The ability of intracellular pathogens to cause infection is related to their capacity to survive and grow inside macrophages or in other cell types. Candida albicans latent virulence is likely to be related to a similar mechanism of avoiding killing by specialized cells and to the resulting ability to grow in such hostile environments. Using a differential display reverse transcription polymerase chain reaction technique, we have identified seven genes induced in C. albicans during macrophage phagocytosis. Sequence analyses and database searches revealed that these cDNAs coded for proteins homologous to yeast metabolic proteins. Interestingly, four of them are putative peroxisomal proteins, and two are involved in environmental signal sensing and transduction. Among the seven genes induced by C. albicans, six represent new information that were not described in other infection models.

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Microsporidia are unicellular and obligate intracellular spore-forming parasites. The spore inoculates the host cell with its non-motile infectious content, the sporoplasm, by way of the polar tube--the typical invasive apparatus of the microsporidian spore. Molecules involved in host cell invasion were investigated in Encephalitozoon intestinalis. Mouse polyclonal and monoclonal antibodies were raised against spore proteins and their reactivity was tested by Western-blotting and immunolocalization techniques, including electron and confocal microscopy. The antibodies thus generated could be divided into two major groups. One group reacted to the surface of the parasite at different developmental stages, mostly presporous stages and mature spores, whereas the other group recognized the polar tube. Of the antibodies reacting to the spore wall, one identified an exospore protein at 125 kDa while all others recognized a major doublet at 55-60 kDa, and minor proteins present at the surface of sporogonic stages and in the endospore. All antibodies recognizing spore wall proteins reacted also to the material forming septa in the parasitophorous vacuole. A major polar tube protein at 60 kDa was identified by another group of antibodies.