Abstract
BACKGROUND: Despite the high transmissibility of SARS-CoV-2, some individuals remain uninfected despite prolonged exposure to a high viral load, suggesting the involvement of an innate resistance mechanism, possibly underpinned by the host's genetic factors. The angiotensin-converting enzyme-1 (ACE1), ACE2, and C-C Chemokine Receptor 5 (CCR5) polymorphisms have been shown to influence susceptibility to the infection. In this study, the role of ACE1, ACE2, and CCR5 gene polymorphisms in modulating susceptibility to SARS-CoV-2 infection within the context of intimate contact was evaluated. METHODS: A cohort of heterosexual couples from Northern Sardinia, characterized by a homogenous genetic background, was recruited during the initial pandemic wave (March-June 2020). In each couple, one partner (index case) tested positive for SARS-CoV-2 by at least two consecutive independent molecular tests (real-time polymerase chain reaction: RT-PCR) on nasopharyngeal swabs. Bed-sharing partners of SARS-CoV-2 positive index cases, resistant and susceptible to the infection, were genotyped for ACE1 287 bp Alu repeat insertion/deletion (I/D) polymorphism, ACE2 G8790A (rs2285666) variant, and a 32-base pair deletion (Δ32) of CCR5. Resistant and susceptible partners to the infection were compared for polymorphisms. RESULTS: Out of 63 couples, 30 partners acquired SARS-CoV-2 infection, while 33 remained uninfected despite intimate exposure. Clinical history was minimal for current or past illnesses. SARS-CoV-2-infected index spouses and partners who acquired the infection developed a mild disease, not requiring hospitalization. The observed distribution of ACE1 I/D and ACE2 G8790A genotypes was consistent with previously reported frequencies in Sardinia and across European populations. None of the study participants carried the CCR5-Δ32 variant. No statistically significant differences (p > 0.05) in the allelic or genotypic frequencies of these polymorphisms were observed between the infected and resistant partners. CONCLUSIONS: No differences in the distribution of ACE1, ACE2, and CCR5 polymorphisms between the two groups were detected. These findings suggest that resistance is likely multifactorial, involving a complex interplay of genetic, immunological, and environmental factors.