Chronic kidney disease (CKD) is a globally increasing condition that almost always finally leads to renal replacement therapy (dialysis treatment). CKD is also a state of immunodeficiency with increased susceptibility to infections that are the second most common cause of death after vascular diseases among dialysis patients (Rocco et al. 2002; Collins et al. 2006; Inaguma et al. 2008). In an earlier Finnish doctoral study in 1985, lymphocyte antigen responses of hemodialysis (HD) patients were only 60% of the controls (Huttunen 1985). The vaccination response is also impaired e.g. against influenza (Beyer et al. 1987; Cavdar et al. 2003).
Uremic toxins, lack of supportive cytokines, constructive cellular factors, dialysis modality and the membranes used in HD are all involved in the immune suppression. An important cause of dysfunction in the cells of the immune system is intracellular hypercalcemia related to secondary hyperparathyroidism (SHPT) caused by retention of phosphate in CKD. Patients with advanced CKD also by nature develop hypovitaminosis D, because the kidneys have lost their ability to synthesize calcitriol, which is known to have immunoregulatory actions. This contributes to SHPT and the numerous immune abnormalities. Initiation of erythropoietin (Epo) treatment has also been shown to affect the immune functions. By and large, the effects of the treatments of CKD on immune functions remain to be clarified.
Aims. In this series of studies we aimed to study the influenza vaccination response against vaccine antigens in CKD of various degrees (I) and HD-patients’ cross-reacting antibody responses to wild influenza virus antigens (II). We also aimed to study whether phosphate binding with calcium carbonate could increase the reduced tetanus vaccination response in uremic rats (IV). We aimed to study the immune effects of ancillary treatments in CKD, calcitriol (III) and Epo (V), on lymphocyte functions.
Subjects and methods. The groups in the clinical studies consisted of patients with all stages of CKD and controls from Tampere University Hospital. Pre-dialysis (Pre-D), HD, peritoneal dialysis (PD) and cardiac control patients were vaccinated against influenza and their antibody response against the influenza vaccine antigens A/H3N2, A/H1N1 and B was measured. HD patients’ sera were additionally studied for cross-reactivity against subsequent years’ virus isolates of A/H3N2 subtype. In vitro calcitriol was added in lymphocyte cultures of HD patients in a lymphocyte antigen response study using tuberculin (PPD) and tetanus toxoid (TT) as antigens. In the experimental study rats underwent a 5/6-nephrectomy or a sham operation, and thereafter they were given a high or control calcium carbonate diet, and their tetanus vaccination response was evaluated. Pre-D patients were tested with 1) antibody tests to Ebstein-Barr virus (EBV) and cytomegalovirus (CMV), 2) lymphocyte subclass analyses and 3) lymphocyte proliferation tests using phytohemagglutinin (PHA), pokeweed mitogen (PWM), PPD and TT as stimulants, before and three months after they begun with Epo treatment.
Results. Influenza vaccination of CKD patients resulted in post-vaccination titres that were almost comparable to those of the controls. Against A/H3N2 antigen they were 84%, 84% and 96% of the controls’ titres (pre-D, HD and PD, respectively). Sixty-one percent of controls and 67% of PD patients reached a protective titre against A/H3N2 but no more than 35% of pre-D and 36% of HD patients. However, the proportion of CKD and control patients that reached protective titres was clearly higher for the two other antigens A/H1N1 and B. Among HD patients, those on intravenous (i.v.) calcitriol seemed to have a better protection than those without i.v. calcitriol (p=0.06, borderline significant). The antibodies efficiently cross-reacted against wild influenza virus A/H3N2 antigens, similarly in HD patients and controls and even in healthy military conscripts who had suffered from an influenza A infection previously.
In the lymphocyte proliferation studies, the effect of in vitro pulse (mimicking i.v.) calcitriol therapy among HD patients had a statistically non-significant enhancing effect on lymphocyte antigen stimulation cultures, whereas having calcitriol continuously in the culture medium was even immunosuppressive to TT (p=0.001).
High calcium diet was beneficial to the tetanus vaccination response of rats with 5/6-nephrectomy: the response of the Ca-NTX rats with high calcium diet was almost as high as (75% of) that of sham-operated (Sham) rats (p=NS), while the NTX rats with control calcium diet had a reduced response (42%) compared to the Sham rats, p<0.008. However, the difference between Ca-NTX and NTX rats was non-significant. Creatinine, phosphate and intact PTH correlated inversely to the tetanus antibody response (p=0.002, 0.03 and 0.02, respectively).
The initiation of Epo treatment in pre-D patients caused lymphopenia and a decrease in lymphocyte proliferation, but no changes in the general antibody production against EBV and CMV. The changes in iron status, reticulocytes, hemoglobin or glomerular filtration rate (GFR) did not explain the decline.
Conclusions. The influenza vaccination responses of regularly monitored patients with CKD were comparable to controls. Especially HD patients’ cross-reactivity against several wild viruses was not inferior to that of the controls. In 5/6-NTX animals, the impaired tetanus vaccination response correlated both to GFR and to the control of hyperphosphatemia and PTH level. Calcitriol in vivo borderline significantly (p=0.06) enhanced the influenza vaccine response and calcitriol in vitro pulse treament slightly (non-significantly) enhanced lymphocyte antigen proliferation of HD patients. Incubation with calcitriol in vitro continuously was immunosuppressive to TT response (p=0.001). Epo had initial immune depressing actions to lymphocyte number and function. There seemed to be clinical benefits of calcitriol and phosphate binding therapies in vaccination response in CKD.
