Asymptomatic COVID-19 Individuals Tend to Establish Relatively Balanced Innate and Adaptive Immune Responses

Abstract

The sharp increase in the proportion of asymptomatic cases and the potential risk of virus transmission have greatly increased the difficulty of controlling the COVID-19 pandemic. The individual immune response is closely associated with clinical outcomes and pathogenic mechanisms of COVID-19. However, the clinical characteristics and immunophenotyping features of immune cells of asymptomatic individuals remain somewhat mysterious. To better understand and predict the disease state and progress, we performed a comprehensive analysis of clinical data, laboratory indexes and immunophenotyping features in 41 patients with SARS-CoV-2 (including 24 asymptomatic cases and 17 symptomatic individuals). Firstly, from the perspective of demographic characteristics, the rate of asymptomatic infection was significantly higher in those with younger age. Secondly, the laboratory test results showed that some indexes, such as CRP (acute phase reaction protein), D-Dimer and fibrinogen (the marker for coagulation) were lower in the asymptomatic group. Finally, symptomatic individuals were prone to establishing a non-protective immune phenotype by abnormally decreasing the lymphocyte count and percentage, abnormally increasing the Th17 percentage and decreasing Treg percentage, which therefore cause an increase in the neutrophil/lymphocyte ratio (NLR), monocytes/lymphocytes ratio (MLR) and Th17/Treg ratio. On the other hand, asymptomatic individuals tended to establish a more effective and protective immune phenotype by maintaining a normal level of lymphocyte count and percentage and a high level of NK cells. At the same time, asymptomatic individuals can establish a relatively balanced immune response through maintaining a low level of monocytes, a relatively low level of Th17 and high level of Treg, which therefore lead to a decrease in MNKR and Th17/Treg ratio and finally the avoidance of excessive inflammatory responses. This may be one of the reasons for their asymptomatic states. This study is helpful to reveal the immunological characteristics of asymptomatic individuals, understand immune pathogenesis of COVID-19 and predict clinical outcomes more precisely. However, owing to small sample sizes, a future study with larger sample size is still warranted.

Stellate ganglion block reduces symptoms of Long COVID: A case series

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Effect of Asymptomatic and Symptomatic COVID-19 on Acute Ischemic Stroke Revascularization Outcomes

“…The pathophysiological mechanisms associated with the risk of intracranial hemorrhage in patients with COVID-19 include systemic inflammation, endothelial dysfunction, increased blood-brain barrier permeability, hyperfibrinolysis, and coagulopathy associated with the infection. [4][5][6][20][21][22][23][24] These alterations have mainly been observed and are more pronounced in symptomatic patients with moderate or severe disease, 25 but they have also been described in asymptomatic infections. [26][27][28] This would explain the excess of bleeding complications after revascularization treatment in patients with both S-COVID and AS-COVID.…”

COVID-19 Infection, Symptoms, and Stroke Revascularization Outcomes: Intriguing Connections

“…Potential underlying mechanisms include systemic inflammation, endothelial dysfunction, blood-brain barrier permeability, hyperfibrinolysis, and infection-associated coagulopathy, which as the authors point out have mostly been observed in moderate or severe disease but have also been reported in asymptomatic infections. [12][13][14] These are considerations that are quite different from typical intercurrent infections and do imply that there may be COVID-specific factors at play.…”