Discussion
The world observed the SARS outbreak in 2002 and 2003, as well as the
MERS spread in 2011, both of which were caused by coronaviruses. Another
coronavirus that causes respiratory disease was found in Wuhan, China,
near the end of 2019, and was formally designated COVID-19. (13) This
infection has advanced to other regions of China and other countries
since late 2019, and its transmission rate, fatality rate, and clinical
manifestations have all been determined. However, it will take several
months, if not years, to completely understand all of the disease’s
qualities and characteristics, including its genesis, symptoms, and the
patient’s immunological response to this infection. The production of
high levels of cytokines such as IL-1, IL-2, IL-4, IL-6, IL-10, IL-17 ,
TNF- alpha and IFN-gamma in infected patients, is involved in the
underlying pathophysiology of the present COVID-19 pandemic,(13,14)
while specific immunoglobulins IgG and IgM (15), cholesterol levels (16)
CRP (17) and lymphocyte counts (18) are implicated in the diagnosis and
progression of the disease.
In our study there was a significant relationship between lymphocyte
count and all parameters including lymphocyte counts, CRP (P=0.02), IL10
(P=0.0), and cholesterol levels in all groups. (19)This is in accordance
with other studies that have indicated that lymphocyte counts are an
important indicator of COVID-19 and disease progression. (19)
In our study lymphocyte counts in unvaccinated patients 50% had higher
lymphocyte counts while in vaccinated patients only 70% had lymphocyte
counts higher than normal. Lymphocyte counts in all control groups were
normal. In our study since the lymphocyte count measurement was made 2-3
weeks after infection only 15.4% of the patients had lower than normal
counts. Many clinical studies indicated a decrease in lymphocyte counts
which was became a standard diagnosis parameter for COVID. These studies
show that severe disease is specifically identified by an increased
neutrophil count is among the key results which is combined with a lower
lymphocyte count (therefore the neutrophil to lymphocyte ratio has
increased significantly). (20)
In unvaccinated patients 65% had higher cholesterol levels, while in
vaccinated patients only 15% had cholesterol levels higher than normal.
Cholesterol levels in all control groups were normal. Our results show
that 65% of unvaccinated patients in this study have higher cholesterol
levels which might be a reason for the higher susceptibility of this
group and the correlation between the studied cytokines and cholesterol
levels is significant (Table1) which indicates a meaningful relationship
in COVID-19 patients and warrants further investigation. (20)
In the unvaccinated patient group 90% had CRP levels significantly
higher than normal (P<0.05) while in the vaccinated patients
group 80% had higher than normal CRP levels. (Figure 5) CRP levels in
all control groups were normal. Our results show that higher CRP levels
are a reliable indicator for COVID-19 diagnosis in most cases and this
result is in accordance with other studies. (21)
In our study 100% of unvaccinated patients and 90% of vaccinated
patients had significantly higher than normal IL6 levels after the
infection. (Figure 2) IL6 in all control groups were normal. Our
findings correlated with many other clinical studies that indicated that
IL6 is a major inflammatory factor in COVID-19 and plays a key role in
the events leading to a cytokine storm. (22) High levels of IL-6, a
pro-inflammatory cytokine, are known to inhibit NK cell function and
have also been linked to an impaired lytic activity. Disease progression
symptoms such as elevated body temperature, elevations in inflammatory
indicators such as CRP and serum ferritin, and advanced chest computed
tomography imaging were related to higher IL-6 levels that decreased
during recovery in COVID-19 patients. This link between IL-6 and
pulmonary diseases has previously been established in individuals with
radiation-induced pneumonia or severe alveolitis. (23) In our work, also
the levels of IL6 after infection (first day of positive PCR) was higher
than after recovery. (Figure 2)
In our work, 95% of unvaccinated patients and 100% of the vaccinated
patients had statistically significant higher than normal levels of IL10
after the infection as compared to healthy controls. IL10 levels in all
control groups were within the normal range. (Figure 3 ) These results
indicate that an increase in IL-10 during COVID-19 is a hallmark of both
vaccinated and unvaccinated patients. IL-10, on the other hand, is an
anti-inflammatory cytokine that has been observed to be increased in
individuals with severe COVID-19. T-cell stress was also observed to be
associated with IL-6, IL-10, and TNF-levels in COVID-19 patients. IL-10
is a key molecule with the main role of suppressing the inflammatory
process. IL-10 has also been associated with T-cell immune activation
and non-responsiveness in anti-tumor cell responses, in addition to
viral infection. Studies show that an antibody against IL-10 or its
receptor or genetic ablation of IL-10 resulted in the eradication of
viral or bacterial pathogen attacks. Thus, higher IL-10 levels in severe
COVID-19 patients were first attributed to a negative feedback
mechanism, including its anti-inflammatory actions. (23)
In our study 95% of unvaccinated patients and 90% of vaccinated
patients had significantly higher IL17 after the infection. IL17 in all
control groups were normal. (Figure 4) IL-17 specifically boosts
proinflammatory, but not antiviral gene expression in human cells
infected with respiratory viruses by stimulating non immune cells
(fibroblasts and epithelial cells) to produce increased amounts of
proinflammatory cytokines and chemokines in response to viral infections
that attract other immune cell types (for example, neutrophils) which
can lead to increased morbidity while simultaneously remaining
inefficient in inhibiting the spread of the pathogen. Th17 cells appear
to play a major role in COVID-19 disease, not only by stimulating the
cytokine pathway, but also by promoting Th2 responses, blocking Th1
differentiation, and inhibiting regulatory T cells. (24)
Also correlation studies in our work show significant correlation
between CRP, IL-6, IL-10 and IL-17 (Figure 6,7) indicating that common
signaling pathways may be involved between inflammatory factors and
these cytokines as other work have indicated.(25)
In conclusion, it may be inferred that while research on the COVID-19
pandemic at the global level is ongoing our clinical studies have
displayed a meaningful relationship between cholesterol levels, IgM/ IgG
detection, CRP levels and IL-6, IL-10 and IL-17 pointing to the
importance of these immune and metabolic factors for diagnosis and
therapy for COVID-19 patients. Further studies on the long term
consequences of COVID on life quality parameters are also underway and
will shed light on the ambiguous dimensions of the Long COVID phenomena.
This study has been performed for the first time in Iraq , Wasit
province and will serve as an important standard for future basic and
clinical research in this field.