Cytolytic T-lymphocyte responses to respiratory syncytial virus: effector cell phenotype and target proteins

Abstract

Cytolytic T-lymphocyte (CTL) activity specific for respiratory syncytial (RS) virus was investigated after intranasal infection of mice with RS virus, after intraperitoneal infection of mice with a recombinant vaccinia virus expressing the F glycoprotein, and after intramuscular vaccination of mice with Formalin-inactivated RS virus or a chimeric glycoprotein, FG, expressed from a recombinant baculovirus. Spleen cell cultures from mice previously infected with live RS virus or the F-protein recombinant vaccinia virus had significant CTL activity after one cycle of in vitro restimulation with RS virus, and lytic activity was derived from a major histocompatibility complex-restricted, Lyt2.2+ (CD8+) subset. CTL activity was not restimulated in spleen cells from mice that received either the Formalin-inactivated RS virus or the purified glycoprotein, FG. The protein target structures for recognition by murine CD8+ CTL were identified by using target cells infected with recombinant vaccinia viruses that individually express seven structural proteins of RS virus. Quantitation of cytolytic activity against cells expressing each target structure suggested that 22K was the major target protein for CD8+ CTL, equivalent to recognition of cells infected with RS virus, followed by intermediate recognition of F or N, slight recognition of P, and no recognition of G, SH, or M. Repeated stimulation of murine CTL with RS virus resulted in outgrowth of CD4+ CTL which, over time, became the exclusive subset in culture. Murine CD4+ CTL were highly cytolytic for RS virus-infected cells, but they did not recognize target cells infected with any of the recombinant vaccinia viruses expressing the seven RS virus structural proteins. Finally, the CTL response in peripheral blood mononuclear cells of adult human volunteers was investigated. The detection of significant levels of RS virus-specific cytolytic activity in these cells was dependent on at least two restimulations with RS virus in vitro, and cytolytic activity was derived primarily from the CD4+ subset.

Pulmonary T cells induced by respiratory syncytial virus are functional and can make an important contribution to long-lived protective immunity

“…To our surprise F‐specific protective T cell immunity waned most rapidly, while both M2 and G specific memory T cells eliminated virus from most mice as late as 100 days after RSV priming. This suggests a different hierarchy of protective pulmonary T cell responses in vivo compared to that defined by restimulation of spleen cells in vitro 29, 40, 41. Interestingly, there were no significant differences in the ability of T cells induced by alocalized pulmonary infection to control virus given via the same route vs. systemically.…”

Picornavirus-specific CD4+ T lymphocytes possessing cytolytic activity confer protection in the absence of prophylactic antibodies

“…We elected to employ A20.J cells as the potential CTL targets on the basis of a number of criteria. A20.J cells are both MHC class I ϩ and II ϩ , thus allowing recognition by CD8 ϩ and CD4 ϩ CTL effector cells (24,34). Demonstrated cytolysis of A20.J targets by vMC 24 -specific bulk-cultured CD4 ϩ T cells would further substantiate an in vivo model in which cardiovirus-infected B cells are killed, suppressing a notable humoral response.…”

Mucosal T cell distribution during infection with respiratory syncytial virus

“…RSVspecific memory cytotoxic T cells have been detected in the spleen of mice after intranasal infection with live virus and intraperitoneal priming with inactivated vi-rus [Bangham et al, 19851. Several epitopes on the virus appear to be T cell stimulating sites Cannon and Bangham, 1989;Nicholas et al, 1990;Openshaw et al, 19901. Little is known about the distribution of T cell subsets and function in the mucosal tissues during primary RSV infection. The only study to date showed that CD8+ cells predominate in bronchoalveolar lavage fluid of mice recovering from RSV infection [Openshaw, 19891. The present studies were undertaken to examine the development and distribution of T cell subsets in the mucosal tissues after primary RSV infection.…”