Intrahost variation and evolutionary dynamics of adenoviruses correlate to neutrophils in infected patients.

With deep sequencing of virus genomes within the hosts, intrahost single nucleotide variations (iSNVs) have been used for analyses of virus genome variation and evolution, which is indicated to correlate with viral pathogenesis and disease severity. Little is known about the features of iSNVs among DNA viruses. We performed the epidemiological and laboratory investigation of one outbreak of adenovirus. The whole genomes of viruses in both original oral swabs and cell-cultured virus isolates were deeply sequenced. We identified 737 iSNVs in the viral genomes sequenced from original samples and 46 viral iSNVs in cell-cultured isolates, with 33 iSNVs shared by original samples and cultured isolates. Meanwhile, we found these 33 iSNVs were shared by different patients, among which, three hot spot areas 6367-6401, 9213-9247, and 10 584-10 606 within the functional genes of the adenovirus genome were found. Notably, the substitution rates of iSNVs were closely correlated with the clinical and immune indicators of the patients. Especially a positive correlation to neutrophils was found, indicating a predictable biomarker of iSNV dynamics. Our findings demonstrated the neutrophil-correlated dynamic evolution features of the iSNVs within adenoviruses, which indicates a virus-host interaction during human infection of a DNA virus.

Mooring Stone-Like Arg114 Pulls Diverse Bulged Peptides: First Insight into African Swine Fever Virus-Derived T Cell Epitopes Presented by Swine Major Histocompatibility Complex Class I.

African swine fever virus (ASFV) is the causative agent of African swine fever (ASF), which is a devastating pig disease threatening the global pork industry. However, currently, no commercial vaccines are available. During the pig immune response, major histocompatibility complex class I (MHC-I) molecules select viral peptide epitopes and present them to host cytotoxic T lymphocytes, thereby playing critical roles in eliminating viral infections. Here, we screened peptides derived from ASFV and determined the molecular basis of ASFV-derived peptides presented by the swine leukocyte antigen 1*0101 (SLA-1*0101). We found that peptide binding in SLA-1*0101 differs from the traditional mammalian binding patterns. Unlike the typical B and F pockets used by the common MHC-I molecule, SLA-1*0101 uses the D and F pockets as major peptide anchor pockets. Furthermore, the conformationally stable Arg114 residue located in the peptide-binding groove (PBG) was highly selective for the peptides. Arg114 draws negatively charged residues at positions P5 to P7 of the peptides, which led to multiple bulged conformations of different peptides binding to SLA-1*0101 and creating diversity for T cell receptor (TCR) docking. Thus, the solid Arg114 residue acts as a "mooring stone" and pulls the peptides into the PBG of SLA-1*0101. Notably, the T cell recognition and activation of p72-derived peptides were verified by SLA-1*0101 tetramer-based flow cytometry in peripheral blood mononuclear cells (PBMCs) of the donor pigs. These results refresh our understanding of MHC-I molecular anchor peptides and provide new insights into vaccine development for the prevention and control of ASF. IMPORTANCE The spread of African swine fever virus (ASFV) has caused enormous losses to the pork industry worldwide. Here, a series of ASFV-derived peptides were identified, which could bind to swine leukocyte antigen 1*0101 (SLA-1*0101), a prevalent SLA allele among Yorkshire pigs. The crystal structure of four ASFV-derived peptides and one foot-and-mouth disease virus (FMDV)-derived peptide complexed with SLA-1*0101 revealed an unusual peptide anchoring mode of SLA-1*0101 with D and F pockets as anchoring pockets. Negatively charged residues are preferred within the middle portion of SLA-1*0101-binding peptides. Notably, we determined an unexpected role of Arg114 of SLA-1*0101 as a "mooring stone" which pulls the peptide anchoring into the PBG in diverse "M"- or "n"-shaped conformation. Furthermore, T cells from donor pigs could activate through the recognition of ASFV-derived peptides. Our study sheds light on the uncommon presentation of ASFV peptides by swine MHC-I and benefits the development of ASF vaccines.