Short-term antibody response after 1 dose of BNT162b2 vaccine in patients receiving hemodialysis

BACKGROUND:Patients receiving in-centre hemodialysis are at high risk of exposure to SARS-CoV-2 and death if infected. One dose of the BNT162b2 SARS-CoV-2 vaccine is efficacious in the general population, but responses in patients receiving hemodialysis are uncertain.METHODS:We obtained serial plasma from patients receiving hemodialysis and health care worker controls before and after vaccination with 1 dose of the BNT162b2 mRNA vaccine, as well as convalescent plasma from patients receiving hemodialysis who survived COVID-19. We measured anti–receptor binding domain (RBD) immunoglobulin G (IgG) levels and stratified groups by evidence of previous SARS-CoV-2 infection.RESULTS:Our study included 154 patients receiving hemodialysis (135 without and 19 with previous SARS-CoV-2 infection), 40 controls (20 without and 20 with previous SARS-CoV-2 infection) and convalescent plasma from 16 patients. Among those without previous SARS-CoV-2 infection, anti-RBD IgG was undetectable at 4 weeks in 75 of 131 (57%, 95% confidence interval [CI] 47% to 65%) patients receiving hemodialysis, compared with 1 of 20 (5%, 95% CI 1% to 23%) controls (p < 0.001). No patient with nondetectable levels at 4 weeks developed anti-RBD IgG by 8 weeks. Results were similar in non-immunosuppressed and younger individuals. Three patients receiving hemodialysis developed severe COVID-19 after vaccination. Among those with previous SARS-CoV-2 infection, median anti-RBD IgG levels at 8 weeks in patients receiving hemodialysis were similar to controls at 3 weeks (p = 0.3) and to convalescent plasma (p = 0.8).INTERPRETATION:A single dose of BNT162b2 vaccine failed to elicit a humoral immune response in most patients receiving hemodialysis without previous SARS-CoV-2 infection, even after prolonged observation. In those with previous SARS-CoV-2 infection, the antibody response was delayed. We advise that patients receiving hemodialysis be prioritized for a second BNT162b2 dose at the recommended 3-week interval.

Patients with end-stage kidney disease receiving incentre hemodialysis have been uniquely vulnerable during the COVID-19 pandemic. For these patients, unlike for most other people, self-isolation to avoid exposure to SARS-CoV-2 is impossible. Most patients receiving hemodialysis must leave their homes 3 times weekly to receive their life-saving treatments, often in shared spaces for hours at a time. COVID-19 case fatality rates are 20%–30% for patients receiving hemodialysis —10 times higher than in the general population.^1,2 Advanced age, multiple comorbidities and blunted immune response likely all contribute to the high COVID-19 death rates in this population. Some hemodialysis centres have thus prioritized these patients for vaccination.To facilitate wider vaccine distribution during current shortages, ³ the National Advisory Committee on Immunization of Canada has recommended delaying the second dose of the BNT162b2 vaccine from 3 to 16 weeks.⁴ In a randomized controlled trial (RCT), the clinical efficacy of the BNT162b2 was reported to be greater than 80% at 3 weeks after the first dose.⁵ However, no patients receiving hemodialysis were enrolled in this trial.⁵ Patients with end-stage kidney disease receiving hemodialysis often have impairments in both humoral and cellular immune responses⁶ and are noted to have lower antibody responses to other vaccines.⁷ Whether patients receiving hemodialysis develop robust immune responses after vaccination against SARS-CoV-2 remains uncertain.⁸ Data are required to better inform Canadian public health policy on whether second doses of vaccine can be safely delayed in this population.Usually, once clinical trials are completed, antibody levels can be used as surrogate measures of vaccine efficacy, such as with hepatitis B⁹ and influenza.¹⁰ With respect to the novel coronavirus SARS-CoV-2, although there is increasing understanding of the antibodies that best correlate with viral neutralization and T-cell responses,^11,12 assays vary from laboratory to laboratory and as yet there are no internationally accepted standards defining what antibody levels constitute immunity.¹³ The only way to evaluate vaccine efficacy using antibody levels, therefore, is through direct experimental comparison with controls who are known to reliably develop immunity after vaccination (i.e., healthy individuals similar to those enrolled in the RCT showing vaccine efficacy⁵) or who have developed immunity after natural infection (i.e., survivors of COVID-19).We sought to determine whether short-term antibody responses after a single dose of the BNT162b2 mRNA vaccine are comparable between patients receiving hemodialysis and healthy individuals, and how this compares with antibody responses in patients receiving hemodialysis who survived natural infection with SARS-CoV-2.     

Regional Variation in the Levels of Transferrin in the CNS of Normal and Myelin-Deficient Rats

Transferrin (Tf), the iron mobilization protein, is synthesized mainly in the liver. Recently, both Tf and a mRNA for Tf have been demonstrated in oligodendrocytes in the rat brain. The present study used a biochemical assay for determining the levels of Tf in various brain regions of normal rats compared with the level of those obtained from rats with a genetic mutation characterized by an almost complete failure to develop myelin. In myelin-deficient (md) rats, no Tf-positive oligodendrocytes were seen immunohistochemically in the gray or white matter of the CNS. Quantitatively, levels of Tf throughout the CNS of the md rat were decreased to approximately 5% of the normal values despite a normal hepatic synthetic rate. In the normal rat brain, the cerebellum contained the highest concentration of Tf, followed by the pons, the cerebral cortex, and the caudate-putamen, with the latter two sites being similar. Regional variation in the amount of Tf was in general agreement with published reports on the variation of iron and Tf receptor levels in the CNS. Immunohistochemical examination with antiserum to galactocerebroside (a myelin-specific lipid) was used for extending biochemical reports that glycolipid-synthesizing enzymes are deficient in md rats. No immunostaining in the md rat was observed following immunoreaction for galactocerebroside, whereas white matter oligodendrocytes were intensely marked in the normal rat. Robust astrogliosis was present in both the gray and white matter of the md rats. It is not known at present whether the ability to accumulate Tf is necessary for oligodendrocytic survival or if Tf accumulation is more directly related to myelinogenesis.(ABSTRACT TRUNCATED AT 250 WORDS)     

Purification and properties of diaminopimelate decarboxylase ofMicrococcus glutamicus

Diaminopimelate decarboxylase (EC 4.1.1.20) ofMicrococcus glutamicus ATCC 13059 was purified to homogeneity. The enzyme had an apparent molecular weight of 191,000 as determined by gel filtration on Sephadex G-200. At protein concentrations of 20 and 10 μg per ml and in the absence of pyridoxal-5′-phosphate, it dissociated into a species of molecular weight 94,000. The polypeptide chain molecular weight as determined by sodium dodecyl sulphate Polyacrylamide gel electrophoresis was 100,000. TheK _m formeso diaminopimelate was 0.5 mM and that for pyridoxal-5′-phosphate was 0.6 μI. Sulphydryl groups and pyridoxal-5′-phosphate were essential for activity and stability. The enzyme was inhibited significantly by L-lysine and DL-aspartic β-semialdehyde.     

Excretion of lysine byMicrococcus glutamicus

Analysis of intracellular and extracellular lysine concentration during lysine fermentation byMicrococcus glutamicus AEC RN-13-6/1 indicated that lysine excretion occurs against a concentration gradient towards the end of the fermentation period. The capacity to excrete lysine against a concentration gradient may be a factor contributing to the high yield of lysine.