Role of Heat Shock Protein against Protozoan Infection

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Exposing cells to a variety of stressful conditions such us elevated temperature, chemical intoxication or infection leads to the transcription of a set of genes and subsequently, to the synthesis of a family of polypeptides called heat shock proteins (HSPs). These proteins have retained highly conserved amino acid sequences throughout evolution from prokaryotes to eukaryotes. Since HSPs are proposed as common immunogens involved in infections with unmerous microorganisms, these proteins are being studied in detail. However, it is difficult to define the role of HSPs in infection and immunity, since these are HSPs in the both hosts and microorganisms in infection states, and since they are highly homologous. For intracellular parasites, HSPs may be essential for the adaptation of those organisms to the strict environment of hosts, and for transformation of organisms to infectious form. HSPs of parasites also function as immunodominant peptides that can be recognized by host humoral and … More cellulaar immune systems. On the other hand, HSPs synthesized as they respond to stress during certain infection may actually play a role in host defense. Thus, HSPs expressed either the hosts or parasites may have a potential to modulate the host-parasite relationship.We investigated the involvement of the 65 kDa heat shock protein (HSP65) in infection with an obligate intracellular protozoan Toxoplasma gondii (T.gondii). In humans, this ubiquitous parasite rarely causes diseases in individuals of normal immunocompetence, but it produces severe symptoms as an opportunistic infection in immunocompromized hosts, for example patient with AIDS.Considering the increasing number of hosts with AIDS throughout the world, it is important to understand the life cycle of this protozoan and how the protective immunity achieves towards this and other parasites.We present here that HSP65 expression on/in host macrophages is induced by gammadelta T cells and that it plays an important role in resistance against infection with T.gondii. Further , we found that HSP65 can be effective in protecting infected macrophages from apoptotic cell death. Analysis of these relationships should contribute to host-parasite interactions with T.gondii and should guide speculation on role playd by HSPs in infection with numerous intracellular pathogens other than T.gondii such as Leishmania major, Trypanosoma cruzi and malaria protozoa. Less