Development of an APC-targeted multivalent E2-based vaccine against Bovine Viral Diarrhea Virus types 1 and 2.

The aim of this study was to develop and test a multivalent subunit vaccine against Bovine Viral Diarrhea Virus (BVDV) based on the E2 virus glycoprotein belonging to genotypes 1a, 1b and 2a, immunopotentiated by targeting these antigens to antigen-presenting cells. The E2 antigens were expressed in insect cells by a baculovirus vector as fusion proteins with a single chain antibody, named APCH I, which recognizes the ß-chain of the MHC Class II antigen. The three chimeric proteins were evaluated for their immunogenicity in a guinea pig model as well as in colostrum-deprived calves. Once the immune response in experimentally vaccinated calves was evaluated, immunized animals were challenged with type 1b or type 2b BVDV in order to study the protection conferred by the experimental vaccine. The recombinant APCH I-tE21a-1b-2a vaccine was immunogenic both in guinea pigs and calves, inducing neutralizing antibodies. After BVDV type 1b and type 2 challenge of vaccinated calves in a proof of concept, the type 1b virus could not be isolated in any animal; meanwhile it was detected in all challenged non-vaccinated control animals. However, the type 2 BVDV was isolated to a lesser extent compared to unvaccinated animals challenged with type 2 BVDV. Clinical signs associated to BVDV, hyperthermia and leukopenia were reduced with respect to controls in all vaccinated calves. Given these results, this multivalent vaccine holds promise for a safe and effective tool to control BVDV in herds.

First finding of genetic and antigenic diversity in 1b-BVDV isolates from Argentina.

Infection with Bovine Viral Diarrhea Viruses (BVDV) in cattle results in a wide range of clinical manifestations, ranging from mild respiratory disease to fetal death and mucosal disease, depending on the virulence of the virus and the immune and reproductive status of the host. In this study 30 Argentinean BVDV isolates were characterized by phylogenetic analysis. The isolates were genotyped based on comparison of the 5' untranslated region (5' UTR) and the E2 gene. In both phylogenetic trees, 76% of the viruses were assigned to BVDV 1b, whereas BVDV 1a, 2a and 2b were also found. Eight of the BVDV 1b isolates were further characterized by cross-neutralization tests using guinea pig antisera and sera from bovines vaccinated with two different commercial vaccines. The results demonstrated the presence of a marked antigenic diversity among Argentinean BVDV isolates and suggest the need to incorporate BVDV 1b isolates in diagnostic strategies.

Dose-dependent immunogenicity of a soluble Neospora caninum tachyzoite-extract vaccine formulated with a soy lecithin/ß-glucan adjuvant in cattle.

Mice immunized with a soluble extract of Neospora caninum tachyzoites (sNcAg) formulated with Providean-AVEC, an aqueous soy-based adjuvant, are fully protected from N. caninum multiplication. Here we evaluated the dose-dependent immunogenicity of this vaccine formulation in cattle. Cattle (N=3 per group) were immunized with two applications (30 days apart) of formulations containing Providean-AVEC and different payloads of sNcAg (100, 50 and 10 µg), that were five to fifty times lower than the only reported study using this same antigen in cattle. Kinetics and magnitude of the vaccine-induced immune responses were dose-dependent. Cattle immunized with 100 µg-sNcAg elicited high-avidity specific antibodies 3 weeks after the primary vaccination while those that received 50 µg of antigen had maximum levels of specific high-avidity antibodies 5 days after the day 30 boost. Vaccination with 10 µg of sNcAg induced comparable antibody responses after 2 weeks post re-vaccination. IgG1 was the predominant isotype in all vaccinated animals. Maximum systemic IFN-γ levels were measured in cattle immunized with 50 and 100 µg-sNcAg (14 ± 2.8 ng/ml). CD4(+)-T cells from vaccinated animals proliferated after sNcAg stimulation in vitro, producing IFN-γ. Recall IFN-γ responses mediated by CD4(+)-T cells were detected up to 140 days post vaccination. Formulations containing Providean-AVEC and 50 µg of sNcAg stimulated broad cellular and humoral immune responses against N. caninum in cattle. The profile and magnitude of the immune response elicited by this vaccine can be modified by the antigen-dose and vaccination schedule. This is the first dose-response study performed in cattle using sNcAg as antigen.

Clinical and reproductive consequences of using BVDV-contaminated semen in artificial insemination in a beef herd in Argentina.

The current report was prompted by an atypical outbreak of mucosal disease that occurred in a beef herd in the southwestern part of Buenos Aires Province, Argentina, where a total of 9/41 (21.9%) yearling bulls died. Blood samples from 73 bulls and 189 heifers were tested for evidence of persistent BVDV infection with Bovine Viral Diarrhea Virus (BVDV). Non-cytopathic BVDV was isolated from 7 (9.6%) 24- to 36-month-old bulls, and 3 (1.6%) 36-month-old heifers. Non-cytopathic BVDV was also detected in the seminal plasma of three of six persistently infected (PI) bulls. Furthermore, a 171 bp genomic fragment of BVDV was consistently detected by nested RT-PCR in one of the two samples of the commercial semen used for artificial insemination, indicating that this semen could be a possible source of infection for the whole herd. To evaluate the possible reproductive consequences of PI heifers and bulls, ovaries and semen were obtained from PI cattle for in vitro assays. The in vitro fertilization of oocytes with semen from PI bulls was associated with decreased cleavage and embryo development rates. Additionally, non-cytopathic BVDV was isolated from the follicular fluid of PI heifers. Genetic typing revealed that all isolates BVDV from the present study had a high percentage of homology and that all of the fragments from the RT-PCR clearly fit with the BVDV 1b cluster. These findings confirm the negative impact that BVDV can have on the reproductive performance of cattle and the importance of applying the proper sanitary controls to minimize the risk of BVDV infection.