To determine the pro-inflammatory and
anti-inflammatory cytokine response in HIV-1 patients on cART, a total of 82
patients on first line with and without persiostent low-level viremia were
analyzed. The results indicated higher levels of IL-17, IFN-?, IL-10 and TGF-?
with a median of 23.8, 28.3, 45.2 and 56.9 pg/ml respectively, in HIV-1
patients with persistent low-level viremia. The higher levels of these
cytokines in HIV-1 patients with persistent low-level viremia may indicate a
complex immune response involving both pro-inflammatory and anti-inflammatory
components. The immune response may be influenced by the ongoing presence of
the virus, the need to control viral replication, and the body’s efforts to
balance the inflammatory and regulatory aspects of the immune system [17]. The
increased levels of cytokines, including IL-17 and IFN-? (pro-inflammatory) and
IL-10 and TGF-? (anti-inflammatory), in HIV-1 patients on first line cART with
persistent low level viremia may have distinct roles in the immune response.
Elevated levels of pro-inflammatory cytokines could be seen as an attempt by
the immune system to strengthen inflammation. In the context of HIV-1
infection, this pro-inflammatory response may be necessary for the functioning
of innate immunity, which plays a crucial role in the early defense against
pathogens including viruses [18]. On the
other hand, the presence of anti-inflammatory cytokines could be interpreted as
an effort to counterbalance the pro-inflammatory response. These anti-inflammatory
cytokines may help regulate and slow down the activities of the
pro-inflammatory cytokines. This balance may be important to prevent excessive
inflammation and tissue damage. The interpretation suggests a dynamic interplay
between pro-inflammatory and anti-inflammatory cytokines in response to
persistent low-level viremia in HIV-1 patients. Such a balance is essential for
the proper functioning of the immune system, as an overly aggressive immune
response can be harmful, while an insufficient response may allow the virus to
replicate-unchecked. Elevated levels of
IL-17 and IFN-? may indicate immune activation and inflammation, while
increased levels of IL-10 and TGF-? suggest regulatory mechanisms to
counterbalance the inflammation. The levels of these cytokines could
potentially reflect the extent of HIV-1 proliferation and disease progression.
Higher levels of pro-inflammatory cytokines might be indicative of a more
active viral replication and immune response, while elevated anti-inflammatory
cytokines could represent an attempt to mitigate excessive inflammation [19].
Higher levels of IL-17 were found in HIV-1patients on first line with
persistent low-level viremia (median 23.8pg/ml; p< 0.001) compared to
HIV-1patients with viral suppression (median 15.5pg/ul; p<0.01).
IL-17, also known as interleukin-17, is a
pro-inflammatory cytokine associated with the activation of immune responses,
and plays a key role in the body's defense against infections to recruit other
immune cells to sites of infection or inflammation, and to promote
inflammation, which is a crucial part of the immune response [20]. The findings
of high levels of IL-17 in this study suggest that there may have been a
pro-inflammatory state in HIV-1 patients with persistent low-level viremia.
This pro-inflammatory state could be attributed to increased immune activation
in response to HIV-1 infection typically implying that the immune system is
actively trying to combat the virus, even in patients with low-level viremia
(low levels of viral replication). The presence of low-level viremia in HIV-1
patients indicates that the virus is not fully suppressed by antiretroviral
therapy (ART). The elevated IL-17 levels may be a reflection of the body's
continued efforts to control the virus, even when it's not replicating at high
levels. This could suggest that the virus may be escaping immune surveillance
to some extent. Similar to findings of this study, Noted higher levels of IL-17
in HIV-1 patients on cART [21]. In the study Zhang et al., it was observed that
higher IL-17 levels were found in HIV-1 patients with low CD4 cell counts (less
than 200cells/ml). CD4 cell count is an important prognostic marker in HIV-1
infection and can help predict the risk of disease progression and
complications [22]. In the context of
HIV-1 infection, there is typically an inverse correlation between CD4 cell
count and HIV-1 viral load. This means that as the HIV-1 viral load increases
(indicating more active viral replication), the CD4 cell count tends to decrease,
and vise versa. As viral load decreases due to successful treatment, the CD4
cell count often stabilizes or increases, reflecting a healthier immune system
[23]. The comparison of IL-17 levels in HIV-1 patients with different CD4 cell
counts reported by Zhang. Revealed that high IL-17 levels were associated with
the end stage of acquired immunodeficiency syndrome (AIDS). The findings of
this study reporting high levels of interleukin-17 (IL-17) in HIV-1 patients
with persistent low-level viremia suggest that IL-17 levels could have clinical
significance in the context of HIV-1 transmission and disease progression.
Findings from the multicentre study conducted by J. M.
Rocco and colleagues in 2020 reinforces the earlier findings by suggesting a
correlation between high levels of IL-17 and viral load, CD4 cell count and
IL-17 in HIV-1 patients. The statistical significance of these findings was
indicated by the p-values (P=0.02; p<0.0001). A viral load greater than 1000
copies/ml suggests an elevated level of viral replication in the bloodstream.
When HIV-1 patients with both a low CD4 count and a high viral load exhibit
high levels of IL-17, it underscores the link between immune activation and the
presence of the virus. The observation of high IL-17 levels in these patients
further supports the idea that IL-17 may be associated with an active and
robust immune response in individuals with advanced HIV-1 infection. This could
be a reflection of the immune system's attempt to control the virus. The implication is that IL-17 levels might
serve as an immunological marker for disease progression in HIV-1 patients as
the observations in the current study appear to align with the findings from
Rocco's study, since both studies found higher levels of IL-17 in HIV-1
patients, the current study having the median IL-17 level of 15.5pg/ml with a
p-value of <0.01. In summary, both studies suggest a correlation between
high IL-17 levels and disease progression in HIV-1 patients. The findings of
the study conducted by Mlambo, which suggest a correlation between high levels
of interleukin-17 (IL-17) and high viral load (p=0.012) in HIV-1 infection,
provide further support for the association between IL-17 and HIV-1 disease
characteristics [24]. High levels of
IL-17 correlating with high viral load in HIV-1 infection indicate that there
may be a connection between IL-17 and the extent of viral replication in the
body. High viral load signifies a greater amount of HIV-1 replication, which
typically indicates more active infection and a potentially higher risk of
disease transmission to others. The current study's results indicated that
IL-17 levels were increased in HIV-1 patients with a median viral load of 407.5
copies/ml. The correlation between IL-17 and high viral load suggests that
IL-17 may be produced in response to the presence of the virus. In HIV-1
infection, IL-17 might play a role in the immune response to control or combat
the virus. This finding underscores the potential clinical significance of
monitoring IL-17 levels in HIV-1 patients. If high IL-17 levels are
consistently associated with high viral loads, healthcare providers may
consider IL-17 as a potential marker for assessing disease activity and the
effectiveness of treatment. Overall, the study by Mlambo and colleagues adds to
the growing body of evidence that IL-17 is linked to HIV-1 disease
characteristics, particularly in relation to viral load. Understanding this
association can aid in monitoring and managing HIV-1 infection more
effectively, as well as potentially informing strategies for disease control
and prevention.
The investigation of pro-inflammatory cytokines, such
as interferon-gamma (IFN-?), in HIV-1 patients receiving combination
antiretroviral therapy (cART) is important for understanding the inflammatory
processes associated with HIV-1 infection and the impact of treatment. IFN-? is
a key cytokine in the immune response and plays a role in antiviral defense.
Higher levels of IFN-? were found in HIV-1patients on first line with
persistent low-level viremia (median 28.3;p<0.001) compared to IFN-? levels
in HIV-1patients with viral suppression (median 11.4; p<0.001). Elevated
levels of IFN-? can indicate ongoing immune activation or inflammation, which
is a characteristic feature of HIV-1 infection. Even when viral replication is
suppressed by cART, chronic immune activation may persist, leading to potential
long-term health complications. The elevated levels of IFN-? found in this
study could be indicative of ongoing immune activation or inflammation in HIV-1
patients on cART. IFN-? is a critical component of the immune system's
antiviral response as the cytokine helps protect the host by inhibiting viral
entry, promoting antiviral activity, and regulating the immune response to
ensure an effective defense against viral infections [25]. The high levels of
IFN-? in patients with persistent low-level viremia found in this study may
indeed have been part of the immune response aimed at inhibiting HIV-1 entry at
various levels, reflecting the immune system’s efforts to control the virus.
The presence of replicating virus, as indicated by the high levels of IFN-?,
suggests an ongoing immune response against HIV-1, which aligns with the idea
that the immune system is actively trying to control the infection. The finding
of higher levels of IFN-? in HIV-1 patients who were on combination
antiretroviral therapy (cART) can be interpreted in the following way: HIV-1
infection leads to chronic immune activation and inflammation in the body. Even
though cART is effective in suppressing viral replication and reducing the
viral load, it may not completely normalize the immune system. In some cases,
individuals on cART may still have residual immune activation, which could
result in higher levels of immune response markers like IFN-?.
When individuals with HIV-1 start cART, their immune
system begins to recover as viral replication is controlled in a process known
as immune reconstitution. As the immune system becomes more functional, it can
mount a more robust immune response against the virus, which could lead to
increased levels of cytokines like IFN-?. Even on cART, there can be low-level
viral replication or viral reservoirs that are not completely eliminated. The
observation of elevated IFN-? levels in HIV-1 patients, possibly in response to
viral replication or viral reservoirs that are not completely eliminated,
aligns with the findings of this study, in which there could have been immune
activation as a result of the presence of viral reservoirs. This observation
underscores the complexity of the interaction between the immune system and
HIV-1, as well as the potential for ongoing immune responses even when viral
replication is suppressed. Monitoring such immune responses is important for
understanding the long-term effects of HIV-1 infection and the impact of cART
on the immune system. The contrasting findings between the current study (which
observed high IFN-? levels in HIV-1 patients on cART with persistent low-level
viremia) and the sampled studies (which found reduced levels of IFN-? in HIV-1
patients without viremia) highlight the complexity of immune responses and the
variability that can occur among individuals with HIV-1. Possible explanations for variations may be
HIV-1 is a highly heterogeneous virus, and individuals infected with it can
have varying immune responses and genetic factors that influence how their
immune system responds to the virus and treatment. Differences in the patient
populations studied could explain the contrasting results. The timing of the
studies and the stage of HIV-1 infection in the patient cohorts can also play a
significant role. IFN-? levels and their impact on HIV-1 infection may change
as the disease progresses. The use of cART and the level of viral suppression
can vary among individuals, affecting the immune response. Variations in the
methods and assays used to measure IFN-? levels can also contribute to
different study results. Different laboratories may use different techniques or
assays, and the sensitivity and specificity of these methods can vary. The size
of the study population and statistical power can influence the ability to
detect differences. Larger sample sizes may provide more robust and
generalizable results. HIV-1 strains and subtypes can vary geographically, and
the immune responses may differ accordingly. Differences in the study
populations, such as geographic location and demographic characteristics, may
contribute to varying results.
To elucidate the anti-inflammatory activity of
cytokines in HIV-1infection, the levels of IL-10 were sought. Higher levels of
IL-10 were found in HIV-1 patients with low-level viremia (median 45.2;
p<0.001), compared to IL-10 levels in HIV-1 patients without low-level
viremia. Interleukin-10 (IL-10) is an anti-inflammatory cytokine that plays a
crucial role in regulating the immune response and reducing inflammation. In
the context of HIV-1 infection, the measurement of IL-10 levels is an important
component of understanding the immune response and the balance between pro-inflammatory
and anti-inflammatory factors. The presence of a high level of interleukin-10
(IL-10) in this study suggests a role in regulating the immune response and
reducing inflammation. High levels of IL-10 may indicate the body's attempt to
regulate and dampen excessive immune response as well as controlling and
limiting inflammation, thereby reducing the risk of immune-mediated damage to
the host. In their multicentre cross-sectional study, Rocco and colleagues
found the HIV-1 patients with low CD4 counts (less than 200cells/mm3) and high
viral loads (HIV-1 RNA >100copies/ml) had higher levels of IL-10 (J. M.
Rocco et al., 2020). High viral loads are often associated with HIV-1 disease
progression, and in some cases, elevated IL-10 levels could be a result of
disease progression. High viral loads typically indicate a greater degree of
viral replication and activity in the body. As HIV-1 replicates and infects
more cells, it can lead to a decline in CD4 T-cell counts and an increased risk
of disease progression. High viral loads are a hallmark of uncontrolled HIV-1
infection. In response to the elevated viral load and ongoing viral
replication, the immune system may become more activated, leading to
inflammation. In an effort to regulate and dampen this excessive immune
response, the body may produce higher levels of IL-10. IL-10 acts as a
counterbalance to limit the inflammatory response and immune-mediated damage.
The presence of high IL-10 levels may represent the immune system's attempt to
control the inflammatory response that results from high viral replication.
While high viral loads often signify HIV-1 disease progression, the
relationship between viral load, IL-10 levels, and disease progression is
multifaceted. High IL-10 levels may be a component of the body's response to
regulate inflammation and immune activation in the face of high viral
replication.
This suggests that the high IL-10 levels found in this
study may have been elevated in patients with more advanced HIV-1 disease and
higher viral replication. Zhang and colleagues found high levels of IL-10 in
HIV-1 patients who were on cART. This is interesting because cART is typically
used to suppress viral replication. Similar to findings of this study of high
levels of IL-10 in HIV-1 patients on cART with persistent low-level viremia,
the elevated IL-10 levels in these patients may indeed indicate the presence of
an anti-inflammatory response, possibly as a counterbalance to the
pro-inflammatory state created by both the virus itself and the immune response
to it. Collectively, these findings
suggest that IL-10 might be involved in regulating the balance between
pro-inflammatory and anti-inflammatory responses in HIV-1 infection. The
additional findings mentioned from studies conducted by Gorenec and Kahle
further support the idea that high levels of IL-10 may be a relevant marker in
HIV-1 infection with potential implications for disease progression and
management. In their study, Gorenec and colleagues found that HIV-1 patients
with low-level viremia who were on cART during the chronic stage of HIV-1
infection had elevated levels of IL-10. Kahle and colleagues associated high
levels of IL-10 with seroconversion in HIV-1 patients. This association
suggests that IL-10 levels may be involved in the transition from acute to
chronic infection. Taken together, these findings suggest that IL-10 may serve
as a marker for HIV-1 disease progression and could potentially be used to
predict persistent low-level viremia. Similar to the high levels of IL-10 found
in this study, the study findings reported by Ngangali and colleagues in 2021,
which indicated a positive correlation between IL-10 and viral load in HIV-1
patients, align with the broader pattern of elevated IL-10 levels in the
context of HIV-1 infection. This positive correlation suggests that IL-10 may
indeed be associated with the level of viral replication in these patients.
IL-10 is known to be an anti-inflammatory cytokine that can limit the immune
response to prevent excessive inflammation. In the case of HIV-1, this
suppression of pro-inflammatory responses could be a double-edged sword.
The virus's ability to persist and hide in reservoirs
within the body is a major challenge. Elevated IL-10 levels may represent an
attempt by the immune system to modulate the inflammatory response to avoid
excessive tissue damage and immune activation without necessarily eliminating
the virus completely. This may contribute to the persistence of low-level
viremia in some patients. The findings reported by Twizerimana, where higher
levels of IL-10 were observed in HIV-1 patients prior to the initiation of
combination antiretroviral therapy (cART), provide valuable insights into the
dynamics of IL-10 in the context of HIV-1 infection. These elevated IL-10 levels
could be indicative of an active immune response is reasonable. The elevation
of IL-10 levels in HIV-1 patients prior to cART initiation suggests that the
immune system is actively responding to the presence of the virus, which
triggers the production of IL-10 as a countermeasure to dampen excessive
inflammation. IL-10's ability to regulate the immune response is indeed
beneficial in certain contexts, such as preventing excessive inflammation and
immune-mediated damage. However, in the context of HIV-1 infection, it can also
contribute to the chronicity of the infection and the persistence of the virus.
The high levels of IL-10 found in this study may be indicative of the immune
system's response to chronic HIV-1 infection, where regulation and limiting
inflammation are important. However, this balance may also have implications
for the persistence of the virus in the body. Contrary to findings of this
study, Pina, demonstrate that IL-10 can be produced in HIV-1 patients who are
treatment-naïve and have undetectable viral loads load [26]. This is an
interesting and somewhat contradictory observation compared to the previous
studies that associated high IL-10 levels with active viral replication.
However, these findings may be explained by the complexity of the host-virus
interactions in HIV-1 infection. This could be explained; in some HIV-1
patients, the virus may be slowly proliferating but still effectively
controlled by the immune response and low-level viremia may not be detectable.
In this scenario, IL-10 production could be an adaptive response to counteract
proinflammatory effects associated with the presence of the virus. This
demonstrates the dynamic nature of the immune response in HIV-1 infection. To
further analyze the immunosuppressive activity of cytokines on HIV-1 patients
on cART, the levels of TGF-? were sought. This study found higher levels of
TGF-? in HIV-1 patients on first line with persistent low-level viremia
compared to HIV-1 patients with viral suppression. Transforming growth factor-beta
(TGF-?), an immunoregulatory cytokine showed higher levels, with a median of
56.9pg/ml. Similar to findings of this
study, Dickinson and colleagues found higher levels of TGF-? in HIV-1 patients
across various stages of infection (acute, sub-acute, and chronic) when
compared to negative controls [27]. The findings of higher levels of
transforming growth factor-beta (TGF-?) in HIV-1 patients across various stages
of infection (acute, sub-acute, and chronic) compared to negative controls are
interesting and indicative of the complex interplay between the virus and the
immune system in the context of HIV-1 infection. In the acute phase, the body
may produce TGF-? as part of the initial response to the virus. In the chronic
phase, elevated TGF-? levels might represent a regulatory mechanism to
counterbalance the immune activation and inflammation associated with long-term
infection.
TGF-? also plays a role in tissue repair and fibrosis.
In the context of HIV-1, tissue damage and fibrosis can be significant,
especially in long-term infection. Elevated TGF-? levels may indicate ongoing
tissue repair processes or, in some cases, excessive fibrosis, which can be
detrimental. The presence of higher TGF-? levels across different stages of
HIV-1 infection suggests that the immune response to the virus is dynamic and
multifaceted. TGF-? may be produced to regulate the immune response and limit
excessive inflammation, but it can also have implications for immune
suppression and immune exhaustion. Musa and colleagues observed elevated TGF-?
levels in HIV-1 non-adherent patients but not in cART-adherent patients or
healthy controls. This finding suggests that TGF-? levels may be linked to cART
adherence and treatment response. It implies that the virus may be more active
in non-adherent patients, leading to higher TGF-? levels [28]. These findings,
along with the findings from the current study regarding TGF-? levels in HIV-1
patients with low-level viremia, collectively indicate that high TGF-? levels
may be associated with HIV-1 progression. TGF-? is known for its role in
regulating immune responses and promoting tissue repair. However, in the
context of HIV-1 infection, the virus's ability to persist and evade the immune
system can lead to ongoing immune activation and inflammation, possibly
resulting in the elevation of TGF-?. The implications of these findings may
suggest that monitoring TGF-? levels could be useful in assessing HIV-1 disease
progression and treatment response. However, further research is needed to
establish the specific mechanisms and clinical utility of TGF-? in HIV-1
management. The findings from Osuji, which show elevated TGF-? levels in HIV-1
patients both before the initiation of combination antiretroviral therapy
(cART) and even 12 months into treatment, are in line with the notion that
TGF-? may play a role in chronic immune stimulation and response to residual
HIV-1. Elevated TGF-? levels in HIV-1 patients prior to starting cART may be
indicative of ongoing immune activation in response to the virus.
To evaluate the viral load in HIV-1 patients with and
without persistent low-level viremia, the viral load was determined. This study
found patients with persistent low-level viremia to have viral loads of varying
levels. The median (IQR) viral load in HIV-1 patients with persistent low-level
viremia was 407.5 (314.5, 445.0) copies per ml. The lowest viral load
considered was 209 copies/ml while the highest had 467 copies/ml (both values
presenting as outliers). Patients without persistent low-level viremia had
undetectable viral loads (below 50 copies/mL). The viral load data obtained
suggests that even among these patients, there can be a wide range of viral
load levels. This variability might be influenced by factors such as the
specific antiretroviral medications used, individual patient characteristics,
and potential drug resistance, among other factors. A median viral load of
407.5 copies per ml in found in this study is indeed a notable finding. While
it's not possible to definitively conclude virological failure based solely on
this information, such a viral load level would raise concerns and warrant
further investigation and clinical assessment. In the context of antiretroviral
therapy (ART), one of the primary goals is to achieve and maintain an
undetectable viral load, typically defined as fewer than 50 copies per ml. To
determine the cause of the elevated viral load and whether it indicates
virological failure, clinical evaluation is necessary. This may involve
assessing treatment adherence, checking for drug resistance, and making
adjustments to the treatment regimen if needed. In clinical practice,
individuals with HIV-1 are regularly monitored for viral load, CD4 T-cell
counts, and other relevant markers. An elevated viral load should prompt
healthcare providers to conduct a thorough evaluation, as it may have
implications for the individual's health and the effectiveness of their
treatment. To gain a deeper understanding of the immune response and its
balance in HIV-1 patients on first line cART with and without low-level
viremia, the IL-17/IL-10 ratio was explored.
The findings from this study, which indicate a slight difference in the
IL-17/IL-10 ratio between the two groups of HIV-1 patients (those without
low-level viremia and those with low-level viremia), are important to report.
In this case, the slight difference is not statistically significant, as
indicated by the Z-score and p-value. As seen earlier, the IL-17/IL-10 ratio is
an indicator of the balance between pro-inflammatory (IL-17) and
anti-inflammatory (IL-10) responses within the immune system. The study
revealed that patients without low-level viremia had a slightly higher
IL-17/IL-10 ratio compared to patients with low-level viremia. This indicates
that the pro-inflammatory component may be slightly more prominent in the group
without low-level viremia. Patients without low level viremia had a slightly
higher IL-17/IL-10 ratio 0.556pg/ml (with a range of 0.450 to 1.178), compared
to patients with low-level viremia 0.552 (with a range of 0.442 to 0.882), Z-
score: 0.264, p-value: 0.792 as indicated in Table 2.
The Z-score and p-value confirm that the observed
difference could have occurred by chance and is not a statistically meaningful
difference. While the findings do not suggest a significant difference in the
IL-17/IL-10 ratio between the two groups, they still contribute to the overall
understanding of the immune response in these patients. This information
provides insights into the immune balance but does not indicate a clear trend
or association between low-level viremia and the IL-17/IL-10 ratio in this
particular study. The IL-17/IL-10 ratio is a measure of the balance between
pro-inflammatory (IL-17) and anti-inflammatory (IL-10) cytokines in the immune
system. An imbalance in this ratio can have implications for the immune
response. In the study by Li, it was found that there is an imbalance in the
IL-17/IL-10 ratio in HIV-1 patients. This suggests that HIV-1 infection may
lead to alterations in the immune system's cytokine profile [29-85]. The study
indicates that this imbalance could promote HIV-1 replication. In the context
of HIV-1 infection, an imbalance towards pro-inflammatory cytokines (such as
IL-17) could potentially enhance viral replication by creating a more
permissive environment for the virus. This study results, which found a slight
increase in the IL-17/IL-10 ratio in suppressed HIV-1 patients, suggests that
there might be ongoing HIV-1 replication or immune activation in these
individuals. An elevated IL-17/IL-10 ratio indicates an imbalance in the
pro-inflammatory (IL-17) and anti-inflammatory (IL-10) milieu. The immune
response to HIV-1 is multifaceted, and these cytokines play a role in
modulating that response. Further research is needed to fully elucidate the
mechanisms involved and their clinical implications.
