Herpes simplex virus infection of mammalian hosts involves lytic replication at a primary site, such as the cornea, translocation by axonal transport to sensory ganglia and replication, and latent infection at a secondary site, ganglionic neurons. The virus-encoded thymidine kinase, which is a target for antiviral drugs such as acyclovir, is not essential for lytic replication yet evidently is required at the secondary site for replication and some phase of latent infection. To determine the specific stage in viral pathogenesis at which this enzyme is required, we constructed virus deletion mutants that were acyclovir resistant and exhibited no detectable thymidine kinase activity. After corneal inoculation of mice, the mutants replicated to high titers in the eye but were severely impaired for acute replication in trigeminal ganglia and failed to reactivate from ganglia upon cocultivation with permissive cells. Nevertheless, latency-associated transcripts were expressed in neuronal nuclei of ganglia from mutantinfected mice and superinfection of the ganglia with a second virus rescued the latent mutant virus. Thus, contrary to a widely accepted hypothesis, the thymidine kinase-negative mutants established latent infections, implying that neither thymidine kinase activity nor ganglionic replication is necessary for establishment of latency. Rather, thymidine kinase appears to be necessary for reactivation from latency. These results suggest that acyclovir-resistant viruses could establish latent infections in clinical settings and have implications for the use of genetically engineered herpesviruses to deliver foreign genes to neurons.

We have generated and characterized a deletion mutant of herpes simplex virus type-1, dlLAT1.8, which lacks the putative promoter region, transcriptional start site, and 1,015 base pairs of the DNA sequences specifying the latency-associated transcripts (LATs). When tested in a CD-1 mouse ocular model, dlLATI.8 was replication competent in the eye and in ganglia during acute infection but reactivated from explant cultures of ganglia with reduced efficiency (49%) relative to those of wild-type and marker-rescued viruses (94 and 85%, respectively) despite the fact that levels of mutant viral DNA in ganglia during latent infection were comparable to wild-type levels. The neurovirulence of KOS was not significantly altered by the removal of sequences specifying the LATs, as judged by numbers of animals dying on or before 30 days postinfection. Examination of ganglia latently infected with dlLAT1.8 by in situ hybridization revealed no LAT expression. The genotype of reactivated virus was identical to that of input dlLAT1.8 virus as judged by Southern blot analysis. These studies suggest that although the LATs are not essential for the establishment and reactivation of latency in our model, they may play a role in determining the frequency of reactivation of virus from the latent state.

A novel cytokine IL-33, an IL-1 family member, signals via ST2 receptor and promotes Th2 responses, through the activation of NF-κB and MAP kinases. Previous studies reported that single Ig IL-1R-related molecule (SIGIRR)/Toll IL-1R8 acts as negative regulator for TLR-IL-1R-mediated signaling. We now found that SIGIRR formed a complex with ST2 upon IL-33 stimulation and specifically inhibited IL-33/ST2-mediated signaling in cell culture model. Furthermore, IL-33-induced Th2 response was enhanced in SIGIRR-deficient mice compared with that in wild-type control mice, suggesting a negative regulatory role of SIGIRR in IL-33/ST2 signaling in vivo. Similar to ST2, SIGIRR was highly expressed in in vitro polarized Th2 cells, but not Th1 cells. SIGIRR-deficient Th2 cells produce higher levels of Th2 cytokines, including IL-5, IL-4, and IL-13, than that in wild-type cells. Moreover, SIGIRR-deficient mice developed stronger Th2 immune response in OVA-challenged asthma model. Taken together, our results suggest that SIGIRR plays an important role in the regulation of Th2 response in vivo, possibly through its impact on IL-33-ST2-mediated signaling.

Cervical carcinogenesis is a complex problem with papillomavirus widely accepted as a causative agent. Integration of a human papillomavirus (HPV) of the high-risk type into the host cell genome is one of the major contributing factors to cervical malignant transformation. In this study, the correlation of CMV, EBV, HSV-1, HSV-2, HHV-6 and HHV-7 infections with the physical status of the HPV genome in cervical cancer and precancerous cervical lesions was investigated in sixty HPV-16-positive women. Cervical secretion samples were submitted to DNA extraction and analyzed by PCR. HPV-16 DNA was confirmed in genotyping with the reverse hybridization line probe assay. Multiplex PCR with specific primers for the E2/E6 genes was used to assess the viral integration status of HPV-16. Our results show that CMV DNA was more frequently present in samples with mixed forms of HPV-16 than in the episomal form (P < 0.025). Such a correlation was also observed in the case of EBV (P < 0.005). The presence of CMV resulted in a six-fold (OR 6.069; 95% CI 1.91-19.22; P = 0.002), while EBV caused a seven-fold (OR 7.11; 95% CI 1.70-29.67; P = 0.007) increase in the risk of the integrated or mixed HPV-16 genome occurrence. Our data suggest that coinfection with herpesviruses, especially CMV and EBV, may be involved in the integration of the HPV-16 genome and may contribute to the development of cervical cancer.