Purpose To describe the humoral immune response to COVID-19 vaccines in people living with HIV and identify factors associated with the magnitude of anti-SARS-CoV-2 antibody concentrations. Methods Retrospective analysis of electronic patient files in a big single HIV center in Munich, Germany. Non-parametric methods were used for descriptive and comparative statistics. Generalized linear models were used to analyze associations of general and HIV-specific variables with anti-SARS-CoV-2 antibody concentrations after standard vaccination. Result Overall, 665 people living with HIV were included into the analysis (median age: 53 [IQR: 43; 59]), 560 [84.2%] males). Median concentration of anti-SARS-CoV-2-antibodies was 1400 (IQR 664; 2130) BAU/mL. In 18 (2.7%) subjects, antibody concentrations below the threshold of 34 BAU/mL were found. Among PLWH with CD4 cell count < 200 cells/µL, median anti-SARS-CoV-2-Abs were 197 (IQR 44.6; 537.2) as compared to 1420 (IQR 687; 2216) for the group ≥ 200 cells/µL ( p < 0.001). In a cumulative logit model, a vaccination scheme including an mRNA vaccine [OR: 4.64 (3.58; 6.02)], being female [OR: 2.14 (1.76; 2.61)], and having higher CD4 cells [OR per 100 cells/µL: 1.06 (1.04; 1.08)] were significantly associated with anti-SARS-CoV-2 antibody concentrations in higher quartiles, when adjusted for the time after vaccination. Conclusion We found a robust antibody response in people living with HIV undergoing standard vaccination against SARS-CoV-2. mRNA-containing vaccination schemes, being female, and having a higher CD4 cell count was associated with a higher concentration of antibodies in people living with HIV in our study sample. Particularly in the subgroup with CD4 cell counts < 200 cells/µL, antibody response was poor.

An improved method for the determination of pyridoxal-5-phosphate using tyrosine decarboxylase is described.Pyridoxal-5-phosphate (PLP) is the coenzyme form of vitamin B6 for a multiplicity of biosynthetic and catabolic enzyme systems. The methods generally used for the determination of PLP in biological samples are either enzymatic or chemical procedures. The method described here is basically the same as other enzymatic procedures (Bhagavan et al., 1976;Chabner and Livingston, 1970;Reinken, 1972), using radioactive tyrosine and the apoenzyme, tyrosine decarboxylase from Streptococcusfaecalis. However, instead of collecting ]4CO2, the other product of the enzymatic reaction, [3H]tyramine, was determined after separation from the substrate, [3H]tyrosine, by a mini DEAE-cellulose column.The assay mixture for PLP measurement contained 0.1 mol/l sodium acetate buffer, pH 5.5, the enzyme, tyrosine decarboxylase (approximately 20mU), PLP (10-300pg) and [aH]tyrosine (0.5~tCi/0.25pmol) in a total volume of 0.3 ml. The reaction mixture was preincubated in the absence of tyrosine for 20 min to allow the formation of the holo enzyme. The reaction was then initiated by addition of tyrosine, incubated for 15 min at 37°C, and terminated by heating the mixture for 3 min at 95 °C. After cooling the mixture in an ice bath, 100 lal of the supernatant was loaded on to a mini DEAEcellulose column (0.9 x 1.0cm) prepared with a 2.5 ml disposable syringe. The preparation of the OH form of

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