Laboratory investigations on "postvaccinall rabies" caused by live sheep-brain vaccine.

The viral ethiology of postvaccinal complications among 30 dogs vaccinated by live antirabies vaccine (Umeno-Doi type, sheep brain vaccine) was fully confirmed. Three lots of virulent vaccine were inoculated subcutaneously into groups of "Wistar" rats according to the different schemes. Between the 1st and 12th day after the end of the vaccination there were no isolations of fixed virus in direct and blind i.c. passages of suspensions made from the thalamus area on succkling mice and rats. Also the viral antigen in the CNS of vaccinated but apparently healthy rats was undetectable. The "postvaccinal rabies" with the next isolation of fixed r.v. in the CNS was developed experimentally in rats only following the subcutaneous injection of the crude sheep-brain's and spinal cord's suspensions--composing the materials to production of antirabies vaccine.     

Biological treatments for the control of decay in tree wounds.: Laboratory tests

Non-decay fungi and bacteria which had been isolated from pruning wounds of beech (Fagus sylvatica) were examined for their ability to check the growth of decay fungi in a number of laboratory tests. Several fungi and bacteria inhibited growth although the degree of inhibition varied to some extent with the test. The most consistently antagonistic fungi were Trichoderma spp., especially an isolate of T. viride. The most antagonistic bacteria were Bacillus spp.     

Laboratory tests of fungicides against Peronospora parasitica (Pers. ex Fr.) Fr

Methods were investigated of culturing Peronospora parasitica on detached cotyledons in plastic box moist chambers in constant-temperature cabinets. Light was essential and a temperature of 15 °C was most suitable for infection and survival of cotyledons. Using such cotyledons the protectant and eradicant actions of various fungicides against P. parasitica were compared with those of zineb. Captafol, Daconil 2787, dichlofluanid and propineb were markedly superior to zineb as protectants, being highly effective at 0·025 % a.i. None of these compounds (at 0·2 % a.i.) checked fungal development when applied 5 h after inoculation, during which time the fungus had penetrated the cotyledons, and it was concluded that the fungicides had thus no internal effect. Internal fungistasis was shown, however, by a maneb-nickel sulphate fungicide and also by nickel sulphate. The latter (at 0·4% NiSO₄.6H₂O) gave some disease control when applied up to 72 h after inoculation and appeared to be translocated within the tissue of the cotyledon.     

A note on single- and two-dose immunogenicity tests of inactive virus vaccine in chicks.

Single dose extinction limit test ot inactive polio vaccine in chicks lasts 4 days and offers the same results as the two-dose test which requires 14 days. When "long-term" incubation instead of "conventional" 2 hours-incubation of the serum/virus mixtures in the neutralization reaction was used, extinction limit values higher by 0.6-0.7 log10 were regularly obtained.     

Laboratory tests for leaf resistance to Botrytis squamosa in onions

Two laboratory methods of testing for resistance to Botrytis squamosa in Allium cepa, A. fistulosum and hybrid material derived from them were developed. In one method, seedlings were sprayed with conidiospores, incubated for 3 days at 15°C (2 days at 100% r.h.) and the numbers of lesions per leaf assessed. This test was destructive. The second method was non-destructive, the plants being retained for breeding purposes. Leaf segments (25 × 15 mm) or leaf discs (14 mm diameter) were inoculated individually with a drop (0·014 ml) of spore suspension, and maintained at 15°C and 100% r.h. with a 12 h photoperiod. The length of the latent period, denned as the number of days for 50% of the leaf portions to produce lesions bearing visible mycelium, was determined for each onion line in a test. The reciprocal (1/t) of the latent period was used to test for significant differences between lines by analysis of variance. With both test methods, spores were applied at concentrations that discriminated relative resistance most readily. In both seedling and leaf segment tests A. fistulosum was more resistant than A. cepa to B. squamosa. The leaf disc test indicated that cultivars of A. fistulosum differed in their resistance. In hybrid material resistance was intermediate or more like that of A. fistulosum.     

Neurovirulence tests of three 17D yellow fever vaccine strains

The results of tests of the neurovirulence of three yellow fever vaccine preparations of different lineages are presented. Two preparations that have been used to make vaccines of acceptable safety and efficacy gave very similar results. A third preparation from the Robert Koch Institute, designated 168-73, was proposed as a reference preparation for the mouse potency assay in 1985 by WHO, but has been more often used as a reference in the monkey neurovirulence test. In the test described here 168-73 was of lower virulence than either of the other two preparations.     

Laboratory experiments with a polyvalent extract vaccine for oral immunization against E. coli enteritis]

Bacteria of E. coli causing enteritis can be extracted by EDTA-sodium. These extracts having lower dry weights result in better protective effects in contrast to sodium-deoxycholate extracts. The EDTA-sodium extracts can be concentrated, purified and sterile filtrated. Thus the production of polyvalent vaccines is possible. A direct relation exists between the effectiveness of the extracts and the virulence of the strains used for extraction. The more virulent the original strain the better is the protective effect of the vaccine produced by extraction of the original strain. The single components of the polyvalent vaccine show a certain improvement of their protective effects. For estimating the immunizing dose, it is necessary to consider the limiting dose. When exceeding this dose the protective effect or the vaccine does not further increase but remains constant of even decreases. The immunizing dose wanted must be greater than the ED50 but smaller than the limiting dose. Extremely high oral doses of vaccine result in symptoms of incompatibility in mice.     

恶性疟原虫抗原表位的亚单位疫苗与DNA疫苗的联合免疫

构建了含有恶性疟原虫抗原基因 ( AWTE)的真核表达质粒 p CMV- AWTE,以及能在大肠杆菌中得到分泌性表达的原核表达质粒 p MC0 5 ,表达的蛋白 AWTE保持了疟原虫抗原的抗原性。将 p CMV- AWTE以及 AWTE两者混合各 1 0μg鼻腔免疫小鼠 ,一次后诱导机体产生了较高水平的体液免疫及细胞免疫