Influenza Vaccination in Orthotopic Liver Transplant Recipients: Absence of Post Administration ALT Elevation

Introduction

Liver transplant recipients and patients with cirrhosis are at risk for complications from influenza virus infection (1,2). Pneumonia (primary viral and secondary bacterial pneumonia) is the most common complication of influenza viral infection, but other complications, especially involving muscle and the central nervous system, also occur.

Annual influenza vaccination is the standard of care during the influenza season in high-risk patients with cardiac, pulmonary and renal diseases, the elderly, diabetics, and immunocompromised patients. Influenza vaccination has reduced the morbidity and perhaps mortality from influenza virus infection in cirrhotic and post liver transplant patients. Several studies have demonstrated acceptable levels of protective postimmunization antibody titers being achieved post liver transplantation (3,4).

Complications from influenza vaccination are rare. Local reactions such as tenderness, redness, or induration and mild constitutional symptoms, fever and malaise, are the most common symptoms reported. Although elevated serum alanine transaminase levels have been reported with influenza infection (5), this has not been associated with influenza vaccination. Acute cellular rejection has been reported in pediatric liver transplant recipient infected with para-influenza virus type 3 (6), but there are no reported cases of hepatic allograft rejection occurring after influenza vaccination.

Genotype 1b strain of the hepatitis C virus (HCV) express an epitope which cross-reacts with an epitope expressed by influenza A virus. The influenza A virus epitope is recognized by HLA A2-restricted cytotoxic T cells (7). There is a theoretical concern that influenza vaccination could trigger cytotoxic T-cell response in patients transplanted for HCV cirrhosis and lead to elevation of liver chemistry tests or acute cellular rejection via stimulation of a nonspecific inflammatory response.

In this study, we determined whether influenza vaccination causes ALT elevations in HCV (+) and HCV (−) liver transplant recipients. In addition, we assessed the protective antibody response to immunization in these patients in an effort to identify the optimal time for vaccination.

Patients and Methods

After providing informed consent, a total of 58 liver transplant recipients were prospectively enrolled in the study between October 2002 and March 2003. Patients aged 18–70 years, who were not actively using alcohol or medications that might affect ALT values (i.e. interferon, cholesterol lowering agents) during the study period, were considered. Exclusion criteria included a history of upper respiratory infection during the 3 weeks prior to vaccination, adjustment in immunosuppressive regimen within 1 month of vaccination, known anaphylactic reaction to eggs, and evidence of concurrent infection e.g. urinary infection. Subjects were also excluded if they had histologically confirmed acute cellular or chronic ductopenic rejection during the previous 3–6 months, or they would be unable to have the follow-up laboratory values assessed. The Institutional Review Board of The Mount Sinai Hospital approved the study.

Four subjects dropped out of the protocol (were unable to follow up with laboratory tests) and three had incomplete data for analysis; 51 subjects completed the study (25 with HCV and 26 without HCV). Pretransplant indication in the non-HCV transplant recipients included: autoimmune hepatitis, four; primary sclerosing cholangitis, four; primary biliary cirrhosis, three; hepatitis B, four; crytogenic cirrhosis, four; amyloidosis, one; alcohol cirrhosis, three; and fulminant hepatic failure, three (two drug induced and one idiopathic).

All patients were maintained on either cyclosporine or tacrolimus-based immunosuppressive regimens. Corticosteroids were tapered off completely by 3 weeks post-transplantation. Mycophenolate mofetil was used as an adjunct in patients with renal insufficiency. None of the subjects received immunoglobulin products post-transplantation. Each subject received a single intramuscular injection (0.5 mL) of the 2002–2003 inactivated trivalent influenza vaccine.

The vaccine contains A/Moscow/10/99-like strain (‘H3’), A/new Caledonia/20/99-like (‘H1’) and B/Hong Kong/330/2001-like strains (‘B’) (52 subjects received Fluvirin, Evans Pharmaceuticals, London; and six subjects received Fluzone; Aventis Pasteur, Swiftwater, PA).

Sera for hemmagglutination inhibition (HAI) assays were obtained before and 4–6 weeks after vaccination. Serologic response was defined as HAI titers ≥ 40 and/or a 4-fold increase in antibody titers from baseline (which similarly confers protection in healthy individuals). Liver chemistry tests were obtained before, at 1 week and 4–6 weeks after vaccination. The serum samples were centrifuged and stored at − 80°C until testing. An ALT elevation was as defined as ≥ 50% elevation in ALT from baseline.

Results

The mean age of the patients and time from transplantation in HCV (+) and HCV (−) subjects were similar 53.64 ± 8.8 years (range 23–67) vs. 53.23 ± 11.8 years (range 25–72), and 37.36 ± 31.2 months (range 3–120) vs. 32.19 ± 34.5 months (2–121), respectively (see Table 1). The numbers of recipients on immunosuppressive drugs were similar in the two groups (see Table 1). In addition, two HCV (−) recipients were on azathioprine and tacrolimus and one was on rapamycine and tacrolimus. Three HCV (+) recipients were on azathioprine and cyclosporine, rapamycine and tacrolimus, and rapamycine only, respectively.

There was no statistically significant difference in the median rise in ALT value from baseline to 1 week or 4–6 weeks post vaccination in either seroconverters [HCV (+): 53,44, and 44, p-value 0.82; HCV (−): 34.5, 41.5, and 35, p-value 0.82] or non seroconverters [HCV (+): 52.5, 43.5, and 45.4, p-value 0.57; HCV (−): 25, 23, and 29, p-value 0.96] to the H1N1 subtype of the influenza virus vaccine. There was no difference in the median ALT level at baseline, 1 week or 4–6 weeks post vaccination between the two groups (p-value 0.18, 0.30 and 0.61, respectively).

The percentage of seroconverters and individual antibody titers against the respective vaccine strains prior to and 4–6 weeks after vaccination are shown in Table 2A–C. A significant number of HCV (+) and HCV (−) subjects achieved potentially adequate protective antibody titers post vaccination (p-value < 0.0001). Overall, there was a better response to the HINI and H3N2 strains with the total number of subjects with adequate seroconversion titers to the H1, H3 and B strain being 37 (73%), 34 (67%) and 22 (43%), respectively. When vaccination was performed at less than 4 months post transplantation, the number of subjects with adequate seroconversion to the H1, H3 and B strains was 1/7 (14%), 3/7 (43%) and 1/7 (14%), respectively. At 4–12 months post transplant, 6/9 (67%), 8/9 (89%) and 5/9 (56%), and after 12 months, 30/35 (86%), 23/35 (66%) and 16/35 (46%) patients had adequate seroconversion. HCV (−) subjects had a better seroconversion titer to the H3 strain of the vaccine at 4–6 weeks compared with HCV (+) subjects, geometric mean titers 5.01 vs. 3.92 (p < 0.01). In HCV (−) recipients with adequate seroconversion, all but one achieved both a 1:40 and > 4 fold rise in titer to the H1N1 and B strains. Only 2 recipients did not achieve a > 4 fold rise in titer to the H3N2 strain. In HCV (+) recipients with adequate seroconversion, all achieved both a 1:40 and > 4 fold rise in titer to the H1N1 and B strains. 4 recipients did not achieve a > 4 fold rise in titer to the H3N2 strain. Of 51 subjects studied, one HCV (−) recipient who received the vaccination within 3 months of transplantation developed acute cellular rejection 10 weeks post vaccination that was treatable with augmentation of immunosuppresion.

Discussion

The current study demonstrates that influenza vaccination is not associated with aminotransferase flares or acute cellular rejection, and a significant number of liver transplant recipients achieved potentially protective antibody titers irrespective of HCV serologic status.

The theoretical concern that influenza vaccination of HLA-A2 patients infected with genotype 1b HCV may cause aminotransferase flares would occur whether the cells were newly created or are memory cells. Cross-reaction would therefore theoretically, only be a problem in people who are HLA-A2 (approximately 50% of Caucasians) and those HCV (+) patients with genotype 1b (typically about 30% of HCV patients in the U.S.). Thus, only a small percentage of HCV patients might be expected to have susceptibility. This study confirms similar findings of safety and lack of ALT elevation reported in decompensated cirrhotic patients receiving influenza vaccination (9).

Cellular immune response contributes to hepatic injury in acute and chronic hepatitis C virus infection. The HCV_(NS3–1073) peptide CVNGVCWTV identified as a HLA-A2-restricted CTL determinant is well conserved among HCV genotype 1B strains while the influenza A virus peptide_(NA–231) CVNGSCFTV is conserved in influenza virus H1N1 strains (included in vaccines). Cross-reactivity between these two epitopes by HCV specific CD8⁺ T cells, and, theoretically, induction of rejection is a feared complication of influenza vaccination. To our knowledge, there have been no reported episodes of hepatic allograft rejection occurring after influenza vaccination. Our study showed one of two HCV (−) patients (50%) who received the vaccination within 3 months of liver transplantation developed acute allograft rejection. This should be interpreted with caution, as there is no conclusive proof that vaccination triggered the cellular rejection in this patient.

Overall, at least 70% of the subjects developed adequate potentially protective antibody titers to the influenza A vaccine compared to 43% to the influenza B vaccine. One possible explanation is that influenza A virus was the predominant and more virulent influenza virus in the last few years accounting for the greater response. It is intriguing to note that >55% of the subjects vaccinated 4–12 months post transplantation had adequate antibody seroconversion to the three strains of the influenza vaccine. These data suggest that adequate immunologic response is triggered by vaccination in the first year post transplantation (especially after the first 3 months) in liver transplant recipients.

Previous studies of antibody seroconversion after influenza vaccination ranged from 15%–95% in liver transplant recipients and 56%–100% in healthy controls to the three influenza virus strains (3–4,10). In a study of 264 health care professionals, overall vaccine response was noted in 57% (41%–78%) of the subjects for the A (H3N2) and in 40% (33%–52%) of subjects for influenza B vaccine (11). Other studies in healthy adults vaccinated with the trivalent inactivated vaccine have reported >90% protective antibody titers in vaccinees within 2 weeks of vaccination (12–15). In this study, at >12-months after transplantation, 86%, 66% and 46% of the subjects had adequate immunologic response to the H1N1, H3N2 and B strains respectively. Compared to published data in healthy adults, it appears that the overall response to all 3 influenza virus strains in liver transplant recipients vaccinated at >12 months post-transplantation in this study were lower. Despite these shortcomings, the current study confirmed earlier studies in adult liver transplant recipients that a significant number of patients achieve adequate potentially protective antibody titers; thus influenza vaccination should be encouraged irrespective of HCV status. One limitation of our study is that it was not powered to detect a significant difference in response to the vaccine between HCV (+) and HCV (−) patients.

Three patients complained of increased malaise and fatigue after vaccination, and two had low-grade fever. To our knowledge, of all the 51 subjects vaccinated, only one HCV (−) subject contracted the flu virus after vaccination without complication or significant morbidity. Thus the vaccination is potentially protective in preventing or decreasing morbidity from influenza infection.

In renal transplant recipients, the age of the subjects, immunosupressive regimen and perhaps the intensity of immunosuppression appear to be important variables which may explain the variability of vaccine efficacy (16). In our study, age and type of immunosuppressive drugs used does not appear to correlate with response to immunization.

In conclusion, influenza vaccination is not associated with ALT flares or acute cellular rejection in postorthotopic liver transplants recipients whether they are infected with HCV or not. Although the optimal time of influenza vaccination in post transplant liver recipients has not been defined, adequate immunologic response is seen at 4-months or later post-transplantation; thus recipients will benefit from vaccination during this period. Larger studies are necessary to define the optimal time for influenza vaccination post liver transplantation.