Abstract
The connection between Zika virus (ZIKV) and neurodevelopmental defects is widely recognized, although the mechanisms underlying the infectivity and pathology in primary human glial cells are poorly understood. Here we show that three isolated strains of ZIKV, an African strain MR766 (Uganda) and two closely related Asian strains R103451 (Honduras) and PRVABC59 (Puerto Rico) productively infect primary human astrocytes, although Asian strains showed a higher infectivity rate and increased cell death when compared to the African strain. Inhibition of AXL receptor significantly attenuated viral entry of MR766 and PRVABC59 and to a lesser extend R103451, suggesting an important role of TAM receptors in ZIKV cell entry, irrespective of lineage. Infection by PRVABC59 elicited the highest release of inflammatory molecules, with a 8-fold increase in the release of RANTES, 10-fold increase in secretion of IP-10 secretion and a 12-fold increase in IFN-β secretion when compared to un-infected human astrocytes. Minor changes in the release of several growth factors, endoplasmic reticulum (ER)-stress response factors and the transcription factor, NF-κB were detected with the Asian strains, while significant increases in FOXO6, MAPK10 and JNK were detected with the African strain. Activation of the autophagy pathway was evident with increased expression of the autophagy related proteins Beclin1, LC3B and p62/SQSTM1 with all three strains of ZIKV. Pharmacological inhibition of the autophagy pathway and genetic inhibition of the Beclin1 showed minimal effects on ZIKV replication. The expression of toll-like receptor 3 (TLR3) was significantly increased with all three strains of ZIKV; pharmacological and genetic inhibition of TLR3 caused a decrease in viral titers and in viral-induced inflammatory response in infected astrocytes. We conclude that TLR3 plays a vital role in both ZIKV replication and viral-induced inflammatory responses, irrespective of the strains, while the autophagy protein Beclin1 influences host inflammatory responses.
Highlights
Zika virus (ZIKV), an emerging infectious flavivirus has caused significant public health threat due to its potential association with neurodevelopmental disorders in fetus and neurodegenerative diseases in adult [1, 2]
ZIKV permissiveness in primary human astrocytes was determined by immunofluorescence RT-PCR and western blot (Fig 1A–1C and S1A Fig)
We further validated the kinetics of viral replication in human astrocytes, using plaque assay in the supernatants collected at 24, 48, 72 and 96 hpi from ZIKV-infected astrocytes
Summary
Zika virus (ZIKV), an emerging infectious flavivirus has caused significant public health threat due to its potential association with neurodevelopmental disorders in fetus and neurodegenerative diseases in adult [1, 2]. Increased cases of fetal malformations such as spontaneous abortion, stillbirth, hydrocephaly and microcephaly, and maternal placental insufficiency to miscarriage collectively known as congenital ZIKV syndrome (CZS) were reported as the consequences of ZIKV infection during gestation [5]. Genetic and phylogenetic studies reveal that ZIKV has evolved into 2 distinct lineages: the African lineage including the West African (Nigerian cluster) and the East African (MR766 prototype cluster) and the Asian lineage including Polynesian and Brazilian clusters. Phylogenetic analysis and amino acid composition analysis of spatiotemporally different ZIKV strains isolated from human, mosquito and nonhuman primates have shown significant amino acid differences throughout the viral polyprotein [7]. Comparative studies of different ZIKV strains have shown inconsistent reports in terms of viral lethality, cellular infectivity, antiviral responses and genetic changes [7,8,9,10,11]
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