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Induction of long-lasting protective immunity against Toxoplasma gondii in BALB/c mice by recombinant surface antigen 1 protein encapsulated in poly (lactide-co-glycolide) microparticles.

Chuang SC, Ko JC, Chen CP, Du JT, Yang CD - Parasit Vectors (2013)

Bottom Line: We examined the ability of PLG-rSAG1 microparticles to induce and prolong effective anti-Toxoplasma immune responses, in comparison with rSAG1 formulated with a Vet L-10 adjuvant (rSAG1 (Vet L-10)).PLG-rSAG1 microparticles can effectively induce not only significant long-lasting SAG1-specific humoral and cell-mediated immune responses but also high protection against T. gondii tachyzoite infection.Our study provides a valuable basis for developing long-lasting vaccines against T. gondii for future use in humans and animals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, College of Medicine, Kaohsiung Medical University, No 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan.

ABSTRACT

Background: Current development efforts of subunit vaccines against Toxoplasma gondii, the etiological agent of toxoplasmosis, have been focused mainly on tachyzoite surface antigen 1 (SAG1). Since microparticles made from poly (lactide-co-glycolide) (PLG) polymers have been developed as safe, potent adjuvants or delivery systems, we aimed to encapsulate recombinant SAG1 (rSAG1) with the PLG polymers to prepare PLG-encapsulated rSAG1 (PLG-rSAG1) microparticles that would sustain rSAG1 release and generate long-lasting protective immunity against T. gondii in BALB/c mice.

Methods: In the present study, rSAG1 was encapsulated into PLG microparticles by the double emulsion method. PLG-rSAG1 microparticles were then intraperitoneally injected twice at a 14-day interval into BALB/c mice. We examined the ability of PLG-rSAG1 microparticles to induce and prolong effective anti-Toxoplasma immune responses, in comparison with rSAG1 formulated with a Vet L-10 adjuvant (rSAG1 (Vet L-10)). Eight weeks after the last immunization, protective activities were also evaluated after a lethal subcutaneous challenge of 1 x 10(4) live T. gondii tachyzoites.

Results: PLG-rSAG1 microparticles, 4.25~6.58 micrometers in diameter, showed 69%~81% entrapment efficiency. The amount of released rSAG1 protein from microparticles increased gradually over a 35-day period and the protein still retained native SAG1 antigenicity. Intraperitoneal vaccination of mice with the microparticles resulted in enhanced SAG1-specific IgG titers as well as lymphocyte proliferation and, more importantly, these enhanced activities were maintained for 10 weeks. In addition, eight weeks after the last immunization, maximum production of gamma interferon was detected in mice immunized with PLG-rSAG1 microparticles. Furthermore, 80% (8/10) of mice immunized with PLG-rSAG1 microparticles survived at least 28 days after a lethal subcutaneous tachyzoite challenge.

Conclusions: Encapsulation of rSAG1 into PLG microparticles preserves the native SAG1 antigenicity and sustains the release of rSAG1 from microparticles. PLG-rSAG1 microparticles can effectively induce not only significant long-lasting SAG1-specific humoral and cell-mediated immune responses but also high protection against T. gondii tachyzoite infection. Our study provides a valuable basis for developing long-lasting vaccines against T. gondii for future use in humans and animals.

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Antigenic specificity of mouse sera. Two weeks after boosting, mouse sera were collected to analyze their antigenic specificity. TsoAg was probed with sera from mice immunized with PLG-rSAG1 microparticles (lane 1), rSAG1 (Vet L-10) (lane 2), soluble rSAG1 alone (lane 3), PLG (lane 4) or PBS (lane 5). The mouse mAb TG-1 (lane 6) was conducted as a positive control for the native SAG1 in TsoAg. Standard protein markers (lane M) are shown at the left.
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Figure 5: Antigenic specificity of mouse sera. Two weeks after boosting, mouse sera were collected to analyze their antigenic specificity. TsoAg was probed with sera from mice immunized with PLG-rSAG1 microparticles (lane 1), rSAG1 (Vet L-10) (lane 2), soluble rSAG1 alone (lane 3), PLG (lane 4) or PBS (lane 5). The mouse mAb TG-1 (lane 6) was conducted as a positive control for the native SAG1 in TsoAg. Standard protein markers (lane M) are shown at the left.

Mentions: The ability of PLG-rSAG1 microparticles to trigger humoral immunity against T. gondii in mice was subsequently evaluated. Western blot studies of sera obtained two weeks after boosting showed that both PLG-rSAG1 microparticles and oil formulation rSAG1 (Vet L-10) resulted in production of serum IgG antibodies against the native SAG1 protein in TsoAg (Figure5, lanes 1 and 2), which was also recognized by the TG-1 mAb (Figure5, lane 6). However, sera from mice immunized with soluble rSAG1 alone, PLG or PBS did not recognize anything in TsoAg (Figure5, lanes 3~5). Therefore, intraperitoneal immunization with rSAG1 could elicit a specific serum response to the native SAG1 protein in TsoAg only when rSAG1 initially formulated with adjuvants, but not in its soluble form. These results were also consistent with those from Figure4 and emphasized again that the released rSAG1 from PLG microparticles retained the native SAG1 antigenicity to induce anti-SAG1 immunity. In addition, the specific anti-Toxoplasma IgG titers of mouse sera, collected every two weeks, were determined by ELISA (Figure6). Four weeks after boosting (the 6th week), IgG titers induced by PLG-rSAG1 microparticles were significantly higher (P<0.05, nested design) than those induced by rSAG1 (Vet L-10) and, more importantly, the high titers were maintained till the 10th week (Figure6). Although high levels of antibodies were also induced by rSAG1 (Vet L-10) in the first six weeks, the levels gradually decreased starting from the 6th week to the 10th week (Figure6). However, mice immunized with soluble rSAG1 alone, PLG or PBS displayed little, if any, anti-Toxoplasma IgG titers (Figure6). Therefore, encapsulation of rSAG1 in PLG microparticles could elicit and prolong the high levels of anti-SAG1 antibodies, indicating the importance of use of the PLG adjuvant.


Induction of long-lasting protective immunity against Toxoplasma gondii in BALB/c mice by recombinant surface antigen 1 protein encapsulated in poly (lactide-co-glycolide) microparticles.

Chuang SC, Ko JC, Chen CP, Du JT, Yang CD - Parasit Vectors (2013)

Antigenic specificity of mouse sera. Two weeks after boosting, mouse sera were collected to analyze their antigenic specificity. TsoAg was probed with sera from mice immunized with PLG-rSAG1 microparticles (lane 1), rSAG1 (Vet L-10) (lane 2), soluble rSAG1 alone (lane 3), PLG (lane 4) or PBS (lane 5). The mouse mAb TG-1 (lane 6) was conducted as a positive control for the native SAG1 in TsoAg. Standard protein markers (lane M) are shown at the left.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3584932&req=5

Figure 5: Antigenic specificity of mouse sera. Two weeks after boosting, mouse sera were collected to analyze their antigenic specificity. TsoAg was probed with sera from mice immunized with PLG-rSAG1 microparticles (lane 1), rSAG1 (Vet L-10) (lane 2), soluble rSAG1 alone (lane 3), PLG (lane 4) or PBS (lane 5). The mouse mAb TG-1 (lane 6) was conducted as a positive control for the native SAG1 in TsoAg. Standard protein markers (lane M) are shown at the left.
Mentions: The ability of PLG-rSAG1 microparticles to trigger humoral immunity against T. gondii in mice was subsequently evaluated. Western blot studies of sera obtained two weeks after boosting showed that both PLG-rSAG1 microparticles and oil formulation rSAG1 (Vet L-10) resulted in production of serum IgG antibodies against the native SAG1 protein in TsoAg (Figure5, lanes 1 and 2), which was also recognized by the TG-1 mAb (Figure5, lane 6). However, sera from mice immunized with soluble rSAG1 alone, PLG or PBS did not recognize anything in TsoAg (Figure5, lanes 3~5). Therefore, intraperitoneal immunization with rSAG1 could elicit a specific serum response to the native SAG1 protein in TsoAg only when rSAG1 initially formulated with adjuvants, but not in its soluble form. These results were also consistent with those from Figure4 and emphasized again that the released rSAG1 from PLG microparticles retained the native SAG1 antigenicity to induce anti-SAG1 immunity. In addition, the specific anti-Toxoplasma IgG titers of mouse sera, collected every two weeks, were determined by ELISA (Figure6). Four weeks after boosting (the 6th week), IgG titers induced by PLG-rSAG1 microparticles were significantly higher (P<0.05, nested design) than those induced by rSAG1 (Vet L-10) and, more importantly, the high titers were maintained till the 10th week (Figure6). Although high levels of antibodies were also induced by rSAG1 (Vet L-10) in the first six weeks, the levels gradually decreased starting from the 6th week to the 10th week (Figure6). However, mice immunized with soluble rSAG1 alone, PLG or PBS displayed little, if any, anti-Toxoplasma IgG titers (Figure6). Therefore, encapsulation of rSAG1 in PLG microparticles could elicit and prolong the high levels of anti-SAG1 antibodies, indicating the importance of use of the PLG adjuvant.

Bottom Line: We examined the ability of PLG-rSAG1 microparticles to induce and prolong effective anti-Toxoplasma immune responses, in comparison with rSAG1 formulated with a Vet L-10 adjuvant (rSAG1 (Vet L-10)).PLG-rSAG1 microparticles can effectively induce not only significant long-lasting SAG1-specific humoral and cell-mediated immune responses but also high protection against T. gondii tachyzoite infection.Our study provides a valuable basis for developing long-lasting vaccines against T. gondii for future use in humans and animals.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, College of Medicine, Kaohsiung Medical University, No 100, Shih-Chuan 1st Road, Kaohsiung 807, Taiwan.

ABSTRACT

Background: Current development efforts of subunit vaccines against Toxoplasma gondii, the etiological agent of toxoplasmosis, have been focused mainly on tachyzoite surface antigen 1 (SAG1). Since microparticles made from poly (lactide-co-glycolide) (PLG) polymers have been developed as safe, potent adjuvants or delivery systems, we aimed to encapsulate recombinant SAG1 (rSAG1) with the PLG polymers to prepare PLG-encapsulated rSAG1 (PLG-rSAG1) microparticles that would sustain rSAG1 release and generate long-lasting protective immunity against T. gondii in BALB/c mice.

Methods: In the present study, rSAG1 was encapsulated into PLG microparticles by the double emulsion method. PLG-rSAG1 microparticles were then intraperitoneally injected twice at a 14-day interval into BALB/c mice. We examined the ability of PLG-rSAG1 microparticles to induce and prolong effective anti-Toxoplasma immune responses, in comparison with rSAG1 formulated with a Vet L-10 adjuvant (rSAG1 (Vet L-10)). Eight weeks after the last immunization, protective activities were also evaluated after a lethal subcutaneous challenge of 1 x 10(4) live T. gondii tachyzoites.

Results: PLG-rSAG1 microparticles, 4.25~6.58 micrometers in diameter, showed 69%~81% entrapment efficiency. The amount of released rSAG1 protein from microparticles increased gradually over a 35-day period and the protein still retained native SAG1 antigenicity. Intraperitoneal vaccination of mice with the microparticles resulted in enhanced SAG1-specific IgG titers as well as lymphocyte proliferation and, more importantly, these enhanced activities were maintained for 10 weeks. In addition, eight weeks after the last immunization, maximum production of gamma interferon was detected in mice immunized with PLG-rSAG1 microparticles. Furthermore, 80% (8/10) of mice immunized with PLG-rSAG1 microparticles survived at least 28 days after a lethal subcutaneous tachyzoite challenge.

Conclusions: Encapsulation of rSAG1 into PLG microparticles preserves the native SAG1 antigenicity and sustains the release of rSAG1 from microparticles. PLG-rSAG1 microparticles can effectively induce not only significant long-lasting SAG1-specific humoral and cell-mediated immune responses but also high protection against T. gondii tachyzoite infection. Our study provides a valuable basis for developing long-lasting vaccines against T. gondii for future use in humans and animals.

Show MeSH
Related in: MedlinePlus