In recent years, the emergence of several highly pathogenic zoonotic diseases in humans has led to a renewed emphasis on the interconnectedness of human, animal, and environmental health, otherwise known as One Health. For example, Hendra virus (HeV), a zoonotic paramyxovirus, was discovered in 1994, and since then, infections have occurred in 7 humans, each of whom had a strong epidemiologic link to similarly affected horses. As a consequence of these outbreaks, eradication of bat populations was discussed, despite their crucial environmental roles in pollination and reduction of the insect population. We describe the development and evaluation of a vaccine for horses with the potential for breaking the chain of HeV transmission from bats to horses to humans, thereby protecting horse, human, and environmental health. The HeV vaccine for horses is a key example of a One Health approach to the control of human disease.

Influenza A virus replicates in the respiratory epithelium and induces an inflammatory infiltrate comprised of mononuclear cells and neutrophils. To understand the development of the cell-mediated immune response to influenza and how leukocyte trafficking to sites of inflammation is regulated, we examined the chemokine expression pattern in lung tissue from A/PR/8/34-infected C57BL/6 mice using an RNase protection assay. Monocyte chemoattractant protein 1, macrophage inflammatory protein 1alpha (MIP-1alpha), MIP-1beta, MIP-3alpha, regulated on activation, normal T expressed and secreted (RANTES), MIP-2, and interferon-inducible protein 10 (IP-10) mRNA expression was up-regulated between days 5 and 15 after infection, consistent with a role for these chemokines in leukocyte recruitment to the lung. Low levels of expression were detected for the CC chemokine receptors (CCR)2 and CCR5, whereas CXC chemokine receptor (CXCR)3 was significantly up-regulated by day 10 after infection, coinciding with peak inflammatory cell infiltration in the airways. As RANTES, IP-10, and their receptors were up-regulated during influenza virus infection, we investigated leukocyte recruitment and viral clearance in mice deficient in RANTES or CXCR3, the receptor for IP-10. Leukocyte recruitment and viral replication in influenza-infected RANTES knockout(-/-) mice were similar to that in control mice, showing that RANTES is not essential for the immune response to influenza infection. Similarly, leukocyte recruitment and viral replication in CXCR3-/- mice were identical to control mice, except at day 8 postinfection, where fewer lymphocytes, neutrophils, and eosinophils were detected in the bronchoalveolar lavage of CXCR3-/- mice. These studies suggest that although the chemokines detected may play a role in regulating leukocyte trafficking to the lung during influenza infection, some may be functionally redundant.

Neutrophils traffic to the lungs in large numbers during influenza virus infection. Although the ability of these cells to respond to numerous chemotactic stimuli has been described in other systems, the chemokine receptors mediating recruitment of neutrophils to the lungs during influenza virus infection and the role of this cell type in viral clearance are currently undefined. In the present study, we used CXCR2(/) mice to investigate the role of the chemokine receptor CXCR2 in neutrophil recruitment to the lungs during influenza virus infection and to determine the role of neutrophils in viral clearance. We infected CXCR2(/) or wild-type mice with influenza and assessed the level of inflammation, the cellular composition of the inflammatory infiltrate, and viral titers in the lungs. Absence of CXCR2 ablated neutrophil recruitment to the lungs, but had no effect on peak viral titers or on the kinetics of viral clearance. Thus, it appears that CXCR2 is the major receptor mediating neutrophil trafficking to the lung during influenza virus infection, but that neutrophils do not play an essential role in viral clearance.