Structural parameters, molecular properties, and biological evaluation of some terpenes targeting schistosoma mansoni parasite

The use of natural products has a long tradition in medicine, and they have proven to be an important source of lead compounds in the development of new drugs. Among the natural compounds, terpenoids present broad-spectrum activity against infective agents such as viruses, bacteria, fungi, protozoan and helminth parasites. In this study, we report a biological screening of 38 chemically characterized terpenes from different classes, which have a hydroxyl group connected by hydrophobic chain or an acceptor site, against the blood fluke Schistosoma mansoni, the parasite responsible for schistosomiasis mansoni. In vitro bioassays revealed that 3,7-dimethyl-1-octanol (dihydrocitronellol) (10) was the most active terpene (IC50 values of 13­52 µM) and, thus, we investigated its antischistosomal activity in greater detail. Confocal laser scanning microscopy revealed that compound 10 induced severe tegumental damage in adult schistosomes and a correlation between viability and tegumental changes was observed. Furthermore, we compared all the inactive compounds with dihydrocitronellol structurally by using shape and charge modeling. Lipophilicity (miLogP) and other molecular properties (e.g. molecular polar surface area, molecular electrostatic potential) were also calculated. From the 38 terpenes studied, compound 10 is the one with the greatest flexibility, with a sufficient apolar region by which it may interact in a hydrophobic active site. In conclusion, the integration of biological and chemical analysis indicates the potential of the terpene dihydrocitronellol as an antiparasitic agent.

Studies on the efficiency of measles virus antigen production using VERO cell culture in a microcarrier system

1. A large amount of antigen is required to conduct seroepidemiologic surveys of measles. Thus, a process to obtain measles virus antigen using a bioreactor was standardized. 2. The virus was grown in a 3.7-1 culture of VERO cells using a Celligen cell culture system containing 2 mg/ml of microcarriers (cytodex I) at 37 degrees C and 60 rpm. The cultures infected with 0.5 m.o.i. of measles virus were harvested after the appearance of the cytopathic effect. The virus suspension was clarified and concentrated by ultracentrifugation. Intracellular and extracellular virus titers were determined by hemagglutination (HA) and by induction of a cytopathic effect in cell culture (TCID50). 3. Intracellular virus presented 5-7 x 10(6) TCID50/0.1 ml, HA activity per 50 microliters equal to 32, with a total HA activity of 4,480 HA units (HAU) and specific activity of 116 HAU/mg. In the concentrated supernatants, the HA titer of extracellular virus was 64, with a total HA activity of 1,024 HAU and a specific activity of 1,600 HAU/mg. 4. The antigen obtained was suitable for the detection of antibodies against measles virus in assays such as ELISA and DOT-ELISA (using 1 micrograms/well to ELISA and 2 micrograms/DOT). 5. The microcarrier system produced antigen sufficient for 26 ELISAs/ml compared to 5.7 ELISAs/ml obtained for the static culture system.

Relationship of interferon synthesis and the resistance of mice infected with street rabies virus

Genetically homogeneous and heterogeneous mouse populations were tested for resistance to experimental street rabies virus infection and their ability to synthesize interferon (IFN) during the infection. The genetically heterogenous HI mouse population was highly resistant (12 per cent mortality), and the genetically homogeneous BALB/c and C3H mice as well as the genetically heterogeneous Sw and LI mouse populations were susceptible (60 to 71 per cent mortality). The genetically homogeneous A/J mice were highly susceptible (85 per cent mortality) to experimental street rabies infection. The ability of these mice to synthesize IFN as measured in serum 4 days after the infection was directly related to the degree of resistance, with the highly resistant HI mice showing large amounts of IFN (850 U/ml), and the susceptible mice showing low amounts of IFN (50 to 280 U/ml). IFN induced within the central nervous system and measured in brain homogenates during infection was not correlated with resistance. The present data suggest that high levels of IFN occurring in serum early during infection with street rabies virus contribute to the resistance of these mice

Preparation of human rabies vaccine in VERO cell culture using a microcarrier system

1. The rabies virus (Pasteur PV strain) was propagated in VERO cells attached to microcarriers in a 3.7-1 bioreactor. Virus titers of about 10(6) LD50/ml were obtained regularly. 2. Ultrafiltration was efficient for concentrating the virus suspensions, and the sucrose gradient reduced the residual VERO cell DNA to acceptable levels (less than 50 pg/dose). The remaining cell DNA content was evaluated by dot-blot hybridization with a probe prepared with VERO cell DNA. 3. The final virus preparations were inactivated by B-propiolactone treatment, showed a potency higher than 2.5 IU/dose and protected mice experimentally infected intracerebrally with rabies virus (CVS-13.2). 4. This methodology for the production of a rabies vaccine for human use should be of interest to countries where high technology facilities are not available