SARS-CoV-2 specific immune responses in overweight and obese COVID-19 patients

Abstract

Obesity is a known risk factor for severe respiratory tract infections. In this prospective study, we assessed the impact of being obese or overweight on longitudinal SARS-CoV-2 humoral and cellular responses up to 18 months after infection. 274 patients provided blood samples at regular time intervals up to 18 months including obese (BMI ≥30, n=32), overweight (BMI 25-29.9, n=103) and normal body weight (BMI 18.5-24.9, n=134) SARS-CoV-2 patients. We determined SARS-CoV-2 spike-specific IgG, IgA, IgM levels by ELISA and neutralising antibody titres by neutralisation assay. RBD- and spike-specific memory B cells were investigated by ELISpot, spike- and non-spike-specific IFN-γ, IL-2 and IFN-γ/IL-2 secreting T cells by FluoroSpot and T cell receptor (TCR) sequencing was performed. Higher BMI correlated with increased COVID-19 severity. Humoral and cellular responses were stronger in overweight and obese patients than normal weight patients and associated with higher spike-specific IgG binding titres relative to neutralising antibody titres. Linear regression models demonstrated that BMI, age and COVID-19 severity correlated independently with higher SARS-CoV-2 immune responses. We found an increased proportion of unique SARS-CoV-2 specific T cell clonotypes after infection in overweight and obese patients. COVID-19 vaccination boosted humoral and cellular responses irrespective of BMI, although stronger immune boosting was observed in normal weight patients. Overall, our results highlight more severe disease and an over-reactivity of the immune system in overweight and obese patients after SARS-CoV-2 infection, underscoring the importance of recognizing overweight/obese individuals as a risk group for prioritisation for COVID-19 vaccination.

Keywords: COVID-19; TCR; cellular; neutralising; obesity; overweight; spike; vaccination.

Figure 1

SARS-CoV-2 specific antibody titres are higher in overweight and obese patients. The pie charts in (A) show the proportion of underweight, normal weight, overweight and obese study participants that were home-isolated (disease severity score 1-2) and hospitalised (disease severity score 4-7). Spike-specific IgG endpoint titres were determined by ELISA (B) and neutralising antibody titres (Inhibitory Concentration 50, IC₅₀) against SARS-CoV-2 (Wuhan) were determined by neutralisation assay (C) at 2, 4, 6 and 12 months post symptom onset for normal weight, overweight and obese patients. The ratio of neutralising to spike-specific IgG levels for normal weigh, overweight and obese patients were calculated for paired samples at 2, 6 and 12 months post symptom onset (D). Fold reduction of spike-specific IgG (E) and neutralisation titres (F) relative to the 2 months values were determined at 6 and 12 months post symptom onset for normal weight, overweight and obese patients. Patients that were vaccinated against COVID-19 before the 12 months follow-up were excluded from the figures at the 12 months time-point (n=20). The results in (D–F) are displayed as means with 95% CIs, the results in (B, C) are displayed as geometric means with 95% CIs. In (B, C), statistically significant differences between overweight and normal weight patients are indicated with orange asterisks, and significant differences between obese and normal weight patients indicated with purple asterisks. A non-parametric Kruskal-Wallis test with Dunn’s multiple comparisons test was used to evaluate statistical significance, with * = p<0.05, ** = p<0.01, *** = p<0.001 and **** = p<0.0001.

Figure 2

Spike- and non-spike-specific T cell receptor sequencing showed higher clonal breadth and depth in overweight and obese than in normal weight COVID-19 patients. Spike-specific (A, C) and non-spike-specific (B, D) T cell receptor clonal breadth (A, B) and depth (C, D) were measured using the immunoSEQ T-MAP™ COVID platform at 2, 4, 6 and 12 months post symptom onset. The results are presented as means with 95% CIs. Patients that were vaccinated against COVID-19 before the 12 months follow-up were excluded from the figures at the 12 months time-point (n=20). A non-parametric Kruskal-Wallis test with Dunn’s multiple comparisons test was used to evaluate statistical significance, with * = p<0.05, ** = p<0.01, *** = p<0.001 and **** = p<0.0001.

Figure 3

Spike- and non-spike-specific cytokine-secreting T cell frequencies were higher in overweight/obese COVID-19 patients. Frequencies of IFNγ, IL-2 and IFNγ/IL-2 spike- (A, B) and non-spike (D, E) specific T cells were determined at 6 (A, D) and 12 months (B, E) for normal weight, overweight and obese COVID-19 patients using FluroSpot assay. The total frequencies of cytokine-secreting spike- (C) and non-spike (F) specific T cells were determined for normal weight and the combined group of overweight and obese patients 6 and 12 months. Results for participants that were vaccinated against COVID-19 before 12 months (n=9) were excluded from the 12 months time-point. The results following vaccination at the 18 months follow-up are included in (C, D). Results are presented as means with 95% CIs. A non-parametric Kruskal-Wallis test with Dunn’s multiple comparisons test was used to evaluate statistical significance, with ** = p<0.01 and **** = p<0.0001.

Figure 4

COVID-19 vaccination boosted SARS-COV-2 specific antibody responses in normal weight, overweight and obese individuals. Spike-specific IgG titres were determined by ELISA (A) and neutralising antibody titres (IC₅₀) by microneutralisation assay (B) for paired samples at 12 (pre-vaccination) and 18 months (post-vaccination) for normal weight, overweight and obese patients. The ratios of neutralising/spike-specific IgG titres were calculated post-vaccination at 18 months (C). The fold increase in spike-specific IgG and neutralising titres post-vaccination was calculated relative to the respective values at 12 months (D). Results from study participants that had received COVID-19 vaccine before 12 months (n=20), and unvaccinated (n=11) or unknown vaccination status (n=1) at 18 months were excluded. Frequencies of spike- and RBD-specific IgG MBCs were assessed in 65 patients with paired samples by ELISpot assay at 12 and 18 months. Participants were excluded from the analyses if they were COVID-19 vaccinated before 12 months (n=6) or were unvaccinated at 18 months (n=1) (D). The results in (A, B) are presented as geometric means with 95% CIs, the results in (C–E) are presented as means with 95% CIs. A non-parametric Kruskal-Wallis test with Dunn’s multiple comparisons test was used to evaluate statistical significance, with * = p<0.05 and **** = p<0.0001.