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    • br Study design br Results We

    2021-01-18


    Study design
    Results We enrolled 50 subjects awaiting SOT (15 kidney, 14 liver, 1 liver + small bowel, 11 lung, 9 heart) and 50 controls (Table 1) who were similar with respect to median age (subjects 49.1 yrs., controls 48.6 yrs.) gender (64% male subjects and controls), and CMV-seropositivity (42% subjects, 54% controls). Of the 21 CMV-seropositive subjects, 7 (33.3%) had potential passive antibodies. Saliva, blood and urine samples were collected from all participants and throat swabs were collected for 99/100.
    Discussion Using a cut-off of 0.075% CMV-TC, CMV-TC levels had excellent sensitivity and specificity in assigning CMV infection status in healthy adults (92%, 100%). Our results were comparable to results from a previous study in adults who were healthy, in chronic renal failure or post-renal transplant, where CMV serostatus was predicted with 100% sensitivity and 98% specificity; they used the assay from which ours was adapted and a cut-off of 0.05% CMV-TC [4]. In the current study of adults awaiting SOT of all organ types, including patients listed at a high-status, the CMV-TC assay discriminated between CMV-seropositive and seronegative adults well (sensitivity 79%, specificity 93% in subjects without passive antibody). The lower sensitivity in our SOT-candidates is likely due to the high severity and chronicity of illness in our pre-SOT subjects which may impair their cell-mediated immune responses. There are available commercial assays, including QuantiFERON®-CMV, and enzyme-linked immunosorbent spot (ELISpot) assays such as T-SPOT®.CMV, for detection of CMV-specific T cell immunity. While many studies have investigated the use of QuantiFERON®-CMV and ELISpot assays to predict the risk of CMV infection and to guide CMV prophylaxis strategies post-transplant, knowledge regarding the use of T-cell assays as an alternative or adjunct to serology in patients with potential passive immunity is limited to a few studies [2,3,11,15,17]. In assignment of pre-transplant CMV infection status, both assay sensitivity and specificity are critical. CMV cell mediated immunity assays using antigens with broad stimulatory capacity, such as CMV lysate used in our study, have higher sensitivity, and thus are preferable to assays using individual antigens for stimulation, such as the commercially available QuantiFERON®-CMV and T-SPOT®.CMV assays [2,4,[17], [18], [19]]. Consistent with previous studies, we identified individuals without passive K-115 receptor whose serology and CMV-TC results were discordant; the presence of CMV-TC may be more useful than serology in predicting the transplant candidate’s ability to control CMV post-transplant, but this requires further investigation [4,17,20,21]. Our study suggests that this CMV-TC assay is useful in CMV risk-stratification in adults awaiting SOT, across multiple organ types, whose serology may be unreliable due to potential passive antibodies. This assay could have other applications where identifying the correct CMV infection status is vital, including recruitment into CMV vaccine trials. Quantification of CD27-CD28- CD4 + T-cells as a marker of CMV infection-status is attractive as, compared to stimulation-based CMV-TC assays, determination of CD27-CD28- CD4 + T-cell frequencies requires a lower blood volume, is less expensive, more rapid (24 h versus 48–72 h reporting time), and does not require a tissue culture facility. A prior study determined that a frequency of ≥0.44% CD27-CD28- CD4 + T-cells discriminated between CMV-seropositive and seronegative adults with 93% sensitivity and 97% specificity and found that frequencies of CD27-CD28- CD4 + T cells and stimulation-induced CMV-TC were strongly positively correlated (rs = 0.73) [9]. In our cohort we found that a similar frequency of ≥0.46% CD27-CD28- CD4 + T cells discriminated between CMV-seropositive and seronegative subjects without passive antibodies with good sensitivity (86%) and reasonable specificity (74%). There was moderate positive correlation between the frequency of CD27-CD28- CD4 + T cells and CMV-TC, with higher correlation in controls (rs = 0.68) than in subjects (rs = 0.52). Although not significantly different, compared with controls seropositive subjects had higher CD27-CD28-CD4 + T cell frequencies and lower CMV-TC frequencies, perhaps related to premature immune aging and waning cellular immunity in patients with chronic or critical illness, which may explain the poorer correlation between the two assays in subjects awaiting SOT [7]. Among the 7 CMV-seropositive adults with potential passive antibodies, there was perfect agreement between the CMV-TC and CD27-CD28-CD4 + T cell assays with 5/7 having detectable CMV-TC and CD27-CD28-CD4 + T cell frequencies above the cut-off and 2/7 having undetectable CMV-TC and CD27-CD28-CD4 + T cell frequencies below the cut-off, which may be considered as a sign of true passive immunity in a CMV non-infected subject.