Host Genetic Variation Has a Profound Impact on Immune Responses Mediating Control of Viral Load in Chronic Gammaherpesvirus Infection

Chronic infection with the gammaherpesvirus EBV is a risk factor for several autoimmune diseases, and poor control of EBV viral load and enhanced anti-EBV responses elevate this risk further. However, the role of host genetic variation in the regulation of immune responses to chronic gammaherpesvirus infection and control of viral replication remains unclear. To address this question, we infected C57BL/6J (B6) and genetically divergent wild-derived inbred PWD/PhJ (PWD) mice with murine gammaherpesvirus-68 (MHV-68), a gammaherpesvirus similar to EBV, and determined the effect of latent gammaherpesvirus infection on the CD4 T cell transcriptome. Chronic MHV-68 infection of B6 mice resulted in a dramatic upregulation of genes characteristic of a cytotoxic Th cell phenotype, including Gzmb, Cx3cr1, Klrg1, and Nkg7, a response that was highly muted in PWD mice. Flow cytometric analyses revealed an expansion of CX3CR1+KLRG1+ cytotoxic Th cell-like cells in B6 but not PWD mice. Analysis of MHV-68 replication demonstrated that in spite of muted adaptive responses, PWD mice had superior control of viral load in lymphoid tissue, despite an absence of a defect in MHV-68 in vitro replication in PWD macrophages. Depletion of NK cells in PWD mice, but not B6 mice, resulted in elevated viral load, suggesting genotype-dependent NK cell involvement in MHV-68 control. Taken together, our findings demonstrate that host genetic variation can regulate control of gammaherpesvirus replication through disparate immunological mechanisms, resulting in divergent long-term immunological sequelae during chronic infection.

The heat shock response shows plasticity in embryonic lake whitefish (Coregonus clupeaformis) exposed to repeated thermal stress

We examined the impact of repeated thermal stress on the heat shock response (HSR) of thermally sensitive lake whitefish (Coregonus clupeaformis) embryos. Our treatments were designed to mimic temperature fluctuations in the vicinity of industrial thermal effluents. Embryos were either maintained at control temperatures (3 ^oC) or exposed to a repeated thermal stress (TS) of 3 or 6 ^oC above control temperature every 3 or 6 days throughout embryonic development. At 82 days post-fertilisation, repeated TS treatments were stopped and embryos received either a high level TS of 12, 15, or 18 ^oC above ambient temperature for 1 or 4 h, or no additional TS. These treatments were carried out after a 6 h recovery from the last repeated TS. Embryos in the no repeated TS group responded, as expected, with increases in hsp70 mRNA in response to 12, 15 and 18 ^oC high-level TS. However, exposure to repeated TS of 3 or 6 ⁰C every 6 days also resulted in a significant upregulation of hsp70 mRNA relative to the controls. Importantly, these repeated TS events and the associated elevations in hsp70 attenuated the upregulation of hsp70 in response to a 1 h, high-level TS of 12 ^oC above ambient, but not to either longer (4 h) or higher (15 or 18 ^oC) TS events. Conversely, hsp90α mRNA levels were not consistently elevated in the no repeated TS groups exposed to high-level TS. In some instances, hsp90α levels appeared to decrease in embryos exposed to repeated TS followed by a high-level TS. The observed attenuation of the HSR in lake whitefish embryos demonstrates that embryos of this species have plasticity in their HSR and repeated TS may protect against high-level TS, but the response differs based on repeated TS treatment, high-level TS temperature and duration, and the gene of interest.

Differential Enhancement of Neutrophil Phagocytosis by Anti-Bactericidal/Permeability-Increasing Protein Antibodies

Bactericidal/permeability-increasing protein (BPI) plays a major role in innate immunity through the ability of the N-terminal domain (NTD) to bind LPS, mediate cytotoxicity, and block LPS-induced inflammation. The C-terminal domain mediates phagocytosis of bacteria bound to the NTD. These two domains are linked by a surface-exposed loop at amino acids 231-249 for human BPI, known as the "hinge region." Autoantibodies to human BPI are prevalent in many chronic lung diseases; their presence is strongly correlated with Pseudomonas aeruginosa and with worse lung function in patients with cystic fibrosis and bronchiectasis. Although prior literature has reported BPI neutralization effect with autoantibodies targeting either NTD or C-terminal domain, the functionality of BPI Ab to the hinge region has never been investigated. Here, we report that Ab responses to the BPI hinge region mediate a remarkably selective potentiation of BPI-dependent phagocytosis of P. aeruginosa with both human and murine neutrophils in vitro and in vivo. These findings indicate that autoantibodies to the BPI hinge region might enhance bacterial clearance.

Analysis of CRISPR/Cas9 Guide RNA Efficiency and Specificity Against Genetically Diverse HIV-1 Isolates

Gene editing approaches using CRISPR/Cas9 are being developed as a means for targeting the integrated HIV-1 provirus. Enthusiasm for the use of gene editing as an anti-HIV-1 therapeutic has been tempered by concerns about the specificity and efficacy of this approach. Guide RNAs (gRNAs) that target conserved sequences across a wide range of genetically diverse HIV-1 isolates will have greater clinical utility. However, on-target efficacy should be considered in the context of off-target cleavage events as these may comprise an essential safety parameter for CRISPR-based therapeutics. We analyzed a panel of Streptococcus pyogenes Cas9 (SpCas9) gRNAs directed to the 5' and 3' long terminal repeat (LTR) regions of HIV-1. We used in vitro cleavage assays with genetically diverse HIV-1 LTR sequences to determine gRNA activity across HIV-1 clades. Lipid-based transfection of gRNA/Cas9 ribonucleoproteins was used to assess targeting of the integrated HIV-1 proviral sequence in cells (in vivo). For both the in vitro and in vivo experiments, we observed increased efficiency of sequence disruption through the simultaneous use of two distinct gRNAs. Next, CIRCLE-Seq was utilized to identify off-target cleavage events using genomic DNA from cells with integrated HIV-1 proviral DNA. We identified a gRNA targeting the U3 region of the LTR (termed SpCas9-127HBX2) with broad cleavage efficiency against sequences from genetically diverse HIV-1 strains. Based on these results, we propose a workflow for identification and development of anti-HIV CRISPR therapeutics.