Vaccine Efficacy in Senescent Mice Challenged with Recombinant SARS-CoV Bearing Epidemic and Zoonotic Spike Variants

BACKGROUND: In 2003, severe acute respiratory syndrome coronavirus (SARS-CoV) was identified as the etiological agent of severe acute respiratory syndrome, a disease characterized by severe pneumonia that sometimes results in death. SARS-CoV is a zoonotic virus that crossed the species barrier, most likely originating from bats or from other species including civets, raccoon dogs, domestic cats, swine, and rodents. A SARS-CoV vaccine should confer long-term protection, especially in vulnerable senescent populations, against both the 2003 epidemic strains and zoonotic strains that may yet emerge from animal reservoirs. We report the comprehensive investigation of SARS vaccine efficacy in young and senescent mice following homologous and heterologous challenge. METHODS AND FINDINGS: Using Venezuelan equine encephalitis virus replicon particles (VRP) expressing the 2003 epidemic Urbani SARS-CoV strain spike (S) glycoprotein (VRP-S) or the nucleocapsid (N) protein from the same strain (VRP-N), we demonstrate that VRP-S, but not VRP-N vaccines provide complete short- and long-term protection against homologous strain challenge in young and senescent mice. To test VRP vaccine efficacy against a heterologous SARS-CoV, we used phylogenetic analyses, synthetic biology, and reverse genetics to construct a chimeric virus (icGDO3-S) encoding a synthetic S glycoprotein gene of the most genetically divergent human strain, GDO3, which clusters among the zoonotic SARS-CoV. icGD03-S replicated efficiently in human airway epithelial cells and in the lungs of young and senescent mice, and was highly resistant to neutralization with antisera directed against the Urbani strain. Although VRP-S vaccines provided complete short-term protection against heterologous icGD03-S challenge in young mice, only limited protection was seen in vaccinated senescent animals. VRP-N vaccines not only failed to protect from homologous or heterologous challenge, but resulted in enhanced immunopathology with eosinophilic infiltrates within the lungs of SARS-CoV–challenged mice. VRP-N–induced pathology presented at day 4, peaked around day 7, and persisted through day 14, and was likely mediated by cellular immune responses. CONCLUSIONS: This study identifies gaps and challenges in vaccine design for controlling future SARS-CoV zoonosis, especially in vulnerable elderly populations. The availability of a SARS-CoV virus bearing heterologous S glycoproteins provides a robust challenge inoculum for evaluating vaccine efficacy against zoonotic strains, the most likely source of future outbreaks

Personal Perspectives on the Relations Between Humans and Nature

In academe we are rarely asked for our personal perspectives. Our colleagues prefer academic perspectives. These should reflect our considered judgment given the accepted methodology and current mainstream academic thinking. A personal perspective implies a release from constraints that is both liberating and scary. At a younger age I might have taken advantage of this freedom by reflecting on the romantic relationship between humans and nature. At my current age, however, I am like the bird who returns to its gilded cage. My personal perspective is the perspective of my discipline. My view of the relationship between humans and nature is very much the anthropocentric utilitarian view of economics

Pollution control under an urban binding minimum wage

In this paper, by using a generalized Harris-Todaro model that incorporates an urban non-polluting sector, and supposes a dual economy inherent in an LDC, we examine the backward incidence of pollution control on some key variables of interest. Given a relatively capital intensive polluting sector, stricter pollution controls may result in a reduction in unemployment, an increase in national income and migration from the agricultural sector. The results from our model differ from that of a previous model that demonstrated a reverse flow of labor to the agricultural sector from stricter pollution controls.