Poliomyelitis and Tetanus Immunization: Antibody Responses in Patients With Cystic Fibrosis

Some patients with cystic fibrosis have progressive immune system impairment with decreased lymphocyte sub-populations. Patients with severe clinical disease and respiratory dysfunction may have abnormally low numbers of T helper and T suppressor cells.1, 2 Although the most severely ill patients invariably have hypergammaglobulinemia, this antibody hyperproduction does not always correspond to adequate antibody function.3 We examined antibody responses in a homogeneous population of patients with cystic fibrosis at various clinical stages of the disease and in two groups of age- and sex-matched controls: patients with gastrointestinal disease; and healthy subjects. All subjects received a standard stimulus with oral poliomyelitis virus vaccine (Sabin) and diphtheria and tetanus antigens. Our aim was to determine whether the patients' gastrointestinal syndrome might reduce their humoral response to orally administered vaccine and hence contraindicate vaccination by this route in patients with cystic fibrosis. Subjects and methods. We studied a group of 26 patients with cystic fibrosis (CF), 13 female and 13 male, ranging in age from 1.5 to 17.3 years (median age, 9.5 years). All CF patients had gastrointestinal and respiratory symptoms; in all cases the diagnosis was confirmed by at least three positive sweat tests and the disease was scored clinically and radiologically according to Schwachman's and Crispin-Norman criteria4, 5 (mean Schwachman score, 84.4 (range, 48 to 100); mean Crispin-Norman score 7.8 (range, 2 to 22)). Controls for antibody responses to oral poliovirus vaccine consisted of 26 age- and sex-matched patients with non-CF-associated gastrointestinal disorders (cow's milk allergy, lactose intolerance, irritable colon, ulcerative colitis and Crohn's disease) and 26 healthy subjects. For purpose of analysis the patients with cystic fibrosis, the patients with gastrointestinal disease and the healthy control group were divided into three age ranges: <4 years, 4 to 8 years and >8 years. Because the tetanus vaccine was given parenterally, antitetanus antibody responses were compared only with those of the healthy control group. Sera were collected for determination of antibody titers after the fourth or last dose of oral poliovirus vaccine received. For determination of antitetanus vaccine antibodies sera were collected after the third dose in patients <3 years of age and after the fourth dose in patients ≥3 years of age. Antibody titers to poliovirus were determined by a microneutralization assay in HEp-2 cells as described elsewhere.6 In brief 2-fold dilutions of sera were challenged with 100 TCID50 of reference poliovirus strains type 1 through 3 (Mahoney, MEF-1 and Leon). Neutralization mixtures were inoculated onto cell monolayers and development of cytopathic effect was scored daily for 3-5 days. Serum neutralizing antibody titers were expressed as the reciprocal of the highest dilution shown to inhibit cytopathic effect completely, with Karber's formula.7 Serum-neutralizing antibody titers <2 were considered negative. Antitetanus antibody was determined by an indirect hemagglutination test with turkey erythrocytes sensitized with tetanus toxin (30 flocculation limit/ml) according to a method described elsewhere.8 Reference standards consisting of human IgG containing 150 IU/ml of tetanus antibody, as determined by serum neutralization test, were included. Titers were expressed in IU/ml. Serum titers <0.1 IU/ml were considered negative. Analysis of variance or Student's test were used for comparisons of antibody titers between groups. Statistical analysis. Antibody titers are expressed as reciprocals of dilution. A two-way analysis of variance or Student's t test on log of titers were used for comparisons between groups. P values of <0.05 were considered to indicate statistical significance. Results. The 26 patients with CF and the 2 control groups (26 patients with gastrointestinal disease and 26 healthy subjects) in the 3 age groups had measurable serum antibody titers to poliovirus types 1, 2 and 3. Except for antibodies to poliovirus type 2, which showed lower titers in the group of CF patients older than 8 years, geometric mean titers for poliovirus did not differ significantly in CF patients and the 2 control groups (Table 1). Patients with CF (children younger than 3 years, who had not received the final booster dose of tetanus vaccine, and those older than 3 years) and age- and sex-matched healthy subjects also had serum antibody titers to tetanus toxin did not differ significantly between groups (Table 2). Discussion. For this study we selected a population of patients with CF in a wide age range (from 1.5 to 17.3 years), and thus with widely varying clinical expression of the disease. As controls we used two age- and sex-matched groups, one consisting of patients with gastrointestinal disease and the other of healthy subjects. Irrespective of severity of disease and of their prominent gastrointestinal tract impairment (chronic diarrhea and malabsorption), all the patients had adequate antibody responses to vaccination stimulation with oral poliomyelitis virus. Although CF patients often had lower anti-polio geometric mean titers than controls, their responses always reached protective titers. Responses to poliovirus types 1 and 3 and to tetanus did not differ significantly in patients with CF and controls. In contrast analysis of variance (F test) showed that the geometric mean titers in response to poliovirus type 2 in the >8-year age group differed significantly among the three groups. Because of its high immunogenicity, oral poliovirus vaccine contains less poliovirus type 2 than types 1 and 3. For this reason cystic fibrosis, a disease accompained by intestinal malabsorption and a known age-related reduction in T helper lymphocytes,1 could cause reduced replication of virus and hence reduced antibody response. No published data about patients with cystic fibrosis are available for comparison with our findings. In a previous study on this CF group,9 we found that the total number of lymphocytes and the number of CD4+ cells decreased in older children, probably in correlation with the severity of the disease. Younger children had normal and older children had higher levels of immunoglobulin classes and subclasses, as reported by others.3 The reason for this normal antibody response may be the absence of immune impairment in younger patients with cystic fibrosis. In older patients the progressive depletion of T helper lymphocytes observed by us (submitted for publication) and by others1 presumably reduces antibody function, despite the presence of hypergammaglobulinemia. This is consistent with findings in patients with congenital immunodeficiency, who also have hypergammaglobulinemia. Nevertheless despite our patients' progressive and severe immunodeficiency this never definitively lowered their humoral immunity. Ample evidence has confirmed this hypothesis also in adult patients with cystic fibrosis, who have worsening disease and therefore severe immune impairment, but still mount an adequate antibody response to stimulation with influenza vaccine.10, 11 Except for oral polio vaccination in CF patients >8 years old, statistical analysis of our data showed no significant differences in antibody titers after oral or after intramuscular vaccination in patients with cystic fibrosis and controls. Although patients with CF >8 years old had significantly lower antibody titers to poliovirus vaccine, they had protective titers. In conclusion in patients with cystic fibrosis, even those who have malabsorption symptoms, poliovirus vaccination is effective and oral vaccination is not contraindicated. Vincenzina Lucidi, M.D.; Lucia Fiore, B.Sc.; Maurizio Caniglia, M.D.; Paola Rosati, M.D.; Francesco Novello, B.Sc.; Bronislava Papadatou, M.D.; Emanuela Medda, B.St.; Giuliano Gentili, B.St.; Concetta Amato; Massimo Castro, M.D. Division of Gastroenterology Centro per la Diagnosi e la Terapia della Fibrosi Cistica Ospedale Bambino Gesù (VL, MC, PR, BP, MC) Laboratories of Virology (LF, FN, CA), Epidemiology (EM) and Immunology (GG) Istituto Superiore di Sanità Rome, Italy