Short-lived AIM2 Inflammasome Activation Relates to Chronic MCMV Infection in BALB/c Mice.

Absent in melanoma 2 (AIM2) inflammasome is a crucial link bridging the innate host defense and the subsequent adaptive immunity when activated by exogenous double stranded DNA (dsDNA). Through establishing models of disseminated murine cytomegalovirus (MCMV) infection in BALB/c and C57BL/6 mice, we evaluated dynamic expression of AIM2 inflammasome components and its relationship with pathological damage and viral replication, trying to figure out whether AIM2 inflammasome is related to the chronic mechanism of MCMV. BALB/c and C57BL/6 mice were sacrificed on day 0, 1, 3, 7, 14 and 28 post infection. Expression levels of AIM2, pro-caspase-1, caspase-1 p20, pro-IL1ß and mature IL1ß in primary peritoneal macrophages (PMs) and spleens were detected by Western blotting. Contents of IL18 in the serum were detected by ELISA. Pathological examinations of livers were performed, and mRNA levels of MCMV glycoprotein B (gB) in salivary glands also assessed. Results showed that expression levels of AIM2 in PMs and spleens of C57BL/6 mice increased on day 3, even continued to day 28; caspase-1 p20 and mature IL1ß increased on day 7, 14 and 28; the persistently high expression of IL18 in the serum started on day 1, showing a double peak curve. As for BALB/c mice, expression of AIM2 in PMs increased on day 1 and day 7, while contents of AIM2 in spleens increased on day 1 and day 3; caspase-1 p20 and mature IL1ß merely increased 7 days fter infection. Thereafter, expression levels of AIM2, caspase-1 p20, mature IL1ß and IL18 were limited; the duration of AIM2 inflammasome activation in BALB/c mice was much shorter than that in C57BL/6 mice. The severer pathological damage and more viral replications in BALB/c mice further proved the deficient antiviral immunity to MCMV. In conclusion, the activation of AIM2 inflammasome in BALB/c mice was short-lived, which is quite possibly related to the chronicity of MCMV infection.

Maternal Murine Cytomegalovirus Infection during Pregnancy Up-regulates the Gene Expression of Toll-like Receptor 2 and 4 in Placenta.

Increasing evidence has revealed that maternal cytomegalovirus (CMV) infection may be associated with neurodevelopmental disorders in offspring. Potential relevance between the placental inflammation and CMV-related autism has been reported by clinical observation. Meanwhile, abnormal expression of Toll-like receptor 2 (TLR2) and TLR4 in placenta of patients with chorioamnionitis was observed in multiple studies. IL-6 and IL-10 are two important maternal inflammatory mediators involved in neurodevelopmental disorders. To investigate whether murine CMV (MCMV) infection causes alterations in placental IL-6/10 and TLR2/4 levels, we analyzed the dynamic changes in gene expression of TLR2/4 and IL-6/10 in placentas following acute MCMV infection. Mouse model of acute MCMV infection during pregnancy was created, and pre-pregnant MCMV infected, lipopolysaccharide (LPS)-treated and uninfected mice were used as controls. At E13.5, E14.5 and E18.5, placentas and fetal brains were harvested and mRNA expression levels of placental TLR2/4 and IL-6/10 were analyzed. The results showed that after acute MCMV infection, the expression levels of placental TLR2/4 and IL-6 were elevated at E13.5, accompanied by obvious placental inflammation and reduction of placenta and fetal brain weights. However, LPS 50 µg/kg could decrease the EL-6 expression at E13.5 and E14.5. This suggests that acute MCMV infection during pregnancy could up-regulate the gene expression of TLR2/4 in placental trophoblasts and activate them to produce more proinflammatory cytokine IL-6. High dose of LPS stimulation (50 µg/kg) during pregnancy can lead to down-regulation of IL-6 levels in the late stage. Imbalance of IL-6 expression in placenta might be associated with the neurodevelopmental disorders in progeny.

Identification of proteins that interact with murine cytomegalovirus early protein M112-113 in brain.

BACKGROUND: Murine cytomegalovirus (MCMV) early protein M112-113 is involved in viral DNA replication and believed to play a crucial role in the viral pathogenesis. To investigate the biological function of M112-113 protein in the pathogenesis of the brain disorders caused by cytomegalovirus (CMV), a screening for proteins interacting with M112-113 was performed by a yeast two-hybrid system. METHODS: Bait plasmid pGBKT7-M112-113 was constructed and transformed into AH109 yeast. After confirmation of the expression of MCMV M112-113 in yeast, the bait yeast was mated with a prey yeast containing mouse brain cDNA library plasmid to screen the proteins interacting with M112-113. Interactions between M112-113 and the obtained proteins were verified by yeast two-hybrid assay and chemiluminescent co-immunoprecipitaion. RESULTS: Two proteins interacting with M112-113 were identified, including metastasis-associated 1 (MTA1) and zinc finger, CCHC domain containing 18 (ZCCHC18). M112-113 protein could interact with MTA1 or ZCCHC18 in yeast and mammalian cells. CONCLUSION: The interactions of M112-113 with MTA1 or ZCCHC18 may be related to the pathogenesis of MCMV-associated disease in central nervous system.