Cellular and Humoral Immune Responses to Influenza Vaccine in SOT Recipients After Thymoglobulin or Basiliximab Induction.

Abstract

Antibody responses to influenza vaccine are suboptimal in SOT recipients due to immunosuppression. We assessed both humoral and cellular responses after influenza vaccination in a cohort of SOT recipients receiving induction therapy with either basiliximab (BSX) or thymoglobulin (Thymo). During the 2012-2013 influenza season patients were vaccinated with the trivalent inactivated influenza vaccine. Blood was collected before and 6 weeks after vaccination. A hemagglutination inhibition (HI) assay was used to assess the humoral response. Seroprotection was defined as a titer ≥40 after vaccination. T-cell responses were assessed by IFN-γ Elispot and by flow cytometry with ICS for IFN-γ, IL-2, and TNF-α. 66 patients (61 kidney, 5 heart) were included (BSX n=39, Thymo n=27). Clinical baseline characteristics were similar between groups. Median time from transplant to vaccination was 31 months for BSX and 22 months for Thymo groups (p=0.24). CD4+ T-cell counts were lower in the Thymo than in the BSX group (307 c/mm3 vs. 673 c/mm3, p<0.001). After vaccination, HI geometric mean titers in the BSX vs. Thymo groups were 53 vs. 55 for H1N1 (p=0.92), 145 vs. 162 for H3N2 (p=0.59) and 11 vs. 28 for B strains (p=0.005). Seroprotective levels were achieved in 62% vs. 56% for H1N1 (p=0.79), 100% vs 100% for H3N2 (p=1.0) and 18% vs. 52% for B (p=0.006). By IFN-γ Elispot, the mean SFU/10e6 PBMC were comparable between the two groups (103 BSX vs. 107 Thymo, p=0.90). Increase of ≥2 times in the number of SFU were seen in 44% in the BSX vs. 52% in the Thymo groups (p=0.61). By ICS (n=51), multifunctional T-cell responses producing all 3 cytokines (IFN+, IL2+, TNF+) were not significantly different between the two groups (p=0.34). Similar results were observed in patients vaccinated during the first year post transplant (n=20). No correlation was noted between HI titers and IFN-γ spots (r=-0.092, p=0.46). No influenza or acute rejection occurred within 6 months post vaccination. Despite differences in CD4+ T-cells at baseline, the induction therapy regimen (BSX vs. Thymo) did not affect the global antibody and multifunctional T-cell responses of SOT recipients to influenza vaccine. Surprisingly, antibody responses to influenza B in the Thymo group were higher than those observed in the BSX group.