Immune Response and Partial Protection against Heterologous Foot-and-Mouth Disease Virus Induced by Dendrimer Peptides in Cattle.

Synthetic peptides mimicking protective B- and T-cell epitopes are good candidates for safer, more effective FMD vaccines. Nevertheless, previous studies of immunization with linear peptides showed that they failed to induce solid protection in cattle. Dendrimeric peptides displaying two or four copies of a peptide corresponding to the B-cell epitope VP1 [136-154] of type O FMDV (O/UKG/11/2001) linked through thioether bonds to a single copy of the T-cell epitope 3A [21-35] (termed B2T and B4T, resp.) afforded protection in vaccinated pigs. In this work, we show that dendrimeric peptides B2T and B4T can elicit specific humoral responses in cattle and confer partial protection against the challenge with a heterologous type O virus (O1/Campos/Bra/58). This protective response correlated with the induction of specific T-cells as well as with an anamnestic antibody response upon virus challenge, as shown by the detection of virus-specific antibody-secreting cells (ASC) in lymphoid tissues distal from the inoculation point.

Systemic Foot-and-Mouth Disease Vaccination in Cattle Promotes Specific Antibody-Secreting Cells at the Respiratory Tract and Triggers Local Anamnestic Responses upon Aerosol Infection.

UNLABELLED: Foot-and-mouth disease (FMD) is a highly contagious viral disease affecting biungulate species. Commercial vaccines, formulated with inactivated FMD virus (FMDV), are regularly used worldwide to control the disease. Here, we studied the generation of antibody responses in local lymphoid tissues along the respiratory system in vaccinated and further aerosol-infected cattle. Animals immunized with a high-payload monovalent FMD vaccine developed high titers of neutralizing antibodies at 7 days postvaccination (dpv), reaching a plateau at 29 dpv. FMDV-specific antibody-secreting cells (ASC), predominantly IgM, were evident at 7 dpv in the prescapular lymph node (LN) draining the vaccination site and in distal LN draining the respiratory mucosa, although in lower numbers. At 29 dpv, a significant switch to IgG1 was clear in prescapular LN, while FMDV-specific ASC were detected in all lymphoid tissues draining the respiratory tract, mostly as IgM-secreting cells. None of the animals (n = 10) exhibited FMD symptoms after oronasal challenge at 30 dpv. Three days postinfection, a large increase in ASC numbers and rapid isotype switches to IgG1 were observed, particularly in LN-draining virus replication sites already described. These results indicate for the first time that systemic FMD vaccination in cattle effectively promotes the presence of anti-FMDV ASC in lymphoid tissues associated with the respiratory system. Oronasal infection triggered an immune reaction compatible with a local anamnestic response upon contact with the replicating FMDV, suggesting that FMD vaccination induces the circulation of virus-specific B lymphocytes, including memory B cells that differentiate into ASC soon after contact with the infective virus. IMPORTANCE: Over recent decades, world animal health organizations as well as national sanitary authorities have supported the use of vaccination as an essential component of the official FMD control programs in both endemic and disease-free settings. Very few works studied the local immunity induced by FMD vaccines at the respiratory mucosa, and local responses induced in vaccinated animals after aerosol infection have not been described yet. In this work, we demonstrate for the first time that systemic FMD vaccination (i) induced the early presence of active antigen-specific ASC along the respiratory tract and (ii) prompted a rapid local antibody response in the respiratory mucosa, triggered upon oronasal challenge and congruent with a memory B-cell response. This information may help to understand novel aspects of protective responses induced by current FMD vaccines as well as to provide alternative parameters to establish protection efficiency for new vaccine developments.

Heterogeneity in the Antibody Response to Foot-and-Mouth Disease Primo-vaccinated Calves.

Foot-and-mouth disease (FMD) vaccines are routinely used as effective control tools in large regions worldwide and to limit outbreaks during epidemics. Vaccine-induced protection in cattle has been largely correlated with the FMD virus (FMDV)-specific antibodies. Genetic control of cattle immune adaptive responses has been demonstrated only for peptide antigens derived from FMDV structural proteins. Here, we quantify the heterogeneity in the antibody response of cattle primo-vaccinated against FMD and study its association with the genetic background in Holstein and Jersey sires. A total of 377 FMDV-seronegative calves (122 and 255 calves from 16 and 15 Holstein and Jersey sires, respectively) were included in the study. Samples were taken the day prior to primo-vaccination and 45 days post-vaccination (dpv). Animals received commercial tetravalent FMD single emulsion oil vaccines formulated with inactivated FMDV. Total FMDV-specific antibody responses were studied against three viral strains included in the vaccine, and antibody titres were determined by liquid-phase blocking ELISA. Three linear hierarchical mixed regression models, one for each strain, were formulated to assess the heterogeneity in the immune responses to vaccination. The dependent variables were the antibody titres induced against each FMDV strain at 45 dpv, whereas sire's 'breed' was included as a fixed effect, 'sire' was included as a random effect, and 'farm' was considered as a hierarchical factor to account for lack of independence of within herd measurements. A significant association was found between anti-FMDV antibody responses and sire's breed, with lower immune responses found in the Jersey sires' offspring compared with those from Holstein sires. No significant intrabreed variation was detected. In addition, farm management practices were similar in this study, and results of the serological assays were shown to be repeatable. It therefore seems plausible that differences in the immune response may be expected in the event of a mass vaccination campaigns.

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.

Early adaptive immune responses in the respiratory tract of foot-and-mouth disease virus-infected cattle.

Foot-and-mouth disease (FMD) is a highly contagious viral disease which affects both domestic and wild biungulate species. This acute disease, caused by the FMD virus (FMDV), usually includes an active replication phase in the respiratory tract for up to 72 h postinfection, followed by hematogenous dissemination and vesicular lesions at oral and foot epithelia. The role of the early local adaptive immunity of the host in the outcome of the infection is not well understood. Here we report the kinetics of appearance of FMDV-specific antibody-secreting cells (ASC) in lymphoid organs along the respiratory tract and the spleen in cattle infected by aerosol exposure. While no responses were observed for up to 3 days postinfection (dpi), all animals developed FMDV-ASC in all the lymphoid organs studied at 4 dpi. Tracheobronchial lymph nodes were the most reactive organs at this time, and IgM was the predominant isotype, followed by IgG1. Numbers of FMDV-ASC were further augmented at 5 and 6 dpi, with an increasing prevalence in upper respiratory organs. Systemic antibody responses were slightly delayed compared with the local reaction. Also, IgM was the dominant isotype in serum at 5 dpi, coinciding with a sharp decrease of viral RNA detection in peripheral blood. These results indicate that following aerogenous administration, cattle develop a rapid and vigorous genuine local antibody response throughout the respiratory tract. Time course and isotype profiles indicate the presence of an efficient T cell-independent antibody response which drives the IgM-mediated virus clearance in cattle infected by FMDV aerosol exposure.