Herpes simplex virus type 1 (HSV-1) glycoprotein gC binds complement component C3b, and purified gC inhibits complement activation. Two HSV strains carrying mutations in the gC gene which rendered them unable to bind C3b were compared with wild-type and marker-rescued viruses to evaluate the role of gC on the virion in protecting HSV-1 from complement-mediated neutralization. The gC mutant viruses were markedly susceptible to neutralization by nonimmune human serum, showing up to a 5,000-fold decline in titer after 1 h of incubation with serum. In contrast, wild-type or marker-rescued viruses showed a twofold reduction in titer. Studies with hypogammaglobulinemic and immunoglobulin G-depleted serum supported the observation that neutralization occurred in the absence of antibody. Neutralization of gC mutant strains by nonimmune serum was rapid; their half-life was 2 to 2.5 min, compared with 1 h for wild-type virus. Ethylene glycol-bis(␤aminoethyl ether)-N,N,N,N-tetraacetic acid (EGTA)-treated human serum or C4-deficient guinea pig serum failed to neutralize gC mutant strains, indicating a role for components of the classical complement pathway. gC had little additional effect on neutralization by the combination of antibody plus complement compared with complement alone. The results indicate that the magnitude of the protection offered by gC-1 is larger than previously recognized; that in the absence of gC-1, complement neutralization is rapid and is mediated by components of the classical complement pathway; and that gC mainly protects against antibody-independent complement neutralization, suggesting a probable role for gC early in infection, before antibodies develop.

Risk for late-onset Alzheimer's disease (LOAD) is driven by multiple loci primarily identified by genome-wide association studies, many of which are common variants with minor allele frequencies (MAF)>0.01. To identify additional common and rare LOAD risk variants, we performed a GWAS on 25,170 LOAD subjects and 41,052 cognitively normal controls in 44 datasets from the International Genomics of Alzheimer's Project (IGAP). Existing genotype data were imputed using the dense, high-resolution Haplotype Reference Consortium (HRC) r1.1 reference panel. Stage 1 associations of P<10-5 were meta-analyzed with the European Alzheimer's Disease Biobank (EADB) (n=20,301 cases; 21,839 controls) (stage 2 combined IGAP and EADB). An expanded meta-analysis was performed using a GWAS of parental AD/dementia history in the UK Biobank (UKBB) (n=35,214 cases; 180,791 controls) (stage 3 combined IGAP, EADB, and UKBB). Common variant (MAF≥0.01) associations were identified for 29 loci in stage 2, including novel genome-wide significant associations at TSPAN14 (P=2.33×10-12), SHARPIN (P=1.56×10-9), and ATF5/SIGLEC11 (P=1.03[mult]10-8), and newly significant associations without using AD proxy cases in MTSS1L/IL34 (P=1.80×10-8), APH1B (P=2.10×10-13), and CLNK (P=2.24×10-10). Rare variant (MAF<0.01) associations with genome-wide significance in stage 2 included multiple variants in APOE and TREM2, and a novel association of a rare variant (rs143080277; MAF=0.0054; P=2.69×10-9) in NCK2, further strengthened with the inclusion of UKBB data in stage 3 (P=7.17×10-13). Single-nucleus sequence data shows that NCK2 is highly expressed in amyloid-responsive microglial cells, suggesting a role in LOAD pathology.

BackgroundRecent reports suggest that the rare apolipoprotein E (APOE) Christchurch mutation and ε2 allele protect against Alzheimer’s disease (AD) pathology by reducing the burden of tau pathology. However, the mechanism(s) underlying the ε2 protective effect linking to tau is largely unknown.MethodsThe role of the ε2 allele in Alzheimer’s disease (AD) was investigated a genome-wide association study (GWAS) for AD among 2,120 ε2 carriers from the Alzheimer Disease Genetics Consortium (ADGC), and then prioritized by gene network analysis, differential gene expression analysis at tissue- and cell-levels as well as methylation profiling of CpG sites, in prefrontal cortex tissue from 761 brains of the Religious Orders Study and Memory and Aging Project (ROSMAP) and the Framingham Heart Study (FHS), Boston University Alzheimer’s Disease Center (BUADC). The levels of two catalytic subunit proteins from protein phosphatase 2A (PPP2CA and PPP2CB) were validated in prefrontal cortex area of 193 of the FHS/BUADC brains. The findings from human autopsied brains were further validated by a co-culture experiment of human isogenic APOE induced pluripotent stem cell (iPSC) derived neurons and astrocytes.ResultsOf the significantly associated loci with AD among APOE ε2 carriers (P<10−6), PPP2CB (P=1.1×10−7) was the key node in the APOE ε2-related gene network and contained the most significant CpG site (P=7.3×10−4) located 2,814 base pair upstream of the top-ranked GWAS variant. Among APOE ε3/ε4 subjects, the level of Aβ42 was negatively correlated with protein levels of PPP2CA (P=9.9×10−3) and PPP2CB (P=2.4×10−3), and PPP2CA level was correlated with the level of pTau231 level (P=5.3×10−3). Significant correlations were also observed for PPP2CB with complement 4B (C4B) protein levels (P=3.3×10−7) and PPP2CA with cross reactive protein (CRP) levels (P=6.4×10−4). C1q level was not associated with Aβ42, pTau231, PPP2CB, or C4B levels. We confirmed the significant correlation of PPP2CB expression with pTau231/tTau ratio (P=0.01) and C4A/B (P=2.0×10−4) expression observed in brain tissue in a co-culture experiment of iPSC derived neurons and astrocytes.ConclusionWe demonstrated for the first time a molecular link between a tau phosphatase and the classical complement pathway, especially C4, and AD-related tau pathology.