Coadministration of plasmid GM-CSF enhances the DNA vaccine-elicited humoral and cellular immune responses, as well as protection, in several models (26, 40, 41)

Coadministration of plasmid GM-CSF enhances the DNA vaccine-elicited humoral and cellular immune responses, as well as protection, in several models (26, 40, 41). parasite that infects all warm-blooded animals, including humans, and causes toxoplasmosis. This broad host range makes it one of the most successful protozoan c-Fms-IN-8 parasites. In primary human infections, various mild symptoms may be observed, such as lymphadenopathy, low-grade c-Fms-IN-8 fever, mild malaise, sore throat, and lethargy. Immunosuppressed patients may exhibit severe symptoms, including encephalitis, myocarditis, pneumonitis, hepatitis, splenomegaly, polymyositis, dermatomyositis, chorioretinitis, and multisystem organ failure. In pregnant women, congenital infection can lead to miscarriage, neonatal malformations, or other defects occurring during the development of the fetus, such as blindness or severe cognitive impairment (22, 37). In animals, toxoplasmosis is of great economic importance worldwide because it causes abortions, stillbirth, and neonatal loss in all types of livestock, especially in sheep and goats (10). In addition, the tissue cysts of in meat of infected livestock are an important source of infection for humans (21). This great worldwide importance for public health and economics of infection makes the development of an effective vaccine for controlling this infection an important goal. So far, the only developed vaccine is the live, attenuated tachyzoite S48 (11). However, this vaccine is not widely accepted because of its side effects, short shelf life, and high cost. Live vaccines also carry a risk of accidental infection of humans and unexpected harmful reverse mutations. In an attempt to overcome these problems, current research is investigating subunit, recombinant and DNA vaccines, but they do not provide complete protection against infection (7). We have focused on the development of a DNA-based vaccine because such vaccines have been shown to elicit potent, long-lasting humoral and cell-mediated immunity, as well as providing protection against viral, bacterial, and parasitic infections (4). The most common method used to deliver DNA vaccines is the intramuscular injection, which is known to induce a Th1-type response (31), which is generally thought to protect the host c-Fms-IN-8 against infection (32). Several trials of DNA-based vaccines against toxoplasmosis have been conducted, mainly with mice and various antigens, such as membrane-associated surface antigen SAG1 (5, 32), excreted-secreted dense-granule proteins GRA1 (33, 38), GRA7 (38), and GRA4 (18), and rhoptry proteins ROP2 (29, 38) c-Fms-IN-8 and ROP1 (14). These trials have been encouraging, in that they have demonstrated the development of different levels of protection in mice. Among the putative vaccine candidates, the micronemal protein MIC3 (90 kDa) looks particularly promising because it is a potent adhesin of (12, 23), that is expressed in all three infectious stages of (tachyzoites, bradyzoites, and sporozoites) and that elicits early and powerful immune responses c-Fms-IN-8 WNT3 in mice and humans (M. Lebrun, personal communication). A number of approaches are being explored that could enhance the efficacy of DNA vaccines, such as the coadministration of cytokine-encoding plasmids (28). Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent cytokine, and its role as potential vaccine adjuvant has already been investigated (25, 39). Coadministration of plasmid GM-CSF enhances the DNA vaccine-elicited humoral and cellular immune responses, as well as protection, in several models (26, 40, 41). All these properties support the use of plasmid encoding GM-CSF as an adjuvant vaccine in this study. The mechanism underlying the adjuvant properties of plasmid encoding GM-CSF may involve increased recruitment of macrophages and dendritic cells at the site of injection (8, 24, 27). We describe here the development and evaluation of a DNA vaccine based on a plasmid encoding the immature form of the MIC3 protein, either alone or combined with another plasmid encoding GM-CSF. In this study, the 76K strain has been used for challenge infection. This strain is a type II isolate, and type II isolates are the predominant isolates in human congenital toxoplasmosis (2, 3). Protection was evaluated in CBA/J mice, which are markedly resistant to acute toxoplasmosis infection but susceptible to cyst formation and development of toxoplasmosis encephalitis in chronic infection. As a protective criterion, we chose to evaluate the decrease in brain cyst load, since the number of brain cysts is one of the most important factors that determine the development of.