Journal: Frontiers in Immunology

Article Title: Early functional maturation of anti-Spike antibodies predicts efficient SARS-CoV-2 RNA clearance

doi: 10.3389/fimmu.2026.1948045

Figure Lengend Snippet: Viral persistence is associated with distinct early antibody responses to SARS-CoV-2. (A–D) Relative levels (OD ratio) of SARS-CoV-2-specific antibodies (anti-Spike IgM, IgA, and IgG, and anti-RBD IgG) in individuals infected with the ancestral Wuhan strain. Participants were stratified into persistent (red) and nonpersistent (blue) groups according to viral RNA persistence during the PCR-positive phase, based on days after symptom onset (DASO). PCR-negative controls are shown in gray. Relative antibody levels were calculated as the ratio between sample absorbance and the cutoff value (CO), defined as the mean absorbance of negative controls plus one standard deviation for each ELISA plate. Values above the cutoff were considered positive. (E–H) Donut charts indicating the proportion and percentage of seropositive and seronegative individuals in the persistent (n = 25) and nonpersistent (n = 35) groups during the early infection phase (0–11 DASO). (I–L) Association between antibody seroconversion and viral load, represented by PCR cycle threshold (Ct) values. Samples collected between 0 and 11 DASO were stratified according to the presence (Ig + ) or absence (Ig - ) of anti-Spike or anti-RBD antibodies. (M) Serum neutralizing activity against the ancestral Wuhan strain measured by PRNT 50 in nonpersistent (blue, n = 13) and persistent (red, n = 14) individuals during early infection (0–11 DASO). Statistical analyses were performed using a mixed-effects model (REML) followed by Tukey’s multiple comparisons test or the Kruskal–Wallis test followed by Dunn’s multiple comparisons post-test, as appropriate. Comparisons between independent groups were performed using the Mann–Whitney U test, and differences in categorical variables, including seropositivity rates, were assessed using Fisher’s exact test. Statistical significance is indicated as follows: ns, not significant; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.

Article Snippet: Next, 50 μL of HRP-conjugated goat anti-human secondary antibody specific for IgG (Fc) (Cat. 2081-05), IgA (Cat. 2053-05), IgM (Cat.2023-05), and IgG subclasses 1–4 (IgG1, Cat. 9054-05; IgG2, Cat.9060-05; IgG3, Cat.9210-05; IgG4, Cat. 9200-05), all from Southern Biotech and diluted 1:8.000 in PBS-1% BSA, were added and incubated for 2h at RT.

Techniques: Infection, Standard Deviation, Enzyme-linked Immunosorbent Assay, Activity Assay, MANN-WHITNEY

Journal: Frontiers in Immunology

Article Title: Early functional maturation of anti-Spike antibodies predicts efficient SARS-CoV-2 RNA clearance

doi: 10.3389/fimmu.2026.1948045

Figure Lengend Snippet: Humoral coordination and IgG subclass dynamics differ between persistent and nonpersistent infection. (A–D) Longitudinal kinetics of SARS-CoV-2 antigen-specific antibody responses in individuals previously infected with the Wuhan strain. The panels display the levels of anti-Spike IgG subclasses (IgG1–4) measured at various time points after symptom onset. Participants are stratified into nonpersistent (blue) and persistent (red) groups based on DASO classification, with PCR-negative controls shown in gray. Repeated-measures analyses were performed using a mixed-effects model (REML) followed by Tukey’s multiple comparisons test or the Kruskal–Wallis test followed by Dunn’s multiple comparisons post-test, as appropriate. (E) Correlation matrices displaying Pearson correlation coefficients between total immunoglobulins and antigen-specific antibodies (anti-Spike IgG1–4 subclasses, anti-Spike IgA/IgM/IgG, anti-RBD IgG, anti-N IgG, and total IgG/IgM) in nonpersistent (left, n = 32) and persistent (right, n = 32) individuals. Color intensity and hue indicate the strength and direction of the correlations (red = negative; blue = positive). Pearson correlation coefficients (r) are shown. Statistical significance: ns (not significant, p ≥ 0.05); *(p < 0.05); **(p < 0.01); ***(p < 0.001); ****(p < 0.0001).

Article Snippet: Next, 50 μL of HRP-conjugated goat anti-human secondary antibody specific for IgG (Fc) (Cat. 2081-05), IgA (Cat. 2053-05), IgM (Cat.2023-05), and IgG subclasses 1–4 (IgG1, Cat. 9054-05; IgG2, Cat.9060-05; IgG3, Cat.9210-05; IgG4, Cat. 9200-05), all from Southern Biotech and diluted 1:8.000 in PBS-1% BSA, were added and incubated for 2h at RT.

Techniques: Infection

Journal: Frontiers in Immunology

Article Title: Early functional maturation of anti-Spike antibodies predicts efficient SARS-CoV-2 RNA clearance

doi: 10.3389/fimmu.2026.1948045

Figure Lengend Snippet: Sustained anti-Spike IgG and ACE2-blocking antibodies despite viral RNA persistence. (A–D) Relative levels (OD ratio) of anti-Spike (anti-S) IgM, IgA, IgG, and anti-RBD IgG in nonpersistent (blue) and persistent (red) individuals during the peri-infection and late convalescence phases. (E–H) Distribution and seroconversion rates of anti-S IgG subclasses (IgG1, IgG2, IgG3, and IgG4) across the same clinical groups and time points. Relative antibody levels were calculated as the ratio between sample absorbance and the cutoff value (CO), defined as the mean absorbance of negative controls plus one standard deviation for each ELISA plate. Values above the cutoff were considered positive. Donut charts indicate the number and percentage of seropositive individuals, with corresponding p-values for inter-group comparisons. (I) Concentration (ng/mL) of ACE2-blocking anti-Spike antibodies measured using multiplex competitive assay in nonpersistent and persistent individuals during the peri-infection and late convalescence phases. Statistical analyses were performed using the Kruskal–Wallis test followed by Dunn’s multiple comparisons post-test and the Mann–Whitney U test, as appropriate. Differences in categorical variables, including seropositivity rates, were assessed using Fisher’s exact test. Statistical significance is indicated as follows: ns, not significant; *p < 0.05; **p < 0.01; ****p<0.0001.

Article Snippet: Next, 50 μL of HRP-conjugated goat anti-human secondary antibody specific for IgG (Fc) (Cat. 2081-05), IgA (Cat. 2053-05), IgM (Cat.2023-05), and IgG subclasses 1–4 (IgG1, Cat. 9054-05; IgG2, Cat.9060-05; IgG3, Cat.9210-05; IgG4, Cat. 9200-05), all from Southern Biotech and diluted 1:8.000 in PBS-1% BSA, were added and incubated for 2h at RT.

Techniques: Blocking Assay, Infection, Standard Deviation, Enzyme-linked Immunosorbent Assay, Concentration Assay, Multiplex Assay, MANN-WHITNEY

Journal: Frontiers in Immunology

Article Title: Early functional maturation of anti-Spike antibodies predicts efficient SARS-CoV-2 RNA clearance

doi: 10.3389/fimmu.2026.1948045

Figure Lengend Snippet: Dynamics of cross-reactive antibodies and early neutralizing capacity against SARS-CoV-2 variants. (A–D) Longitudinal kinetics of cross-reactive anti-Spike IgG responses against SARS-CoV-2 variants (Gamma, Beta, Delta, and Omicron) during the PCR-positive phase, stratified by days after symptom onset (DASO). PCR-negative controls are shown in gray. Relative antibody levels are expressed as OD ratios (sample absorbance/cutoff [CO]); values above the cutoff were considered positive. (E, F) Early cross-reactive anti-Spike IgG responses (0–11 DASO) against the ancestral Wuhan strain and variants of concern in nonpersistent (blue, n = 35) and persistent (red, n = 25) individuals. Donut charts indicate the number and percentage of seropositive individuals for each variant, with corresponding p-values for comparisons relative to the ancestral strain. (G) Early serum neutralizing antibody activity (0–11 DASO) against the Wuhan strain and Omicron variant in nonpersistent (n = 13) and persistent (n = 12) individuals, expressed as PRNT. Repeated-measures analyses were performed using a mixed-effects model (REML) followed by Tukey’s multiple comparisons test or the Kruskal–Wallis test followed by Dunn’s multiple comparisons post-test, as appropriate. Comparisons between independent groups were performed using the Mann–Whitney U test, while paired comparisons were analyzed using the Wilcoxon matched-pairs signed-rank test. Differences in categorical variables, including seropositivity rates, were assessed using Fisher’s exact test. Statistical significance is indicated as follows: ns, not significant; *p<0.05; **p<0.01; ***p<0.001; ****p<0.0001.

Article Snippet: Next, 50 μL of HRP-conjugated goat anti-human secondary antibody specific for IgG (Fc) (Cat. 2081-05), IgA (Cat. 2053-05), IgM (Cat.2023-05), and IgG subclasses 1–4 (IgG1, Cat. 9054-05; IgG2, Cat.9060-05; IgG3, Cat.9210-05; IgG4, Cat. 9200-05), all from Southern Biotech and diluted 1:8.000 in PBS-1% BSA, were added and incubated for 2h at RT.

Techniques: Variant Assay, Activity Assay, MANN-WHITNEY

Journal: Frontiers in Immunology

Article Title: Early functional maturation of anti-Spike antibodies predicts efficient SARS-CoV-2 RNA clearance

doi: 10.3389/fimmu.2026.1948045

Figure Lengend Snippet: Cross-reactive anti-Spike IgG responses to SARS-CoV-2 variants during peri-infection and late convalescence. (A, B, D, E) Relative levels (OD ratio) of cross-reactive anti-Spike IgG against the ancestral Wuhan strain and SARS-CoV-2 variants (Gamma, Beta, Delta, and Omicron) in nonpersistent (blue) and persistent (red) individuals during the peri-infection (A, B) and late convalescence (D, E) phases. (C, F) Inter-group comparisons of antibody levels during the peri-infection and late convalescence phases, respectively. Donut charts indicate the proportion of seropositive individuals, with corresponding p-values for group comparisons. Repeated-measures analyses were performed using a mixed-effects model (REML) followed by Tukey’s multiple comparisons test. Comparisons between independent groups were performed using the Mann–Whitney U test. Differences in categorical variables, including seropositivity rates, were assessed using Fisher’s exact test. Statistical significance is indicated as follows: ns, not significant; *p < 0.05; **p < 0.01; ***p < 0.001; ****p < 0.0001.

Article Snippet: Next, 50 μL of HRP-conjugated goat anti-human secondary antibody specific for IgG (Fc) (Cat. 2081-05), IgA (Cat. 2053-05), IgM (Cat.2023-05), and IgG subclasses 1–4 (IgG1, Cat. 9054-05; IgG2, Cat.9060-05; IgG3, Cat.9210-05; IgG4, Cat. 9200-05), all from Southern Biotech and diluted 1:8.000 in PBS-1% BSA, were added and incubated for 2h at RT.

Techniques: Infection, MANN-WHITNEY

Journal: Frontiers in Immunology

Article Title: Early functional maturation of anti-Spike antibodies predicts efficient SARS-CoV-2 RNA clearance

doi: 10.3389/fimmu.2026.1948045

Figure Lengend Snippet: Longitudinal dynamics of SARS-CoV-2-specific antibody responses following vaccination in convalescent individuals. (A–L) Longitudinal dynamics of anti-Spike antibody responses following vaccination in persistent (red, n = 23) and nonpersistent (blue, n = 10) individuals. (A–C) show anti-Spike IgM, IgA, and IgG responses against the ancestral Wuhan strain, respectively, while (D) shows anti-RBD IgG levels. (E–H) represent anti-Spike IgG subclass responses (IgG1–IgG4) against the Wuhan strain. (I–L) show cross-reactive anti-Spike IgG responses against SARS-CoV-2 variants of concern (Gamma, Beta, Delta, and Omicron). Antibody kinetics were monitored longitudinally from the last convalescence time point through the post-vaccination period. Relative antibody levels are expressed as OD ratios (sample absorbance/cutoff [CO]); values above the cutoff were considered seropositive. Solid lines represent Lowess regression curves. (M) Concentration (ng/mL) of ACE2-blocking anti-Spike antibodies measured using multiplex competitive assay, between nonpersistent (n = 10) and persistent (n = 20) individuals following vaccination. Statistical analyses were performed using the Mann–Whitney U test. ns, not significant.

Article Snippet: Next, 50 μL of HRP-conjugated goat anti-human secondary antibody specific for IgG (Fc) (Cat. 2081-05), IgA (Cat. 2053-05), IgM (Cat.2023-05), and IgG subclasses 1–4 (IgG1, Cat. 9054-05; IgG2, Cat.9060-05; IgG3, Cat.9210-05; IgG4, Cat. 9200-05), all from Southern Biotech and diluted 1:8.000 in PBS-1% BSA, were added and incubated for 2h at RT.

Techniques: Concentration Assay, Blocking Assay, Multiplex Assay, MANN-WHITNEY