Human respiratory syncytial virus (HRSV) is a leading cause of severe lower respiratory tract infection in children under five years of age. IL-17 and Th17 responses are increased in children infected with HRSV and have been implicated in both protective and pathogenic roles during infection. Bovine RSV (BRSV) is genetically closely related to HRSV and is a leading cause of severe respiratory infections in young cattle. While BRSV infection in the calf parallels many aspects of human infection with HRSV, IL-17 and Th17 responses have not been studied in the bovine. Here we demonstrate that calves infected with BRSV express significant levels of IL-17, IL-21 and IL-22; and both CD4 T cells and γδ T cells contribute to this response. In addition to causing significant morbidity from uncomplicated infections, BRSV infection also contributes to the development of bovine respiratory disease complex (BRDC), a leading cause of morbidity in both beef and dairy cattle. BRDC is caused by a primary viral infection, followed by secondary bacterial pneumonia by pathogens such as Mannheimia haemolytica. Here, we demonstrate that in vivo infection with M. haemolytica results in increased expression of IL-17, IL-21 and IL-22. We have also developed an in vitro model of BRDC and show that co-infection of PBMC with BRSV followed by M. haemolytica leads to significantly exacerbated IL-17 production, which is primarily mediated by IL-17-producing γδ T cells. Together, our results demonstrate that calves, like humans, mount a robust IL-17 response during RSV infection; and suggest a previously unrecognized role for IL-17 and γδ T cells in the pathogenesis of BRDC.

Respiratory syncytial virus (RSV) infection is a leading cause of severe acute lower respiratory tract infection in infants and children worldwide. Vitamin A deficiency (VAD) is one of the most prevalent nutrition-related health problems in the world and is a significant risk factor in the development of severe respiratory infections in infants and young children. Bovine RSV (BRSV) is a primary cause of lower respiratory tract disease in young cattle. The calf model of BRSV infection is useful to understand the immune response to human RSV infection. We have previously developed an amphiphilic polyanhydride nanoparticle (NP)-based vaccine (i.e., nanovaccine) encapsulating the fusion and attachment proteins from BRSV (BRSV-NP). Calves receiving a single, intranasal dose of the BRSV-NP vaccine are partially protected from BRSV challenge. Here, we evaluated the impact of VAD on the immune response to the BRSV-NP vaccine and subsequent challenge with BRSV. Our results show that VAD calves are unable to respond to the mucosal BRSV-NP vaccine, are afforded no protection from BRSV challenge and have significant abnormalities in the inflammatory response in the infected lung. We further show that acute BRSV infection negatively impacts serum and liver retinol, rendering even well-nourished individuals susceptible to VAD. Our results support the use of the calf model for elucidating the impact of nutritional status on mucosal immunity and respiratory viral infection in infants and underline the importance of VA in regulating immunity in the respiratory mucosa.

Mycobacterium bovis Bacillus Calmette-Guérin (BCG) is a live attenuated vaccine for use against tuberculosis (TB); however, it is known to reduce childhood mortality from infections other than TB. The unspecific protection induced by BCG vaccination has been associated with the induction of memory-like traits of the innate immune system identified as ‘trained’ immunity. In humans and mouse models, in vitro and in vivo BCG training leads to enhanced production of monocyte-derived proinflammatory cytokines in response to secondary unrelated bacterial and fungal pathogens. While BCG has been studied extensively for its ability to induce innate training in humans and mouse models, BCG’s nonspecific protective effects have not been defined in agricultural species. Here, we show that in vitro BCG training induces a functional change in bovine monocytes, characterized by increased transcription of proinflammatory cytokines upon restimulation with the toll-like receptor agonists. Importantly, in vivo , aerosol BCG vaccination in young calves also induced a ‘trained’ phenotype in circulating peripheral blood mononuclear cells (PBMCs), that lead to a significantly enhanced TLR-induced proinflammatory cytokine response and changes in cellular metabolism compared to PBMCs from unvaccinated control calves. Similar to the long-term training effects of BCG reported in humans, our results suggest that in young calves, the effects of BCG induced innate training can last for at least 3 months in circulating immune populations. Interestingly, however, aerosol BCG vaccination did not ‘train’ the innate immune response at the mucosal level, as alveolar macrophages from aerosol BCG vaccinated calves did not mount an enhanced inflammatory response to secondary stimulation, compared to cells isolated from control calves. Together, our results suggest that, like mice and humans, the innate immune system of calves can be ‘trained’; and that BCG vaccination could be used as an immunomodulatory strategy to reduce disease burden in juvenile food animals before the adaptive immune system has fully matured.

Tuberculosis (TB) remains a leading cause of death from infectious diseases worldwide. Mycobacterium bovis is the causative agent of bovine TB and zoonotic TB infection. gd T cells are known to participate in the immune control of mycobacterial infections. Data in human and nonhuman primates suggest that mycobacterial infection regulates memory/effector phenotype and adaptive immune functions of gd T cells. To date, the impact of M. bovis infection on bovine gd T cells and their effector and memory differentiation remains unknown. In this study, we show that circulating gd T cells from M. bovis-infected cattle can be differentiated based on the expression of CD27, which is indicative of their capacity to respond to virulent M. bovis infection: CD27 + gd T cells proliferated in response to M. bovis Ag and, thus, may comprise the adaptive gd T cell compartment in cattle. We further show that bovine M. bovis-specific gd T cells express surface markers characteristic of central memory T cells (CD45R 2 CD27 + CD62L hi) and that M. bovis-specific CD4 and gd T cells both upregulate the expression of the tissue-homing receptors CXCR3 and CCR5 during infection. Our studies contribute significantly to our understanding of gd T cell differentiation during TB infection and provide important insights into the link between phenotypic and functional subsets in the bovine. Accurate characterization of gd T cell effector and memory-like responses induced during mycobacterial infection will contribute to improved strategies for harnessing the gd T cell response in protection against TB for humans and animals.

Respiratory syncytial virus (RSV) is a significant cause of pediatric respiratory tract infections. It is estimated that two-thirds of infants are infected with RSV during the first year of life and it is one of the leading causes of death in this age group worldwide. Similarly, bovine RSV is a primary viral pathogen in cases of pneumonia in young calves and plays a significant role in bovine respiratory disease complex. Importantly, naturally occurring infection of calves with bovine RSV shares many features in common with human RSV infection. Herein, we update our current understanding of RSV infection in cattle, with particular focus on similarities between the calf and human infection, and the recent reports in which the neonatal calf has been employed for the development and testing of vaccines and therapeutics which may be applied to hRSV infection in humans.