The tubes were incubated at 37 °C in a humid atmosphere containing 5% CO2 BTK inhibitor mouse for 16 h, after which 0.5 mL of Trizol (Invitrogen) were added; the tubes were stored at −80 °C until use. RNA extraction was performed according to the manufacturer’s instructions. RNA quality and quantity were assessed by spectrophotometric measurements at 260/280 nm (Nanodrop); 1 μg of total RNA was treated with DNAse-I (Invitrogen) and immediately subjected to cDNA synthesis with random primers (Invitrogen) and M-MLV reverse transcriptase (Invitrogen). Real-time PCR was performed using the QuantiTect® SYBR® Green PCR
Kit (Qiagen) in a Rotor-Gene 6000 (Corbett), as follows. Primers (see Table
1) were used at a final concentration of 0.9 μM. The cycling conditions were 15 min at 95 °C, followed by 40 cycles at 95 °C for 15 s, and 60 °C for 1 min during which the TSA HDAC mw fluorescence data were collected. The expression level of the genes of interest was normalized using β-actin as housekeeping gene. The relative mRNA amount in each sample was calculated using the 2−ΔΔCt method [24] where ΔCt = Ctgene of interest − CtActbβAct, and expressed as relative mRNA level in the test group compared to the non-stimulate control group. The data were expressed as mean ± standard error (S.E.) or standard deviation (S.D.) and examined for statistical significance with the Student’s t-test. P-values
of less than 0.05 were considered to be statistically significant. Fig. 1a shows the haemolytic activities of QB-90U and Quil A. Their respective HD50 values were 125 ± 5 μg/mL and 52 ± 2 μg/mL, and their haemolytic activities at the crotamiton concentrations used for vaccination (100 and 50 μg/mL) were about 15% and 55%, respectively. Thus, compared with Quil A, QB-90U was only slightly haemolytic at the concentration used for immunization. Its low haemolytic activity allowed including QB-90U in the inoculated preparation at a higher concentration than is possible for Quil A. A similar result was obtained in the cytotoxicity assay, which is shown in Fig. 1b. Indeed, the toxicity of Quil A against VERO cells was much higher than that of QB-90U. At a concentration of 100 μg/mL, more than 80% of cells were viable after incubating for 48 h at 37 °C with QB-90U, while at the same concentration of Quil A just about 20% were viable. At 50 μg/mL, the concentration used for immunization with Quil A, a viability of approximately 30% was observed with this saponin fraction, whereas no toxicity was detected with QB-90U These results on the in vitro toxicity of QB-90U and Quil A agree with previous reports on their in vivo toxicity in mice [11], [15] and [17].