TASK DEFINITION: In this task, you're given a paragraph from the research paper and your task is to generate a suitable title for the research paper based on the given paper. Under 100 words is a good title length.
PROBLEM: The presentation of viral peptide epitopes to host cytotoxic T lymphocytes (CTLs) is crucial for adaptive cellular immunity to clear the virus infection, especially for some chronic viral infections. Indeed, hosts have developed effective strategies to achieve this goal. The ideal scenario would be that the peptide epitopes stimulate a broad spectrum of CTL responses with diversified T-cell receptor (TCR) usage (the TCR repertoire). It is believed that a diversified TCR repertoire requires a "featured" peptide to be presented by the host major histocompatibility complex (MHC). A featured peptide can be processed and presented in a number of ways. Here, using the X-ray diffraction method, the crystal structures of an antigenic peptide derived from rinderpest virus presented by bovine MHC class I N*01801 (BoLA-A11) have been solved, and two distinct conformations of the presented peptide are clearly displayed. A detailed analysis of the structure and comparative sequences revealed that the polymorphic amino acid isoleucine 73 (Ile73) is extremely flexible, allowing the MHC groove to adopt different conformations to accommodate the rinderpest virus peptide. This makes the peptide more featured by exposing different amino acids for T-cell recognition. The crystal structures also demonstrated that the N*01801 molecule has an unusually large A pocket, resulting in the special conformation of the P1 residue at the N terminus of the peptide. We propose that this strategy of host peptide presentation might be beneficial for creating a diversified TCR repertoire, which is important for a moreeffective CTL response. Viral diseases and other infections caused by intracellular pathogens of cattle result in large global economic losses every year. In the past several decades, rinderpest virus (RPV) (23, 40), foot-and-mouth disease virus (FMDV) (7), and bovine tuberculosis infection (62) have brought disastrous consequences, including social panic and even a threat to human health. Nearly 6 decades ago, most countries were committed to developing more-effective vaccines (46), and remarkable achievements were made in controlling threatening bovine viral infectious diseases and other zoonoses (23, 46). In the 1960s, British virologist Walter Plowright developed a live attenuated vaccine against rinderpest virus, which was widely used in rinderpest eradication efforts (40). However, it still remains extremely challenging for humans to completely eradicate a virus. The questions of how the bovine attenuated vaccine induces immune responses and how the viral peptides are presented and recognized by host immune molecules are still largely unanswered. Therefore, studies on bovine immunity against the rinderpest virus may provide clues for our battle against other viral infections. Generally speaking, effective vaccines have common characteristics: they are rich in T-cell and B-cell epitopes and can induce the immune system to generate protective immune responses (3, 36, 54) . During this process, major histocompatibility complex (MHC) molecules play a pivotal role in the host. MHC class I (MHC I) molecules form a heterotrimer complex composed of the heavy chain of MHC, the antigenic peptide, and 2 -microglobulin ( 2 m). Generally, MHC I loads endogenous peptides, including the virus-derived peptides. Briefly, at the initial stage of virus infection, antigenic proteins are processed in a proteasome-dependent or -independent manner. The resultant short peptides are then transported to the endoplasmic reticulum and are loaded onto the peptidebinding grooves of MHC I molecules. Consequently, the peptide-loading MHC I complexes are translocated to the cell surface and are recognized by cytotoxic T lymphocytes (CTLs) with specific T-cell receptors (TCRs) (49, 63). This immune recognition induces an MHC-restricted CD8 T-cell response that is characterized by the killing and elimination of the infected cells by effector T cells. The majority of virus-derived peptides are processed and presented through this pathway

SOLUTION: Two Distinct Conformations of a Rinderpest Virus Epitope Presented by Bovine Major Histocompatibility Complex Class I N*01801: a Host Strategy To Present Featured Peptides

PROBLEM: The performance of a recently developed real-time PCR system, the ExiStation HBV diagnostic system, for quantitation of hepatitis B virus (HBV) in human blood was evaluated. The detection limit, reproducibility, cross-reactivity, and interference were evaluated as measures of analytical performance. For the comparison study, 100 HBV-positive blood samples and 100 HBV-negative samples from Korean Blood Bank Serum were used, and the results of the ExiStation HBV system showed good correlation with those obtained using the Cobas TaqMan (r 2 = 0.9931) and Abbott real-time PCR systems (r 2 = 0.9894). The lower limit of detection was measured as 9.55 IU/mL using WHO standards and the dynamic range was linear from 6.68 to 6.68 10 9 IU/mL using cloned plasmids. The within-run coefficient of variation (CV) was 9.4%, 2.1%, and 1.1%, and the total CV was 11.8%, 3.6%, and 1.7% at a concentration of 1.92 log 10 IU/mL, 3.88 log 10 IU/mL, and 6.84 log 10 IU/mL, respectively. No cross-reactivity or interference was detected. The ExiStation HBV diagnostic system showed satisfactory analytical sensitivity, excellent reproducibility, no cross-reactivity, no interference, and high agreement with the Cobas TaqMan and Abbott real-time PCR systems, and is therefore a useful tool for the detection and monitoring of HBV infection.

SOLUTION: Performance evaluation of ExiStation HBV diagnostic system for hepatitis B virus DNA quantitation

PROBLEM: Porcine reproductive and respiratory syndrome virus (PRRSV) is an enveloped, positive-sense singlestranded RNA virus belonging to the Arteriviridae family. Arteriviruses and coronaviruses are grouped together in the order Nidovirales, based on similarities in genome organization and expression strategy. Over the past decade, crystal structures of several viral proteins, electron microscopic studies of the virion, as well as biochemical and in vivo studies on protein-protein interactions have led to a greatly increased understanding of PRRSV structural biology. At this point, crystal structures are available for the viral proteases NSP1, NSP1 and NSP4 and the nucleocapsid protein, N. The NSP1 and NSP1 structures have revealed additional non-protease domains that may be involved in modulation of host functions. The N protein forms a dimer with a novel fold so far only seen in PRRSV and other nidoviruses. Cryo-electron tomographic studies have shown the three-dimensional organization of the PRRSV virion and suggest that the viral nucleocapsid has an asymmetric, linear arrangement, rather than the isometric core previously described. Together, these studies have revealed a closer structural relationship between arteri-and coronaviruses than previously anticipated.

SOLUTION:
The structural biology of PRRSV