Characterizing the current population structure of potentially invasive species provides a critical context for identifying source populations and for understanding why invasions are successful. Non-native populations inevitably lose genetic diversity during initial colonization events, but subsequent admixture among independently introduced lineages may increase both genetic variation and adaptive potential. Here we characterize the population structure of the gypsy moth (Lymantria dispar Linnaeus), one of the world's most destructive forest pests. Native to Eurasia and recently introduced to North America, the current distribution of gypsy moth includes forests throughout the temperate region of the northern hemisphere. Analyses of microsatellite loci and mitochondrial DNA sequences for 1738 individuals identified four genetic clusters within L. dispar. Three of these clusters correspond to the three named subspecies; North American populations represent a distinct fourth cluster, presumably a consequence of the population bottleneck and allele frequency change that accompanied introduction. We find no evidence that admixture has been an important catalyst of the successful invasion and range expansion in North America. However, we do find evidence of ongoing hybridization between subspecies and increased genetic variation in gypsy moth populations from Eastern Asia, populations that now pose a threat of further human-mediated introductions. Finally, we show that current patterns of variation can be explained in terms of climate and habitat changes during the Pleistocene, a time when temperate forests expanded and contracted. Deeply diverged matrilines in Europe imply that gypsy moths have been there for a long time and are not recent arrivals from Asia.
Two enzyme immunoassays for detection of antibody to rodent coronaviruses were compared. Mouse hepatitis virus (MHV), strain JHM, antigen was in the form of formalin-fixed, infected 17 C1 1 cells. This antigen detected antibody to the homologous strain of MHV as well as to two heterologous MHV strains and a serologically related rat coronavirus, sialodacryodenititis virus. Antibody titers in assays using horseradish peroxidase (HRP)-conjugated or ureiase-conjugated anti-mouse IgG were substantially higher than in an indirect immunofluorescence assay. The ureiase assay was somewhat more sensitive than the HRP assay. MHV-JHM antigen was stable under a variety of storage conditions for at least two months.
Because many strains of mouse hepatitis virus (MHV) infect laboratory mice, no effective vaccine has yet been developed. An alternative approach to control MHV disease is the use of a host cell receptor-targeted ligand. To address the potential usefulness of this approach, a monoclonal antibody directed against the host cell receptor for the coronavirus MHV-A59 was administered to infant mice that were then challenged oronasally with 10(4) intracerebral infant mouse median lethal doses of MHV-A59. Antibody treatment of virus-challenged mice resulted in lower proportions of mice with MHV-A59 in target organs and markedly reduced viral titers in these organs compared with mock-treated infected mice. Some antibody-treated infected mice survived for 7 days after viral challenge, whereas no mock-treated, infected mice survived beyond day 3 after viral inoculation. These results support a receptor-targeted approach to intervention in coronavirus disease.
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