Feline leukemia virus (FeLV) is a common naturally occurring gammaretrovirus of domestic cats that is associated with degenerative diseases of the hematopoietic system, immunodeficiency, and neoplasia. Although the majority of cats exposed to FeLV develop a transient infection and recover, a proportion of cats become persistently viremic and many subsequently develop fatal diseases. To define the dominant host immune effector mechanisms responsible for the outcome of infection, we studied the longitudinal changes in FeLVspecific cytotoxic T lymphocytes (CTLs) in a group of naïve cats following oronasal exposure to FeLV. Using 51 Cr release assays to measure ex vivo virus-specific cytotoxicity, the emerging virus-specific CTL response was correlated with modulations in viral burden as assessed by detection of infectious virus, FeLV p27 capsid antigen, and proviral DNA in the blood. High levels of circulating FeLV-specific effector CTLs appeared before virus neutralizing antibodies in cats that recovered from exposure to FeLV. In contrast, persistent viremia was associated with a silencing of virus-specific humoral and cell-mediated host immune effector mechanisms. A single transfer of between 2 ؋ 10 7 and 1 ؋ 10 8 autologous, antigen-activated lymphoblasts was associated with a downmodulation in viral burden in vivo. The results suggest an important role for FeLV-specific CTLs in retroviral immunity and demonstrate the potential to modulate disease outcome by the adoptive transfer of antigen-specific T cells in vivo.
This study illustrates, in the context of vocabulary assessment research, a procedure for analysing a single subject's variability of response times (RTs) in a simple, timed lexical decision task. Following the interpretation developed in Segalowitz and Segalowitz (1993) for RT variability as reflection of the automatic/controlled nature of underlying processing mechanisms, it was possible to draw conclusions about the extent to which second language English word recognition in this subject was subserved by automatic as opposed to controlled processes. The study also examined the development of automaticity in word recognition skill for a small, selected vocabulary as a function of reading experience during a three-week testing period. The general implications of this methodology for assessing vocabulary skill in a single case are discussed.
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