Varicella-zoster Virus-specific Immunity Research Articles

Development of an IFN-γ ELISpot Assay to Assess Varicella-Zoster Virus-specific Cell-mediated Immunity Following Umbilical Cord Blood Transplantation

Varicella zoster virus (VZV) is a significant cause of morbidity and mortality following umbilical cord blood transplantation (UCBT). For this reason, antiherpetic prophylaxis is administrated systematically to pediatric UCBT recipients to prevent complications associated with VZV infection, but there is no strong, evidence based consensus that defines its optimal duration. Because T cell mediated immunity is responsible for the control of VZV infection, assessing the reconstitution of VZV specific T cell responses following UCBT could provide indications as to whether prophylaxis should be maintained or can be discontinued. To this end, a VZV specific gamma interferon (IFN-γ) enzyme-linked immunospot (ELISpot) assay was developed to characterize IFN-γ production by T lymphocytes in response to in vitro stimulation with irradiated live attenuated VZV vaccine. This assay provides a rapid, reproducible and sensitive measurement of VZV specific cell mediated immunity suitable for monitoring the reconstitution of VZV specific immunity in a clinical setting and assessing immune responsiveness to VZV antigens.

Development of an IFN-γ ELISpot assay to assess varicella-zoster virus-specific cell-mediated immunity following umbilical cord blood transplantation.

Varicella zoster virus (VZV) is a significant cause of morbidity and mortality following umbilical cord blood transplantation (UCBT). For this reason, antiherpetic prophylaxis is administrated systematically to pediatric UCBT recipients to prevent complications associated with VZV infection, but there is no strong, evidence based consensus that defines its optimal duration. Because T cell mediated immunity is responsible for the control of VZV infection, assessing the reconstitution of VZV specific T cell responses following UCBT could provide indications as to whether prophylaxis should be maintained or can be discontinued. To this end, a VZV specific gamma interferon (IFN-γ) enzyme-linked immunospot (ELISpot) assay was developed to characterize IFN-γ production by T lymphocytes in response to in vitro stimulation with irradiated live attenuated VZV vaccine. This assay provides a rapid, reproducible and sensitive measurement of VZV specific cell mediated immunity suitable for monitoring the reconstitution of VZV specific immunity in a clinical setting and assessing immune responsiveness to VZV antigens.

Incidence and Risk of Postherpetic Neuralgia after Varicella Zoster Virus Infection in Hematopoietic Cell Transplantation Recipients: Hokkaido Hematology Study Group

To assess the incidence of and risk factors associated with postherpetic neuralgia (PHN) after hematopoietic cell transplantation (HCT) varicella zoster virus (VZV) infection, we conducted a retrospective chart review of 418 consecutive patients who underwent HCT between April 2005 and March 2007. The male/female ratio was 221/197, median age at HCT was 47 years (range: 0-69 years), and autologous/allogeneic/syngeneic HCT ratio was 154/263/1. Seventy-eight patients developed VZV infection after HCT. Sixty-two patients had localized zoster, 11 patients had disseminated zoster (rash like chicken pox), and 4 patients had visceral zoster. All cases were treated with acyclovir (ACV) or valacyclovir (VACV), and there was no VZV infection-related death. Twenty-seven (35%) of the 78 patients with VZV infection suffered PHN after resolution of VZV infection. Multivariate analysis showed that advanced age is the only risk factor in autologous HCT (P = .0075; odds ratio [OR] = 1.14; 95% confidence interval [CI], 0.97-1.33). On the other hand, advanced age (P = .0097; OR = 1.06; 95% CI, 1.01-1.12), male gender (P = .0055; OR = 12.7; 95% CI, 1.61-100.1), and graft-versus-host disease (GVHD) prophylaxis with a tacrolimus-based regimen (P = .0092; OR = 9.56; 95% CI, 1.44-63.3) were associated with increased risk of PHN in allogeneic HCT. This study for the first time clarified the risk of PHN in HCT recipients.

Loss of Varicella Zoster Virus Antibodies Despite Detectable Cell Mediated Immunity after Vaccination

Vaccination of children against VZV has been included in the recommendations of the "permanent committee of vaccination" (STIKO; Ständige Impfkommission of the Robert Koch Institute, Berlin, Germany) in July 2004. Due to this recommendation the medical practitioner and the laboratories will be confronted with the problem of serologic non-responders or loss of humoral immunity more frequently. Here we report the case of a Varicella Zoster Virus (VZV) vaccinee, who lost detectable VZV antibodies although she had a persisting VZV specific CD4 cellular immune response. We compare these parameters to the VZV specific CD4 T cell responses of VZV seronegative and seropositive healthy persons, as well as patients with VZV disease. VZV specific CD4 frequencies of VZV antibody seronegative persons remained on the average below 0.1% (median 0.04%, +/- SD 0.03, range 0.01-0.08%) and were significantly lower than VZV specific frequencies of seropositive healthy persons (median 0.3%, +/- SD 0.24, range 0.06-0.81%; Mann-Whitney U-test p = 0.001). The samples of patients with VZV associated disease showed an even higher median level of VZV specific CD4 cell response than the VZV seropositive healthy persons (median 1.04%, +/- SD 1.06, range 0.51-2.92%, Mann-Whitney U-test p = 0.008). The VZV specific immune response of the health care worker directly after vaccination was comparable to the VZV specific immunity in VZV seropositive healthy adults. Despite serological reconversion 1.5 years later the VZV specific CD4 response still remained measurable and positive. The new general VZV vaccination recommendation for children in Germany will probably increase the number of persons that will be seronegative after vaccination. To gain more information concerning the absence of seroconversion or the loss of immunity, it will be necessary to focus future post-VZV vaccination immunity studies not only on serologic testing but also on the measuring of the cell mediated immunity.