Sex differences in the recognition of and innate antiviral responses to Seoul virus in Norway rats.

Among rodents that carry hantaviruses, more males are infected than females. Male rats also have elevated copies of Seoul virus RNA and reduced transcription of immune-related genes in the lungs than females. To further characterize sex differences in antiviral defenses and whether these differences are mediated by gonadal hormones, we examined viral RNA in the lungs, virus shedding in saliva, and antiviral defenses among male and female rats that were intact, gonadectomized neonatally, or gonadectomized in adulthood. Following inoculation with Seoul virus, high amounts viral RNA persisted longer in lungs from intact males than intact females. Removal of the gonads in males reduced the amount of viral RNA to levels comparable with intact females at 40 days post-inoculation (p.i.). Intact males shed more virus in saliva than intact females 15 days p.i.; removal of the gonads during either the neonatal period or in adulthood increased virus shedding in females and decreased virus shedding in males. Induction of pattern recognition receptors (PRRs; Tlr7 and Rig-I), expression of antiviral genes (Myd88, Visa, Jun, Irf7, Ifnbeta, Ifnar1, Jak2, Stat3, and Mx2), and production of Mx protein was elevated in the lungs of intact females compared with intact males. Gonadectomy had more robust effects on the induction of PRRs than on downstream IFNbeta or Mx2 expression. Putative androgen and estrogen response elements are present in the promoters of several of these antiviral genes, suggesting the propensity for sex steroids to directly affect dimorphic antiviral responses against Seoul virus infection.

DNA end sequestration by DNA-dependent protein kinase and end joining of sterically constrained substrates in whole-cell extracts.

Extracts of Xenopus eggs and of cultured human and hamster cells have the capacity to join nonhomologous DNA ends, and all do so with similar specificity. To examine the formation of repair complexes on DNA under conditions of end joining, end-labeled fragments were incubated with the various extracts and then subjected to DNase-I footprinting. Human and Xenopus extracts produced footprints virtually identical to that of purified DNA-dependent protein kinase holoenzyme (Ku plus DNA-PKcs), with protection of the terminal 28 bp. Extracts of hamster cells were more variable, but usually produced a 16-bp footprint, similar to that of Ku alone. In all cases a 28-bp holoenzyme-like footprint was associated with wortmannin-sensitive end joining, minimal 3'-5' exonucleolytic resection, and a predominance of accurate end-joining products. To determine whether the short segments of DNA occupied by Ku and DNA-PK were sufficient to support end joining, Y-shaped substrates were constructed in which only one arm was available for end joining. A Y substrate with a 31-bp arm bearing a partially cohesive 3' overhang was accurately joined by a Xenopus egg extract, whereas a substrate with a 21-bp arm was not. Surprisingly, a human cell extract did not join the Y substrates at all. The results suggest that differences in wortmannin sensitivity and in the distribution of in vitro end-joining products may be attributable to the variations in the levels of DNA-PKcs in the extracts. In addition, end joining in human extracts appears to involve interactions with significantly longer segments of DNA than the approximately 28 bp occupied by DNA-PK.

Social status does not predict responses to Seoul virus infection or reproductive success among male Norway rats.

Trade-offs exist among life history strategies that are used to increase survival and reproduction; such that, males that engage in more competitive behaviors may be more susceptible to infection. Hantaviruses are transmitted horizontally between rodents through the passage of virus in saliva during wounding and male rodents are more likely to be infected with hantaviruses than females. To determine whether a trade-off exists between dominance and susceptibility to Seoul virus infection, male Long Evans rats were group housed (3/cage) with a female rat and aggressive and subordinate behaviors were monitored during a 10 day group housing condition. After behavioral testing, males were individually housed, inoculated with Seoul virus, and blood, saliva, and fecal samples were collected. Dominant males initiated more aggressive encounters than subordinate males. Dominant and subordinate males, however, had similar steroid hormone concentrations, anti-Seoul virus IgG responses, and weight gain over the course of infection. A similar proportion of dominant and subordinate males shed virus in saliva and feces during infection. Using microsatellite DNA markers paternity was assigned to pups derived during the group housing period. In contrast to our initial hypothesis, dominant and subordinate males sired a similar percentage of pups. Taken together, host social status may not predict reproductive success or susceptibility to hantaviruses in rodent reservoir populations.