Clinical Trial Details
— Status: Completed
Administrative data
NCT number |
NCT05222347 |
Other study ID # |
SBUSAH GETAT 2020-011 |
Secondary ID |
|
Status |
Completed |
Phase |
|
First received |
|
Last updated |
|
Start date |
September 1, 2020 |
Est. completion date |
September 5, 2021 |
Study information
Verified date |
February 2022 |
Source |
Bezmialem Vakif University |
Contact |
n/a |
Is FDA regulated |
No |
Health authority |
|
Study type |
Observational
|
Clinical Trial Summary
During the Coronavirus Disease-2019 (COVID-19) pandemic, in addition to the current measures,
boosting the immune system seems to be one of preventive measures that can be taken against
COVID-19 infection. Various natural agents have been recommended to boost the immune system.
The aim of this study was to investigate the possible immunomodulatory and preventive effects
of Olive Leaf Tea (OLT) drinking with regards to COVID-19 infection. The study was conducted
among 249 workers in a tractor factory where OLT was served. Of the 249 workers, 168 of them
were OLT drinkers and 81 were not OLT drinkers. Drinking at least one cup of OLT per day for
a minimum of one month was the inclusion criteria used in the study. The workers with a
history of infection or vaccination of COVID-19 were excluded. Lymphocyte subsets, IL2,
INF-gamma, specific IgM, and IgG levels were analyzed in all the study subjects. The results
showed higher values of CD3-/CD16/56 (NK) cells, CD3+/CD16/56 (NKT) cells, total NK (NK+NKT)
cells, and serum IFN-gamma and IL-2 levels in OLT drinkers as compared to the nondrinkers.
These immune changes are indicative of immune defense mechanisms. Although all the OLT
drinkers and non-drinkers reported no history of COVID-19, specific COVID-19 IgG levels were
found positive in 60% of OLT drinkers and 38% OLT non-drinkers. There were significant
negative correlations between age and NK cells, number of cigarettes smoked and NK cells,
number of cigarettes smoked and TNK; and there were positive correlations between OLT
drinking frequency and TNF-alpha, IL-2 and IFN-gamma. Also, serum creatinine levels in OLT
non-drinkers were found significantly higher than in the OLT drinkers. In conclusion,
drinking OLT may contribute fighting against COVID-19 by boosting the innate immune system.
Description:
Coronavirus Disease-2019 (COVID-19) is caused by severe acute respiratory syndrome
coronavirus 2 (SARS-CoV-2). It emerged out of China in late 2019 and rapidly led to a
pandemic in early 2020. As the mutations of the virus continue to increase, the pandemic has
become difficult to control and no specific treatment has been proven to be effective.
According to the European Centre for Disease Prevention and Control (ECDC), until a safe and
effective vaccine is available, non-pharmaceutical tools are accepted as the most effective
public health interventions against COVID-19. World Health Organization (WHO) states that in
addition to public health and social measures, it is also beneficial for individuals to
maintain a balanced diet, stay well hydrated, exercise regularly and sleep well.
It is now clear that there is a close interaction between the COVID-19 and the immune system
of an individual resulting in diverse clinical manifestations of the disease. While some
patients present severe complications, some individuals remain asymptomatic. Weakened
immunity is responsible for most COVID-19 deaths, therefore, elderly people with chronic
diseases are considered at high risk from COVID-19.
As soon as SARS-CoV-2 binds to angiotensin converting enzyme 2 (ACE2) receptors and releases
viral RNA for replication, both the innate and adaptive immune responses are triggered.
Natural killer (NK) cells are innate effector lymphocytes that play a critical role in the
first line of defense against tumor cells and viral infections. They are essential in the
early immune response against viral infections, mainly through the clearance of
virus-infected cells. Human NK cells, CD3-CD56+ NK, represent an average of 15% of peripheral
blood and they can be subdivided based on the relative expression of the surface markers CD16
and CD56. Additionally, in chronic viral infections, CD56-CD16+ NK cells are expanded and
seems to represent an exhausted/anergic subset of NK cells. Through several mechanisms, NK
cells provide exocytosis of perforin and granzyme causing lysis of the infected cell, Fas
ligand-mediated induction of apoptosis, and antibody-dependent cellular cytotoxicity (ADCC),
while having an essential role as immunomodulatory cells that bridge the innate and adaptive
immune responses. Natural killer T cells (NKT) are cells that express a semi-invariant T cell
receptor (TCR). Crucial cytokines for the cytotoxic activity of NK and NKT cells are IL-2 and
INF-gamma, and these cytokines enhance the killing properties and proliferation of these
cells. Both IL-2 and IFN-gamma secretions are induced in a healthy young individual while
this effect decreases in the elderly.
Immune system boosting nutrition may play a role to lower the risk of infections by
inhibiting virus replication, promoting virus clearance, inducing tissue repair, and
triggering a prolonged adaptive immune response against viruses. Besides, certain medicinal
plants are known for their antiviral bioactivities and immune boosting capacity. Some herbs
have immunomodulatory potential and can be applied as a preventive medicine to combat
COVID-19. Olive-leaf tea (OLT) is widely used in the traditional medicine in the
Mediterranean region. Due to the high concentration of phenolic compounds, of which most
abundant is oleuropein, interest in olive leaf has increased recently. The components of the
olive leaves are known for their immune-modulatory, anti-inflammatory, antioxidant,
hypoglycemic, antihypertensive, antimicrobial, and anti-atherosclerotic effects. Although its
antiviral mechanism of action is not fully known, many studies have been conducted on the
antiviral effects of olive leaf extract . However, studies on the protective or immune system
strengthening effect of olive leaf extract against viral diseases are limited. There is only
one available in vitro study that shows olive leaf extract alters the immune response by
increasing the number of CD8 + and NK cells and IFN-gamma. The aim of this study is to
investigate the possible immunomodulatory and preventive effects of OLT against COVID-19.