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Distinct time effects of vaccination on long-term proliferative and IFN-gamma-producing T cell memory to smallpox in humans.

Combadiere B, Boissonnas A, Carcelain G, Lefranc E, Samri A, Bricaire F, Debre P, Autran B - J. Exp. Med. (2004)

Bottom Line: Only 20% of the vaccinees displayed both immediate IFN-gamma-producing effector-memory responses and proliferative memory responses at 6 d; 52.5% showed only proliferative responses; and 27.5% had no detectable vaccinia-specific responses at all.The number of recalls did not affect the persistence of residual effector-memory T cells.Programmed revaccination boosted both IFN-gamma and proliferative responses within 2 mo of recall, even in vaccinees with previously undetectable residual effector-memory cells.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire d'Immunologie Cellulaire, INSERM U543, Paris, France.

ABSTRACT
Residual immunity to the smallpox virus raises key questions about the persistence of long-term immune memory in the absence of antigen, since vaccination ended in 1980. IFN-gamma-producing effector-memory and proliferative memory T cells were compared in 79 vaccinees 13-25 yr after their last immunization and in unvaccinated individuals. Only 20% of the vaccinees displayed both immediate IFN-gamma-producing effector-memory responses and proliferative memory responses at 6 d; 52.5% showed only proliferative responses; and 27.5% had no detectable vaccinia-specific responses at all. Both responses were mediated by CD4 and CD8 T cells. The vaccinia-specific IFN-gamma-producing cells were composed mainly of CD4Pos CD45RANeg CD11aHi CD27Pos and CCR7Neg T cells. Their frequency was low but could be expanded in vitro within 7 d. Time since first immunization affected their persistence: they vanished 45 yr after priming, but proliferative responses remained detectable. The number of recalls did not affect the persistence of residual effector-memory T cells. Programmed revaccination boosted both IFN-gamma and proliferative responses within 2 mo of recall, even in vaccinees with previously undetectable residual effector-memory cells. Such long-term maintenance of vaccinia-specific immune memory in the absence of smallpox virus modifies our understanding of the mechanism of persistence of long-term memory to poxviruses and challenges vaccination strategies.

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Residual T cell–mediated immune responses to vaccinia virus in smallpox vaccinees. We examined fresh PBMCs from healthy individuals including 79 long-term vaccinees (VAC) (age, 25–68 yr; median, 39) and 10 unvaccinated unexposed volunteers (UNVAC) (age, 19–24 yr; median, 23). (a) Results from IFN-γ ELISpot assays after stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median for responders, 98; range, 53–843 SFCs/million PBMCs) and unvaccinated volunteers (white bar). Results from 3H-thymidine proliferation assays after 7 d stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median proliferation index, 15.5; range, 3–163); unvaccinated volunteers (white bars). (b) Reciprocal distributions of ELISpot and proliferation assays are represented for long-term vaccinees (•) and unvaccinated unexposed individuals (○). Positive responses were defined after analysis of responses obtained in unvaccinated control individuals: proliferative stimulation index ≥3 and IFN-γ–producing cells ≥50 SFCs/million PBMCs after subtraction of the background (shown by dashed lines). The percentage of vaccinees in each quadrant is indicated.
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fig1: Residual T cell–mediated immune responses to vaccinia virus in smallpox vaccinees. We examined fresh PBMCs from healthy individuals including 79 long-term vaccinees (VAC) (age, 25–68 yr; median, 39) and 10 unvaccinated unexposed volunteers (UNVAC) (age, 19–24 yr; median, 23). (a) Results from IFN-γ ELISpot assays after stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median for responders, 98; range, 53–843 SFCs/million PBMCs) and unvaccinated volunteers (white bar). Results from 3H-thymidine proliferation assays after 7 d stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median proliferation index, 15.5; range, 3–163); unvaccinated volunteers (white bars). (b) Reciprocal distributions of ELISpot and proliferation assays are represented for long-term vaccinees (•) and unvaccinated unexposed individuals (○). Positive responses were defined after analysis of responses obtained in unvaccinated control individuals: proliferative stimulation index ≥3 and IFN-γ–producing cells ≥50 SFCs/million PBMCs after subtraction of the background (shown by dashed lines). The percentage of vaccinees in each quadrant is indicated.

Mentions: We first studied the residual cell-mediated immune responses to the vaccinia virus in 89 healthy volunteers: 79 vaccinees, aged 25–68 yr, who had received one to five vaccinations from 1943 through 1989, and 10 unvaccinated unexposed individuals, younger than 25 yr. We stimulated PBMCs in vitro with the live vaccinia virus to activate all donor cells. We chose live virus because the limited number of CD8 epitopes defined are restricted to the HLA-A2 type (23). We counted the number of rapidly mobilized, “immediate” vaccinia-specific effector–memory T cells during this short-term PBMC stimulation in an 18-h IFN-γ ELISpot assay (Fig. 1 a). Because cell frequencies were expected to be low, the specificity and sensitivity of the ELISpot assay were carefully established first (as described in Materials and Methods). The median IFN-γ–producing cell frequency for the 10 unvaccinated donors was 1 SFCs/million PBMCs above background (range, 0–40) (Fig. 1 a). Therefore, positive response to vaccinia was defined as >50 SFCs/million PBMCs over background, and this threshold, commonly used for monitoring T cell responses to new vaccines (24, 25), was used to assess the assay specificity. Only 20% (n = 16) of the vaccinees showed vaccinia-specific effector–memory cells above this threshold (median for responders, 98 SFCs/million PBMCs; range, 53–843). Similarly, we defined positive proliferative responses (Fig. 1 b) in comparison with responses in unvaccinated donors. In contrast to the low percentage of vaccinees with IFN-γ–producing cell responses, vaccinia-specific proliferative responses were detected in vitro after 6 d of virus exposure in the PMBCs of 72.5% of the vaccinees (50 of 69 tested) (Fig. 1 a). The simultaneous evaluation of both functions showed that: (a) when detectable (20% of cases), the rapidly mobilized effector–memory–type lymphocytes producing IFN-γ were always associated with a proliferative memory response to vaccinia; (b) 52.5% of the vaccinees displayed only an expandable pool of memory T cells (without IFN-γ response); and (c) 27.5% displayed neither effector–memory or proliferating memory T cell responses as defined above (Fig. 1 b). Simultaneous analysis of proliferative and IFN-γ–producing cells against vaccinia and smallpox thus showed that rapidly mobilized effector–memory responses and the expandable pool of memory T cells had clearly distinct patterns of long-term maintenance in the absence of antigen.


Distinct time effects of vaccination on long-term proliferative and IFN-gamma-producing T cell memory to smallpox in humans.

Combadiere B, Boissonnas A, Carcelain G, Lefranc E, Samri A, Bricaire F, Debre P, Autran B - J. Exp. Med. (2004)

Residual T cell–mediated immune responses to vaccinia virus in smallpox vaccinees. We examined fresh PBMCs from healthy individuals including 79 long-term vaccinees (VAC) (age, 25–68 yr; median, 39) and 10 unvaccinated unexposed volunteers (UNVAC) (age, 19–24 yr; median, 23). (a) Results from IFN-γ ELISpot assays after stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median for responders, 98; range, 53–843 SFCs/million PBMCs) and unvaccinated volunteers (white bar). Results from 3H-thymidine proliferation assays after 7 d stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median proliferation index, 15.5; range, 3–163); unvaccinated volunteers (white bars). (b) Reciprocal distributions of ELISpot and proliferation assays are represented for long-term vaccinees (•) and unvaccinated unexposed individuals (○). Positive responses were defined after analysis of responses obtained in unvaccinated control individuals: proliferative stimulation index ≥3 and IFN-γ–producing cells ≥50 SFCs/million PBMCs after subtraction of the background (shown by dashed lines). The percentage of vaccinees in each quadrant is indicated.
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Related In: Results  -  Collection

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getmorefigures.php?uid=PMC2211784&req=5

fig1: Residual T cell–mediated immune responses to vaccinia virus in smallpox vaccinees. We examined fresh PBMCs from healthy individuals including 79 long-term vaccinees (VAC) (age, 25–68 yr; median, 39) and 10 unvaccinated unexposed volunteers (UNVAC) (age, 19–24 yr; median, 23). (a) Results from IFN-γ ELISpot assays after stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median for responders, 98; range, 53–843 SFCs/million PBMCs) and unvaccinated volunteers (white bar). Results from 3H-thymidine proliferation assays after 7 d stimulation with the live Copenhagen vaccinia strain are represented as the percentage of healthy responders who are long-term vaccinees (black bars) (median proliferation index, 15.5; range, 3–163); unvaccinated volunteers (white bars). (b) Reciprocal distributions of ELISpot and proliferation assays are represented for long-term vaccinees (•) and unvaccinated unexposed individuals (○). Positive responses were defined after analysis of responses obtained in unvaccinated control individuals: proliferative stimulation index ≥3 and IFN-γ–producing cells ≥50 SFCs/million PBMCs after subtraction of the background (shown by dashed lines). The percentage of vaccinees in each quadrant is indicated.
Mentions: We first studied the residual cell-mediated immune responses to the vaccinia virus in 89 healthy volunteers: 79 vaccinees, aged 25–68 yr, who had received one to five vaccinations from 1943 through 1989, and 10 unvaccinated unexposed individuals, younger than 25 yr. We stimulated PBMCs in vitro with the live vaccinia virus to activate all donor cells. We chose live virus because the limited number of CD8 epitopes defined are restricted to the HLA-A2 type (23). We counted the number of rapidly mobilized, “immediate” vaccinia-specific effector–memory T cells during this short-term PBMC stimulation in an 18-h IFN-γ ELISpot assay (Fig. 1 a). Because cell frequencies were expected to be low, the specificity and sensitivity of the ELISpot assay were carefully established first (as described in Materials and Methods). The median IFN-γ–producing cell frequency for the 10 unvaccinated donors was 1 SFCs/million PBMCs above background (range, 0–40) (Fig. 1 a). Therefore, positive response to vaccinia was defined as >50 SFCs/million PBMCs over background, and this threshold, commonly used for monitoring T cell responses to new vaccines (24, 25), was used to assess the assay specificity. Only 20% (n = 16) of the vaccinees showed vaccinia-specific effector–memory cells above this threshold (median for responders, 98 SFCs/million PBMCs; range, 53–843). Similarly, we defined positive proliferative responses (Fig. 1 b) in comparison with responses in unvaccinated donors. In contrast to the low percentage of vaccinees with IFN-γ–producing cell responses, vaccinia-specific proliferative responses were detected in vitro after 6 d of virus exposure in the PMBCs of 72.5% of the vaccinees (50 of 69 tested) (Fig. 1 a). The simultaneous evaluation of both functions showed that: (a) when detectable (20% of cases), the rapidly mobilized effector–memory–type lymphocytes producing IFN-γ were always associated with a proliferative memory response to vaccinia; (b) 52.5% of the vaccinees displayed only an expandable pool of memory T cells (without IFN-γ response); and (c) 27.5% displayed neither effector–memory or proliferating memory T cell responses as defined above (Fig. 1 b). Simultaneous analysis of proliferative and IFN-γ–producing cells against vaccinia and smallpox thus showed that rapidly mobilized effector–memory responses and the expandable pool of memory T cells had clearly distinct patterns of long-term maintenance in the absence of antigen.

Bottom Line: Only 20% of the vaccinees displayed both immediate IFN-gamma-producing effector-memory responses and proliferative memory responses at 6 d; 52.5% showed only proliferative responses; and 27.5% had no detectable vaccinia-specific responses at all.The number of recalls did not affect the persistence of residual effector-memory T cells.Programmed revaccination boosted both IFN-gamma and proliferative responses within 2 mo of recall, even in vaccinees with previously undetectable residual effector-memory cells.

View Article: PubMed Central - PubMed

Affiliation: Laboratoire d'Immunologie Cellulaire, INSERM U543, Paris, France.

ABSTRACT
Residual immunity to the smallpox virus raises key questions about the persistence of long-term immune memory in the absence of antigen, since vaccination ended in 1980. IFN-gamma-producing effector-memory and proliferative memory T cells were compared in 79 vaccinees 13-25 yr after their last immunization and in unvaccinated individuals. Only 20% of the vaccinees displayed both immediate IFN-gamma-producing effector-memory responses and proliferative memory responses at 6 d; 52.5% showed only proliferative responses; and 27.5% had no detectable vaccinia-specific responses at all. Both responses were mediated by CD4 and CD8 T cells. The vaccinia-specific IFN-gamma-producing cells were composed mainly of CD4Pos CD45RANeg CD11aHi CD27Pos and CCR7Neg T cells. Their frequency was low but could be expanded in vitro within 7 d. Time since first immunization affected their persistence: they vanished 45 yr after priming, but proliferative responses remained detectable. The number of recalls did not affect the persistence of residual effector-memory T cells. Programmed revaccination boosted both IFN-gamma and proliferative responses within 2 mo of recall, even in vaccinees with previously undetectable residual effector-memory cells. Such long-term maintenance of vaccinia-specific immune memory in the absence of smallpox virus modifies our understanding of the mechanism of persistence of long-term memory to poxviruses and challenges vaccination strategies.

Show MeSH
Related in: MedlinePlus