Macavirus latency-associated protein evades immune detection through regulation of protein synthesis in cis depending upon its glycin/glutamate-rich domain

PLoS Pathog. 2017 Oct 23;13(10):e1006691. doi: 10.1371/journal.ppat.1006691. eCollection 2017 Oct.

Abstract

Alcelaphine herpesvirus 1 (AlHV-1) is a γ-herpesvirus (γ-HV) belonging to the macavirus genus that persistently infects its natural host, the wildebeest, without inducing any clinical sign. However, cross-transmission to other ruminant species causes a deadly lymphoproliferative disease named malignant catarrhal fever (MCF). AlHV-1 ORF73 encodes the latency-associated nuclear antigen (LANA)-homolog protein (aLANA). Recently, aLANA has been shown to be essential for viral persistence in vivo and induction of MCF, suggesting that aLANA shares key properties of other γ-HV genome maintenance proteins. Here we have investigated the evasion of the immune response by aLANA. We found that a glycin/glutamate (GE)-rich repeat domain was sufficient to inhibit in cis the presentation of an epitope linked to aLANA. Although antigen presentation in absence of GE was dependent upon proteasomal degradation of aLANA, a lack of GE did not affect protein turnover. However, protein self-synthesis de novo was downregulated by aLANA GE, a mechanism directly associated with reduced antigen presentation in vitro. Importantly, codon-modification of aLANA GE resulted in increased antigen presentation in vitro and enhanced induction of antigen-specific CD8+ T cell responses in vivo, indicating that mRNA constraints in GE rather than peptidic sequence are responsible for cis-limitation of antigen presentation. Nonetheless, GE-mediated limitation of antigen presentation in cis of aLANA was dispensable during MCF as rabbits developed the disease after virus infection irrespective of the expression of full-length or GE-deficient aLANA. Altogether, we provide evidence that inhibition in cis of protein synthesis through GE is likely involved in long-term immune evasion of AlHV-1 latent persistence in the wildebeest natural host, but dispensable in MCF pathogenesis.

MeSH terms

  • Animals
  • Antigen Presentation / immunology
  • Cattle
  • Gammaherpesvirinae / immunology*
  • Glutamic Acid / immunology
  • Glycine / immunology
  • Immune Evasion / immunology*
  • Malignant Catarrh / immunology*
  • Viral Proteins / chemistry*
  • Viral Proteins / immunology*
  • Virus Latency / immunology

Substances

  • Viral Proteins
  • Glutamic Acid
  • Glycine

Grants and funding

This work was supported by the following grants: FSR-"crédit classique" from the University of Liège (C-13/97), and an Incentive Grant for Scientific Research "MAGIL" from the F.R.S.-FNRS (F.4501.15). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.