Treatment of hyperphosphatemia, secondary hyperparathyroidism and hypocalcemia with calcium carbonate favorably modulates vaccination response in uremic rats.

AIMS

Immune dysfunction is characteristic of renal failure, leading to suboptimal antibody generation and increased susceptibility to infections. We tested whether the treatment of uremic phosphate retention by increased calcium carbonate intake will beneficially influence vaccination response in 5/6-nephrectomized rats.

METHODS

The nephrectomized (uremic) and sham-operated (control) rats were either fed 0.3% calcium diet (NTX and Sham groups, respectively) or 3% high-calcium diet (Ca-NTX and Ca-Sham groups). All rats were immunized with tetanus toxoid 6 weeks after the operations, and antitoxin levels were measured 7 weeks later.

RESULTS

Plasma creatinine was significantly elevated after the nephrectomy: the values (mean +/- SD) in the NTX (n = 16), Ca-NTX (n = 11), Sham (n = 14) and Ca-Sham (n = 8) groups were 97 +/- 14, 93 +/- 17, 66 +/- 7, and 69 +/- 8 micromol/l, respectively. The NTX group developed phosphate retention and secondary hyperparathyroidism, which were completely prevented by the high calcium diet. The mean tetanus antitoxin concentrations of the groups were: NTX 0.25 +/- 0.32; Ca-NTX 0.45 +/- 0.44; Sham 0.58 +/- 0.24 and Ca-Sham 0.64 +/- 0.25 IU/ml (log of geometric mean concentration). The antibody response in the NTX group was significantly lower, i.e. 43% of that in the Sham group (p = 0.003), while the response in the Ca-NTX group was not different from that in the Sham group. The tetanus response of all the uremic rats inversely correlated with the plasma levels of phosphate (r = 0.447, p = 0.02), parathormone (r = -0.409, p = 0.03) and creatinine (r = 0.578, p = 0.002).

DISCUSSION

We conclude that renal failure impairs vaccination response in rats, the impairment of which can be favorably modulated by phosphate-binding and PTH-suppressing high-calcium diet.