Antibody responses and protective efficacy of influenza vaccination in patients with chronic HHV-8 infection and classic Kaposi’s sarcoma

Background: Human herpesvirus-8 (HHV-8) is the etiological agent of classic Kaposi’s sarcoma (cKS), a lymphoangioproliferative disease found mainly in older men of Eastern European and Mediterranean origin. B cells represent a major virus reservoir in cKS patients. We recently demonstrated that chronic HHV-8 infection in these patients leads to expansion of the preimmune/natural effector B cell compartment, in particular of transitional and marginal zone-like B cell subpopulations. In this study we investigated whether B cell alterations may alter the response to influenza vaccination, in terms of clinical efficacy, antibody production and safety. Methodology: Adjuvated trivalent influenza vaccine was administered to 59 cKS patients (mean age 72 years, range 49-95) and 57 age- and sex-matched healthy controls. Influenza symptoms and side effects were recorded by daily diary cards supplied to the patients. Blood analysis and measurement of serum antibodies against vaccine antigens (H1N1, H3N2 and B) were performed before, 1 and 3 months post vaccination. Principal findings: The clinical efficacy of vaccination was similar in cKS patients and controls. Seroconversion and seroprotection occured equally in the two groups (range 51-71% in cKS vs 68-73% in controls; and 64-86% vs 77-82%, respectively). A mild increase in HHV-8 viremia was observed in a significant proportion of cKS patients (20%) after vaccination, without concomitant worsening of cKS lesions. The safety of vaccination did not differ between cKS patients and controls. Conclusion: This study demonstrates that influenza vaccination is effective and safe in cKS patients despite their B cell alterations. This is relevant to the fact that annual influenza vaccination may be particularly recommended for cKS patients because of their advanced age and comorbidity