A comprehensive analysis of direct and photosensitized attenuation of Toxoplasma gondii tachyzoites

In the present work, we have evaluated the effect of three different types of radiation: UVC (254±5nm), UVA (365±20nm) and visible (420±20nm) on different morphological and biological functions of Toxoplasma gondii tachyzoites. Briefly, UVC and UVA showed an inhibitory effect on parasite invasion in a dose-dependent manner. UVC showed the strongest effect inducing both structural damage (antigens) and functional inhibition (i.e., invasion and replication). On its own, visible light induces a quite distinctive and selective pattern of parasite-attenuation. This type of incident radiation inhibits the replication of the parasite affecting neither the capability of invasion/attachment nor the native structure of proteins (antigens) on parasites. Such effects are a consequence of photosensitized processes where phenol red might act as the active photosensitizer. The potential uses of the methodologies investigated herein are discussed. In the presence of phenol red, visible light might represent a good candidate as irradiation source for the development of live attenuated vaccines against intracellular parasites and also to study the role of immune activation following T. gondii infections. [Display omitted] •We analyze the effect of UVC, UVA and visible radiation on Toxoplasma gondii (T. gondii) tachyzoites.•UVC inhibits both invasion and replication processes.•UVA inhibits only parasite's invasion via photosensitized processes where endogenous photosensitizers might play a key role.•Visible light, in combination with phenol red (PR), inhibits only T. gondii replication capability.•In the absence of light, PR slightly reduces T. gondii replication rate.