Ubiquitin cross-reactive protein is released by the bovine uterus in response to interferon during early pregnancy

A 16-kDa protein has been identified that is secreted by the bovine endometrium in response to conceptus-derived interferon (IFN)-tau during early pregnancy. Because this uterine protein was similar in size to a human ubiquitin cross-reactive protein (hUCRP) that also was regulated by IFN, we suspected that they might be related. To test this hypothesis, uterine flushings, medium from cultured endometrium, and endometrial tissues were examined for the presence of ubiquitin-immunoreactive proteins. Immunoreacting proteins were detected through use of one-dimensional (1D)-PAGE and Western blotting with ubiquitin and hUCRP antiserum (1:500). A 16-kDa protein that cross-reacted with ubiquitin and hUCRP antisera was released by the endometrium and was present in uterine flushings from all Day 18 pregnant females examined (n = 12). The immunoreacting 16-kDa protein was absent in all nonpregnant females examined (n = 23). Regulation of this uterine protein by recombinant type I IFNs (rbIFN-tau, rbIFN-alpha, and roIFN-tau), using 0, 0.5, 5, and 25 nm of each IFN, was evaluated in nonpregnant (Day 12) heifers (n = 5) using 1D-PAGE and Western blotting. Release of the 16-kDa protein into medium was negligible in controls (0 nm IFN). For each IFN, a dose-dependent increase (p < 0.05) in release of the immunoreacting 16-kDa protein was noted. We conclude that the 16-kDa protein that is produced by the endometrium in response to IFN-tau during early pregnancy also shares epitopes with hUCRP and ubiquitin. The 16-kDa protein has been named bovine UCRP.

Absence of transovarial transmission of bluetongue virus in Culicoides variipennis: immunogold labelling of bluetongue virus antigen in developing oocytes from Culicoides variipennis (Coquillett)

1. Culicoides variipennis midges were fed on a blood meal containing bluetongue virus (BTV) serotype 11 (BTV-11) and on four subsequent non-infective blood meals at 4-day intervals. 2. Eggs were collected before each blood-feeding and reared to adults. 3. Progeny from each egg batch were incubated for 14 days (20 degrees C, 40-60% RH) before plaque assay. 4. Oocytes from several parent flies were sectioned for immunoelectron microscopy. 5. Thirty-two percent of the parent females tested by plaque assay were positive for BTV. 6. All 993 progeny flies were negative for BTV. 7. BTV antigen was dense in proteid yolk bodies and in the vitelline membrane of the developing oocytes.

In vitro neutralization of antigenic variants of bluetongue virus is related to in vivo protection

Neutralization resistant variants of bluetongue virus serotype 10 were selected with a neutralizing monoclonal antibody. Three variants were selected for further characterization. One of these variants was completely resistant to neutralization, while the other two variants showed intermediate resistance to neutralization as compared to the parent virus. The completely resistant variant failed to bind the selecting monoclonal antibody as determined by immune precipitation and enzyme linked immunosorbent assay; whereas, the other two variants bound antibody to a similar extent as the parent virus as determined by these tests. The ability of the variants to bind monoclonal antibody correlated with passive protection in the newborn mouse model. These results indicate that the ability of the virus to bind antibody is directly related to in vivo protection and that in vitro neutralization and in vivo protection are also related.

Protein coding assignment for the genome of epizootic haemorrhagic disease virus

Viral genomic RNA was purified from BHK-21 cells infected with epizootic haemorrhagic disease virus and the 10 dsRNA genome segments were isolated by polyacrylamide gel electrophoresis. These genome segments were translated in vitro using the rabbit reticulocyte lysate system and the synthesized proteins were detected by immune precipitation and gel electrophoresis. This allowed the assignment of protein coding to the genome segments and the identification of two additional virus-specified proteins not readily detectable in lysates of virus-infected cells.

Correlation of serotype specificity and protein structure of the five U.S. serotypes of bluetongue virus

The relationship between serotype specificity and protein structure was studied by polyacrylamide gel electrophoresis, peptide mapping and radioimmune precipitation (RIP) of structural and non-structural proteins of the five U.S. serotypes of bluetongue virus (BTV). The surface proteins, VP2 and VP5, showed the most variation in size among the serotypes. Peptide mapping of the proteins showed that VP2 is unique for each of the U.S. serotypes. The nucleocapsid and non-structural proteins showed a high degree of conservation, whereas the other surface protein, VP5, showed intermediate conservation among the serotypes. Monospecific neutralizing antiserum produced in rabbits against each serotype was used in cross-RIP against cytoplasmic extracts prepared from cells infected with each BTV serotype. There were extensive cross-reactions among those proteins which showed a high degree of structural conservation, whereas VP2 was immunoprecipitated best in the homologous RIP system. Thus, a correlation between serotype specificity and protein structure was shown among the five U.S. serotypes of BTV.