Mucosal and systemic adjuvant activity of alphavirus replicon particles - PubMed (original) (raw)

Mucosal and systemic adjuvant activity of alphavirus replicon particles

Joseph M Thompson et al. Proc Natl Acad Sci U S A. 2006.

Abstract

Vaccination represents the most effective control measure in the fight against infectious diseases. Local mucosal immune responses are critical for protection from, and resolution of, infection by numerous mucosal pathogens. Antigen processing across mucosal surfaces is the natural route by which mucosal immunity is generated, as peripheral antigen delivery typically fails to induce mucosal immune responses. However, we demonstrate in this article that mucosal immune responses are evident at multiple mucosal surfaces after parenteral delivery of Venezuelan equine encephalitis virus replicon particles (VRP). Moreover, coinoculation of null VRP (not expressing any transgene) with inactivated influenza virions, or ovalbumin, resulted in a significant increase in antigen-specific systemic IgG and fecal IgA antibodies, compared with antigen alone. Pretreatment of VRP with UV light largely abrogated this adjuvant effect. These results demonstrate that alphavirus replicon particles possess intrinsic systemic and mucosal adjuvant activity and suggest that VRP RNA replication is the trigger for this activity. We feel that these observations and the continued experimentation they stimulate will ultimately define the specific components of an alternative pathway for the induction of mucosal immunity, and if the activity is evident in humans, will enable new possibilities for safe and inexpensive subunit and inactivated vaccines.

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Conflict of interest statement

Conflict of interest statement: J.M.T. and R.E.J. are listed inventors on a patent application related to the subject matter of this article. R.E.J. is the unpaid Executive Director of Global Vaccines, Inc., a not-for-profit company that holds a license to the technology described in the article.

Figures

Fig. 1.

Fig. 1.

VRP induce mucosal immune responses. Groups of animals were immunized in the rear footpad with diluent, 10 μg of I-Flu (solid bars), 105 IU of HA-VRP (open bars), or 10 μg of I-Flu plus 105 IU of GFP-VRP (hatched bars) at weeks 0 and 4. Three weeks after the second inoculation, lymphoid organ cultures were established from the nasal epithelium (A and B) and spleen (C and D). Culture supernatants were evaluated for flu-specific IgG (A and C) and IgA antibodies (B and D) by ELISA. Data are presented as the geometric mean ± SEM. ∗, P < 0.05; ∗∗, P < 0.01; ∗∗∗, P < 0.001 compared with I-Flu alone, as determined by ANOVA.

Fig. 2.

Fig. 2.

VRP adjuvant activity for particulate antigens. Groups of eight animals were immunized in the rear footpad with 0.1 or 1.0 μg of I-Flu in the presence (hatched bars) or absence (solid bars) of 106 IU of null VRP at weeks 0 and 4. Two weeks after the second inoculation, flu-specific IgG antibodies were measured in sera (A) and fecal extracts (B), and flu-specific IgA antibodies were measured in fecal extracts (C) by ELISA. Data are presented as the geometric mean ± SEM. ∗, P < 0.02; ∗∗, P < 0.005; ∗∗∗, P < 0.0003 compared with I-Flu alone, as determined by Mann–Whitney.

Fig. 3.

Fig. 3.

Systemic and mucosal adjuvant activity of UV-treated VRP. Groups of six animals were immunized in the rear footpad with 10 μg of OVA alone or coinoculated with 1.0 μg of CT, 104 IU of null VRP, 104 IU of UV-VRP, or 106 IU of null VRP at weeks 0 and 4. One week after the second inoculation, splenocytes (open bars) and nasal lymphocytes (solid bars) were isolated from immunized animals and analyzed for the presence of OVA-specific IgG-secreting cells (A) and IgA-secreting cells (B) by ELISPOT. Data are presented as the geometric mean ± SEM. ∗, P < 0.05; ∗∗, P < 0.01; ∗∗∗, P < 0.001 compared with OVA alone, as determined by ANOVA.

Fig. 4.

Fig. 4.

Systemic and mucosal adjuvant activity of VRP compared with CpG DNA. Groups of eight animals were immunized in the rear footpad with 10 μg of OVA alone (solid bars) or coinoculated with 105 IU of null VRP (hatched bars) or 1.0 μg of CpG DNA (open bars) at weeks 0 and 4. Two weeks after the second inoculation, splenocytes were isolated and analyzed for the presence of OVA-specific IgG ASCs, and nasal lymphocytes were isolated and analyzed for the presence of OVA-specific IgA ASCs by ELISPOT. Data are presented as the geometric mean ± SEM. ∗, P < 0.001 compared with OVA alone; †, P < 0.01 compared with CpG; ‡, P < 0.05 compared with CpG.

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