Leishmania tropica: The comparison of two frequently-used methods of parasite load assay in vaccinated mice

Objective: To compare limiting dilution assay and real-time PCR methods in Leishmania tropica parasite load measurement in vaccinated mice. Methods: BALB/c mice were vaccinated by Leishmania tropica soluble Leishmania antigen or recombinant Leishmania tropica stress-inducibleprotein-1 with/without adjuvant. After three vaccinations, mice were challenged by Leishmania tropica promastigotes. Two months after challenge, the draining lymph nodes of mice footpad were removed and parasite load was assayed by limiting dilution assay and real-time PCR methods. Limiting dilution assay was done by diluting tissue samples to extinction in a biphasic medium. For real-time PCR, DNA of the lymph nodes was extracted, equal dilutions of each sample were prepared and hot-start real-time PCR was done using appropriate primers. The data of the two methods were compared by appropriate statistical methods. Results: Both methods were able to measure different levels of parasite load in vaccinated/unvaccinated mice. In addition, wherever parasite load of a group was estimated high (or low) by one method, the estimated parasite load by another method was the same, although statistically significant differences were found between some groups. Conclusions: Both methods lead to approximately similar results in terms of differentiating parasite load of the experimental groups. However, due to the lower errors and faster process, the real-time PCR method is preferred.

Role of higher levels of post-challenge antibodies in protective vaccination against Leishmania tropica infection of BALB/c mice

Objective: To study the role of antibodies in protection against Leishmania tropica (L. tropica) infection in the experimental model of BALB/c mice. Methods: BALB/c mice were vaccinated against L. tropica by soluble Leishmania antigen or recombinant L. tropica stress-inducible protein-1 (LtSTI1) of L. tropica, and against Leishmania major (L. major) by soluble Leishmania antigen. Monophosphoryl lipid A was used as an adjuvant. The L. tropica- or L. major-vaccinated mice were challenged by L. tropica or L. major, respectively. The levels of anti-Leishmania antibodies (IgG1 and IgG2a) were determined after vaccination and after challenge. Results: All vaccinated groups caused a higher antibody response in comparison with the control group. The L. major-vaccinated group showed lower IgG1 response than the control group after the challenge. Conversely, in L. tropica-vaccinated mice, the levels of antibodies were higher than the control group. Moreover, the group receiving rLtSTI1 and monophosphoryl lipid A showed higher levels of antibodies than those of the rLtSTI1 group. In vaccinated mice, antibody responses against L. tropica remained high until 16 weeks after the challenge. Conclusions: The higher levels of post-challenge antibodies are associated with protective vaccination against L. tropica infection of BALB/c mice. Our findings provide new insight into the association of antibody with vaccine-induced protective immunity against L. tropica infection. More studies are needed to clarify the role of antibody in protection against L. tropica.

Impact of thyroid dysfunction on antioxidant capacity, superoxide dismutase and catalase activity

In hypothyroidism and hyperthyroidism, disturbance of oxidant/antioxidant balance leads to reactive oxygen species [ROS] generation. The aim of this study is assaying total antioxidant capacity and superoxide dismutase and catalase activities in patients with hypo-and hyperthyroidism in order to control the progression of its pathology and health care. This case-control study was performed on 85 patients with hypothyroidism, 66 patients with hyperthyroidism and 74 normal individuals as control that referred to the clinic of the Research Institute for Endocrine Sciences of Shahid-Beheshti University in year 2010. Serum enzymatic activity of catalase, superoxide dismutase and total antioxidant capacity was measured in the fasting state. Data was described as mean +/- SD and data means of the two groups was compared by independent t-test. Data was analyzed by SPSS-18 application. The total antioxidant capacity in individuals with hyperthyroidism decreased compared to healthy controls, but individuals with hypothyroidism compared to the healthy control group showed no significant difference. Catalase and superoxide dismutase activity in hypo-and hyperthyroidism were significantly increased compared with healthy controls [p=0.005]. Decreasing of antioxidant capacity in hyperthyroid patients is probably because of increased production of free radicals. There was not observed significant difference in total antioxidant capacity in hypothyroid patients. Also in hypo-and hyperthyroidism patients, increasing of enzymes activity is probably due to increasing of the production of ROS

Fluorimetry as a simple and sensitive method for determination of catalase activity

Catalase enzyme plays an important role in the anti-oxidation defense of body so it is important to measure its activity. Nowadays catalase activity measurement is performed by expensive imported kits in various scientific fields. The purpose of this study was to design a sensitive fluorimetry method for measuring catalase activity with improved sensitivity, accuracy and speed. In this study, the reaction of hydrogen peroxide with peroxidase [as a reaction accelerator] was used in fluorimetry for catalase activity measuring in serum samples in order to increase the sensitivity of the assay. The sensitivity and intra- and inter-assay accuracy, verification test, recovery and parallelism tests, comparison method and correlation and coherence investigation methods were also performed. In order to increase the accuracy and speed of reading, the assay was performed in microplates and reading was done in fluorimetry plates. The percentage of intra- and inter-assay variation coefficients were measured 3.8-6.6% and 4.1-7.3%, respectively. Comparison of the results of mentioned method for 50 serum samples with common colorimetric method showed a good correlation [0.917]. In assessing the accuracy, the recovery percent was obtained 91% to 107%. The test sensitivity was measured 0.02 IU/ml. The fluorimetry method by microplate reading has a sufficient precision, accuracy and efficiency for catalase activity measuring as well as speed of measurement. Thus it can be an alternative method to conventional imported colorimetric methods

Expression and purification of neurotoxin associated protein HA-33/A from clostridium botulinum and evaluation of its antigenicity

Botulinum neurotoxin [BoNT] complexes consist of neurotoxin and neurotoxin-associated proteins. Hemagglutinin-33 [HA-33] is a member of BoNT type A [BoNT/A] complex. Considering the protective role of HA-33 in preservation of BoNT/A in gastrointestinal harsh conditions and also its adjuvant role, recombinant production of this protein is favorable. Thus in this study, HA-33 was expressed and purified, and subsequently its antigenicity in mice was studied. Initially, ha-33 gene sequence of Clostridium botulinum serotype A was adopted from GenBank. The gene sequence was optimized and synthesized in pET28a [+] vector. E. coli BL21 [DE3] strain was transformed by the recombinant vector and the expression of HA-33 was optimized at 37°C and 5 h induction time. The recombinant protein was purified by nickel nitrilotriacetic acid agarose affinity chromatography and confirmed by immunoblotting. Enzyme Linked Immunoassay showed a high titer antibody production in mice. The results indicated a highly expressed and purified recombinant protein, which is able to evoke high antibody titers in mice

Comparative study of immunological and structural properties of two recombinant vaccine candidates against botulinum nurotoxin type E

Recently, botulinum neurotoxin [BoNT]-derived recombinant proteins have been suggested as potential botulism vaccines. Here, with concentrating on BoNT type E [BoNT/E], we studied two of these binding domain-based recombinant proteins: a multivalent chimer protein, which is composed of BoNT serotypes A, B and E binding subdomains, and a monovalent recombinant protein, which contains 93 amino acid residues from recombinant C-terminal heavy chain of BoNT/E [rBoNT/E-HCC]. Both proteins have an identical region [48 aa] that contains one of the most important BoNT/E epitopes [YLTHMRD sequence]. The recombinant protein efficiency in antibody production, their structural differences, and their BoNT/E-epitope location were compared by using ELISA, circular dichroism, computational modeling, and hydrophobicity predictions. Immunological studies indicated that the antibody yield against rBoNT/E-HCC was higher than chimer protein. Cross ELISA confirmed that the antibodies against the chimer protein recognized rBoNT/E-HCC more efficiently. However, both antibody groups [anti-chimer and anti-rBoNT/E-HCC antibodies] were able to recognize other proteins. Structural studies with circular dichroism showed that chimer proteins have slightly more secondary structures than rBoNT/E-HCC. The immunological results suggested that the above-mentioned identical region in rBoNT/E-HCC is more exposed. Circular dichroism, computational protein modeling and hydrophobicity predictions indicated a more exposed location for the identical region in rBoNT/E-HCC than the chimer protein, which is strongly in agreement with immunological results