In this task, you are given a passage which has a question and the context. You have to generate an answer to the question based on the information present in the context.

[Q]: Context: To investigate the role of the anti-cellular immune response in the protection of rhesus macaques against infection with the simian immunodeficiency virus SIVmac. To determine the biological differences between SIV challenge stocks grown either on human T-cell lines or on monkey peripheral blood mononuclear cells (MPBMC).', 'A protective SIVmac split vaccine was administered to rhesus macaques and their anti-, B- and T-cell response monitored. Vaccinees and controls were challenged with SIVmac grown either on human or on monkey cells. The in vivo replication rate of, and the immune response to, the two viruses was compared.', 'Five rhesus macaques were immunized with a total of 2 mg each of purified SIVmac251/32H grown on the human C8166 T-cell line. The antibody and proliferative T-cell responses were evaluated by enzyme-linked immunosorbent assay and T-cell proliferation assay, respectively. Four protected animals and four controls were reboosted and challenged with MPBMC-grown SIVmac251 (SIVmac251/MPBMC). Cell-free virus load was determined by titration of plasma for SIV infectivity on C8166 cells and antigen with a core antigen capture assay.', 'Protection from virus challenge with C8166-grown SIVmac251/32H or SIVmac251/MPBMC did not correlate with anti-cellular antibodies or proliferative T-cell reactivities. Control animals infected with SIVmac251/MPBMC showed high persistent antigenaemia and high plasma virus titres. Both were absent in controls infected with complement C8166-grown SIVmac251/32H. Whereas the latter always seroconverted against the full panel of viral polypeptides, SIVmac251/MPBMC-infected animals showed a drastically decreased antibody response.\Question: Does protection of monkeys by a split vaccine against SIVmac depend upon biological properties of the challenge virus?
[A]: Neither the antibody nor the proliferative T-cell response to SIVmac correlates with protection from virus challenge. In contrast to SIVmac251/32H grown on C8166 cells, the MPBMC-grown challenge virus SIVmac251 appears to belong to the 'rapid-high' phenotype, possibly explaining the lack of protection against this SIV.


[Q]: Context: Objective analysis of surgical skill is necessary. A novel method of assessment using simple error analysis in synthetic models is examined for construct validity.', 'Two examination protocols were devised using synthetic models. These contained either a purpose made error or were representative of good surgical practice. Protocol one contained models of skin closure and minor operations. Protocol two in addition more complex procedures. Face validity was established by the approval of senior surgeons. Junior surgeons were recruited to undertake the assessment. A p value of less than 0.05 was deemed to be significant.', 'Eighty-nine surgeons were recruited. Both protocol one and two were able to discriminate between groups at statistically significant levels.\Question: Is the surgical error examination a novel method for objective technical knowledge assessment?
[A]: Construct validity has been established by showing that error analysis is able to distinguish surgeons with varying levels of experience.


[Q]: Context: To compare optic nerve head (ONH) morphology between eyes with normal-tension glaucoma (NTG) and primary open-angle glaucoma (POAG).', 'Seventy-eight NTG patients and 78 POAG patients matched according to age and axial length were analyzed. Optic nerve head tilt and torsion were identified from cross-sectional images of optical coherence tomography. The degree of horizontal, vertical, and maximum ONH tilt and torsion was compared between NTG and POAG eyes, and additional comparisons were based on the presence of myopia and the location of the visual field defect. Logistic regression analysis was used to determine the factors related to the degree of ONH torsion.', 'Vertical (P = 0.610) and horizontal tilt degree (P = 0.746) did not differ between NTG and POAG eyes. However, torsion degree (P = 0.022) differed significantly between NTG and POAG eyes. Direction of vertical tilt (P = 0.040) and torsion (P < 0.001) showed more prevalent superior tilt and torsion in NTG eyes (21.8% and 33.3%, respectively) compared to POAG eyes (10.3% and 10.3%, respectively). Myopic NTG eyes showed greater torsion degree (P = 0.014) than nonmyopic NTG eyes, which was not observed in the comparison between myopic and nonmyopic POAG eyes. Only NTG eyes showed a significant difference in the degree of maximum tilt (P < 0.001) and torsion (P < 0.001) and the direction of vertical tilt (P < 0.001) and torsion (P = 0.010) by the location of visual field defect. Longer axial length, maximum tilt degree, and diagnosis of NTG were the factors related to the degree of ONH torsion.\Question: Is torsion of the optic nerve head a prominent feature of normal-tension glaucoma?
[A]:
Normal-tension glaucoma eyes had a greater ONH torsion compared to POAG eyes with matched axial length. The direction of the ONH tilt and torsion was related to the location of the visual field defect only in NTG eyes.