Immune response after adjuvant mucosal immunization of mice with inactivated influenza virus

CpG DNA facilitate the inactivated transmissible gastroenteritis virus in enhancing the local and systemic immune response of pigs via oral administration

Transmissible gastroenteritis virus (TGEV) replicates in the small intestine and induces enteritis and watery diarrhea. Establishment of local immunity in the intestine would thus prevent TGEV transmission. CpG DNA has been reported as a promising mucosal adjuvant in some animals. The effects of oral immunization of CpG DNA together with inactivated TGEV (ITGEV) were investigated in this study. Pigs (6 weeks old) were orally immunized with ITGEV plus CpG DNA. The TGEV-specific IgA level in the intestinal tract and the TGEV-specific IgG level in serum significantly increased following immunization with ITGEV plus CpG DNA (P ≤ 0.05). Moreover, populations of IgA-secreting cells, CD3+ T lymphocytes and intraepithelial lymphocytes (IELs), in the intestine increased significantly after immunization with ITGEV plus CpG DNA (P ≤ 0.05). Furthermore, the expression of IL-6, IL-12 and interferon-γ (IFN-γ) in ligated intestine segments increased significantly after injection with ITGEV plus CpG DNA (P ≤ 0.05). Taken together, these data suggest that oral immunization of ITGEV plus CpG DNA elicits a local immune response. Further studies are required to determine whether this immunity provides protection against TGEV in pigs.

A novel combined adjuvant strongly enhances mucosal and systemic immunity to low pathogenic avian influenza after oral immunization in ducks

As natural reservoirs of avian influenza viruses, waterfowl play an important role in the generation, spread, and enzootic transmission of avian influenza. To prevent avian influenza in waterfowl through a simple, noninvasive, and needle-free route, ducks were immunized orally with an inactivated avian influenza virus (H9N2, IAIV) combined with CpG DNA and high-dose glucose, and then the local and systemic immune responses of these ducks were investigated. In addition, the immune protection was assayed after viral challenge. After the oral administration of IAIV combined with CpG DNA and glucose, the expression levels of interleukin-2 and interleukin-6 in the small intestine tissues increased significantly in the early period after booster immunization relative to the levels after immunization with IAIV and a single adjuvant. Significant increases were also observed in the IgA and IgG antibody levels in the local intestinal tract tissues and serum at wk 3, 5, and 7 after the first immunization. Furthermore, enhanced hemagglutination inhibition titers were also detected in serum samples taken between the third and seventh weeks after immunization with IAIV and both adjuvants. In the viral challenge and transmission study, the prior administration of IAIV combined with both CpG DNA and glucose reduced the viral titers observed for the cloaca swabs and colon tissues of challenged ducks and prevented virus transmission between ducks. Our study suggests that the combination of CpG DNA and high-dose glucose can improve immunization with inactivated H9N2 virus by enhancing the local and systemic immune responses and reducing viral shedding.

Protection against avian metapneumovirus subtype C in turkeys immunized via the respiratory tract with inactivated virus

Avian metapneumovirus subtype C (aMPV/C) causes a severe upper respiratory tract (URT) infection in turkeys. Turkeys were inoculated oculonasally with inactivated aMPV/C adjuvanted with synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid (Poly IC). Immunized turkeys had elevated numbers of mucosal IgA+ cells in the URT and increased levels of virus-specific IgG and IgA in the lachrymal fluid and IgG in the serum. After 7 or 21 days post immunization, turkeys were challenged oculonasally with pathogenic aMPV/C. Immunized groups were protected against respiratory lesions induced by the challenge virus. Further, the viral copy number of the challenge virus in the URT were significantly lower in the immunized turkeys than in the unimmunized turkeys (P<0.05). These results showed that inactivated aMPV/C administered by the respiratory route induced protective immunity against pathogenic virus challenge.

Adjuvant effect of Bacillus firmus on the expression of cytokines and toll-like receptors in mouse nasopharynx-associated lymphoid tissue (NALT) after intranasal immunization with inactivated influenza virus type A

Due to the persisting threat of development of new highly pathogenic influenza A subtypes, a mucosal vaccination which would induce a potent and cross-protective reaction is desirable. We succeeded in mucosal immunization of mice with an inactivated influenza A virus by using delipidated Bacillus firmus (DBF) as adjuvant. The mechanism of adjuvant effect was followed in NALT by comparing the response after intranasal immunization by inactivated influenza virus type A (H1N1) alone, adjuvant alone (DBF), or by a mixture of virus+DBF. Expression of selected gene groups was tested via qPCR at 7 different time-points: cytokines (IL-2, IFN-γ, IL-4, IL-6, and IL-10), type I interferons (IFN-α4, IFN-α11, IFN-α12, and IFN-β), toll-like receptors (TLR2, TLR3, TLR7, and TLR9), iNOS and CCR7. Intranasally administered DBF and the mixture of virus+DBF induced an elevated expression of IFN-γ, IL-6 and IL-10 cytokines, type I interferons, iNOS, and pDC markers in NALT. Multimarker qPCR data was analyzed by relative quantification and by principal component analysis. DBF has been shown to be a very efficient adjuvant for the stimulation of innate immunity after IN immunization. DBF accelerated, increased, and prolonged the antiviral response.

Co-administration of inactivated avian influenza virus with CpG or rIL-2 strongly enhances the local immune response after intranasal immunization in chicken

Intranasal delivery of vaccines is the most effective means of inducing effective immunity in the upper respiratory tract as well as other mucosal lymphoid tissues. To evaluate the effects of the H5N2 inactivated virus with adjuvant, 120 one-day-old chicks were intranasal immunized with the H5N2 inactivated virus respectively mixed with adjuvant CpG or recombinant IL-2 (rIL-2). The local immunocompetent cells on the respiratory tract were detected. The results showed that the number of intraepithelial lymphocytes (IELs), CD3(+) T lymphocytes and mast cells in respiratory tract increased significantly respectively and the number of IgA and IgG secreting cells increased significantly after immunization. However, there was no significant change in the immunocompetent cells of the animals administrated H5N2 inactivated virus alone compared to the control group. Our results indicated that intranasal administration of H5N2 inactivated virus with adjuvant CpG or rIL-2 could be beneficial to the local immune response in the respiratory tract.

Effect of compound mucosal immune adjuvant on mucosal and systemic immune responses in chicken orally vaccinated with attenuated Newcastle-disease vaccine

In order to compare the adjuvant activity of compound mucosal immune adjuvant (cMIA), two novel compound adjuvants (cMIA I and cMIA II) were prepared and mixed with Newcastle-disease (ND) vaccine, respectively, to vaccinate 7-day-old chickens, taking the non-adjuvant vaccines and PBS as controls. Serum were sampled on weeks 1-7 and tissues on weeks 3, 5 and 7 after vaccination, respectively. The humoral and cellular immune responses were determined by means of hemagglutination inhibition test, enzyme linked immunosorbent assay, semi-quantitative RT-PCR, immunohistochemical examination and histological examination. The results showed that two compound adjuvants could promote CD3+ T lymphocytes, IgA secreting cells, intestinal intraepithelial lymphocytes (iIEL) and Mast cells formation and enhance serum and content antibody titer. The best adjuvant activity of cMIA II in promoting cellular immunity and cMIA I in enhancing humoral immunity occurred in whole immune period. Based on good synergistic effects of their components, two cMIAs would be expected as new-type mucosal immune adjuvants for mucosal immune.

Immunomodulatory effects ofBacillus firmus on mouse peritoneal cellsin Vitro

The effect of nonpathogenic G+ bacterium B. firmus (BF) on stimulation of mouse peritoneal cells in vitro was evaluated by testing nitric-oxide-synthesis induction and cytokine formation. The reactivity was compared of peritoneal cells from two inbred mouse strains, C57B1/6 and BALB/c, which differ in their immunological reactivity. Peritoneal macrophages from C57B1/6 produced more nitric oxide after a 1-d cultivation with inactivated BF than those of BALB/c mice. In both strains, production can be further increased by adding exogenous IFN-gamma to the culture. There were no significant differences between peritoneal cells of these two mouse strains in cytokine production after optimal in vitro stimulation with BF. BF effectively activated peritoneal cells for the production of TNF-alpha, IL-1beta and IL-10, delipidated bacterium (DBF) being more efficient than BF in induction of IL-10 and TNF-alpha. On the other hand, BF had only small effect on IFN-gamma production and no detectable effect on IL-12 production. Macrophage activation by BF/DBF can represent one of the mechanisms responsible for previously described immunomodulatory activity of BF.

Adjuvant effect ofBacillus firmus in intranasal immunization of guinea pigs with inactivated type B influenza virus

Intranasal immunization of guinea pigs with inactivated type B influenza virus plus inactivated Bacillus firmus as an adjuvant compared to the virus alone yields higher titers of serum hemagglutination-inhibiting antibodies and virus-neutralizing antibodies. This phenomenon could be useful in standard serology, especially in the preparation of immune sera against highly pathogenic strains for in vitro diagnosis.