Immunogenic reactivity of recombinant PKF and AbOmpA proteins as serum resistance factors against sepsis of Acinetobacter baumannii.

Acinetobacter baumannii is considered as a major cause of nosocomial infection worldwide. Various vaccine formulations have been mostly studied based on secreted or surface-exposed proteins of A. baumannii in murine models. Serum resistance proteins are critical virulence factors in bloodstream infections. AbOmpA and PKF are two major factors involved in serum resistance and could be considered as promising vaccine targets. In this study IgG1, IgG2c, Total-IgG concentrations, survival rates and spleen bacterial loads were studied in C57/BL mice model according to PKF, AbOmpA and AbOmpA + PKF vaccine formulations. The findings showed significant raises of IgG2c and Total-IgG in all three vaccinated groups in comparison with the control group. Whereas, there were low concentrations of IgG1 in all immunization plans. Colony counts of mice spleen showed the bacterial load of PKF plan had the most decrease of bacterial load (DBL = 5 log10 CFU/g). Taken together, this evaluation indicated that PKF vaccination plan induced a polarized Th1 response and rendered an effective protection against bloodstream infection caused by A. baumannii.

Evaluation of G2 Citric Acid-Based Dendrimer as an Adjuvant in Veterinary Rabies Vaccine.

For induction of an appropriate immune response, especially in the case of an inactivated vaccine, the use of an adjuvant is crucial. In this study, adjuvanticity effect of G2 dendrimer in veterinary rabies vaccine has been investigated. A nonlinear globular G2 dendrimer comprising citric acid and polyethylene glycol 600 (PEG-600) was synthesized and the toxicity was studied in vitro on the J774A.1 cell line. The adjuvanticity effect of the dendrimer was then investigated on rabies virus in NMRI mice as a model. Different concentrations of dendrimer were used to determine the best formulation for the survival of the mice after virus challenge. The rise of neutralizing antibody was also checked by rapid fluorescent focus inhibition test (RFFIT). The relative potency of the prepared formulation was finally calculated using standard NIH test and the results were compared (and discussed) with the commercially available rabies vaccine. The accuracy of dendrimer synthesis was confirmed using Fourier transform infrared (FT-IR), size, and zeta potential analysis. The in vitro toxicity assay revealed that no significant toxic effect is observed in cells when data are compared with the control group. The in vivo assay showed that a higher survival rate in the mice received a special formulation due to adjuvanticity effect of dendrimer, which is also confirmed by RFFIT. However, the relative potency of that formulation does not give expected results when compared with the alum-containing rabies vaccine. In the current investigation, the adjuvanticity effect of G2 dendrimer was demonstrated for the first time in rising of neutralizing antibodies against rabies virus. Our data confirm that nanoparticles can enhance immune responses in an appropriate manner. Moreover, engineered nanoparticles will enable us to develop novel potent multivalent adjuvants in vaccine technology.

Development of a Time and Cost Benefit Antibody Binding Test-Based Method for Determination of Rabies Vaccine Potency.

This study is an improvement on the antibody binding test, known as ABT method, to develop a simple and fast method in comparison with NIH for determination of rabies vaccine potency. In the current study, several commercial human and veterinary vaccines were tested using both modified ABT and NIH methods. The ED50 was calculated using the probit method and the relative potency of each vaccine was measured based on the reference vaccine. The test was repeated four times to calculate the reproducibility of the method. Statistical analysis indicated that there was no significant difference between the result obtained from NIH and modified ABT method for either human or veterinary vaccines (p > 0.05). In addition, the linearity of the method (R2) was calculated as 0.94 by serial dilution of a test vaccine. Coefficient variances were determined as less than and more than 10% for the human and veterinary rabies vaccines, respectively. In conclusion, the findings suggest that the modified method could be considered as an alternative approach for rabies vaccine potency determination in in-process quality control tests at industrial scale. It is a time and cost benefit method and accuracy may further be increased by employing monoclonal antibodies against trimeric form of G glycoprotein. However, the use of serum samples may be useful compared with an artificial mix of antibodies because other components from the serum samples could have a positive impact on cell sensitivity and mimic more the complexity of the immune response. Although the modified test has solved a fundamental problem, it is still not sensitive enough for veterinary vaccine assessment and needs further modifications to obtain the acceptability criteria.

Green synthesis and evaluation of silver nanoparticles as adjuvant in rabies veterinary vaccine.

BACKGROUND: Green synthesis of nanoparticles by plant extracts plays a significant role in different applications. Recently, several studies were conducted on the use of nanoparticles as adjuvant. The main aim of this study was to evaluate green synthesized silver nanoparticles (AgNPs) as adjuvant in rabies veterinary vaccine and compare the results with the existing commercially available alum adjuvant. MATERIALS AND METHODS: In the current study, AgNPs were prepared by the reduction of aqueous silver nitrate by leaf extract of Eucalyptus procera. The formation of AgNPs was confirmed by ultraviolet (UV)-visible spectrophotometer, scanning electron microscopy, dynamic light scattering, and X-ray diffraction analysis. Then, different amounts of AgNPs (200 µg, 400 µg, 600 µg, and 800 µg) were added to 1 mL of inactivated rabies virus. The loaded vaccines (0.5 mL) were injected intraperitoneally into six Naval Medical Research Institute mice in each group on days 1 and 7. On the 15th day, the mice were intracerebrally challenged with 0.03 mL of challenge rabies virus (challenge virus strain-11, 20 lethal dose [20 LD50]), and after the latency period of rabies disease in mice (5 days), the mice were monitored for 21 days. Neutralizing antibodies against rabies virus were also investigated using the rapid fluorescent focus inhibition test method. The National Institutes of Health test was performed to determine the potency of optimum concentration of AgNPs as adjuvant. In vitro toxicity of AgNPs was assessed in L929 cell line using MTT assay. In addition, in vivo toxicity of AgNPs and AgNPs-loaded vaccine was investigated according to the European Pharmacopeia 8.0. RESULTS: AgNPs were successfully synthesized, and the identity was confirmed by UV-visible spectrophotometry and X-ray diffraction analysis. The prepared AgNPs were spherical in shape, with an average size of 60 nm and a negative zeta potential of -14 mV as determined by dynamic light scattering technique. The highest percentage of viability was observed at 15 mg/kg and 20 mg/kg of AgNPs-loaded vaccine concentrations after injecting into the mice. The calculated potencies for alum-containing vaccine and AgNPs-loaded vaccine (dose 15 mg/kg) were 1.897 and 1.303, respectively. MTT assay demonstrated that alum at the concentration of 10 mg/mL was toxic, but AgNPs were not toxic. The in vivo toxicity also elucidated the safety of AgNPs and AgNPs-loaded vaccine in mice and dogs, respectively. CONCLUSION: In the current study, for the first time, the adjuvanticity effect of green synthesized AgNPs on veterinary rabies vaccine potency with no in vivo toxicity was elucidated according to the European Pharmacopeia 8.0.

Antibody persistence, 32 years after post-exposure prophylaxis with human diploid cell rabies vaccine (HDCV).

In 1975-1976 forty-five persons severely bitten by rabid wolves and dogs in Iran were treated successfully against rabies with HDCV. In this study contact was made with 26 of 45 above persons, 32 years after their initial treatment and all had rabies neutralizing antibody ranging from 0.3 to 2.69 IU/ml of serum. Of the 26 persons, 17 had received a booster dose of HDCV, 28 years ago and the remaining 9 persons, who had not received any booster since the initial treatment, were given one booster dose of HDCV. All 9 of these patients developed an anamnestic response after their booster inoculation. This study confirms the persistence of rabies neutralizing antibody in persons that received post-exposure vaccination with HDCV, 32 years previously. Furthermore, a single booster inoculation with HDCV resulted in anamnestic response in all individuals.