Infectious Entry and Neutralization of Pathogenic JC Polyomaviruses

Summary: Progressive multifocal leukoencephalopathy (PML) is a lethal brain disease caused by uncontrolled replication of JC polyomavirus (JCV). JCV strains recovered from the brains of PML patients carry mutations that prevent the engagement of sialylated glycans, which are thought to serve as receptors for the infectious entry of wild-type JCV. In this report, we show that non-sialylated glycosaminoglycans (GAGs) can serve as alternative attachment receptors for the infectious entry of both wild-type and PML mutant JCV strains. After GAG-mediated attachment, PML mutant strains engage non-sialylated non-GAG co-receptor glycans, such as asialo-GM1. JCV-neutralizing monoclonal antibodies isolated from patients who recovered from PML appear to block infection by preventing the docking of post-attachment co-receptor glycans in an apical pocket of the JCV major capsid protein. Identification of the GAG-dependent/sialylated glycan-independent alternative entry pathway should facilitate the development of infection inhibitors, including recombinant neutralizing antibodies. : Geoghegan et al. show that JC polyomavirus strains that cause brain disease infect cells via a pathway involving a heparin-like attachment receptor and a non-sialylated co-receptor. Candidate therapeutic human monoclonal antibodies neutralize by blocking co-receptor engagement. Keywords: polyomavirus, JC, BK, SV40, progressive multifocal leukoencephalopathy, PML, monoclonal antibody, mAb, virus entry, recepto

Agonist-induced Ca(2+) entry determined by inositol 1,4,5-trisphosphate recognition

It has been considered that Ca(2+) release is the causal trigger for Ca(2+) entry after receptor activation. In DT40 B cells devoid of inositol 1,4,5-trisphosphate receptors (IP(3)R), the lack of Ca(2+) entry in response to receptor activation is attributed to the absence of Ca(2+) release. We reveal in this article that IP(3)R recognition of IP(3) determines agonist-induced Ca(2+) entry (ACE), independent of its Ca(2+) release activity. In DT40 IP(3)R(–/–) cells, endogenous ACE can be rescued with type 1 IP(3)R mutants (both a ΔC-terminal truncation mutant and a D2550A pore mutant), which are defective in Ca(2+) release channel activity. Thus, in response to B cell receptor activation, ACE is restored in an IP(3)R-dependent manner without Ca(2+) store release. Conversely, ACE cannot be rescued with mutant IP(3)Rs lacking IP(3) binding (both the Δ90–110 and R265Q IP(3)-binding site mutants). We conclude that an IP(3)-dependent conformational change in the IP(3)R, not endoplasmic reticulum Ca(2+) pool release, triggers ACE