SNPs of ACE1 (rs4343) and ACE2 (rs2285666) genes are linked to SARS-CoV-2 infection but not with the severity of disease

ACE and ACE2 activities and polymorphisms assessment: A populational study from Ipaussu (SP, Brazil) during the COVID-19 pandemic

AIM

The angiotensin-converting enzyme 2 (ACE2) and its homolog, the angiotensin converting enzyme 1 (ACE), are involved in COVID-19 physiopathology. Alterations in the enzymatic structure, expression, and/or activity may influence the risk of infection and severity of disease. For this reason, we aimed to identify different allelic forms of ACE2 G8790A and ACE I/D polymorphisms in a Brazilian cohort and evaluate their impact on ACE and ACE2 activities and their association with COVID-19 susceptibility and severity.

MAIN METHODS

A total of 549 COVID-19-negative and 270 COVID-19-positive participants from Ipaussu, Sao Paulo, Brazil, were recruited. ACE2 and ACE activities were measured by fluorogenic assays using MCA-Ala-Pro-Lys(Dnp) as the substrate for ACE2 and Z-Phe-His-Leu-OH (Z-FHL) and Hippuryl-His-Leu-OH (h-HL) as substrates for ACE. Genomic DNA was extracted from EDTA-peripheral blood, and the regions of the genes containing ACE2 G8790A and ACE I/D polymorphisms were amplified by PCR-restriction fragment length polymorphism and real-time PCR, respectively.

KEY FINDINGS

The G allele of ACE2 G8790A polymorphism and D allele of ACE I/D polymorphism are associated with increased ACE and ACE2 activities. ACE activity ratio (Z-FHL/h-HL), an inflammatory marker, is increased in women with GG genotype and COVID-19-positive diagnosis.

SIGNIFICANCE

For the first time, it was demonstrated that in females, the GG genotype is associated with increased ACE activity ratio (Z-FHL/h-HL) in the COVID-19-positive group. Elevated ACE activity ratio (Z-FHL/h-HL) is highly linked to inflammation and may justify the associations between the G genotype and COVID-19 severity of symptoms and outcomes.

Role of ACE2 and TMPRSS2 polymorphisms in clinical severity and outcomes of COVID-19 in Egypt

Background

The clinical presentations of coronavirus disease 2019 (COVID-19) exhibit significant variation, ranging from asymptomatic cases to mortality resulting from severe pneumonia. Host genetics can partially explain this variation.

Objective

This study evaluated possible associations between severity and outcome of COVID-19 and single nucleotide polymorphism (SNP) rs2285666 in the ACE2 gene and SNP rs2070788 in the TMPRSS2 gene.

Methods

The study included a sample of 100 consecutive adult patients admitted to the COVID-19 Isolation and Intensive Care Units of the Zagazig University Hospitals, Zagazig, Egypt from July 2021 to November 2021. For rs2285666, polymerase chain reaction-restriction fragment length polymorphism was carried out. For rs2070788, real-time polymerase chain reaction was performed.

Results

For rs2285666, the GA genotype was the most frequent among female patients (39% [16/41]) and the A genotype was more prevalent among male patients (54.2% [32/59]). For rs2070788, the AA genotype was the most frequent among all patients (46% [46/100]). No rs2285666 or rs2070788 genotypes or allele frequencies had significant associations with either severity or outcomes of patients.

Conclusion

This study found no significant associations of COVID-19 severity or outcomes of patients with genotypes or allele frequencies of the rs2285666 SNP in the ACE2 gene or the rs2070788 SNP of the TMPRSS2 gene. The search for other genetic associations with COVID-19 infection is still required.

What this study adds

The study reveals that host genetics explain the variation observed in the disease. Specific genetic variants can confer either increased susceptibility or resistance to the disease.

Genetic Polymorphisms of Angiotensin-Converting Enzyme 1 (ACE1) and ACE2 Associated With Severe Acute Respiratory Syndrome COVID-19 in the Palestinian Population

As a key enzyme of the renin-angiotensin system (RAS), angiotensin-converting enzyme 2 (ACE2) is a validated receptor for SARS-CoV-2, linking RAS to COVID-19. Functional ACE1/ACE2 gene polymorphisms likely cause an imbalance in the ACE1/ACE2 ratio, triggering RAS imbalance and may contribute to COVID-19 complications. This study aimed to investigate four single nucleotide polymorphisms (SNPs) of ACE1 and ACE2 genes, three for ACE1 (rs4343, rs4342, rs4341) and one for ACE2 (rs2285666), in patients with COVID-19 among the Palestinian population. A total of 130 blood samples were collected, including 50 negative controls without COVID-19 infection, 50 cases with COVID-19 infection but not hospitalized, and 30 patients with severe COVID-19 infection hospitalized in the intensive care unit. Fragments of the ACE1 and ACE2 genes, including the targeted SNPs, were amplified using multiplex PCR and subsequently genotyped by next-generation sequencing with specific virtual probes. Our results revealed that ACE2 rs2285666 GG genotype carriers were more prevalent in COVID-19 patients compared to the control group (P=0.049), while no statistical differences were observed in the distribution of ACE1 (rs4343, rs4342, rs4341) variants between COVID-19 patients and the control group. GA carriers of ACE2, rs2285666, among cases and ICU groups were at lower risk of getting COVID-19 infection (P=0.002 and P=0.013, respectively), and they were unlikely to develop fatigue (P=0.043), headache (P=0.007), loss of smell (P=0.028), and dyspnea (P=0.005). Age and comorbidities such as hypertension and coronary artery disease (CAD) were independent risk factors for COVID-19 disease. Symptoms of COVID-19 patients such as fatigue, headaches, runny noses, and loss of smell were significantly higher in non-hospitalized cases of COVID-19, while dyspnea was more frequent in the ICU patients. In conclusion, these findings indicate that the ACE2 rs2285666 GG genotype is associated with an increased risk of COVID-19 infection. This association suggests a potential genetic predisposition linked to the ACE2 gene, which may influence the susceptibility and severity of the disease.

Impacts of Inflammatory Cytokines Variants on Systemic Inflammatory Profile and COVID-19 Severity

BACKGROUND

Cytokine storm is known to impact the prognosis of coronavirus disease 2019 (COVID-19), since pro-inflammatory cytokine variants are associated with cytokine storm. It is tempting to speculate that pro-inflammatory cytokines variants may impact COVID-19 outcomes by modulating cytokine storm. Here, we verified this hypothesis via a comprehensive analysis.

METHODS

PubMed, Cochrane Library, Central, CINAHL, and ClinicalTrials.gov were searched until December 15, 2023. Case-control or cohort studies that investigated the impacts of rs1800795 or rs1800629 on COVID-19 susceptibility, severity, mortality, IL-6, TNF-α, or CRP levels were included after an anonymous review by two independent reviewers and consultations of disagreement by a third independent reviewer.

RESULTS

47 studies (8305 COVID-19 individuals and 17,846 non-COVID-19 individuals) were analyzed. The rs1800629 A allele (adenine at the -308 position of the promoter was encoded by the A allele) was associated with higher levels of tumor necrosis factor-α (TNF-α) and C-reactive protein (CRP). In contrast, the rs1800795 C allele (cytosine at the -174 position of the promoter was encoded by the C allele) was linked to higher levels of interleukin-6 (IL-6) and CRP. In addition, the A allele of rs1800629 increased the severity and mortality of COVID-19. However, the C allele of rs1800795 only increased COVID-19 susceptibility.

CONCLUSIONS

rs1800629 and rs1800795 variants of pro-inflammatory cytokines have significant impacts on systemic inflammatory profile and COVID-19 clinical outcomes. rs1800629 may serve as a genetic marker for severe COVID-19.

Serum ACE2 and S19P gene polymorphism in Egyptian patients with COVID-19 infection: correlation with disease severity

The expression of ACE2 is linked to disease severity in COVID-19 patients. The ACE2 receptor gene polymorphisms are considered determinants for SARS-CoV-2 infection and its outcome. In our study, serum ACE2 and its genetic variant S19P rs73635825 polymorphism were investigated in 114 SARS-CoV-2 patients. The results were compared with 120 control subjects. ELISA technique and allele discrimination assay were used for measuring serum ACE2 and genotype analysis of ACE2 rs73635825. Our results revealed that serum ACE2 was significantly lower in SARS-CoV-2 patients (p = 0.0001), particularly in cases with hypertension or diabetes mellitus. There was a significant difference in the genotype distributions of ACE2 rs73635825 A > G between COVID-19 patients and controls (p-value = 0.001). A higher frequency of the heterozygous AG genotype (65.8%) was reported in COVID-19 patients. The G allele was significantly more common in COVID-19 patients (p < 0.0001). The AG and GG genotypes were associated with COVID-19 severity as they were correlated with abnormal laboratory findings, GGO, CXR, and total severity scores with p < 0.05. Our results revealed that the ACE2 S19P gene variant is correlated with the incidence of infection and its severity, suggesting the usefulness of this work in identifying the susceptible population groups for better disease control.

The Role of Angiotensin-Converting Enzyme (ACE) Polymorphisms in the Risk of Development and Treatment of Diabetic Nephropathy

BACKGROUND

Angiotensin-converting enzyme (ACE) is responsible for the production of angiotensin II, and increased production of angiotensin II is observed in diabetes. What is more, ACE polymorphisms may play a role in the development of diabetic nephropathy. The aim of this study was to assess the role of selected ACE polymorphisms (rs4343 and rs4646994) in the risk of development of diabetic nephropathy and in the likelihood of renal replacement therapy.

METHODS

ACE polymorphisms were analyzed in a group of 225 patients who were divided into three subgroups. The rs4343 polymorphism was determined using the PCR-RFLP, and the rs4646994 polymorphism was determined using the PCR. Molecular docking between domains of ACE and its ligands was performed by using AutoDock Vina.

RESULTS

The G/G genotype of rs4343 polymorphism is associated with increased odds of developing diabetic nephropathy. The G allele is also associated with a higher risk of this disease. Similar results were obtained in patients who had already had a kidney transplant as a result of diabetic nephropathy.

CONCLUSIONS

The presence of G/G and G/A genotypes, and the G allele increases the likelihood of developing diabetic nephropathy. This may also be a risk factor for renal replacement therapy.

Genetic association of ACE2 and TMPRSS2 polymorphisms with COVID-19 severity; a single centre study from Egypt

BACKGROUND

Since the emergence of the COVID-19 infection in China, it has caused considerable morbidity, mortality, and economic burden. It causes the vast majority of clinical manifestations, ranging from mild or even no symptoms to severe respiratory failure. There are many risk factors for severe COVID-19, such as old age, male gender, and associated comorbidities. A major role for genetic factors may exist. The SARS-CoV-2 virus enters the cell primarily through ACE2 receptors. rs2285666 is one of many polymorphisms found in the ACE2 receptor gene. To enable endosome-independent entry into target cells, the transmembrane protease serine-type 2 (TMPRSS2) is necessary to cleave the virus' spike (S) glycoprotein. TMPRSS2 is characterized by an androgen receptor element. The rs12329760 polymorphism in TMPRSS2 may explain different genetic susceptibilities to COVID-19.

METHOD

This cross-sectional study was held in Mansoura University Hospitals during the period from June 2020 to April 2022 on patients who had mild and severe COVID-19. Demographic, clinical, and laboratory data were collected, and the TaqMan real-time polymerase chain was used for allelic discrimination in the genotyping of rs2285666 and rs12329760.

RESULTS

This study included 317 Egyptian patients, aged from 0.2 to 87 years. Males were 146, while females were 171. They were divided into mild and severe groups (91 and 226 patients, respectively) based on their clinical symptoms. There was a significant association between COVID-19 severity and male gender, hypertension, diabetes mellitus, and high CRP. The genotype and allele frequency distributions of the ACE2 rs2285666 polymorphism showed no significant association with the severity of COVID-19 in both. In contrast, in TMPRSS2 rs12329760 minor T allele and CT, TT genotypes were significantly associated with a reduced likelihood of developing severe COVID-19.

CONCLUSION

Our study indicates that the ACE2 rs2285666 polymorphism is not related to the severity of COVID-19, whether genotypes or alleles. In TMPRSS2 rs12329760, the dominant model and T allele showed significantly lower frequencies in severe cases, with a protective effect against severity. The discrepancies with previous results may be due to variations in other ACE2 receptor-related genes, inflammatory mediators, and coagulation indicators. Haplotype blocks and differences in racial makeup must be taken into consideration. Future research should be done to clarify how ethnicity affects these polymorphisms and how other comorbidities combine to have an additive effect.

ACE I/D polymorphism is a risk factor for the clinical severity of COVID-19 in Brazilian male patients

BACKGROUND

The renin-angiotensin system is potentially involved in the pathogen-host interaction in the disease caused by SARS-CoV-2, since the angiotensin-converting enzyme (ACE) 2 serves as a receptor for the virus. The impact of the pandemic in specific regions and ethnic groups highlights the importance of investigating genetic factors that disrupt the balance of the system in response to SARS-CoV-2 infection, especially in genes with ethnic frequency variations. Therefore, this study aimed to evaluate the influence of the ACE I/D polymorphism on the incidence and severity of COVID-19 in a sample of the Brazilian population.

METHODS AND RESULTS

70 severe cases and 355 mild cases patients were evaluated. DNA extraction was performed using a QIAamp DNA Blood Mini kit. Genotyping of ACE I/D polymorphism was performed. Clinical outcomes were obtained from the patients' records. We found an association between the ACE I/D polymorphism and the incidence or severity of COVID-19 in male participants. Moreover, we observed a relationship between severity and increasing age and body weight and a higher frequency of II genotype individuals among those who had a cough as their symptoms in mild patients. No differences were observed in leukocyte count or other parameters related to the inflammatory response in severe patients.

CONCLUSIONS

Our data showed the influence of the ACE I/D polymorphism on severity of COVID-19 in males, as well as on the occurrence of cough in patients with mild symptoms, with a higher incidence in those carrying the I allele.

Association of genetic polymorphisms with COVID-19 infection and outcomes: An updated meta-analysis based on 62 studies

Background

The relationship between genetic polymorphisms and coronavirus disease 2019 (COVID-19) remains to be inconsistent. This meta-analysis aimed to provide an updated evaluation of the role of genetic polymorphisms in the infection, severity and mortality of COVID-19 based on all available published studies.

Methods

A systematic search was performed using six databases: PubMed, Embase, Web of Science, Cochrane Library, Chinese National Knowledge Infrastructure (CNKI) and Wanfang. Summary odds ratios (ORs) and corresponding 95 % confidence intervals (CIs) were used to calculate the genotypic comparison. All statistical analyses were conducted in Stata 12.0.

Results

A total of 62 studies with 19600 cases and 28899 controls was included in this meta-analysis. For COVID-19 infection, ACE Ins/Del polymorphism might be related with significantly decreased risk of COVID-19 infection under dominant, homozygote and allelic models. Meanwhile, the IFITM3 rs12252 and TMPRSS2 rs12329760 polymorphisms were significantly associated with the increased risk of COVID-19 infection under one or more models. Regarding COVID-19 severity, ACE2 rs2074192, ACE2 rs2106809, IFITM3 rs12252 and VDR rs1544410 polymorphisms might be related with significantly increased risk of COVID-19 severity in one or more models. Moreover, the analysis of TMPRSS2 rs2070788 indicated that a variant A allele decreased the risk of COVID-19 severity in recessive model. For COVID-19 mortality, the variant C allele of IFITM3 rs12252 polymorphism might be related with significantly increased risk of COVID-19 mortality under all genetic models.

Conclusions

This meta-analysis indicated that he infection, severity or mortality of COVID-19 were related to the above genetic polymorphisms, which might provide an important theoretical basis for understanding the clinical feature of COVID-19 disease.

Angiotensin-Converting Enzyme-2 (ACE-2) with Interferon-Induced Transmembrane Protein-3 (IFITM-3) Genetic Variants and Interleukin-6 as Severity and Risk Predictors among COVID-19 Egyptian Population

Introduction

The host genetic background is a crucial factor that underlies the interindividual variability of COVID-19 fatality and outcomes. Angiotensin-converting enzyme-2 (ACE-2) and interferon-induced transmembrane protein-3 (IFITM-3) have a key role in viral cell entrance and priming. The evoked immune response will also provide a predictive prognosis for COVID-19 infection. This study aimed to explore the association between ACE-2 and IFITM-3 genotypes and their corresponding allele frequencies with disease severity indices in the Egyptian COVID-19 population. The serum level of interleukin-6, as a biomarker of hyperinflammatory response, and cytokine storm, was correlated with disease progression, single nucleotide polymorphisms (SNPs) of the selected receptors, and treatment response. Methodology. We enrolled 900 COVID-19-confirmed cases and 100 healthy controls. Genomic DNA was extracted from 200 subjects (160 patients selected based on clinical and laboratory data and 40 healthy controls). The ACE-2 rs2285666 and IFITM-3 rs12252 SNPs were genotyped using the TaqMan probe allelic discrimination assay, and the serum IL-6 level was determined by ELISA. Logistic regression analysis was applied to analyze the association between ACE-2 and IFITM-3 genetic variants, IL-6 profile, and COVID-19 severity.

Results

The identified genotypes and their alleles were significantly correlated with COVID-19 clinical deterioration as follows: ACE2 rs2285666 CT + TT, odds ratio (95% confidence interval): 12.136 (2.784-52.896) and IFITM-3 rs12252 AG + GG: 17.276 (3.673-81.249), both p < 0.001. Compared to the controls, the heterozygous and mutant genotypes for both SNPs were considerable risk factors for increased susceptibility to COVID-19. IL-6 levels were significantly correlated with disease progression (p < 0.001).

Conclusion

ACE-2 and IFITM-3 genetic variants are potential predictors of COVID-19 severity, critical outcomes, and post-COVID-19 complications. Together, these SNPs and serum IL-6 levels explain a large proportion of the variability in the severity of COVID-19 infection and its consequences among Egyptian subjects.

Genetic polymorphisms of ACE1, ACE2, IFTM3, TMPRSS2 and TNFα genes associated with susceptibility and severity of SARS-CoV-2 infection: a systematic review and meta-analysis

BACKGROUND

Some human polymorphisms of ACE1, ACE2, IFITM3, TMPRSS2 and TNFα genes may have an effect on the susceptibility to SARS-CoV-2 infection and increase the risk to develop severe COVID-19. We conducted a systematic review of current evidence to investigate the association of genetic variants of these genes with the susceptibility to virus infection and patient prognosis.

METHODS

We systematically searched Medline, Embase and The Cochrane Library for articles published until May 2022, and included observational studies covering genetic association of ACE1, ACE2, IFITM3, TMPRSS2 and TNFα genes with COVID-19 susceptibility or prognosis. We evaluated the methodological quality of included studies, and pooled data as convenient in meta-analysis (MA). Odds ratio (OR) values and 95% confidence intervals were calculated.

RESULTS

We included 35 studies (20 on ACE, 5 each on IFITM3, TMPRSS2, TNFα), enrolling 21,452 participants, of them 9401 were COVID-19 confirmed cases. ACE1 rs4646994 and rs1799752, ACE2 rs2285666, TMPRSS2 rs12329760, IFITM3 rs12252 and TNFα rs1800629 were identifies as common polymorphisms. Our MA showed an association between genetic polymorphisms and susceptibility to SARS-CoV-2 infection for IFITM3 rs12252 CC (OR 5.67) and CT (OR 1.64) genotypes. Furthermore, MA uncovered that both ACE DD (OR 1.27) and IFITM3 CC (OR 2.26) genotypes carriers had a significantly increased risk of developing severe COVID-19.

DISCUSSION

These results provide a critical evaluation of genetic polymorphisms as predictors in SARS-CoV-2 infection. ACE1 DD and IFITM3 CC polymorphisms would lead to a genetic predisposition for severe lung injury in patients with COVID-19.

Genotype variation of ACE and ACE2 genes affects the severity of COVID-19 patients

OBJECTIVE

Genetic polymorphisms in ACE and ACE2 genes are involved in the RAS regulation of blood pressure and their activity may confer susceptibility to hypertension. In addition, they may play a role in SARS-CoV-2 pathogenesis and the severity of COVID-19. This study aims to determine the effect of genetic variations in the ACE (rs4331) and ACE2 (rs2074192) genes with hypertension comorbidity on the severity of COVID-19 in the Indonesian population.

RESULT

186 patients were enrolled and assigned into the COVID-19 group (n = 95) and non-COVID-19 group (n = 91) in this cross-sectional study. GG genotype frequency was dominant in ACE gene, but there were no significant differences between the groups (p = 0.163). The two groups had a significant difference (p = 0.000) for the CC genotype frequency (0,37 vs. 0.01) in the ACE2 gene. The proportion of women with COVID-19 is higher (51%), but men with hypertension had more severe symptoms (44%). Men with hypertension comorbidity, GG (ACE), and TT (ACE2) genotypes tended to have moderate-to-severe symptoms (25%). Similarly, women with hypertension as well as GG and CT genotypes tended to have moderate-to-severe symptoms (21%). We conclude that hypertension and mutations in the ACE (rs4331) and ACE2 (rs2074192) genes affect the severity of COVID-19.

A comprehensive review of ACE2, ACE1, TMPRSS2 and IFITM3 gene polymorphisms and their effect on the severity of COVID-19

Recent events have raised concerns about the outbreak of a pandemic by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). An infection caused by a virus can provoke an inflammatory reaction, which can result in severe lung damage, failure of several organs, and death. The unique genetic makeup of each individual may be a component in the development of each of these responses. In this context, genetic variants of the genes linked to the invasion of the virus into the host's body can be analyzed. Various elements have a function in viral entry. ACE2 is used by SARS-CoV-2 as a receptor to enter the cell. TMPRSS2 is then responsible for cutting the virus into its components. In addition, lung damage occurs when there is an imbalance between ACE1 and ACE2. Another component that plays a significant role in virus penetration is called IFITM3, which is created as a reaction to interferon. This protein prevents viruses in the Coronaviridae family from entering cells. This study aimed to analyze DNA polymorphisms in the ACE2, ACE1, TMPRSS2, and IFITM3 genes. Findings showed certain polymorphisms appear to be associated with the severity of the disease, including respiratory, coronary, and neurological disorders. The results also indicated that certain polymorphisms were protective against this virus. Varying populations have a different frequency of high-risk polymorphisms, so different treatment and preventative techniques must be implemented. Additional population studies should be conducted in this region to reduce the incidence of COVID-19-related morbidity and mortality.

The impact of ACE2 polymorphisms (rs1978124, rs2285666, and rs2074192) and ACE1 rs1799752 in the mortality rate of COVID-19 in different SARS-CoV-2 variants

BACKGROUND

Clinical severity of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outcomes could be influenced by genetic polymorphisms in angiotensin I-converting enzyme (ACE1) and ACE2. This study aims to examine three polymorphisms (rs1978124, rs2285666, and rs2074192) on the ACE2 gene and ACE1 rs1799752 (I/D) in patients who have coronavirus disease 2019 (COVID-19) with various SARS-CoV-2 variants.

METHODS

Based on polymerase chain reaction-based genotyping, four polymorphisms in the ACE1 and ACE2 genes have been identified in 2023 deceased patients and 2307 recovered patients.

RESULTS

The ACE2 rs2074192 TT genotype was associated with the COVID-19 mortality in all three variants, whereas the CT genotype was associated with the Omicron BA.5 and Delta variants. ACE2 rs1978124 TC genotypes were related to COVID-19 mortality in the Omicron BA.5 and Alpha variants, but TT genotypes were related to COVID-19 mortality in the Delta variant. It was found that ACE2 rs2285666 CC genotypes were associated with COVID-19 mortality in Delta and Alpha variants, and CT genotypes in Delta variants. There was an association between ACE1 rs1799752 DD and ID genotypes in the Delta variant and COVID-19 mortality, whereas there was no association in the Alpha or Omicron BA.5 variants. In all variants of SARS-CoV-2, CDCT and TDCT haplotypes were more common. In Omicron BA.5 and Delta, CDCC and TDCC haplotypes were linked with COVID-19 mortality. In addition to COVID-19 mortality, the CICT, TICT, and TICC were significantly correlated.

CONCLUSION

The ACE1/ACE2 polymorphisms had an impact on COVID-19 infection, and these polymorphisms had different effects in various SARS-CoV-2 variants. To confirm these results, however, more research needs to be conducted.

Angiotensin-converting enzyme 2 (ACE2) polymorphisms and susceptibility of severe SARS-CoV-2 in a subset of Pakistani population

Science is digging for the varied presentation of COVID-19 patients exposed to the same risk factors, and medical conditions may be influenced by the presence of polymorphic genetic variants. This study investigated the link between ACE2 gene polymorphisms and the severity of SARS-CoV-2. This cross-sectional study recruited COVID-19 PCR-positive patients by consecutive sampling from Ziauddin Hospital from April to September 2020. DNA was extracted from whole blood, followed by gene amplification and Sanger's sequencing. Most of the patients, 77: 53.8%, were serious. Males were higher (80; 55.9%) with age more than 50 years (106: 74.1%). We found 22 ACE2 SNPs. rs2285666 SNP was most prevalent with 49.2% CC, 45.2% TT, 4.8% CT heterozygosity, and 0.8% AA genotypes. Variants with multiple genotypes were also insignificantly associated with the severity of COVID-19 in the analysis of the dominant model. Only rs2285666 had a significant statistical link with gender (p-value 0.034, OR; 1.438, CI; 1.028-2.011) while rs768883316 with age groups (p-value 0.026, OR; 1.953, CI; 1.085-3.514). Haplotypes ATC of three polymorphisms (rs560997634, rs201159862, and rs751170930) commonly found in 120 (69.77%) and TTTGTAGTTAGTA haplotype consisting of 13 polymorphisms (rs756737634, rs146991645, rs1601703288, rs1927830489, rs1927831624, rs764947941, rs752242172, rs73195521, rs781378335, rs756597390, rs780478736, rs148006212, rs768583671) in 112 (90.32%) had statistically significant association with the severity having p = value 0.029 and 0.001 respectively. Males of old age and diabetics are found to have more severe COVID-19 infection in the current study. We also found that common ACE2 polymorphism rs2285666 influences the susceptibility of acquiring the severe SARS-CoV-2 infection.

Analyzing the role of ACE2, AR, MX1 and TMPRSS2 genetic markers for COVID-19 severity

BACKGROUND

The use of molecular biomarkers for COVID-19 remains unconclusive. The application of a molecular biomarker in combination with clinical ones that could help classifying aggressive patients in first steps of the disease could help clinician and sanitary system a better management of the disease. Here we characterize the role of ACE2, AR, MX1, ERG, ETV5 and TMPRSS2 for trying a better classification of COVID-19 through knowledge of the disease mechanisms.

METHODS

A total of 329 blood samples were genotyped in ACE2, MX1 and TMPRSS2. RNA analyses were also performed from 258 available samples using quantitative polymerase chain reaction for genes: ERG, ETV5, AR, MX1, ACE2, and TMPRSS2. Moreover, in silico analysis variant effect predictor, ClinVar, IPA, DAVID, GTEx, STRING and miRDB database was also performed. Clinical and demographic data were recruited from all participants following WHO classification criteria.

RESULTS

We confirm the use of ferritin (p < 0.001), D-dimer (p < 0.010), CRP (p < 0.001) and LDH (p < 0.001) as markers for distinguishing mild and severe cohorts. Expression studies showed that MX1 and AR are significantly higher expressed in mild vs severe patients (p < 0.05). ACE2 and TMPRSS2 are involved in the same molecular process of membrane fusion (p = 4.4 × 10^-3), acting as proteases (p = 0.047).

CONCLUSIONS

In addition to the key role of TMPSRSS2, we reported for the first time that higher expression levels of AR are related with a decreased risk of severe COVID-19 disease in females. Moreover, functional analysis demonstrates that ACE2, MX1 and TMPRSS2 are relevant markers in this disease.

Genetic Variants within SARS-CoV-2 Human Receptor Genes May Contribute to Variable Disease Outcomes in Different Ethnicities

The novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has evolved into a global pandemic, with an alarming infectivity and mortality rate. Studies have examined genetic effects on SARS-CoV-2 disease susceptibility and severity within Eurasian populations. These studies identified contrasting effects on the severity of disease between African populations. Genetic factors can explain some of the diversity observed within SARS-CoV-2 disease susceptibility and severity. Single nucleotide polymorphisms (SNPs) within the SARS-CoV-2 receptor genes have demonstrated detrimental and protective effects across ethnic groups. For example, the TT genotype of rs2285666 (Angiotensin-converting enzyme 2 (ACE2)) is associated with the severity of SARS-CoV-2 disease, which is found at higher frequency within Asian individuals compared to African and European individuals. In this study, we examined four SARS-CoV-2 receptors, ACE2, Transmembrane serine protease 2 (TMPRSS2), Neuropilin-1 (NRP1), and Basigin (CD147). A total of 42 SNPs located within the four receptors were reviewed: ACE2 (12), TMPRSS2 (10), BSG (CD147) (5), and NRP1 (15). These SNPs may be determining factors for the decreased disease severity observed within African individuals. Furthermore, we highlight the absence of genetic studies within the African population and emphasize the importance of further research. This review provides a comprehensive summary of specific variants within the SARS-CoV-2 receptor genes, which can offer a better understanding of the pathology of the SARS-CoV-2 pandemic and identify novel potential therapeutic targets.

Single Nucleotide Variants (SNVs) of Angiotensin-Converting Enzymes (ACE1 and ACE2): A Plausible Explanation for the Global Variation in COVID-19 Prevalence

Background. Although it is common knowledge that the coronavirus disease of 2019 (COVID-19) and other viral infections have an uneven impact globally, the reasons for this are still indistinct. The absence of equivalent capacities worldwide in screening, testing, and reporting of cases is one of the ideas put forward to explain this discrepancy. The molecular developments are noteworthy, particularly the role played by single nucleotide polymorphisms (SNPs) in ACEs (ACE1 and ACE2). The virus can enter the host cell thanks to the transmembrane protein ACE2, which is a homolog of ACE1. Objectives. With a focus on the I/D genotype of ACE1 and the rs2285666 SNV of ACE2, we elucidated the prevalence of SNPs in ACE1 and ACE2 in various geographic locations. We examined the relationship between these SNPs and the global patterns of COVID-19 prevalence. Methods. 66 of the 127 articles obtained using PubMed, Google Scholar, and Google directly conformed to the search terms; geographical distribution of viral infections, the prevalence of COVID-19, ACE1, ACE2, SNPs, and prevalence of the DD genotype, and rs2285666. Results. The DD genotype of ACE1 and the rs2285666 SNV of ACE2 are vital in their gene expression and contribute greatly to viral disease susceptibility, development, and severity. There was generally a high prevalence of the DD genotype in Europe and America, where COVID-19 had a more devastating effect than in Asia and Africa. The prevalence of the SNV rs2285666 varied in the following order: East Asia> South Asia >America>Europe >Africa. However, there were conflicting agreements in the association of rs2285666 with COVID-19 susceptibility and prevalence. Conclusion. The ACE1 DD genotype and COVID-19 prevalence have been positively linked in a number of studies. The ACE2 rs2285666 SNV, however, has yielded no definitive results. To determine the relationship between these SNVs and COVID-19 incidence, more research is required.

Study of frequency and inheritance model of ACE1 I/D and ACE2 rs2285666 polymorphisms in COVID-19 patients with varying severity of lung involvement and its effect on serum cytokines levels

The angiotensin-converting enzyme (ACE) has been shown to play a role as a receptor for the COVID-19 virus. This virus usually gets into cells and infects them by attaching to their glycoprotein receptors, which are found on the ACE2 receptor. The aim of this study was to evaluate the frequency and inheritance of ACE1 I/D and ACE2 rs2285666 polymorphisms in COVID-19 patients with varying severity of lung involvement and its effect on serum cytokines levels of interleukin (IL)-1 and IL-6 and laboratory parameters. One hundred eighty-five COVID-19 patients were grouped according to the severity of lung involvement. (I/D) polymorphism of the ACE1 gene and rs2285666 polymorphism of the ACE2 gene were determined by single specific primer-polymerase chain reaction and restriction fragment length reaction-polymerase chain reaction methods, respectively. Serum levels of IL-1 and IL-6 were also measured by the enzyme linked immunosorbent assay technique. No statistically significant association of ACE2 rs2285666 polymorphism genotypes and ACE1 I/D with the severity of lung involvement was noted. However, there was a statistically significant association between I/D ACE1 polymorphism genotypes and IL-6, white blood cells (WBC), and neutrophil-to-lymphocyte ratio (NLR) levels. Also, there was no statistically significant association between rs2285666 polymorphism genotypes and patients' blood oxygen saturation level, IL-6, IL-1β, lactate dehydrogenase activity, WBC count, and NLR. In patients with COVID-19, the rs2285666 polymorphism of the ACE2 gene and the I/D polymorphism of the ACE1 gene were not significantly associated with the severity of COVID-19 disease and serum IL-6 and IL-1 cytokine levels.

Relevance of TMPRSS2, CD163/CD206, and CD33 in clinical severity stratification of COVID-19

Background

Approximately 13.8% and 6.1% of coronavirus disease 2019 (COVID-19) patients require hospitalization and sometimes intensive care unit (ICU) admission, respectively. There is no biomarker to predict which of these patients will develop an aggressive stage that we could improve their quality of life and healthcare management. Our main goal is to include new markers for the classification of COVID-19 patients.

Methods

Two tubes of peripheral blood were collected from a total of 66 (n = 34 mild and n = 32 severe) samples (mean age 52 years). Cytometry analysis was performed using a 15-parameter panel included in the Maxpar® Human Monocyte/Macrophage Phenotyping Panel Kit. Cytometry by time-of-flight mass spectrometry (CyTOF) panel was performed in combination with genetic analysis using TaqMan® probes for ACE2 (rs2285666), MX1 (rs469390), and TMPRSS2 (rs2070788) variants. GemStone™ and OMIQ software were used for cytometry analysis.

Results

The frequency of CD163+/CD206- population of transitional monocytes (T-Mo) was decreased in the mild group compared to that of the severe one, while T-Mo CD163-/CD206- were increased in the mild group compared to that of the severe one. In addition, we also found differences in CD11b expression in CD14dim monocytes in the severe group, with decreased levels in the female group (p = 0.0412). When comparing mild and severe disease, we also found that CD45- [p = 0.014; odds ratio (OR) = 0.286, 95% CI 0.104–0.787] and CD14dim/CD33+ (p = 0.014; OR = 0.286, 95% CI 0.104–0.787) monocytes were the best options as biomarkers to discriminate between these patient groups. CD33 was also indicated as a good biomarker for patient stratification by the analysis of GemStone™ software. Among genetic markers, we found that G carriers of TMPRSS2 (rs2070788) have an increased risk (p = 0.02; OR = 3.37, 95% CI 1.18–9.60) of severe COVID-19 compared to those with A/A genotype. This strength is further increased when combined with CD45-, T-Mo CD163+/CD206-, and C14dim/CD33+.

Conclusions

Here, we report the interesting role of TMPRSS2, CD45-, CD163/CD206, and CD33 in COVID-19 aggressiveness. This strength is reinforced for aggressiveness biomarkers when TMPRSS2 and CD45-, TMPRSS2 and CD163/CD206, and TMPRSS2 and CD14dim/CD33+ are combined.

The effect of ACE2 receptor, IFN-γ, and TNF-α polymorphisms on the severity and prognosis of the disease in SARS-CoV-2 infection

To investigate the effect of genetic variations in the angiotensin converting enzyme (ACE), interferon (IFNG) and tumor necrosis factor (TNF-α) genes on the severity of coronavirus disease (COVID-19). Between September and December 2021, 33 patients with COVID-19 were included in this prospective study. The patients were classified and compared according to disease severity: mild&moderate (n = 26) vs severe&critical (n = 7). These groups were evaluated to assess possible relationships with ACE, TNF-α and IFNG gene variations using univariate and multivariable analyses. The median age of the mild&moderate group was 45.5 (22-73), and that of the severe&critical group was 58 (49-80) years (p = 0.014). Seventeen (65.4%) of the mild&moderate patients and 3 (42.9%) of severe&critical patients were female (p = 0.393). According to results of univariate analysis, the percentage of patients with the c.418-70C>G variant of the ACE gene was significantly higher in the mild&moderate group (p = 0.027). The ACE gene polymorphisms, c.2312C>T, c.3490G>A, c.3801C>T, and c.731A>G, were each only seen in separate patients with critical disease. The following variants were observed more frequently in the mild&moderate group: c.582C>T, c.3836G>A, c.511+66A>G, c.1488-58T>C, c.3281+25C>T, c.1710-90G>C, c.2193A> G, c.3387T>C for ACE; c.115-3delT for IFNG; and c.27C>T for TNF. It can be expected that patients carrying the ACE gene c.418-70C>G variant may present with a mild clinical manifestation of COVID-19. Several genetic polymorphisms may be associated with pathophysiology, as they appear to help predict COVID-19 severity and enable early identification of the patients requiring aggressive treatment.

Polymorphisms in ACE1, TMPRSS2, IFIH1, IFNAR2, and TYK2 Genes Are Associated with Worse Clinical Outcomes in COVID-19

Although advanced age, male sex, and some comorbidities impact the clinical course of COVID-19, these factors only partially explain the inter-individual variability in disease severity. Some studies have shown that genetic polymorphisms contribute to COVID-19 severity; however, the results are inconclusive. Thus, we investigated the association between polymorphisms in ACE1, ACE2, DPP9, IFIH1, IFNAR2, IFNL4, TLR3, TMPRSS2, and TYK2 and the clinical course of COVID-19. A total of 694 patients with COVID-19 were categorized as: (1) ward inpatients (moderate symptoms) or patients admitted at the intensive care unit (ICU; severe symptoms); and (2) survivors or non-survivors. In females, the rs1990760/IFIH1 T/T genotype was associated with risk of ICU admission and death. Moreover, the rs1799752/ACE1 Ins and rs12329760/TMPRSS2 T alleles were associated with risk of ICU admission. In non-white patients, the rs2236757/IFNAR2 A/A genotype was associated with risk of ICU admission, while the rs1799752/ACE1 Ins/Ins genotype, rs2236757/IFNAR2 A/A genotype, and rs12329760/TMPRSS2 T allele were associated with risk of death. Moreover, some of the analyzed polymorphisms interact in the risk of worse COVID-19 outcomes. In conclusion, this study shows an association of rs1799752/ACE1, rs1990760/IFIH1, rs2236757/IFNAR2, rs12329760/TMPRSS2, and rs2304256/TYK2 polymorphisms with worse COVID-19 outcomes, especially among female and non-white patients.

ACE2 polymorphisms impact COVID-19 severity in obese patients

A strong association between obesity and COVID-19 complications and a lack of prognostic factors that explain the unpredictable severity among these patients still exist despite the various vaccination programs. The expression of angiotensin converting enzyme 2 (ACE2), the main receptor for severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), is enhanced in obese individuals. The occurrence of frequent genetic single nucleotide polymorphisms (SNPs) in ACE2 is suggested to increase COVID-19 severity. Accordingly, we hypothesize that obesity-associated ACE2 polymorphisms increase the severity of COVID-19. In this study, we profiled eight frequently reported ACE2 SNPs in a cohort of lean and obese COVID-19 patients (n = 82). We highlight the significant association of rs2285666, rs2048683, rs879922, and rs4240157 with increased severity in obese COVID-19 patients as compared to lean counterparts. These co-morbid-associated SNPs tend to positively correlate, hence proposing possible functional cooperation to ACE2 regulation. In obese COVID-19 patients, rs2285666, rs879922, and rs4240157 are significantly associated with increased blood nitrogen urea and creatinine levels. In conclusion, we highlight the contribution of ACE2 SNPs in enhancing COVID-19 severity in obese individuals. The results from this study provide a basis for further investigations required to shed light on the underlying mechanisms of COVID-19 associated SNPs in COVID-19 obese patients.

Systematic review and meta-analysis of human genetic variants contributing to COVID-19 susceptibility and severity

The COVID-19 pandemic has spawned global health crisis of unprecedented magnitude, claiming millions of lives and pushing healthcare systems in many countries to the brink. Among several factors that contribute to an increased risk of COVID-19 and progression to exacerbated manifestations, host genetic landscape is increasingly being recognized as a critical determinant of susceptibility/resistance to infection and a prognosticator of clinical outcomes in infected individuals. Recently, several case-control association studies investigated the influence of human gene variants on COVID-19 susceptibility and severity to identify the culpable mutations. However, a comprehensive synthesis of the recent advances in COVID-19 host genetics research was lacking, and the inconsistent findings of the association studies required reliable evaluation of the strength of association with greater statistical power. In this study, we embarked on a systematic search of all possible reports of genetic association with COVID-19 till April 07, 2022, and performed meta-analyses of all the genetic polymorphisms that were examined in at least three studies. After identifying a total of 84 studies that investigated the association of 130 polymorphisms in 61 genes, we performed meta-analyses of all the eligible studies. Seven genetic polymorphisms involving 15,550 cases and 444,007 controls were explored for association with COVID-19 susceptibility, of which, ACE1 I/D rs4646994/rs1799752, APOE rs429358, CCR5 rs333, and IFITM3 rs12252 showed increased risk of infection. Meta-analyses of 11 gene variants involving 6702 patients with severe COVID-19 and 8640 infected individuals with non-severe manifestations revealed statistically significant association of ACE2 rs2285666, ACE2 rs2106809, ACE2 rs2074192, AGTR1 rs5186, and TNFA rs1800629 with COVID-19 severity. Overall, our study presents a synthesis of evidence on all the genetic determinants implicated in COVID-19 to date, and provides evidence of correlation between the above polymorphisms with COVID-19 susceptibility and severity.

Global distribution of ACE1 (rs4646994) and ACE2 (rs2285666) polymorphisms associated with COVID-19: A systematic review and meta-analysis

BACKGROUND

Recent studies emphasize the significant impact of the renin-angiotensin aldosterone system (RAAS) as a risk factor associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, according to the literature, the effect of rs4646994 and rs2285666 polymorphisms on susceptibility and progression to severe clinical outcomes is still controversial. Our aim was to investigate the effect of polymorphisms such as rs4646994 and rs2285666 on susceptibility to coronavirus disease-2019 (COVID-19).

METHODS

We conducted a comprehensive literature search using databases such as ISI Web of Science, PubMed, Scopus, and Google Scholar to retrieve studies on the effect of two polymorphisms (rs4646994 and rs2285666) of the angiotensin-converting enzyme (ACE) gene on COVID-19. Finally, the effect of each polymorphism on SARS-CoV-2 infection was measured based on the odds ratio with 95% confidence intervals.

RESULTS

Analysis of the rs4646994 polymorphism showed that the frequency of the D allele in patients infected with COVID-19 was higher than that the I allele. Moreover, the authors found that the DD genotype increased the risk of severe disease by 1.7-fold in Asian population, whereas, this was not the case in the Western population. However, the rs4646994 II genotype plays a protective role against COVID-19 in Western countries. In the case of the rs2285666 polymorphism based on patient ethnicity, the C allele had the highest frequency. Interestingly, in people harboring the GG and TT genotypes, the risk of progression to severe disease significantly increased, while people with genotypes such as GA, AA and CC seem to be more resistant to severe Covid-19.

CONCLUSIONS

Based on geographical region, the rs4646994 DD genotype may be considered as a predictive biomarker to identify the susceptibility of human to SARS-CoV-2 infection and severe COVID-19 outcomes. We also concluded that individuals with GG and TT genotypes are significantly more susceptible to severe outcomes of disease, while conversely, individuals with GA, AA, and CC genotypes are less susceptible to severe COVID-19.

Inflammasome Genetic Variants Are Associated with Protection to Clinical Severity of COVID-19 among Patients from Rio de Janeiro, Brazil

COVID-19 has a broad spectrum of clinical manifestations, from asymptomatic or mild/moderate symptoms to severe symptoms and death. The mechanisms underlying its clinical evolution are still unclear. Upon SARS-CoV-2 infection, host factors, such as the inflammasome system, are activated by the presence of the virus inside host cells. The search for COVID-19 risk factors is of relevance for clinical management. In this study, we investigated the impact of inflammasome single-nucleotide polymorphisms (SNPs) in SARS-CoV-2-infected individuals with distinct severity profiles at clinical presentation. Patients were divided into two groups according to disease severity at clinical presentation based on the WHO Clinical Progression Scale. Group 1 included patients with mild/moderate disease (WHO < 6; n = 76), and group 2 included patients with severe/critical COVID-19 (WHO ≥ 6; n = 357). Inpatients with moderate to severe/critical profiles were recruited and followed-up at Hospital Center for COVID-19 Pandemic – National Institute of Infectology (INI)/FIOCRUZ, RJ, Brazil, from June 2020 to March 2021. Patients with mild disease were recruited at Oswaldo Cruz Institute (IOC)/FIOCRUZ, RJ, Brazil, in August 2020. Genotyping of 11 inflammasome SNPs was determined by real-time PCR. Protection and risk estimation were performed using unconditional logistic regression models. Significant differences in NLRP3 rs1539019 and CARD8 rs2043211 were observed between the two groups. Protection against disease severity was associated with the A/A genotype (OR_adj = 0.36; P = 0.032), allele A (OR_adj = 0.93; P = 0.010), or carrier-A (OR_adj = 0.45; P = 0.027) in the NLRP3 rs1539019 polymorphism; A/T genotype (OR_adj = 0.5; P = 0.045), allele T (OR_adj = 0.93; P = 0.018), or carrier-T (OR_adj = 0.48; P = 0.029) in the CARD8 rs2043211 polymorphism; and the A-C-G-C-C (OR_adj = 0.11; P = 0.018), A-C-G-C-G (OR_adj = 0.23; P = 0.003), C-C-G-C-C (OR_adj = 0.37; P = 0.021), and C-T-G-A-C (OR_adj = 0.04; P = 0.0473) in NLRP3 genetic haplotype variants. No significant associations were observed for the other polymorphisms. To the best of our knowledge, this is the first study demonstrating an association between CARD8 and NLRP3 inflammasome genetic variants and protection against COVID-19 severity, contributing to the discussion of the impact of inflammasomes on COVID-19 outcomes.

Angiotensin-converting enzyme 2 rs2285666 polymorphism and clinical parameters as the determinants of COVID-19 severity in Iranian population

Host genetic factors may be correlated with the severity of coronavirus disease 2019 (COVID-19). Angiotensin-converting enzyme 2 (ACE2) plays a vital role in viral cell entrance. The current study aimed to evaluate the association of ACE2 rs2285666 polymorphism and clinical parameters with COVID-19 mortality. The ACE2 rs2285666 polymorphism was genotyped using the polymerase chain reaction-restriction fragment length polymorphism in 556 recovered and 522 dead patients. In this study, the frequency of ACE2 rs2285666 CC was significantly higher than TT genotype in dead patients. The multivariate logistic regression analysis results showed that the higher levels of alanine aminotransferase, alkaline phosphatase, creatinine, erythrocyte sedimentation rate, and C-reactive protein and the low levels of uric acid, cholesterol, low density lipoprotein, 25-hydroxyvitamin D, real-time PCR Ct values, and ACE2 rs2285666 CC genotype were associated with increased mortality rates after COVID-19. In conclusion, our findings demonstrated a possible link between COVID-19 mortality, clinical parameters, and ACE2 rs2285666 CC. Further research is required to confirm these results.

Efficacy of SARS-CoV-2 Vaccination in Dialysis Patients: Epidemiological Analysis and Evaluation of the Clinical Progress

This study investigated the impact of the fourth COVID-19 pandemic wave on dialysis patients of Romagna territory, assessing the associations of vaccination status with infection risk, clinical severity and mortality. From November 2021 to February 2022, an epidemiological search was conducted on 829 patients under dialysis treatment for at least one month. The data were then analyzed with reference to the general population of the same area. A temporal comparison was also carried out with the previous pandemic waves (from March 2020 to October 2021). The epidemiological evolution over time in the dialysis population and in Romagna citizens replicated the global trend, as the peak of the fourth wave corresponded to the time of maximum diffusion of omicron variant (B.1.1.529). Of 771 prevalent dialysis patients at the beginning of the study, 109 (14.1%) contracted SARS-CoV-2 infection during the 4-month observation period. Vaccine adherence in the dialysis population of the reference area was above 95%. Compared to fully or partially vaccinated subjects, the unvaccinated ones showed a significantly higher proportion of infections (12.5% vs. 27.0% p = 0.0341), a more frequent need for hospitalization (22.2% vs. 50.0%) and a 3.3-fold increased mortality risk. These findings confirm the effectiveness of COVID-19 vaccines in keeping infectious risk under control and ameliorating clinical outcomes in immunocompromised patients.

Revealing the mystery of persistent smell loss in Long COVID patients

COVID-19 is hopefully approaching its end in many countries as herd immunity develops and weaker strains of SARS-CoV-2 dominate. However, a new concern occurs over the long-term effects of COVID-19, collectively called "Long COVID", as some symptoms of the nervous system last even after patients recover from COVID-19. This review focuses on studies of anosmia, i.e., impairment of smell, which is the most common sensory defect during the disease course and is caused by olfactory dysfunctions. It remains mysterious how the olfactory functions are affected since the virus can't invade olfactory receptor neurons. We describe several leading hypotheses about the mystery in hope to provide insights into the pathophysiology and treatment strategies for anosmia.