Rubella virus infection dysregulates the pattern of p63 expression

Rubella virus perturbs autophagy

Autophagy is a cellular catabolic process implicated in numerous physiological processes and pathological conditions, including infections. Viruses have evolved different strategies to modulate the autophagic process. Since the effects of rubella virus (RV) on autophagy have not yet been reported, we evaluated the autophagic activity in the Statens Seruminstitut Rabbit Cornea cell line infected with the To336 strain of RV. Our results showed that RV lowered the levels of microtubule-associated protein 1 light chain 3 B-II (LC3B-II) and the autophagy-related gene 12-autophagy-related gene 5 conjugate, inhibited the autophagic flux, suppressed the intracellular redistribution of LC3B, decreased both the average number and the size of autophagosomes per cell and impeded the formation of acidic vesicular organelles. Induction of autophagy by using rapamycin decreased both the viral yields and the apoptotic rates of infected cultures. Besides its cytoprotective effects, autophagy furnishes an important antiviral mechanism, inhibition of which may reorchestrate intracellular environment so as to better serve the unique requirements of RV replication. Together, our observations suggest that RV utilizes a totally different strategy to cope with autophagy than that evolved by other positive-stranded RNA viruses, and there is considerable heterogeneity among the members of the Togaviridae family in terms of their effects on the cellular autophagic cascade.

Analysis of gene expression in fetal and adult cells infected with rubella virus

Congenital infection with rubella virus (RUB) leads to persistent infection and congenital defects and we showed previously that primary human fetal fibroblasts did not undergo apoptosis when infected with RUB, which could promote fetal virus persistence [Adamo, P., Asís, L., Silveyra, P., Cuffini, C., Pedranti, M., Zapata, M., 2004. Rubella virus does not induce apoptosis in primary human embryo fibroblasts cultures: a possible way of viral persistence in congenital infection. Viral Immunol. 17, 87-100]. To extend this observation, gene chip analysis was performed on a line of primary human fetal fibroblasts (10 weeks gestation) and a line of human adult lung fibroblasts (which underwent apoptosis in response to RUB infection) to compare gene expression in infected and uninfected cells. A total of 632 and 516 genes were upregulated or downregulated in the infected fetal and adult cells respectively in comparison to uninfected cells, however only 52 genes were regulated in both cell types. Although the regulated genes were different, across functional gene categories the patterns of gene regulation were similar. In general, regulation of pro- and anti-apoptotic genes following infection appeared to favor apoptosis in the adult cells and lack of apoptosis in the fetal cells, however there was a greater relative expression of anti-apoptotic genes and reduced expression of pro-apoptotic genes in uninfected fetal cells versus uninfected adult cells and thus the lack of apoptosis in fetal cells following RUB infection was also due to the prevailing background of gene expression that is antagonistic to apoptosis. In support of this hypothesis, it was found that of a battery of five chemicals known to induce apoptosis, two induced apoptosis in the adult cells, but not in fetal cells, and two induced apoptosis more rapidly in the adult cells than in fetal cells (the fifth did not induce apoptosis in either). A robust interferon-stimulated gene response was induced following infection of both fetal and adult cells and many of the genes upregulated in both cell types were those involved in establishment of an antiviral state; this is the first demonstration of an interferon response at this early stage of human embryonic development. In both fetal and adult cells, interferon controlled but did not eliminate virus spread and apoptosis was not induced in infected fetal cells in the absence of interferon. In addition to the interferon response, chemokines were induced in both infected fetal and adult cells. Thus, it is possible that fetal damage following congenital RUB infection, which involves cell proliferation and differentiation, could be due to induction of the innate immune response as well as frank virus infection.