Eosinophils inhibit retroviral transduction of human target cells by a ribonuclease-dependent mechanism.
Human eosinophils contain a number of granule proteins for which specific physiological roles remain unclear. The combined ribonucleolytic and membrane disruptive properties of the eosinophil-derived neurotoxin and eosinophil cationic protein, respectively, suggest the possibility that eosinophils might participate in host defense against enveloped single-stranded RNA viruses. To test this hypothesis, stocks of a replication-defective retrovirus encoding the reporter gene beta-galactosidase were pretreated with isolated human eosinophils, then used to transduce human erythroleukemia (K-562) target cells. Histochemical staining for beta-galactosidase activity was used to detect and quantitate the transduced cells. Co-incubation of retrovirus with eosinophils (0.4 x 10[6]/mL) before target cell transduction resulted in a marked decrease in transduction efficiency corresponding to an approximately 20-fold dilution of viral stock (P < 0.01), an effect that was directly proportional to the concentration of eosinophils, and that was reversed in the presence of ribonuclease inhibitor. Reverse transcriptase-polymerase chain reaction analysis demonstrated loss of the retroviral RNA genome as a result of eosinophil pretreatment, indicating that eosinophils are capable of mediating direct ribonucleolytic destruction of the isolated retroviral particles. Our results demonstrate that eosinophils function as effective anti-retroviral agents in vitro via the actions of their secreted ribonucleases, and suggest that eosinophils may represent an unrecognized arm of host defense against enveloped single-stranded RNA viral pathogens.
Domachowske
J B
JB
Laboratory of Host Defenses, National Institutes of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, USA.
Rosenberg
H F
HF
D004804:Eosinophils / Q000201:enzymology / Q000502:physiology*; D006801:Humans; D007111:Immunity, Cellular; D012190:Retroviridae / Q000254:growth & development*; D012192:Retroviridae Infections / Q000276:immunology*; D012260:Ribonucleases / Q000378:metabolism*; D014161:Transduction, Genetic
D012260:Ribonucleases