Inactivation and stability of viral diagnostic reagents treated by gamma radiation

Differential viral levels and immune gene expression in three stocks of Apis mellifera induced by different numbers of Varroa destructor

The viral levels and immune responses of Italian honey bees (IHB), Russian honey bees (RHB) and an outcross of Varroa Sensitive Hygienic bees (POL) deliberately infested with one or two foundress Varroa were compared. We found that the Deformed wing virus (DWV) level in IHB inoculated with one or two foundress Varroa increased to about 10(3) or 10(5) fold the levels of their uninfested brood. In contrast, POL (10(2) or 10(4) fold) and RHB (10(2) or l0(4) fold) supported a lower increase in DWV levels. The feeding of different stages of Varroa nymphs did not increase DWV levels of their pupal hosts. Analyses of their corresponding Varroa mites showed the same trends: two foundress Varroa yielded higher DWV levels than one foundress, and the addition of nymphs did not increase viral levels. Using the same pupae examined for the presence of viruses, 16 out of 24 genes evaluated showed significant differential mRNA expression levels among the three honey bee stocks. However, only four genes (Defensin, Dscam, PPOact and spaetzle), which were expressed at similar levels in uninfested pupae, were altered by the number of feeding foundress Varroa and levels of DWV regardless of stocks. This research provides the first evidence that immune response profiles of different honey bee stocks are induced by Varroa parasitism.

Bovine Babesiosis Live Vaccine Production

Gamma irradiation on bovine serum and red blood cells (RBC) allows proliferation and growth of in vitro-cultured Babesia sp., and has potential application to inactivate contaminating viruses and bacteria from the substrate. Gamma irradiation with 25 kGy in a source of (60)Co was able to inactivate infectious bovine rinotracheitis (IBR) and bovine viral diarrhea (BVD) viruses in artificially contaminated serum; besides, bacteria were also eliminated. In vitro culture of Babesia bovis (B. bovis) in modified substrate, by adding irradiated serum with (60)Co at 25 kGy was propagated from 24-well culture plates to 225 cm(2) tissue culture flasks, and percentages of parasitized erythrocytes (PPE) from 2.4% to 8.8% were obtained. Infected RBC adapted to Irrad S were transferred to the irradiated substrate in vitro culture system, by using serum irradiated at 25 kGy and RBC from 10 to 70 Gy. The PPE ranged from 3.1 to 11. Culture of Babesia bigemina (B. bigemina) was established with Irrad S (25 kGy); its propagation was achieved in tissue culture flasks reaching PPE from 0.5 to 4.3 with no statistical difference (P > 0.05) when compared to the nonirradiated control culture (1.2-4.8). B. bigemina-infected RBCs were transferred to the modified culture system by adding irradiated serum and RBC (25 kGy and 70 Gy, respectively). PPE obtained in culture flasks were from 0.8 to 4.2. The results indicate that gamma irradiation is a suitable method to inactivate potential viral contamination and eliminate bacteria from bovine serum, to produce a live attenuated vaccine through the in vitro culture.

Comparison of gamma and neutron radiation inactivation of influenza A virus

Radiation inactivation of viral pathogens has potential application in sterilization and in the manufacture of biological reagents, including the production of non-infectious viral antigens. Viral inactivation by gamma radiation has been extensively investigated, but few direct comparisons to other qualities of radiation have been explored. Experiments were designed to examine direct radiation damage by both gamma photons (gamma) and neutrons (n) while minimizing methodological differences. Frozen samples of influenza A X31/H3N2 and PR8/H1N1 were exposed to gamma and n at doses between 0 and 15.6 kGy. Other experimental parameters, including dose-rate, were not varied. Virus titers were determined by tissue culture infectious dose (TCID(50)) and plaque forming unit (PFU) assays. D(10) values, kGy per log reduction, were calculated from these assays. PR8 D(10) values based on PFU assays were approximately 2 and 5 kGy for gamma and n exposures, respectively, and those based on TCID(50) were approximately 6 and 14 kGy. Similar results were obtained for the A/X31 strain. The data demonstrate that gamma was 2-3-fold more effective than n, with a relative biological effectiveness (RBE) range of 0.43-0.65. These neutron results are likely the first reported for a medically relevant virus. PAGE analysis of viral proteins and RNAs failed to show macromolecular damage. D(10) values were found to be similar to a broad summary of previously reported gamma inactivation values for other virus types. The dependence of the magnitudes of D(10) on titer assay in this study suggests that more than one titer method should be used to determine if complete inactivation has occurred.

Reprocessing of thermosensitive materials--efficacy against bacterial spores and viruses

To estimate process parameters for non-thermal methods of antimicrobial inactivation, the half-cycle method is very often used. However, the essential premise of this method of estimation, the independence of microbial inactivation kinetics from the microbial load, seems not to be true. Consequently, the attainment of the sterility assurance level as recommended by the pharmacopoeias by a process which has been validated using the half cycle method is not guaranteed. For the evaluation of such chemo-thermo disinfection processes, the quantification of remaining hepatitis B virus DNA (HBV-DNA) traces on the surface of instruments is a useful tool. An infection can be excluded if a decrease of the HBN3-DNA residues on the instruments below the minimum infective dose can be demonstrated. Using the signal amplification technique to detect HBV-DNA on instruments, the safety of an reprocessing procedures can be improved.