<i>Gambiense</i> Human African Trypanosomiasis and Immunological Memory: Effect on Phenotypic Lymphocyte Profiles and Humoral Immunity

<div><p>In mice, experimental infection with <i>Trypanosoma brucei</i> causes decreased bone marrow B-cell development, abolished splenic B-cell maturation and loss of antibody mediated protection including vaccine induced memory responses. Nothing is known about this phenomenon in human African trypanosomiasis (HAT), but if occurring, it would imply the need of revaccination of HAT patients after therapy and abolish hope for a HAT vaccine. The effect of <i>gambiense</i> HAT on peripheral blood memory T- and B-cells and on innate and vaccine induced antibody levels was examined. The percentage of memory B- and T-cells was quantified in peripheral blood, prospectively collected in DR Congo from 117 <i>Trypanosoma brucei gambiense</i> infected HAT patients before and six months after treatment and 117 controls at the same time points. Antibodies against carbohydrate antigens on red blood cells and against measles were quantified. Before treatment, significantly higher percentages of memory B-cells, mainly T-independent memory B-cells, were observed in HAT patients compared to controls (CD20+CD27+IgM+, 13.0% versus 2.0%, <i>p</i><0.001). The percentage of memory T-cells, mainly early effector/memory T-cells, was higher in HAT (CD3+CD45RO+CD27+, 19.4% versus 16.7%, <i>p</i> = 0.003). After treatment, the percentage of memory T-cells normalized, the percentage of memory B-cells did not. The median anti-red blood cell carbohydrate IgM level was one titer lower in HAT patients than in controls (<i>p</i><0.004), and partially normalized after treatment. Anti-measles antibody concentrations were lower in HAT patients than in controls (medians of 1500 versus 2250 mIU/ml, <i>p</i> = 0.02), and remained so after treatment, but were above the cut-off level assumed to provide protection in 94.8% of HAT patients, before and after treatment (versus 98.3% of controls, <i>p</i> = 0.3). Although functionality of the B-cells was not verified, the results suggest that immunity was conserved in <i>T.b. gambiense</i> infected HAT patients and that B-cell dysfunction might not be that severe as in mouse models.</p></div

Peripheral blood T-cell subsets in HAT and in controls.

<p>Blood was taken from HAT patients and non-HAT controls at inclusion (T = 0 months) and after treatment or at the same time point (T = 7 months). All comparisons were performed with the Wilcoxon Signed Rank Test. T-cells expressed as percentage of all lymphocytes. All the T-cell subsets are expressed as percentages of T-cells. Q1–4 refers to the corresponding quarters in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003947#ppat-1003947-g002" target="_blank">Figure 2</a>. Individual data are shown in <a href="http://www.plospathogens.org/article/info:doi/10.1371/journal.ppat.1003947#ppat.1003947.s002" target="_blank">Fig. S2</a>, and can be obtained from the authors upon request.</p

Flow chart of the cases selected for each analysis.

<p>Flow chart of the cases selected for each analysis.</p

Association between clinical characteristics and laboratory-confirmed monkeypox (MPX) or varicella (VZV) case classification.

<p>Association between clinical characteristics and laboratory-confirmed monkeypox (MPX) or varicella (VZV) case classification.</p

Summary of the diagnostic parameters for both case definitions.

<p>Summary of the diagnostic parameters for both case definitions.</p

Flow cytometry dot plot of the CD3+ T-cell population in HAT and in a control.

<p>T-cell subsets were based on the CD27 and CD45RO cell surface markers. A HAT patient before and after treatment (T = 0 and 7 months), and a control at the same time points are shown. Cut-offs for considering a cell surface marker positive or negative are shown as solid lines, and subdivide the graph into 4 quadrants (Q1–Q4). T-cell subsets in each quadrant are expressed as percentages of CD3+ T cells.</p

Iso-agglutinin end-titres in HAT and in controls.

<p>Blood was taken from HAT patients before and after treatment (T = 0 and T = 7 months) and from non-HAT controls at the same time points. n: number of matched pairs used for comparison.</p>a<p>Not calculated due to data loss. Full data can be obtained from the authors upon request.</p

Flow cytometry dot plot of the CD20+ B-cell population in HAT and in a control.

<p>B-cell subsets were based on the CD27 and IgM cell surface markers. A HAT patient before and after treatment (T = 0 and 7 months), and a healthy control subject at the same time points are shown. Cut-offs for considering a cell surface marker positive or negative were based on isotype controls and are shown as solid lines, and subdivide the graph into 4 quadrants (Q1–Q4). B-cell subsets in each quadrant are expressed as percentages of CD20+ B-cells.</p

Characteristics of suspect monkeypox (MPX) cases identified between December 2009 and February 2014 (n = 752).

<p>Characteristics of suspect monkeypox (MPX) cases identified between December 2009 and February 2014 (n = 752).</p

The number of suspect monkeypox (MPX) cases that were captured by Case Definitions A and B by their MPX laboratory case classification.

<p>The number of suspect monkeypox (MPX) cases that were captured by Case Definitions A and B by their MPX laboratory case classification.</p