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Active immunization with human interleukin-15 induces neutralizing antibodies in non-human primates

View Article: PubMed Central - PubMed

ABSTRACT

Background: Interleukin-15 is an immunostimulatory cytokine overexpressed in several autoimmune and inflammatory diseases such as Rheumatoid Arthritis, psoriasis and ulcerative colitis; thus, inhibition of IL-15-induced signaling could be clinically beneficial in these disorders. Our approach to neutralize IL-15 consisted in active immunization with structurally modified human IL-15 (mhIL-15) with the aim to induce neutralizing antibodies against native IL-15. In the present study, we characterized the antibody response in Macaca fascicularis, non-human primates that were immunized with a vaccine candidate containing mhIL-15 in Aluminum hydroxide (Alum), Montanide and Incomplete Freund’s Adjuvant.

Results: Immunization with mhIL-15 elicited a specific antibodies response that neutralized native IL-15-dependent biologic activity in a CTLL-2 cell proliferation assay. The highest neutralizing response was obtained in macaques immunized with mhIL-15 adjuvanted in Alum. This response, which was shown to be transient, also inhibited the activity of simian IL-15 and did not affect the human IL-2-induced proliferation of CTLL-2 cells. Also, in a pool of synovial fluid cells from two Rheumatoid Arthritis patients, the immune sera slightly inhibited TNF-α secretion. Finally, it was observed that this vaccine candidate neither affect animal behavior, clinical status, blood biochemistry nor the percentage of IL-15-dependent cell populations, specifically CD56+ NK and CD8+ T cells.

Conclusion: Our results indicate that vaccination with mhIL-15 induced neutralizing antibodies to native IL-15 in non-human primates. Based on this fact, we propose that this vaccine candidate could be potentially beneficial for treatment of diseases where IL-15 overexpression is associated with their pathogenesis.

No MeSH data available.


Related in: MedlinePlus

Abs response in macaques from the Alum group throughout the immunization scheme. a Titers of anti-IL-15 Abs detected by ELISA in macaques immunized with mhIL-15 adjuvanted in Alum. The plate was coated with 1 μg/ml mhIL-15 and serum was evaluated in twofold serial dilutions (starting dilution 1:1000). The Abs titers of pre-immune animals, placebo group and the monkeys immunized with mhIL-15 in Alum after the second, third, fourth and fifth immunization are shown. The line represents the mean values of Abs titers calculated from duplicate samples of individual animals (n = 3) during the scheme. b Proliferation assay in CTLL-2 cells with the serum of one animal from the Alum group. Cells were cultured in the presence of native IL-15, IL-15 plus dilutions of the pre-immune serum, or serum from each immunization (starting dilution 1:100), IL-15 plus serial dilutions of an anti-human IL-15 Ab and cells culture in medium without cytokine. Cell proliferation was evaluated by MTT staining. Similar results were obtained when the sera of other animals from the same group were assessed. d: days after immunization; m: months after immunization
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Fig4: Abs response in macaques from the Alum group throughout the immunization scheme. a Titers of anti-IL-15 Abs detected by ELISA in macaques immunized with mhIL-15 adjuvanted in Alum. The plate was coated with 1 μg/ml mhIL-15 and serum was evaluated in twofold serial dilutions (starting dilution 1:1000). The Abs titers of pre-immune animals, placebo group and the monkeys immunized with mhIL-15 in Alum after the second, third, fourth and fifth immunization are shown. The line represents the mean values of Abs titers calculated from duplicate samples of individual animals (n = 3) during the scheme. b Proliferation assay in CTLL-2 cells with the serum of one animal from the Alum group. Cells were cultured in the presence of native IL-15, IL-15 plus dilutions of the pre-immune serum, or serum from each immunization (starting dilution 1:100), IL-15 plus serial dilutions of an anti-human IL-15 Ab and cells culture in medium without cytokine. Cell proliferation was evaluated by MTT staining. Similar results were obtained when the sera of other animals from the same group were assessed. d: days after immunization; m: months after immunization

Mentions: Spaced immunizations were performed using Alum as adjuvant to address the duration of the Abs response. Figure 4a summarizes the course of the Abs response to the mhIL-15/Alum group throughout the scheme. Three months after the third immunization, the anti-human IL-15 Abs titers declined in more than 50 % with an average titer of 1:9475 while after the six months the average titer was 1:3930. In order to assess if we could reach levels of Abs titers similar to those obtained previously through re-immunization, we performed two additional immunizations. As shown in the graph, the Abs titers after the fourth immunization were very similar to those achieved after the third inoculation. Decreases in specific Abs titers were detected in the samples taken 300 days after the fourth dose (average titer 1:1333). However, in response to the fifth immunization we observed a full recovery of the Abs response, to levels similar to those obtained in previous immunizations (Fig. 4a).Fig. 4


Active immunization with human interleukin-15 induces neutralizing antibodies in non-human primates
Abs response in macaques from the Alum group throughout the immunization scheme. a Titers of anti-IL-15 Abs detected by ELISA in macaques immunized with mhIL-15 adjuvanted in Alum. The plate was coated with 1 μg/ml mhIL-15 and serum was evaluated in twofold serial dilutions (starting dilution 1:1000). The Abs titers of pre-immune animals, placebo group and the monkeys immunized with mhIL-15 in Alum after the second, third, fourth and fifth immunization are shown. The line represents the mean values of Abs titers calculated from duplicate samples of individual animals (n = 3) during the scheme. b Proliferation assay in CTLL-2 cells with the serum of one animal from the Alum group. Cells were cultured in the presence of native IL-15, IL-15 plus dilutions of the pre-immune serum, or serum from each immunization (starting dilution 1:100), IL-15 plus serial dilutions of an anti-human IL-15 Ab and cells culture in medium without cytokine. Cell proliferation was evaluated by MTT staining. Similar results were obtained when the sera of other animals from the same group were assessed. d: days after immunization; m: months after immunization
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Related In: Results  -  Collection

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Fig4: Abs response in macaques from the Alum group throughout the immunization scheme. a Titers of anti-IL-15 Abs detected by ELISA in macaques immunized with mhIL-15 adjuvanted in Alum. The plate was coated with 1 μg/ml mhIL-15 and serum was evaluated in twofold serial dilutions (starting dilution 1:1000). The Abs titers of pre-immune animals, placebo group and the monkeys immunized with mhIL-15 in Alum after the second, third, fourth and fifth immunization are shown. The line represents the mean values of Abs titers calculated from duplicate samples of individual animals (n = 3) during the scheme. b Proliferation assay in CTLL-2 cells with the serum of one animal from the Alum group. Cells were cultured in the presence of native IL-15, IL-15 plus dilutions of the pre-immune serum, or serum from each immunization (starting dilution 1:100), IL-15 plus serial dilutions of an anti-human IL-15 Ab and cells culture in medium without cytokine. Cell proliferation was evaluated by MTT staining. Similar results were obtained when the sera of other animals from the same group were assessed. d: days after immunization; m: months after immunization
Mentions: Spaced immunizations were performed using Alum as adjuvant to address the duration of the Abs response. Figure 4a summarizes the course of the Abs response to the mhIL-15/Alum group throughout the scheme. Three months after the third immunization, the anti-human IL-15 Abs titers declined in more than 50 % with an average titer of 1:9475 while after the six months the average titer was 1:3930. In order to assess if we could reach levels of Abs titers similar to those obtained previously through re-immunization, we performed two additional immunizations. As shown in the graph, the Abs titers after the fourth immunization were very similar to those achieved after the third inoculation. Decreases in specific Abs titers were detected in the samples taken 300 days after the fourth dose (average titer 1:1333). However, in response to the fifth immunization we observed a full recovery of the Abs response, to levels similar to those obtained in previous immunizations (Fig. 4a).Fig. 4

View Article: PubMed Central - PubMed

ABSTRACT

Background: Interleukin-15 is an immunostimulatory cytokine overexpressed in several autoimmune and inflammatory diseases such as Rheumatoid Arthritis, psoriasis and ulcerative colitis; thus, inhibition of IL-15-induced signaling could be clinically beneficial in these disorders. Our approach to neutralize IL-15 consisted in active immunization with structurally modified human IL-15 (mhIL-15) with the aim to induce neutralizing antibodies against native IL-15. In the present study, we characterized the antibody response in Macaca fascicularis, non-human primates that were immunized with a vaccine candidate containing mhIL-15 in Aluminum hydroxide (Alum), Montanide and Incomplete Freund’s Adjuvant.

Results: Immunization with mhIL-15 elicited a specific antibodies response that neutralized native IL-15-dependent biologic activity in a CTLL-2 cell proliferation assay. The highest neutralizing response was obtained in macaques immunized with mhIL-15 adjuvanted in Alum. This response, which was shown to be transient, also inhibited the activity of simian IL-15 and did not affect the human IL-2-induced proliferation of CTLL-2 cells. Also, in a pool of synovial fluid cells from two Rheumatoid Arthritis patients, the immune sera slightly inhibited TNF-α secretion. Finally, it was observed that this vaccine candidate neither affect animal behavior, clinical status, blood biochemistry nor the percentage of IL-15-dependent cell populations, specifically CD56+ NK and CD8+ T cells.

Conclusion: Our results indicate that vaccination with mhIL-15 induced neutralizing antibodies to native IL-15 in non-human primates. Based on this fact, we propose that this vaccine candidate could be potentially beneficial for treatment of diseases where IL-15 overexpression is associated with their pathogenesis.

No MeSH data available.


Related in: MedlinePlus