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. 2026 Feb 13;17(3):e01709-25. doi: 10.1128/mbio.01709-25

Fig 1.

Graphs show a requirement for heat-sensitive factors, targeting enveloped but not non-enveloped viruses, titer stability, involvement of the classical complement pathway and IgM, and lack of correlation with serum IgM levels or heavy chain alleles.

Identifying the cause of non-specific neutralization. (A) Neutralization of EBOV-GFP with heated or not heated human serum samples (n = 58). Mean and standard deviation from 1 to 3 repeat experiments/serum are shown. (B) Comparing EBOV-GFP neutralization to SUDV-ZSG and LUJV-ZSG neutralization with a subset of the samples in panel A. Means of 2–3 repeat experiments are shown (n = 20). (C) Neutralization of Wad Medani reovirus with the serum samples from panel B. Mean data from two repeat experiments are shown. (D) Stability of neutralization titer in three individuals. Paired serum samples for three donors, with the samples in teal drawn 5.5–9.5 months after the samples in purple. Mean and range of 2–3 repeats. (E) A serum sample without intrinsic neutralization activity can rescue the activity of a heated sample. Three sera (Neut.X, Y, and Z) were used to neutralize EBOV-GFP either without heat treatment, with heat treatment, or mixed with a non-neutralizing serum (Non.x, y, or z) that had no neutralizing activity of its own. Means and standard deviations from three repeats are shown. (F) Dependency of non-specific neutralization on complement cascade factors. Unheated sera were mixed with mAbs (final 20 µg/mL) or AMY-101 acetate (final 5 µM) or vehicle controls prior to adding EBOV-GFP in a neutralization format. Normalized infectivity from three experimental repeats (mean and standard deviation) with three neutralizing sera and one non-neutralizing serum is shown. (G) EBOV-GFP neutralization curves with selected sera after resin depletion of IgG, IgM, or IgA antibodies. (H) Correlation of EBOV-GFP neutralization titers with IgM concentration. Pearson r and two-tailed P-value shown (n = 20). (I) The observed FRNT50 titers grouped by donor IGHM alleles. (J) Serum IgM titers grouped by donor IGHM alleles. FRNT50(80), focus-reduction neutralization titer 50 (80) %; the titer reducing focus counts by either 50% or 80% (for numerical comparisons, the mid-curve value FRNT50 is used). SUDV-ZSG, Sudan virus with ZsGreen reporter gene. LUJV, Lujo virus.