In addition to expression on activated CTLs, NKG2D is also a primary cytotoxicity receptor for NKCs and NKC activity is certainly modulated by viral infection. We chose to specifically focus on the role of NKG2D on antiviral CTLs because the number of NKCs present within the brain during the peak of viral clearance is low compared to CTLs (ca. 10% of CD45 hi cells are NK1.1-positive at 7 dpi; data not shown). However, we certainly cannot rule out a role for NKC-mediated recognition of NKG2D ligands on infected neural cells as part of an early response required for viral clearance. Likewise, NKG2D is expressed by subpopulations of CD4 T cells (Saez-Borderias et al, 2006) , γδ T cells (Dandekar et al, 2005) , and macrophages (Baba et al, 2006) , suggesting that mutliple cells types may be inhibited by CX5 treatment. Regardless, our observations provide evidence that NKG2D-mediated recognition of virus-infected targets by CTLs participates in the clearance of picornaviruses from the CNS. These findings extend previous studies regarding the immunovirology of NKG2D ligand expression which have largely focused on viral evasion of immune surveillance (Lodoen et al, 2003; Lodoen et al, 2004; Vilarinho et al, 2007) and add to the potential repertoire of therapeutic strategies for reducing and controlling CNS picornaviral infections . NKG2D-positive antiviral CD8 + T cells infiltrate the brain during acute infection with TMEV. Brain-infiltrating leukocytes (BILs) were isolated from mice at 3 (A-C) and 7 (D-F) days postinfection (dpi) and analyzed by flow cytometry. The number of CD45 hi CD8 + cells increased between 3 (A) and 7 (D) dpi. Likewise, the number of CD45 hi cells positive for both CD8 and NKG2D increased from 20% at 3 dpi (B) to 76% at 7 dpi (E). Moreover, the intensity of NKG2D surface labeling increased from a mean fluorescence intensity (MFI) of 35 at 3 dpi (shaded histogram in C) to 89 at 7 dpi (shaded histogram in F). The MFI for the isotype control was 4 at 3 dpi (open histogram in C) and 5 at 7 dpi (open histogram in F). BILs were further analyzed for antiviral specificity by costaining with an MHC class I tetramer loaded with the VP2121-130 H-2D b -specific viral peptide (G-I). Of the cells that were both CD8 + and tetramer-positive (box "H" in G), 81% were also NKG2D-positive, with an MFI of 136 (H). In contrast, only 12% of cells that were CD8 + but tetramer-negative (box "I" in G) were also NKG2D-positive, with an MFI of only 18 (I). NKG2D ligands are upregulated in the hippocampus during acute infection with TMEV and interference with NKG2D recognition of these ligands increases viral load in the CNS. qRTPCR analysis of brain mRNA revealed a 10-fold upregulation of Rae1 at 7 dpi (A) as compared to the uninfected brain. Likewise, H60 and Mult1 were also upregulated throughout the acute phase of infection (A). Western blot analysis of hippocampal protein lysates showed the translational upregulation of H60, with peak expression at 7 dpi (B). The 50 kDa band (arrow) upregulated in hippocampus was also present in YAC-1 cell lysates (B). Treatment with the CX5 anti-NKG2D function blocking antibody throughout the acute phase of infection resulted in a 10-fold increase in viral load within the brain at 7 dpi (C). Bar graph shows mean ± 95% confidence interval. Five mice were treated in each group and individual viral titers are shown as black circles in (C). All CX5-treated mice showed increased viral titer. Discovery and Genomic Characterization of a Novel Ovine Partetravirus and a New Genotype of Bovine Partetravirus Partetravirus is a recently described group of animal parvoviruses which include the human partetravirus, bovine partetravirus and porcine partetravirus (previously known as human parvovirus 4, bovine hokovirus and porcine hokovirus respectively). In this report, we describe the discovery and genomic characterization of partetraviruses in bovine and ovine samples from China. These partetraviruses were detected by PCR in 1.8% of bovine liver samples, 66.7% of ovine liver samples and 71.4% of ovine spleen samples. One of the bovine partetraviruses detected in the present samples is phylogenetically distinct from previously reported bovine partetraviruses and likely represents a novel genotype. The ovine partetravirus is a novel partetravirus and phylogenetically most related to the bovine partetraviruses. The genome organization is conserved amongst these viruses, including the presence of a putative transmembrane protein encoded by an overlapping reading frame in ORF2. Results from the present study provide further support to the classification of partetraviruses as a separate genus in Parvovirinae. The parvoviruses are a group of small, non-enveloped animal viruses with a single-stranded DNA genome between 4 and 6 kb in size [1] . At least 2 open reading frames (ORF) are present in the parvovirus genome, with ORF1 encoding the non-structural proteins and ORF2 encoding the viral capsid proteins. Some parvovirus genomes may contain an additional ORF encoding for other proteins, such as the non-structural protein NP1 found in human bocavirus and bovine parvovirus. Under the current International Committee on Taxonomy of Viruses (ICTV) classification system, the Parvoviridae are divided into two subfamilies based on their host range: the Parvovirinae which infect vertebrates, and the Densovirinae which mainly infect insects and other arthropods. The Parvovirinae are further subdivided into 5 genera: the amdoviruses, bocaviruses, dependoviruses, erythroviruses, and the parvoviruses. Novel parvoviruses discovered in recent years, such as the human partetravirus (previously known as human parvovirus 4 or PARV4) [2] , are not included in the current classification system, and will be addressed by the ICTV in an upcoming update. Some human parvoviruses are well-known pathogens associated with a range of diseases in infected patients. Parvovirus B19 (also known as erythrovirus B19) can cause syndromes ranging from erythema infectiosum in children to late intrauterine death in pregnant women. The human bocavirus, a parvovirus discovered only in 2005, was associated with respiratory disease and could be detected in stool of children [3, 4, 5, 6, 7, 8] , although clear assessment of its pathogenicity is confounded by the frequent codetection of other respiratory viruses [9, 10] and its presence in the stool of healthy children. On the other hand, the human partetravirus was initially discovered in patients suffering from acute viral syndrome [2] , but its association with clinical disease has yet to be confirmed despite positive PCR detection in blood products, HIV-infected patients, intravenous drug users, transplant patients and blood donors in different localities [11, 12, 13, 14, 15, 16, 17, 18] .