INTRODUCTION
Hepatitis A characteristically is an acute, self-limiting illness associated with fever, malaise, jaundice, anorexia, and nausea, but some patients can develop fulminant hepatitis with fatality rates around 60–80% or extrahepatic complications [Reference Koff1]. Fulminant hepatitis is rare but is more common in people with underlying liver disease [Reference Koff1–Reference Debray3]. There are differences in hepatitis A virus (HAV) prevalence and outcome, particularly between developed and developing countries. In Turkey anti-HAV prevalence in different age groups and regions ranges from 7·8% to 98·0% [Reference Erdoğan4–Reference Yapicioglu8]. The reported rates of HAV seropositivity were 19·9–87·4% in children [Reference Erdoğan4–Reference Yapicioglu8] and 71·3% in people aged <30 years [Reference Kanra, Tezcan and Badur5]. There is a shift in the age of hepatitis A seropositivity from childhood to adulthood in intermediate endemic regions of world like Turkey, and the severity of the disease increases progressively with age [Reference Erdoğan4, Reference Tosun9]. While HAV infection during childhood is often asymptomatic, occurrence during adulthood is symptomatic and associated with a mortality rate of up to 2% in industrialized countries in patients aged >40 years [Reference Koff1]. However, hepatitis A was the most commonly detected cause in cases with fulminant hepatic failure in Turkish children [Reference Aydoğdu2, Reference Debray3]. HAV infection also can cause haematological complications [Reference Maiga10]. Wünschmann et al. reported a maturational defect of human peripheral blood monocytes upon challenge with HAV in vitro, which might contribute to functional abnormalities of the bone marrow stroma and which may lead to mild perturbations of immunoregulation and haematopoiesis observed during acute HAV infections in vivo [Reference Wünschmann, Becker and Vallbracht11]. In order to protect haematopoietic stem cell transplant (HSCT) recipients against HAV infection it is important to determine the loss of HAV antibodies, especially in endemic countries. The pre-conditioning regimen, viral infections, graft vs. host disease (GVHD), and veno-occlusive disease are responsible for the unwanted effects of HSCT on liver. Hepatic complications including viral infections can be observed as causes of morbidity and mortality in HSCT recipients [Reference Kupeli12]. Because of the above-mentioned reasons, even though complications or fulminant course of HAV infection in HSCT recipients has not been reported, patients should be protected against HAV infection.
Hepatitis A vaccine is inactivated. According to the Infectious Diseases Working Party of the European Group for HSCT, routine administration of hepatitis A vaccine is not recommended but can be considered at ⩾12 months after HSCT for people who have chronic liver disease or people from areas with endemic infection or outbreaks of hepatitis A [Reference Ljungman13]. In this study, we aimed to evaluate the duration of HAV seropositivity in HSCT recipients and affecting factors in an intermediate endemic region, Turkey.
MATERIALS AND METHODS
Patients
HSCT patients in Hacettepe University Faculty of Medicine, Adult and Paediatric HSCT units from 2000 to 2007 were evaluated. Patients who were aged <1 year, and cases with severe combined immunodeficiency (SCID) receiving intravenous immunoglobulin (IVIG) regularly prior to HSCT were excluded from the study. In total, 80 patients whose pre- and post-transplant hepatitis A serology was known and who were not vaccinated with HAV vaccine and who had a disease-free survival of at least 1 year after HSCT were included. The prevalence of HAV seropositivity was 85% (n=68) before HSCT. Seropositivity was 76·9% in transplant cases aged <18 years and 100% in transplant cases aged ⩾18 years. Of these 68 seropositive patients, six had autologous HSCT and these patients were seropositive during the study period; median follow-up of the six autologous patients was 34·5 months (range 28–56 months). Therefore, the remaining 62 patients with allogeneic-related HSCT were included in this study. Stem cell source was bone marrow in 61 patients and cord blood in one patient. From these patients, a total of 189 samples had been tested for HAV seropositivity and median number of samples was three (range 1–6) per patient after HSCT.
Patients' files were evaluated retrospectively in terms of age at transplantation, gender, underlying diseases, type of HSCT, donor age, conditioning regimen, history or presence of GVHD, and duration of IVIG, immunosuppressive medications and HAV seropositivity.
Laboratory method
HAV IgG antibodies were analysed using a qualitative commercially available chemiluminescent microparticle immunoassay (CMIA) (Architect® HAVAb-IgG, Abbott Diagnostic Division, Germany) and expressed as positive or negative at the hospital of Hacettepe University Laboratory of Biochemistry.
Statistical analysis
All analyses were performed with SPSS for Windows (SPSS Inc., USA). The cumulative duration of HAV seropositivity was calculated by the Kaplan–Meier method and the differences on the duration of HAV seropositivity were analysed by a log-rank test. Estimated means and standard errors were calculated. Cox regression models [backward-stepwise (likelihood ratio)] were performed to assess the impact of factors including age at the time of transplantation (<18 vs. ⩾18 years), gender, donor age (<18 vs. ⩾18 years), conditioning regimen (myeloablative, reduced), history or presence of GVHD, duration of IVIG (<4 vs. ⩾4 months) and administration of immunosuppressive medications ⩾12 months after HSCT on the duration of HAV seropositivity. Hazard ratios with 95% confidence intervals (CI) were used to quantify the strength of these associations. P values <0·05 were considered significant [Reference Dawson and Trapp14].
RESULTS
The median age of the seropositive patients with allogeneic HSCT (n=62) was 17 years (range 2·5–56·0) and 67·7% of the patients were male. The most common underlying diseases were haematological disorders (Table 1). After Kaplan–Meier analysis, estimated mean time to persistence of HAV antibodies was 48·6 months after transplantation (Table 2). The percentage of seropositive and seronegative patients during follow-up is shown in Figure 1. Four (6·5%) patients were still seropositive 54 months after HSCT. The factors associated with persistence of HAV antibodies were older age (⩾18 years) at transplantation and older (⩾18 years) donor. Gender, conditioning regimen, duration of IVIG and immunosuppressive medications, and presence of GVHD did not affect the duration of HAV seropositivity after HSCT in univariate analysis (Table 2). Cox backward-stepwise regression confirmed older age of recipient at transplantation was the only significant parameter for HAV seropositivity (hazard ratio 3·70, 95% CI 1·08–12·64, P=0·037).
The percentage of seropositive (SP) and seronegative (SN) patients during follow-up [n (%)].
Patient characteristics (n=62)
Risk factors associated with the loss of hepatitis A antibodies after HSCT
HSCT, Haematopoietic stem cell transplant.
DISCUSSION
In our study HAV seroprevalence was 85% before HSCT. Seropositivity increased with age at transplantation: it was 76·9% for patients aged <18 years and 100% for patients aged ⩾18 years. Seroprevalence rates were similar with previous epidemiological studies from Turkey [Reference Erdoğan4–Reference Tosun9]. Unal Ince et al. have recently reported that seroprevalence was 75·5% in paediatric allogeneic HSCT recipients in Turkey [Reference Unal Ince15]. A study in Brazil reported the prevalence of HAV antibodies as 92·2% before HSCT with the patients' average age 26 years (range 3–58) [Reference Godoi16]. In Argentina, Dignani et al. reported that 68% of peripheral stem cell transplant recipients aged 14–66 years were seropositive before transplantation [Reference Dignani17]. There was no history of HAV vaccine application in the above-mentioned studies before transplantation, therefore all seropositive patients reflected naturally acquired HAV immunity.
In the present study, estimated mean time to loss of HAV seropositivity was 48·6 months with 30 months of median follow-up period (range 12–65 months) in allogeneic HSCT patients; 6·5% of the patients were still seropositive at 54 months. Median time to loss of HAV antibodies was reported in two studies as 358 days [Reference Dignani17] and 12 months [Reference Unal Ince15] and median follow-up was 12 months (range 1–51) and 56 months (range 21–123), respectively. An advantage of our study was that we used the Kaplan–Meier method which took into account ‘censored’ data – analysis of the case before the final outcome is observed [Reference Dawson and Trapp14].
Older age (⩾18 years) at transplantation was found to be the only risk factor for persistence of HAV antibodies in our study. In accord, Godoi et al. reported that loss of HAV antibodies was significantly associated with younger age [Reference Godoi16]. Their patient population was also similar to our study. However, we showed that donor age (⩾18 years) was a significant risk factor in univariate analysis and this is the first study showing the relevance of donor age in the persistence of HAV antibodies after HSCT. A limitation of our study was that we did not know the serology of HAV in donors but it was assumed that older age reflects natural infection because of high seroprevalence rates with increasing age in Turkey [Reference Erdoğan4–Reference Tosun9]. In a previous study, Ljungman et al. showed that a young donor is a significant risk factor in univariate analysis for becoming seronegative against measles [Reference Ljungman18]. These authors also reported that patients having previously been vaccinated against measles were much more likely to become seronegative during follow-up than patients who had experienced a natural measles infection [Reference Ljungman18]. In our study the persistence of HAV antibodies in older age at transplantation and older donors could be explained by naturally acquired infection.
Godoi et al. also reported that the loss of HAV antibodies was significantly associated with longer follow-up and acute GVHD [Reference Godoi16]. In our study the possible impact of other factors such as gender, donor age, conditioning regimen (myeloablative, reduced), GVHD (acute, chronic), duration of IVIG and application of immunosuppressive medications 12 months after transplantation were not found to be statistically significant on HAV serology. Unal Ince et al. also showed that the loss of HAV antibodies was high (43%) in paediatric HSCT recipients but they did not detect any significant risk factor [Reference Unal Ince15]. Dignani et al. also failed to report any predictor factor for loss of HAV antibodies in peripheral stem cell transplant recipients [Reference Dignani17]. These results are related to the limited number of patients in this field.
Hepatitis A infection is a widespread vaccine-preventable disease that can cause liver failure and some haematological complications [Reference Koff1–Reference Debray3, Reference Maiga10, Reference Wünschmann, Becker and Vallbracht11]. These potential problems of hepatitis A infection might make follow-up of HSCT recipients difficult and can increase morbidity and mortality. Therefore, HSCT recipients should be vaccinated when they become seronegative. In our study, child and adult HSCT recipients in an intermediate endemic country were evaluated. We showed that older age (⩾18 years) at transplantation affected the persistence of HAV antibodies. It is obvious that children need to be vaccinated earlier than adult HSCT recipients. However, further studies with larger numbers of HSCT recipients can reveal the predictive factors for loss of HAV antibodies and the role of donor immunity.
DECLARATION OF INTEREST
None.
