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Title: Toxoplasma gondii: humoral and cellular immune response of BALB/c mice immunized via intranasal route with rTgROP2

item Igarashi, Michelle
item Zulpo, Dauton
item De Cunha, Ivo
item Barros, Luiz
item Pereira, Vanessa
item Taroda, Alessandra
item Navarro, Italmar
item Vidotto, Odilon
item Vidotto, Marilda
item Jenkins, Mark
item Garcia, Joao

Submitted to: Brazilian Journal of Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/15/2010
Publication Date: 12/17/2010
Citation: Igarashi, M., Zulpo, D.L., De Cunha, I.A., Barros, L., Pereira, V., Taroda, A., Navarro, I.T., Vidotto, O., Vidotto, M.C., Jenkins, M.C., Garcia, J.L. 2010. Toxoplasma gondii: humoral and cellular immune response of BALB/c mice immunized via intranasal route with rTgROP2. Brazilian Journal of Veterinary Parasitology. 19:210-216.

Interpretive Summary: Toxoplasma gondii is a parasite that is a leading cause of birth defects in humans caused by an infectious agent. The parasite is transmitted after humans (and other warm-blooded animals) ingest either the oocyst stage (contaminating cat litter) or meat containing T. gondii cysts. A vaccine to prevent toxoplasmosis is desired as a way to prevent infection in humans and animals. A candidate vaccine comprised of an immunogenic T. gondii protein, namely TgROP2, was evaluated in the present study. Mice were vaccinated by nasal immunization with a recombinant TgROP2 protein that was produced in Escherichia coli using DNA cloning technology. Vaccinated mice produced antibodies specific for TgROP2. In addition, a cellular immune response to TgROP2 was observed in vaccinated mice. These data indicate that immunizing animals (and possibly humans) with recombinant TgROP2 protein via nasal route of administration may be a viable way to elicit protective immunity against toxoplasmosis. This information will be of interest to vaccine producers and health care workers in developing immunization strategies against Toxoplasmosis.

Technical Abstract: TgROP2 is an intracellular protein associated with rhoptries of Toxoplama gondii and an antigen component of a candidate vaccine for toxoplasmosis. The purpose of the present study was to evaluate the efficacy of rTgROP2 to stimulate humoral and cellular immune responses in BALB/c mice via intranasal injection. TgROP2 partial coding sequence was (196-561) amplified by PCR from genomic T. gondii RH strain DNA and cloned into the pTrcHis expression vector. Escherichia coli Rosetta 2 cells transformed with pTrcHis-TgROP2 showed high levels (1 mg/mL) of recombinant protein after 4 hours of IPTG induction. Recombinant TgROP2 exhibited an apparent Mr equal to 54 kDa. In order to test immunogenicity of the recombinant protein, 10 BALB/c mice received 10 ìg of rROP2 protein + 10 ìg of Quil-A via intranasal injection. Doses were administered at days 0, 21, and 42. Three animals were euthanized and used to evaluate cellular immune response on day 62. Five (50%) and two (20%) out of ten animals produced IgG (DO mean = 0.307; cut-off = 0.240) and IgA (DO mean = 0.133, cut-off = 0.101), respectively, by ELISA on day 62. The proliferation of splenocytes revealed high stimulation index (SI) when co-cultured with 5, 10 and 15 ug/mL of rTgROP2. These results indicate that intranasal immunization with recombinant protein ROP2 plus Quil-A can elicit both cellular and humoral immune responses in BALB/c mice.