Abstract
To protect the health of sows and gilts, significant investments are directed toward the development of vaccines against infectious agents that impact reproduction. We developed an intrauterine vaccine that can be delivered with semen during artificial insemination to induce mucosal immunity in the reproductive tract. An in vitro culture of uterine epithelial cells was used to select an adjuvant combination capable of recruiting antigen-presenting cells into the uterus. Adjuvant polyinosinic:polycytidylic acid (poly I:C), alone or in combination, induced expression of interferon gamma, tumor necrosis factor alpha, and select chemokines. A combination adjuvant consisting of poly I:C, host defense peptide and polyphosphazene (Triple Adjuvant; TriAdj), which previously was shown to induce robust mucosal and systemic humoral immunity when administered to the uterus in rabbits, was combined with boar semen to evaluate changes in localized gene expression and cellular recruitment, in vivo. Sows bred with semen plus TriAdj had decreased γδ T cells and monocytes in blood, however, no corresponding increase in the number of monocytes and macrophages was detected in the endometrium. Compared to sows bred with semen alone, sows bred with semen plus TriAdj showed increased CCL2 gene expression in the epithelial layer. These data suggest that the adjuvants may further augment a local immune response and, therefore, may be suitable for use in an intrauterine vaccine. When inactivated porcine parvovirus (PPV) formulated with the TriAdj was administered to the pig uterus during estrus along with semen, we observed induction of PPV antibodies in serum but only when the pigs were already primed with parenteral PPV vaccines. Recombinant protein vaccines and inactivated PPV vaccines administered to the pig uterus during breeding as a primary vaccine alone failed to induce significant humoral immunity. More trials need to be performed to clarify whether repeated intrauterine vaccination can trigger strong humoral immunity or whether the primary vaccine needs to be administered via a systemic route to promote a mucosal and systemic immune response.
Highlights
MATERIALS AND METHODSMucosal vaccination of livestock has the potential for several benefits over classical parenteral vaccinations, including the initiation of a strong mucosal and systemic immune response [1, 2] while reducing the incidence of common needle-stick injuries by veterinarians [3]
transepithelial electrical resistance (TEER) values returned to initial levels by 24 h poststimulation (Supplementary Figure 4B) which suggest that these combinations of adjuvants may transiently impact tight-junction integrity
Immunostimulatory adjuvants frequently considered for use in mucosal vaccines are TLR agonists and other pattern recognition receptor ligands that act through the inflammasome
Summary
Mucosal vaccination of livestock has the potential for several benefits over classical parenteral vaccinations, including the initiation of a strong mucosal and systemic immune response [1, 2] while reducing the incidence of common needle-stick injuries by veterinarians [3]. The i.u. vaccine was comprised of 1 × 107 TCID50 BEI-inactivated PPV (NADL-7; American Type Culture Collection) along with 400 μg poly I:C, 800 μg HDP, and 400 μg PCEP adjuvants (TriAdj) in 1 ml total volume, which were administered to the semen bag immediately prior to breeding. The uterine horns were removed from the sows and flushed with 25 ml PBS + 1% BSA (Sigma-Aldrich) per horn to collect luminal cell populations, which were counted and stained for immunotyping by flow cytometry analysis and to quantify CCL2 (see below). Cells collected from uterine flush were washed 2x in PBS + 0.1% EDTA at 400 × g for 15 min and counted by a coulter counter (Beckman Coulter) Both PBMCs and cells flushed from the uterine tissues (from Trial 1) were stained for flow cytometry (FCM) analysis in 96 well plates with 1 × 106 cells/wells. Significant differences were reported by ∗p < 0.05, ∗∗P < 0.01, and ∗∗∗P < 0.001
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