Photodynamic nasal SARS-CoV-2 decolonization shortens infectivity and influences specific T-Cell responses

Abstract

Background: The main objective was to evaluate the efficacy of intranasal photodynamic therapy (PDT) in SARS-CoV-2 mildly symptomatic carriers on decreasing the infectivity period. SARS-CoV-2-specific immune-stimulating effects and safety were also analysed.

Methods: We performed a randomized, placebo-controlled, clinical trial in a tertiary hospital (NCT05184205). Patients with a positive SARS-CoV-2 PCR in the last 48 hours were recruited and aleatorily assigned to PDT or placebo. Patients with pneumonia were excluded. Participants and investigators were masked to group assignment. The primary outcome was the reduction in in vitro infectivity of nasopharyngeal samples at days 3 and 7. Additional outcomes included safety assessment and quantification of humoral and T-cell immune-responses.

Findings: Patients were recruited between December 2021 and February 2022. Most were previously healthy adults vaccinated against COVID-19 and most carried Omicron variant. 38 patients were assigned to placebo and 37 to PDT. Intranasal PDT reduced infectivity at day 3 post-treatment when compared to placebo with a β-coefficient of -812.2 (CI95%= -478660 - -1.3, p<0.05) infectivity arbitrary units. The probability of becoming PCR negative (ct>34) at day 7 was higher on the PDT-group, with an OR of 0.15 (CI95%=0.04-0.58). There was a decay in anti-Spike titre and specific SARS-CoV-2 T cell immunity in the placebo group 10 and 20 weeks after infection, but not in the PDT-group. No serious adverse events were reported.

Interpretation: Intranasal-PDT is safe in pauci-symptomatic COVID-19 patients, it reduces SARS-CoV-2 infectivity and decelerates the decline SARS-CoV-2 specific immune-responses.

Keywords: COVID19; SARS-CoV-2; anti-spike antibody; infectivity; inmunity; photodisinfection; photodynamic therapy.

Figure 1

Flow Chart of patient recruitment. RR , Retention Rate Rate; PDT , Photodynamic Treatment; Ag, Antigen; EOT, End of Treatment; D,Day; W, Week.

Figure 2

Results of infectivity assays and RT-PCR on Nasopharyngeal Swabs. (A) Infectivity assays. Subjects recruited in the study underwent nasopharyngeal swabs at baseline (Day 0), at day 2 and at day 7. The sample was collected in Viral transport medium and was subsequently used for the analysis of infectivity on VeroE6 cells. Seventy-two hours after infection, the supernatant was tested for the presence and quantity of SARS-CoV-2 using RT-PCR for Orf1b gene and human beta actin. Data is expressed in log10 of the delta between beta actin and Orf1b gene fluorescence threshold cycle. A Wilcoxon test for paired data was used for comparing baseline to D2 and D2 to D7. (B) RT-PCR of E and N genes of SARS-CoV-2 from nasopharyngeal swab samples immediately after collection. Data is expressed in fluorescence threshold cycle. A Wilcoxon test for paired data was used for comparing baseline to D2 and D2 to D7. (C) Percentage of “positive” and “negative” individuals in each of the two groups at baseline, D2 and D7, depending on which cycle threshold was chosen. NS, Non Significant; NC, Negative Control; PDT, Photodynamic Therapy.

Figure 3

Results of humoral immunity assays. Patients were followed up after intranasal PDT treatment for 20 weeks. On week 10 and week 20, a sample of plasma and peripheral CD4 and CD8 T lymphocyte was collected (A) Detection of plasma total anti-Spike antibodies. (B) Detection of plasma total anti-Nucleocapsid antibodies. (C) Change of median levels at 20 weeks when compared to 10 weeks. (D) Percentage of change of median antibody levels at 20 weeks with respect to 10 weeks. Anti-S, Anti-Spike, Anti N, Anti Nucleocapsid, W10, 10^th week after End of treatment, W20, 20^th week after End of treatment, PDT, Pthotodynamic Treatment.

Figure 4

Results of cellular immunity assays. Quantiferon assay was used to analyse the specific T-cell responses against specific purified peptides from the spike antigen (S1, S2, RBD subdomains) either using isolated CD4 (A) or a combination of CD4/CD8 (B) T cells from placebo and PDT-treated subjects, or against additional specific peptides from the full genome of SARS-CoV-2 (S, N and M domains) testing both CD4 and CD8 responses (C). (D) Change of median values of IFN units at 20 weeks when compared to 10 weeks for the three assays. (E) Percentage of change of median IFN units at 20 weeks when compared to 10 weeks. Pla, Placebo; PDT, Photodynamic Therapy; W, Week; IFN, Interferon gamma.