Bovine brucellosis control and eradication programme in Chile: vaccine use as a tool within the programme.

In 1975 Chile began the bovine brucellosis control programme in the south central area of the country, where the 92% of the bovine population is located. In 1992 the programme was evaluated and the prevalence showed almost no change for the last nine years, Therefore, a comprehensive Brucellosis eradication programme began. Based on the information gathered by a surveillance system on cattle market and dairy herds from 1999 to 2003 the advances in the process are shown. By applying this programme it has been possible to eradicate brucellosis from the XII Region, and in 2003 was declared brucellosis free with vaccination. In Region XI the project is in its final year and during the last semester no reactor animals have been found. The central south regions began their eradication in 1996. This is the area of the country where the largest bovine population is concentrated, and also the highest brucellosis prevalence. Now the situation has been changing and the trend shows fewer reactors in auction markets and milk plants. The effect of the vaccine (Strain 19 at the beginning and Strain RB 51 from 1997) has been important in impeding the infection of negative herds that are in infected areas. It is also used with success in infected herds, applying "whole herd vaccination" to create a quick herd immunity. This has been important since in Chile there is no paid compensation for reactor animals and the infected animals remain for a variable period in the herd before being destroyed.

Different properties in lymphoblastoid cell lines from patients with Bloom syndrome.

In 3 lymphoblastoid cell lines derived from 3 patients with Bloom syndrome (BS), the baseline frequency of sister chromatid exchanges (SCEs), chromosomal breakage, sensitivity to ethylmethane-sulfonate (EMS), and bromodeoxyuridine (BrdUrd) were examined. The SCE frequency of 2 BS lines (EB-BS-NoKi-2 and EB-BS-AkSak) was about 2 to 2.5 times those of the normal cell lines, while that of another BS line (EB-BS-2KA) was about 10 to 11 times. The net increase in the number of SCEs in EB-BS-NoKi-2 and EB-BS-AkSak lines induced by EMS was similar to that of normal cell lines, but it was high in the BS-2KA line. Sensitivity to BrdUrd was examined using SCE induction at different concentrations of BrdUrd and by cell cycle analysis. EB-BS-NoKi-2 and EB-BS-AkSak lines were no more sensitive than normal cell lines, while the EB-BS-2KA line was more sensitive than controls. High frequency of chromosomal breakage was found only in the EB-BS-2KA line. These results suggest that 2 types of cells exist in the B-lymphoblastoid cells of BS.

Expression of varicella-zoster virus-related antigens in biochemically transformed cells.

L(O)cl 3 and L(K)cl 1 cells, biochemically transformed by varicella-zoster virus (VZV), were labelled with L-[35S]methionine and [32P]orthophosphate. Cell extracts were immunoprecipitated with anti-VZV monkey serum and analysed by SDS-polyacrylamide gel electrophoresis. Four polypeptides of apparent mol. wt. 135000 (135K), 48K, 44K and 35K were detected in the L-[35S]methionine-labelled extracts, and, of these, the 35K band showed marked intensity. However, this band was not detected in extracts from cells infected with a VZV tk- strain (Kanno strain). Also, the 35K polypeptide showed very low intensity when immunoprecipitated from extracts of transformed cells grown in non-selective (NS) medium, i.e. cells that had a very low thymidine kinase (tk) activity. In the case of [32P]orthophosphate-labelled cells, polypeptides of apparent mol. wt. 180K, 81K, 48K, 44K and 37K were obtained. In both instances, the 44K polypeptide was not immunoprecipitated from L(K)cl 1 cell extracts. From our data it is postulated that the expression of the 35K polypeptide is correlated with the VZV-specific tk activity of the cells.

Deoxythymidine kinases in varicella-zoster virus infected and biochemically transformed cells.

Deoxythymidine kinase (TK) activity induced in varicella-zoster virus (VZV)-infected human embryonic fibroblast (HEF) cells was immunologically distinguishable from that in non infected HEF cells and also from that in herpes simplex virus type 1 (HSV-1) infected HEF cells. The TKs in VZV-biochemically transformed cells were immunologically the same as that induced in VZV-infected human cells and immunologically different from that in Ltk- cells or in HSV-biochemically transformed cells. One peak of TK activity with an Rm value of 0.8-0.9, corresponding to mitochondrial TK, was observed on polyacrylamide gel electrophoresis of Ltk- cell extracts. VZV infected Ltk- cells had two peaks of TK activity with Rm values of 0.45-0.5 (peak I) and 0.8-0.9 (peak II). Peak I and II were concluded to be virus-specific TK and mitochondrial TK, respectively. VZV-biochemically transformed cells had a peak of activity with an Rm value of 0.4-0.5, corresponding to peak I in VZV-infected Ltk- cells; that is VZV-specific TK activity. The present study indicates that VZV has a gene coding for its own TK.

Biochemical transformation of mouse cells by varicella-zoster virus.

Mouse L cells lacking the enzyme thymidine kinase (Ltk-) were infected with varicella-zoster virus (VZV). Even though virus did not replicate in Ltk- cells, the presence of virus antigen could be observed by use of an anti-complement immunofluorescent technique at 4 h post-infection and the VZV-specific thymidine kinase could be detected in VZV-infected Ltk- cells. Ltk-cells were converted to a tk+ phenotype (Ltk+) by infection with cell-associated VZV. Clones possessing the ability to grow in selective medium were isolated and cultured successfully for more than 20 passages. One of the clones grew very slowly, but other clones showed almost the same growth rate as that of the parental Ltk- cells. The chromosome analyses of Ltk- cells and transformed cells revealed that the isolated clones were of mouse origin. VZV-specific antigen could be detected in the nuclei of Ltk+ cell clones by an immunofluorescent test, while tk activity was greatly enhanced in extracts prepared from transformed cells and its activity was neutralized by hyperimmune serum against VZV.