ACE2 variants show sex-specific signals in hospitalized COVID-19 cases
Genetic variation in ACE2 is drawing attention because the protein sits at the center of SARS-CoV-2 entry into human cells. In this Iranian hospital-based case-control study, three single-nucleotide polymorphisms — rs2285666, rs4646127, and rs971249 — were examined for links to hospitalized COVID-19, normalized viral load, and mortality. The cohort included 441 participants: 226 hospitalized COVID-19 cases and 215 hospitalized controls who were SARS-CoV-2 negative but admitted with other severe acute conditions.
The study design matters because it compares two hospitalized groups rather than the general population. The signal therefore speaks to relative differences among very ill patients, not to broad community susceptibility. Even so, the sex-stratified results were striking enough to merit close attention.
In males, the T alleles of rs971249 and rs4646127 were associated with lower odds of hospitalized SARS-CoV-2 infection and remained significant after Benjamini-Hochberg correction. The raw p values were 0.003 and 0.002, with q values of 0.048 and 0.036, respectively. In females, rs971249 showed a higher frequency of the T allele among controls than cases, but the association lost significance after multiple-testing correction. rs2285666 did not produce a significant association in either sex.
A sex-dependent pattern in a viral entry gene is biologically plausible. ACE2 sits at the intersection of host cell binding, tissue tropism, and the renin-angiotensin system, so a functional variant could influence how efficiently the virus attaches, enters, or propagates in the airway and beyond. If a polymorphism alters ACE2 expression or activity in a sex-specific way, the downstream effect could differ between men and women, especially in a disease already known to behave differently across sex. The study does not establish mechanism, but it provides a genetic clue worth testing in functional models.
Viral load stayed largely detached from corrected genetic signals
The investigators also quantified viral load using qRT-PCR and normalized it to the RNase P gene. Across the three ACE2 variants, no association with normalized viral load survived correction for multiple comparisons. Every q value was above 0.05.
One signal hovered near the threshold in women: rs971249 heterozygous females showed a trend toward higher viral load, with a raw p value of 0.052 and q value of 0.18. In practical terms, that finding is too unstable to treat as evidence, but it does hint that genotype could influence how much virus is present once infection has taken hold. The absence of a corrected association also shows how easily a plausible biological hypothesis can fail when tested against stricter statistical control.
The viral-load result is important because it separates infection risk from within-host viral burden. A variant may alter the chance of hospitalization without necessarily changing the amount of viral RNA detected at sampling. Timing of sampling, host inflammatory response, and disease stage can all blur the relationship between genotype and measured viral burden, especially in hospitalized patients whose disease course has already evolved.
Mortality findings in women remain exploratory
For mortality, the study reported nominal associations in females for rs971249 and rs4646127, with adjusted odds ratios of 2.54 and 2.73 after accounting for age, comorbidities, and sampling time. These findings were not corrected with Benjamini-Hochberg testing because the mortality analysis was exploratory. They should be read as hypothesis-generating, not definitive.
A further caution sits in the control data: rs971249 deviated from Hardy-Weinberg equilibrium in female controls, with p = 0.010. In genetic association studies, that kind of departure can reflect chance, selection effects, genotyping issues, or population structure. Here, it weakens confidence in the female mortality signal and makes replication essential before any clinical inference is drawn.
Still, the pattern is difficult to ignore. A variant associated with sex-specific protection against hospitalization can also appear linked to survival differences in the opposite direction if the underlying biology is tangled with host response, disease severity at presentation, or residual confounding. The study does not resolve that problem, but it frames a set of questions that future cohorts will need to answer with better-powered analyses.
What the Iranian cohort can and cannot tell clinicians
This is a study of hospitalized patients in Iran, not a population screening exercise. The controls were sick enough to require hospitalization, which makes the comparison clinically relevant but also narrows the interpretation. These are differences between two severe inpatient groups, not proof that the variants change community-level susceptibility to SARS-CoV-2.
The sample size was modest, and the most notable signals emerged only after sex stratification. Sex-specific analyses can reveal meaningful biology, yet they also increase the risk of unstable findings when numbers are small. That tension is especially apparent here, where one variant crossed the significance threshold after correction in men but not in women, and where the female mortality signal remained uncorrected and exploratory.
Even with those caveats, the paper adds to a growing body of work suggesting that host genetics may help explain why COVID-19 does not strike every patient in the same way. ACE2 remains a biologically credible candidate because it governs viral entry and participates in pathways that influence vascular function and inflammation. The present data do not justify clinical genotyping for routine care. They do, however, justify larger studies with population-based controls, diverse ethnic groups, and functional assays that can determine whether rs971249 and rs4646127 meaningfully alter ACE2 biology in men and women differently.
Until that evidence arrives, the safest reading is restrained: the T alleles of rs971249 and rs4646127 may mark reduced risk of hospitalized SARS-CoV-2 infection in this Iranian cohort of men, while female mortality and viral-load signals remain preliminary and vulnerable to correction, sampling effects, and replication failure.