The IgG1 and IgG2 responses to BRSV vaccination at earlier time points correlated with their next corresponding time points. All animals had declining maternally derived BRSV specific antibodies prior to vaccination and the levels of BRSV specific antibody prior to vaccination were found to be under polygenic control with several QTL detected. Heifers from the same population (n = 195) were subsequently immunised with a 40-mer Foot-and-Mouth Disease Virus peptide (FMDV) in a previous publication. Several (+)-Clopidogrel hydrogen sulfate (Plavix) of these QTL associated with the FMDV traits had overlapping peak positions with QTL in the current study, including the QTL on BTA23 which included the bovine Major Histocompatibility Complex (BoLA), and QTL on BTA9 and BTA24, suggesting that the genes underlying these QTL may control responses to multiple antigens. These results lay the groundwork for future investigations to identify the genes underlying the variation in clearance of maternal antibody and response to vaccination. == Introduction == Infectious disease in livestock is a cause for great concern for both farmers and governments worldwide. Although many FOXO1A countries maintain good animal husbandry, farm management practices and vaccinate their livestock, failure in one or more of these control measures allows infectious disease to prevail[1]. More effective vaccines and the ability to breed for resistance have the potential to provide solutions for the control of both endemic and emerging or re-emerging infectious disease. An understanding of the underlying genetics that control variation in immune responses and infectious disease outcomes may lead to the selection of more resistant animals, as well as identifying new strategies for improving vaccine efficacy. One example where genetic selection for improved resistance has the potential to make an impact is Bovine Respiratory Disease (BRD). Bovine respiratory disease has a complex aetiology caused by many different pathogens including viruses and bacteria[2][4]and affects cattle world-wide, resulting in major welfare problems and economic losses[5]. Both dairy and beef cattle show a wide range of clinical signs related to BRD, including nasal discharge, coughing, fever and decreased appetite when infected. There is (+)-Clopidogrel hydrogen sulfate (Plavix) evidence the genetic makeup of the sponsor contributes to the variance in BRD end result although heritability estimations are low[5][9]. However, this evidence comes from field studies where the causal pathogen(s) were not identified, and thus the heritability of response to particular infections may be underestimated. Bovine Respiratory Syncytial Disease (BRSV) is the most common viral pathogen implicated in outbreaks of BRD[10],[11], with an estimated 70% of calves in the UK becoming seropositive to the disease by 1 year of age[10]. Genetic factors have been shown to play a role in human being susceptibility to the related pathogen, Human being Respiratory Syncytial Disease (HRSV)[12], and as the epidemiology and pathology of HRSV and BRSV are related[11], it is possible that at least a proportion of the genetic variation associated with BRD end result[9],[13], may be related (+)-Clopidogrel hydrogen sulfate (Plavix) to the genetically controlled response to BRSV illness[14]. However, to date, no study of the genetic control of the response to a BRSV illness has been carried out in cattle. Although vaccination is generally considered to be a useful means of controlling certain respiratory diseases in cattle populations, neither natural illness nor vaccination induces long lasting immunity[15]and young calves can be repeatedly infected. From studies of rodent models and humans, it has been suggested that a Th2 biased response may predispose the sponsor to higher levels of pathology, whereas a T helper (Th) 1 biased response may be associated with safety[15]. Indeed, there are no licensed HRSV vaccines for humans, because following vaccination having a formalin-inactivated viral vaccine severe lung pathology was caused by natural illness[15]. Similarly in cattle there is evidence that an IgE Th2 biased response may be associated with higher medical signs in both naturally infected calves and in response to formalin inactivated vaccines[16]. However, both revised live and inactivated viral vaccines are available for BRSV and are considered to be safe for use in cattle[14]. The effectiveness of these vaccines is, however, low, especially in younger animals, with immature immune systems[17]. A further problem is definitely that maternal antibody may also inhibit the induction of safety induced by vaccination[18]. Immunity to BRSV is generally considered to require neutralising antibody, but cellular immunity also takes on an important part. However, cellular immunity may also induce pathology[19]. A fine balance between Th1 versus (+)-Clopidogrel hydrogen sulfate (Plavix) Th2 reactions may be essential in determining the outcome of both BRSV vaccination and illness. In.