Efficacy of Modified Levamisole Adjuvant on Inactivated Virus Vaccine

Saponin-adjuvanted vaccine protects chickens against velogenic Newcastle disease virus

Despite extensive vaccination campaigns, Newcastle disease virus (NDV) remains endemic in many countries worldwide, and factors that contribute to this failure include mismatched vaccines, partial immunization, and poor husbandry practices. In order to overcome the problem of genetic divergence between circulating field strains and vaccine strains, we saponin-adjuvanted an Egyptian field strain and assessed its safety and immunogenicity in chickens. Immunization of chickens with the vaccine followed by challenge with a velogenic reference strain revealed the potential of the saponin-adjuvanted vaccine to induce a strong immune response that resulted in complete protection of chickens. Importantly, in vaccinated chickens, virus shedding was abolished, providing an added advantage over the currently available commercial live-attenuated and inactivated vaccines, which are unable to prevent shedding. A histopathological investigation demonstrated that the vaccinated chickens had less-severe lesions than challenged unvaccinated and mock-vaccinated chickens. We propose using this formulation as an alternative and improved NDV vaccine platform that can be exploited to control disease not only in Egypt but also in other disease-endemic countries.

Respiratory and GIT tract immune responses of broiler chickens following experimental infection with Newcastle disease's virus

Newcastle disease causes a lymphoproliferative response in the tracheal and intestinal mucosa of the infected birds. In this study, the Hitchner B1 and I-2 vaccine and challenging of ND field strains were used to evaluate the populations of T lymphocyte subsets infiltrated intestinal and tracheal, also to shed some light on cell-mediated immune response using enzyme-linked immunosorbent assay (ELISA) detecting chicken's serum interferon-γ. Three hundred-day-old broilers were randomly divided into four groups. Groups 1 and 2 received I-2 and B1 vaccines, respectively, while groups 3 and 4 were challenged-unvaccinated and unchallenged-unvaccinated groups. Blood samples were taken from five random chicks and were then tested with ELISA test. Three chicks of each group were euthanized after vaccine administration and also challenging with acute virus. Interferon-γ changes were significant in time (p < 0.001). Totally, there was no significant difference between I-2 and B1 groups. The number of CD3+, CD4+, and CD8+ cells of I-2 and B1 vaccinated group's intestine and the trachea samples was significantly increased compared with the negative control group (p < 0.001). The results indicated the significant increase in CD4+ and CD8+ in intestinal and tracheal tissues, while the level of interferon-γ of the vaccinated group was more than the unvaccinated one. Finding no significant differences between the vaccinated groups indicated the potential of both vaccines in producing CD4+ and CD8+ in the tracheal and intestinal tissues and the equality of interferon-γ production in the sera.

A bacterial ghost improves the immunological efficacy of a Newcastle disease virus inactivated vaccine

Newcastle disease (ND) is one of the most common contagious viral infectious diseases of poultry. Vaccination is an effective way to protect chickens from Newcastle disease virus (NDV), and large efforts have been made to acquire not only new vaccines but also new adjuvants to improve the efficiency of existing inactivated vaccines. Here, we observed the adjuvanticity of the bacterial ghost (BG) on the effectiveness of inactivated NDV vaccine in a chicken model. We found that BG, as an adjuvant with inactivated NDV vaccine, substantially strengthened the ND-specific antibody response and protection against lethal challenge in a chicken model, reduced viral shedding, strengthened the time duration of antibody titers, produced an available immunization effect with a low dose of vaccine, and improved serum IL-2 and IFN-γ concentrations. Our results demonstrate that BG significantly improved the immunogenicity of an inactivated NDV vaccine and is a new immune adjuvant candidate.

Influence of levamisole and Freund's adjuvant on mouse immunisation with antigens of adults of the liver fluke Fasciola hepatica Linnaeus, 1758

We have studied the influence of both levamisole (AL) and Freund's adjuvant (AF) on the immunisation of mice with the secretory antigens of adults of the liver fluke Fasciola hepatica Linnaeus, 1758. Total IgG antibodies were detected in all groups where the F. hepatica antigen was administered, been levels of IgG1 increased respect to IgG2a antibodies. During immunisation, IL-4 and IFN-γ were only detected in AL and AF groups, but after infection, IL-4 boosted in all groups. IFN-γ increased two fold in AF and AL groups compared to the saline solution (AS) group. Worm recovering was of 32-35% in groups administered without antigen whereas in AS, AL and AF groups recovering was of 25%, 12% and 8%, respectively. Macroscopical lesions in the liver were scarce in AL and AF groups. Our data suggest that immunisation of mice with antigens of F. hepatica enhances the immune response avoiding both liver damage and worm establishment after challenge infection. The murine model of fasciolosis has appeared to be useful to elucidate the mechanism by which the parasite modulates immune responses toward a Th2 type but also the development of Th1 type-inducing vaccines.

Inactivated vaccine with adjuvants consisting of pattern recognition receptor agonists confers protection against avian influenza viruses in chickens

Use of adjuvant containing pathogen pattern recognition receptor agonists is one of the effective strategies to enhance the efficacy of licensed vaccines. In this study, we investigated the efficacy of avian influenza vaccines containing an adjuvant (CVCVA5) which was composed of polyriboinosinic polyribocytidylic, resiquimod, imiquimod, muramyl dipeptide and levomisole. Avian influenza vaccines adjuvanted with CVCVA5 were found to induce significantly higher titers of hemagglutiniton inhibition antibodies (P≤0.01) than those of commercial vaccines at 2-, 3- and 4-week post vaccination in both specific pathogen free (SPF) chickens and field application. Furthermore, virus shedding was reduced in SPF chickens immunized with H9-CVCVA5 vaccine after H9 subtype heterologous virus challenge. The ratios of both CD3(+)CD4(+) and CD3(+)CD8(+) lymphocytes were slowly elevated in chickens immunized with H9-CVCVA5 vaccine. Lymphocytes adoptive transfer study indicates that CD8(+) T lymphocyte subpopulation might have contributed to improved protection against heterologous virus challenge. Results of this study suggest that the adjuvant CVCVA5 was capable of enhancing the potency of existing avian influenza vaccines by increasing humoral and cellular immune response.

Immune responses of poultry to Newcastle disease virus

Newcastle disease (ND) remains a constant threat to poultry producers worldwide, in spite of the availability and global employment of ND vaccinations since the 1950s. Strains of Newcastle disease virus (NDV) belong to the order Mononegavirales, family Paramyxoviridae, and genus Avulavirus, are contained in one serotype and are also known as avian paramyxovirus serotype-1 (APMV-1). They are pleomorphic in shape and are single-stranded, non-segmented, negative sense RNA viruses. The virus has been reported to infect most orders of birds and thus has a wide host range. Isolates are characterized by virulence in chickens and the presence of basic amino acids at the fusion protein cleavage site. Low virulent NDV typically produce subclinical disease with some morbidity, whereas virulent isolates can result in rapid, high mortality of birds. Virulent NDV are listed pathogens that require immediate notification to the Office of International Epizootics and outbreaks typically result in trade embargos. Protection against NDV is through the use of vaccines generated with low virulent NDV strains. Immunity is derived from neutralizing antibodies formed against the viral hemagglutinin and fusion glycoproteins, which are responsible for attachment and spread of the virus. However, new techniques and technologies have also allowed for more in depth analysis of the innate and cell-mediated immunity of poultry to NDV. Gene profiling experiments have led to the discovery of novel host genes modulated immediately after infection. Differences in virus virulence alter host gene response patterns have been demonstrated. Furthermore, the timing and contributions of cell-mediated immune responses appear to decrease disease and transmission potential. In view of recent reports of vaccine failure from many countries on the ability of classical NDV vaccines to stop spread of disease, renewed interest in a more complete understanding of the global immune response of poultry to NDV will be critical to developing new control strategies and intervention programs for the future.

Chronic heat stress inhibits immune responses to H5N1 vaccination through regulating CD4⁺ CD25⁺ Foxp3⁺ Tregs

Chronic heat stress (CHS) is known to have negative impacts on the immune responses in animals and increases their susceptibility to infections including the highly pathogenic avian influenza virus H5N1. However, the role of regulatory T cells (Tregs) in CHS immunosuppression remains largely undefined. In this study, we demonstrated a novel mechanism by which CHS suppressed both Th1 and Th2 immune responses and dramatically decreased the protective efficacy of the formalin-inactivated H5N1 vaccine against H5N1 influenza virus infection. This suppression was found to be associated with the induced generation of CD4⁺CD25⁺FoxP3⁺ Tregs and the increased secretions of IL-10 and TGF-β in CD4⁺ T cells. Adoptive transfer of the induced Tregs also suppressed the protective efficacy of formalin-inactivated H5N1 virus immunization. Collectively, this study identifies a novel mechanism of CHS immunosuppression mediated by regulating CD4⁺CD25⁺Foxp3⁺ Tregs.

Comparative effects of levamisole, Staphylococcus, and Freund's adjuvant on rat immunization with excretory and secretory antigens of Trichinella spiralis muscle larvae

A comparison was made of the effects of levamisole, the bacterial fractions of Staphylococcus, and Freund's adjuvant on the immunization of rats with the excretory and secretory antigens of Trichinella spiralis muscle larvae. Wistar rats were immunized with the antigen and a saline solution, levamisole (LV), Staphylococcus (ST), or Freund's adjuvant (FA). After immunization, rats were infected, and the parasite burden at muscular phase was calculated for each group. Levels of IgG1 and IgG2 antibodies, as well as levels of two cytokines, IL-4 and IFN-γ, were evaluated during the immunization and postinfection periods. Differences were found in the kinetics of antibody production between groups (p < 0.01). In all cases, there was reactivity with the main 45-, 50-, and 55-kDa antigens of Trichinella muscle larvae. Immunization with FA and ST enhanced the production of IgG1, but only FA showed a significant increase in the production of IFN-γ (p < 0.01), resulting in 86% protection against the infection. In contrast, only 60-70% protection was attained in the ST and LV groups (p < 0.01). These data support the idea that levamisole and Staphylococcus can be used as adjuvant to enhance the humoral response and, at the same time, demonstrate that IFN-γ could be involved in protection against Trichinella.

Immune responses induced by heterologous boosting of recombinant bacillus Calmette-Guerin with Ag85B-ESAT6 fusion protein in levamisole-based adjuvant

In the present study, we evaluated the effectiveness of a levamisole-based adjuvant (ADL) to enhance the ability of the Ag85B-ESAT6 fusion protein to boost immune responses after primary vaccination with recombinant bacillus Calmette-Guerin (rBCG) in Balb/c mice. The results were compared with that of the control adjuvant formulation of dimethyl dioctadecylammonium bromide (DDA) and monophosphoryl lipid A (MPL), which has previously been shown to induce T-helper type 1 (Th1)-biased responses. Enzyme-linked immunospot (ELISPOT) assay with Ag85B and ESAT6 derived peptides corresponding to CD4+ and CD8+ T cell restricted epitopes and cell surface immunostaining indicated that Ag85B-ESAT6/ADL predominantly triggered activation of CD4+ T cells. Functional CD8+ T cells with interferon (IFN)-γ production or cytotoxicity were undetectable all vaccinated mice. The ADL adjuvant modified T-helper (Th) subtypes by up-regulating multiple signature cytokines. Furthermore, profiles of the immunoglobulin G (IgG) subtypes indicated ADL enhanced the secretion of Th1-associated IgG2a antibodies and decreased the yield of Th2-associated IgG1 subtype. These observations suggest that the ADL adjuvant formulated with a protein booster may induce Th1-biased cellular and humoral immune responses to primary vaccination with a live attenuated bacterial TB vaccine.

Effect of oral administration of ginseng stem-and-leaf saponins (GSLS) on the immune responses to Newcastle disease vaccine in chickens

This study was designed to evaluate the effect of oral administration of ginseng stem-and-leaf saponin (GSLS) on immune responses in chickens vaccinated with live Newcastle disease (ND) vaccines. In experiment 1, chickens were orally administered GSLS (2.5, 5, 10, and 20mg/kg) in drinking water for 3 days, and then intranasally vaccinated with ND vaccine. Hemagglutination inhibition (HI) test showed that the optimal dose of GSLS for enhancing HI titers was 5mg/kg. In experiment 2, chickens were fed with GSLS (5mg/kg) for 7, 5 or 3 days before vaccination. Result indicated that GSLS enhanced HI titers in a time-dependent manner. The order of the duration for drinking GSLS on increasing HI titers was 7 days>5 days>3 days. In experiment 3, chickens were fed with GSLS before or after immunization. Serum was sampled at a week interval for 5 weeks for HI test, splenic lymphocytes were prepared at weeks 2 and 4 after the booster immunization for lymphocyte proliferation test (LPT) and intestinal tissues were sampled at week 4 after the booster immunization for immunohistochemistry and histological examination. Results showed that HI titer, LPT, IgA+ cells and intestinal intraepithelial lymphocytes (iIELs) were significantly higher in chickens drinking GSLS before vaccination than those after vaccination. Therefore, oral administration of GSLS in drinking water at a dose of 5mg/kg for 7 days significantly increased systemic as well as gut mucosal immunity in chickens immunized with ND vaccine. Considering the immune potentiating effect of GSLS on ND vaccine, GSLS should be evaluated for its oral adjuvant effect on the immune response against other diseases such avian influenza and infectious bursal disease.

Prophylactic, therapeutic and immune enhancement effect of liposome-encapsulated PolyICLC on highly pathogenic H5N1 influenza infection

BACKGROUND

In view of the magnitude and severity of outbreaks of the highly pathogenic H5N1 influenza virus (H5N1-HPIV) and the threat to public health, there is an urgent need to develop broad-spectrum prophylactic and therapeutic agents against infection by H5N1-HPIV and other subtypes.

METHODS AND RESULTS

In the present study, we explored the use of LE-PolyICLC, a liposome encapsulated double-stranded RNA, as a possible prophylactic, therapeutic and immune enhancement agent. In a mouse infection model, we showed that the administration of LE-PolyICLC intranasally before or shortly after infection could inhibit virus replication, leading to a significant reduction in pulmonary viral titres and a higher survival rate of infected mice. When used as a molecular adjuvant, LE-PolyICLC significantly enhanced both the humoral and cellular responses elicited by inactivated H5N1 vaccine and augmented the protective efficacy provided by vaccination. Most importantly, the data also demonstrate that LE-PolyICLC could effectively attenuate the development of pulmonary fibrosis during the restoration period at day 14 after H5N1 infection.

CONCLUSIONS

Taken together, the data obtained in the present study suggest that strong consideration should be given for the use of LE-PolyICLC as prophylactic and therapeutic agents and also as a vaccination adjuvant to combat highly pathogenic influenza infection and its associated complications such as pulmonary fibrosis.

The protective efficacy against Schistosoma japonicum infection by immunization with DNA vaccine and levamisole as adjuvant in mice

Levamisole (LMS) as an adjuvant enhances cell-mediated immunity in DNA vaccination; we investigated the efficacy and liver immunopathology alleviation of a DNA vaccine, VR1012-SjGST-32, in a LMS formulation in the murine challenge model. Compared to controls, the VR1012-SjGST-32 plus LMS can reduce worm and egg burdens, as well as, immunopathological complications associated chronic inflammation significantly in liver, which were apparently associated with Th1-type response. Together, these results suggest that the LMS as a potential Schistosome DNA vaccine adjuvant can enhance both worm killing and disease prevention, which is possibly mediated through the induction of a strong Th1-dominant environment in immunized mice.

Effects of chronic heat stress on immune responses of the foot-and-mouth disease DNA vaccination

The main purpose of this study was to assess the effects of chronic heat stress (CHS) on humoral and cellular responses of DNA vaccination. Mice with the CHS were exposed to a temperature set at 38 +/- 1 degrees C, 2h per day, for 35 days, and mice with thermoneutral (TN) temperature were maintained at 24 +/- 1 degrees C for the same period of time. Both groups of mice were immunized with a DNA vaccine-expressed viruscapsid protein 1 (VP1) of foot-and-mouth disease virus (FMDV), and we tested their antigen-specific humoral and cellular responses during the treatments. Compared with the TN group, titers of total Imunoglobulin G (IgG) and IgG1 and expression of interleukin 4 (IL-4) in CD4(+) cells of CHS group were not affected significantly. In contrast, the levels of IgG2a, T cell proliferations, and expression of interferon-gama (IFN-gamma) in both CD4(+) and CD8(+) cells were suppressed significantly, and cytotoxic T-lymphocyte (CTL) responses in vivo were also weakened by the CHS condition. These results indicate that the CHS treatment has negatively affected the immune responses of DNA vaccination and particularly impaired to the cell-mediated responses. It suggests that vaccination in animals is affected by the changes of ambient temperature.