub-lethal infection.
- UV-B inhibited plasma IFN-γ production and decreased macrophage activation in resistant mice.
- IFN-γ administration achieved a 60% cure rate in UV-B irradiated, resistant mice.
Conclusions:
- UV-B radiation increases susceptibility to malaria.
- UV-B impairs crucial immune responses, specifically IFN-γ production, in malaria-resistant mice.
- Targeting IFN-γ may offer a therapeutic strategy against UV-B exacerbated malaria.