Therapeutic Potential of a Natural Blend of , , and Extracts in Treating Upper Respiratory Tract Infections: Preliminary Clinical and In Vitro Immunomodulatory Insights.

Upper respiratory tract infections (URTIs) are a prevalent health issue, causing considerable morbidity. Despite the availability of conventional treatments, there is an increasing interest in natural products due to their potential antiviral and immunomodulatory benefits. This study aims to evaluate the efficacy of an ELA blend (E-, L-, A-) in preventing and alleviating the symptoms of URTIs. Additionally, the study examines the blend's antiviral and immunomodulatory effects both in vitro and through a clinical trial. A randomized, double-blind, placebo-controlled trial involved 61 participants prone to URTIs, with a 60-day treatment and follow-up period. A placebo group later received the ELA blend for 60 days. The ELA blend significantly reduced the incidence of URTIs during the observation period (2 vs. 8; = 0.044) and, in particular, throat-related symptoms (8 vs. 16; = 0.038). Analyses of PBMCs showed that baseline production of the cytokines IFN-γ ( = 0.020), IL-1β ( = 0.004), IL-2( < 0.001), IL-6 ( < 0.001), and TNF-α ( < 0.001) increased after ELA blend treatment. Moreover, the ELA blend modulated cytokine production in response to PHA-L stimulation, decreasing IFN-γ ( = 0.008) and IL-2 ( = 0.012) while increasing IL-1β ( = 0.005). Following R848 stimulation, the ELA blend enhanced the production of INF-α ( = 0.012) and IL-2 ( = 0.025), and decreased IL-1β ( < 0.001), IL-6 ( < 0.001), and TNF-α ( = 0.049). The blend suppressed VSV replication and significantly increased cytokine levels, with IFN-γ increasing by 98 pg/mL ( = 0.002), IL-1β rising by 233.0 pg/mL ( = 0.004), and TNF-α showing an increase of 2905 pg/mL ( = 0.002). These findings highlight the ELA blend's potential to alleviate URTI symptoms, modulate inflammatory and antiviral immune responses, and inhibit viral replication. Further investigations should aim to validate these findings through large-scale studies, and explore the ELA blend's long-term safety and efficacy in diverse populations. Additionally, research should investigate optimal dosing strategies and explore potential synergistic effects with conventional treatments to maximize clinical outcomes. Trial registration: retrospectively registered under NCT06020001.