SARS-CoV-2 Infects Hamster Testes

Association Between Single-Nucleotide Polymorphisms in Toll-like Receptor 3 (tlr3), tlr7, tlr8 and tirap Genes with Severe Symptoms in Children Presenting COVID-19

The global number of COVID-19 deaths has reached 7 million, with 4% of these deaths occurring in children and adolescents. In Brazil, around 1500 children up to 11 years old died from the disease. The most common symptoms in children are respiratory, potentially progressing to severe illnesses, such as severe acute respiratory syndrome (SARS) and MIS-C. Studies indicate that comorbidities and genetic factors, such as polymorphisms in immune response genes, can influence the severity of COVID-19. This study investigates the occurrence of single-nucleotide polymorphisms (SNPs) in innate immune response genes in children with COVID-19. Seventy-three samples were analyzed from children under 13 years old hospitalized at João Paulo II Children's Hospital due to COVID-19. The evaluated SNPs were tlr8 (1) (rs3764879), tlr8 (2) (rs2407992), tlr7 (rs179008), tlr3 (rs3775291), tirap (rs8177374), and mcp-1 (rs1024611), considering four categories of severity: mild, moderate, severe, and critical COVID-19. To identify the SNPs, PCR and sequencing were performed. The frequencies of the SNPs obtained were not discrepant when compared to the frequencies described in the Global ALFA, Global 1000 Genomes, Global gnomAD, American 1000 Genomes, and American gnomAD databases, except for the SNP in TLR7. Comparing severe and critical cases to mild and moderate cases, we found a higher relative risk associated with mutations in tlr8 (1), tlr7, tlr3, and tirap (p < 0.05). No association was found for SNPs in tlr8 (2) and mcp-1. Our analyses suggest an association between SNPs in innate immune response genes and severity of symptoms in children with COVID-19 (or SARS-CoV-2 infected children).

CD8+ T cells promote ZIKV clearance and mitigate testicular damage in mice

Zika virus (ZIKV) causes human testicular inflammation and alterations in sperm parameters and causes testicular damage in mouse models. The involvement of individual immune cells in testicular damage is not fully understood. We detected virus in the testes of the interferon (IFN) α/β receptor-/- A129 mice three weeks post-infection and found elevated chemokines in the testes, suggesting chronic inflammation and long-term infection play a role in testicular damage. In the testes, myeloid cells and CD4+ T cells were absent at 7 dpi but were present at 23 days post-infection (dpi), and CD8+ T cell infiltration started at 7 dpi. CD8-/- mice with an antibody-depleted IFN response had a significant reduction in spermatogenesis, indicating that CD8+ T cells are essential to prevent testicular damage during long-term ZIKV infections. Our findings on the dynamics of testicular immune cells and the importance of CD8+ T cells function as a framework to understand mechanisms underlying observed inflammation and sperm alterations in humans.

Host factors of SARS-CoV-2 in infection, pathogenesis, and long-term effects

SARS-CoV-2 is the causative virus of the devastating COVID-19 pandemic that results in an unparalleled global health and economic crisis. Despite unprecedented scientific efforts and therapeutic interventions, the fight against COVID-19 continues as the rapid emergence of different SARS-CoV-2 variants of concern and the increasing challenge of long COVID-19, raising a vast demand to understand the pathomechanisms of COVID-19 and its long-term sequelae and develop therapeutic strategies beyond the virus per se. Notably, in addition to the virus itself, the replication cycle of SARS-CoV-2 and clinical severity of COVID-19 is also governed by host factors. In this review, we therefore comprehensively overview the replication cycle and pathogenesis of SARS-CoV-2 from the perspective of host factors and host-virus interactions. We sequentially outline the pathological implications of molecular interactions between host factors and SARS-CoV-2 in multi-organ and multi-system long COVID-19, and summarize current therapeutic strategies and agents targeting host factors for treating these diseases. This knowledge would be key for the identification of new pathophysiological aspects and mechanisms, and the development of actionable therapeutic targets and strategies for tackling COVID-19 and its sequelae.

Systematic analyses of the factors influencing sperm quality in patients with SARS-CoV-2 infection

To figure out how does SARS-CoV-2 affect sperm parameters and what influencing factors affect the recovery of sperm quality after infection? We conducted a prospective cohort study and initially included 122 men with SARS-CoV-2 infection. The longest time to track semen quality after infection is 112 days and 58 eligible patients were included in our study eventually. We subsequently exploited a linear mixed-effects model to statistically analyze their semen parameters at different time points before and after SARS-CoV-2 infection. Semen parameters were significantly reduced after SARS-CoV-2 infection, including total sperm count (211 [147; 347] to 167 [65.0; 258], P < 0.001), sperm concentration (69.0 [38.8; 97.0] to 51.0 [25.5; 71.5], P < 0.001), total sperm motility (57.5 [52.3; 65.0] to 51.0 [38.5; 56.8], P < 0.001), progressive motility (50.0 [46.2; 58.0] to 45.0 [31.5; 52.8], P < 0.001). The parameters displayed the greatest diminution within 30 days after SARS-CoV-2 infection, gradually recovered thereafter, and exhibited no significant difference after 90 days compared with prior to COVID-19 infection. In addition, the patients in the group with a low-grade fever showed a declining tendency in semen parameters, but not to a significant degree, whereas those men with a moderate or high fever produced a significant drop in the same parameters. Semen parameters were significantly reduced after SARS-CoV-2 infection, and fever severity during SARS-CoV-2 infection may constitute the main influencing factor in reducing semen parameters in patients after recovery, but the effect is reversible and the semen parameters gradually return to normal with the realization of a new spermatogenic cycle.

Combination therapy with oral antiviral and anti-inflammatory drugs improves the efficacy of delayed treatment in a COVID-19 hamster model

BACKGROUND

Pulmonary infection with SARS-CoV-2 stimulates host immune responses and can also result in the progression of dysregulated and critical inflammation. Throughout the pandemic, the management and treatment of COVID-19 has been continuously updated with a range of antiviral drugs and immunomodulators. Monotherapy with oral antivirals has proven to be effective in the treatment of COVID-19. However, treatment should be initiated in the early stages of infection to ensure beneficial therapeutic outcomes, and there is still room for further consideration on therapeutic strategies using antivirals.

METHODS

We studied the therapeutic effects of monotherapy with the oral antiviral ensitrelvir or the anti-inflammatory corticosteroid methylprednisolone and combination therapy with ensitrelvir and methylprednisolone in a delayed dosing model of hamsters infected with SARS-CoV-2.

FINDINGS

Combination therapy with ensitrelvir and methylprednisolone improved respiratory conditions and reduced the development of pneumonia in hamsters even when the treatment was started after 2 days post-infection. The combination therapy led to a differential histological and transcriptomic pattern in comparison to either of the monotherapies, with reduced lung damage and down-regulation of expression of genes involved in the inflammatory response. Furthermore, we found that the combination treatment is effective in case of infection with either the highly pathogenic delta or circulating omicron variants.

INTERPRETATION

Our results demonstrate the advantage of combination therapy with antiviral and corticosteroid drugs in COVID-19 treatment from the perspective of lung pathology and host inflammatory responses.

FUNDING

Funding bodies are described in the Acknowledgments section.

SARS-CoV-2 replicates in the human testis with slow kinetics and has no major deleterious effects ex vivo

IMPORTANCE

SARS-CoV-2 is a new virus responsible for the Covid-19 pandemic. Although SARS-CoV-2 primarily affects the lungs, other organs are infected. Alterations of testosteronemia and spermatozoa motility in infected men have raised questions about testicular infection, along with high level in the testis of ACE2, the main receptor used by SARS-CoV-2 to enter host cells. Using an organotypic culture of human testis, we found that SARS-CoV-2 replicated with slow kinetics in the testis. The virus first targeted testosterone-producing Leydig cells and then germ-cell nursing Sertoli cells. After a peak followed by the upregulation of antiviral effectors, viral replication in the testis decreased and did not induce any major damage to the tissue. Altogether, our data show that SARS-CoV-2 replicates in the human testis to a limited extent and suggest that testicular damages in infected patients are more likely to result from systemic infection and inflammation than from viral replication in the testis.

Testicular pathological alterations associated with SARS-CoV-2 infection

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is the etiologic agent of the coronavirus disease 2019 (COVID-19), which caused one of the pandemics with the highest mortalities with millions of deaths and hundreds of millions of cases to date. Due to its potential for airborne transmission, many studies have focused on SARS-CoV-2 primarily as a respiratory disease. However, the spread of SARS-CoV-2 to non-respiratory organs has been experimentally demonstrated and clinically observed. During autopsy studies, histopathological lesions, and disruption of the blood-testes barrier (BTB) have been observed in the male reproductive tract. Here, we review findings from both autopsy cases and animal models that demonstrate testicular disease due to COVID-19 and present an overview of the pathological alterations that occur in the testes resulting from SARS-CoV-2 infection and explore its potential mechanisms.

SARS-CoV-2 Systemic Effects: New Clues

To date, much discussion has been had on severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) lung infection associated with COVID-19 onset, of which the major manifestation is characterized by a "cytokine storm" [...].

SARS-CoV-2 Enters Human Leydig Cells and Affects Testosterone Production In Vitro

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), a SARS-like coronavirus, continues to produce mounting infections and fatalities all over the world. Recent data point to SARS-CoV-2 viral infections in the human testis. As low testosterone levels are associated with SARS-CoV-2 viral infections in males and human Leydig cells are the main source of testosterone, we hypothesized that SARS-CoV-2 could infect human Leydig cells and impair their function. We successfully detected SARS-CoV-2 nucleocapsid in testicular Leydig cells of SARS-CoV-2-infected hamsters, providing evidence that Leydig cells can be infected with SARS-CoV-2. We then employed human Leydig-like cells (hLLCs) to show that the SARS-CoV-2 receptor angiotensin-converting enzyme 2 is highly expressed in hLLCs. Using a cell binding assay and a SARS-CoV-2 spike-pseudotyped viral vector (SARS-CoV-2 spike pseudovector), we showed that SARS-CoV-2 could enter hLLCs and increase testosterone production by hLLCs. We further combined the SARS-CoV-2 spike pseudovector system with pseudovector-based inhibition assays to show that SARS-CoV-2 enters hLLCs through pathways distinct from those of monkey kidney Vero E6 cells, a typical model used to study SARS-CoV-2 entry mechanisms. We finally revealed that neuropilin-1 and cathepsin B/L are expressed in hLLCs and human testes, raising the possibility that SARS-CoV-2 may enter hLLCs through these receptors or proteases. In conclusion, our study shows that SARS-CoV-2 can enter hLLCs through a distinct pathway and alter testosterone production.

Transporter Inhibition Profile for the Antivirals Tilorone, Quinacrine and Pyronaridine

Pyronaridine, tilorone and quinacrine are cationic molecules that have in vitro activity against Ebola, SARS-CoV-2 and other viruses. All three molecules have also demonstrated in vivo activity against Ebola in mice, while pyronaridine showed in vivo efficacy against SARS-CoV-2 in mice. We have recently tested these molecules and other antivirals against human organic cation transporters (OCTs) and apical multidrug and toxin extruders (MATEs). Quinacrine was found to be an inhibitor of OCT2, while tilorone and pyronaridine were less potent, and these displayed variability depending on the substrate used. To assess whether any of these three molecules have other potential interactions with additional transporters, we have now screened them at 10 μM against various human efflux and uptake transporters including P-gp, OATP1B3, OAT1, OAT3, MRP1, MRP2, MRP3, BCRP, as well as confirmational testing against OCT1, OCT2, MATE1 and MATE2K. Interestingly, in this study tilorone appears to be a more potent inhibitor of OCT1 and OCT2 than pyronaridine or quinacrine. However, both pyronaridine and quinacrine appear to be more potent inhibitors of MATE1 and MATE2K. None of the three compounds inhibited MRP1, MRP2, MRP3, OAT1, OAT3, P-gp or OATP1B3. Similarly, we previously showed that tilorone and pyronaridine do not inhibit OATP1B1 and have confirmed that quinacrine behaves similarly. In total, these observations suggest that the three compounds only appear to interact with OCTs and MATEs to differing extents, suggesting they may be involved in fewer clinically relevant drug-transporter interactions involving pharmaceutical substrates of the other major transporters tested.

Infection of SARS-CoV-2 causes severe pathological changes in mouse testis

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has affected more than 600 million people worldwide. Several organs including lung, intestine, and brain are infected by SARS-CoV-2. It has been reported that SARS-CoV-2 receptor angiotensin-converting enzyme-2 (ACE2) is expressed in human testis. However, whether testis is also affected by SARS-CoV-2 is still unclear. In this study, we generate a human ACE2 (hACE2) transgenic mouse model in which the expression of hACE2 gene is regulated by hACE2 promoter. Sertoli and Leydig cells from hACE2 transgenic mice can be infected by SARS-CoV-2 pseudovirus in vitro, and severe pathological changes are observed after injecting the SARS-CoV-2 pseudovirus into the seminiferous tubules. Further studies reveal that Sertoli and Leydig cells from hACE2 transgenic mice are also infected by authentic SARS-CoV-2 virus in vitro. After testis interstitium injection, authentic SARS-CoV-2 viruses are first disseminated to the interstitial cells, and then detected inside the seminiferous tubules which in turn cause germ cell loss and disruption of seminiferous tubules. Our study demonstrates that testis is most likely a target of SARS-CoV-2 virus. Attention should be paid to the reproductive function in SARS-CoV-2 patients.

The Complex Interplay between Serum Testosterone and the Clinical Course of Coronavirus Disease 19 Pandemic: A Systematic Review of Clinical and Preclinical Evidence

Since the beginning of the coronavirus disease 19 (COVID-19) pandemic, efforts in defining risk factors and associations between the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), clinical, and molecular features have initiated. After three years of pandemic, it became evident that men have higher risk of adverse outcomes. Such evidence provided the impetus for defining the biological fundaments of such a gender disparity. Our objective was to analyze the most recent literature with the aim of defining the relationship between COVID-19 and fertility, in particular, we assessed the interplay between SARS-CoV-2 and testosterone in a systematic review of literature from December 2019 (first evidence of a novel coronavirus in the Hubei province) until March 2022. As a fundamental basis for understanding, articles pertaining preclinical aspects explaining the gender disparity (n=9) were included. The main review categories analyzed the risk of being infected with SARS-CoV-2 according to testosterone levels (n=5), the impact of serum testosterone on outcomes of COVID-19 (n=23), and the impact SARS-CoV-2 on testosterone levels after infection (n=19). Preclinical studies mainly evaluated the relation between angiotensin-converting enzyme 2 (ACE2) and its androgen-mediated regulation, articles exploring the risk of COVID-19 according to testosterone levels were few. Although most publications evaluating the effect of COVID-19 on fertility found low testosterone levels after the infection, follow-up was short, with some also suggesting no alterations during recovery. More conclusive findings were observed in men with low testosterone levels, that were generally at higher risk of experiencing worse outcomes (i.e., admission to intensive care units, longer hospitalization, and death). Interestingly, an inverse relationship was observed in women, where higher levels of testosterone were associated to worse outcomes. Our finding may provide meaningful insights to better patient counselling and individualization of care pathways in men with testosterone levels suggesting hypogonadism.

Animal models for COVID-19: advances, gaps and perspectives

COVID-19, caused by SARS-CoV-2, is the most consequential pandemic of this century. Since the outbreak in late 2019, animal models have been playing crucial roles in aiding the rapid development of vaccines/drugs for prevention and therapy, as well as understanding the pathogenesis of SARS-CoV-2 infection and immune responses of hosts. However, the current animal models have some deficits and there is an urgent need for novel models to evaluate the virulence of variants of concerns (VOC), antibody-dependent enhancement (ADE), and various comorbidities of COVID-19. This review summarizes the clinical features of COVID-19 in different populations, and the characteristics of the major animal models of SARS-CoV-2, including those naturally susceptible animals, such as non-human primates, Syrian hamster, ferret, minks, poultry, livestock, and mouse models sensitized by genetically modified, AAV/adenoviral transduced, mouse-adapted strain of SARS-CoV-2, and by engraftment of human tissues or cells. Since understanding the host receptors and proteases is essential for designing advanced genetically modified animal models, successful studies on receptors and proteases are also reviewed. Several improved alternatives for future mouse models are proposed, including the reselection of alternative receptor genes or multiple gene combinations, the use of transgenic or knock-in method, and different strains for establishing the next generation of genetically modified mice.

SARS-CoV-2 Omicron variant causes mild pathology in the upper and lower respiratory tract of hamsters

Since its discovery in 2019, multiple variants of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) have been identified. This study investigates virus spread and associated pathology in the upper and lower respiratory tracts of Syrian golden hamsters at 4 days post intranasal SARS-CoV-2 Omicron infection, in comparison to infection with variants of concern (VOCs) Gamma and Delta as well as ancestral strain 614 G. Pathological changes in the upper and lower respiratory tract of VOC Omicron infected hamsters are milder than those caused by other investigated strains. VOC Omicron infection causes a mild rhinitis with little involvement of the olfactory epithelium and minimal lesions in the lung, with frequent sparing of the alveolar compartment. Similarly, viral antigen, RNA and infectious virus titers are lower in respiratory tissues of VOC Omicron infected hamsters. These findings demonstrate that the variant has a decreased pathogenicity for the upper and lower respiratory tract of hamsters.

Since the emergence of SARS-CoV-2 several variants of concerns have been identified, with altered disease progression and transmission dynamics. Here, Armando et al. compare virus spread and pathology in the upper and lower respiratory tracts of Syrian golden hamster after 4 days post infection for VOCs Gamma, Delta and Omicron and find milder pathology for Omicron.

SARS-CoV-2 Nucleocapsid Protein is Associated With Lower Testosterone Levels: An Experimental Study

The ongoing COVID-19 pandemic represents an extra burden in the majority of public and private health systems worldwide beyond the most pessimistic expectations, driving an urgent rush to develop effective vaccines and effective medical treatments against the SARS-CoV-2 pandemic. The Nucleocapsid structural viral protein is remarkably immunogenic and hugely expressed during infection. High IgG antibodies against Nucleocapsid protein (N protein) levels were detected in the serum of COVID-19 patients, confirming its pivotal antigen role for a T lymphocyte response in a vaccine microenvironment. Currently, adverse events associated with immunizations have raised some degree of concern, irrespective of its huge benefits in dealing with disease severity and decreasing mortality and morbidity. This hitherto study evaluates histological changes in rats’ testes, epididymis, prostate, and seminal vesicles and analyzes hormone levels after solely N protein inoculation. Therefore, we exposed a group of Lewis rats to weekly injections of the recombinant N protein for 28 days, while a control group was inoculated with a buffer solution. The N group revealed a more significant number of spermatozoa. Spermatozoa in the seminiferous tubules were counted in twenty 400 × microscopy fields (mean of 9.2 vs. 4.6 in the control group; p &lt; 0,01), but significantly lower testosterone levels (mean of 125.70 ng/dl vs. 309,00 ng/dl in the control group; p &lt; 0,05) were found. No other histological and biochemical changes were displayed. Conclusively, these data suggest testicular hormonal imbalance mediated by the SARS-CoV-2 N protein that could be linked to reported post-COVID-19 syndrome hypogonadism. More relevant research might be performed to confirm this viral antigen’s deleterious mechanism in the human testicular microenvironment, particular in Leydig cell function.

An immunoPET probe to SARS-CoV-2 reveals early infection of the male genital tract in rhesus macaques

The systemic nature of SARS-CoV-2 infection is highly recognized, but poorly characterized. A non-invasive and unbiased method is needed to clarify whole body spatiotemporal dynamics of SARS-CoV-2 infection after transmission. We recently developed a probe based on the anti-SARS-CoV-2 spike antibody CR3022 to study SARS-CoV-2 pathogenesis in vivo. Herein, we describe its use in immunoPET to investigate SARS-CoV-2 infection of three rhesus macaques. Using PET/CT imaging of macaques at different times post-SARS-CoV-2 inoculation, we track the 64Cu-labelled CR3022-F(ab')2 probe targeting the spike protein of SARS-CoV-2 to study the dynamics of infection within the respiratory tract and uncover novel sites of infection. Using this method, we uncovered differences in lung pathology between infection with the WA1 isolate and the delta variant, which were readily corroborated through computed tomography scans. The 64Cu-CR3022-probe also demonstrated dynamic changes occurring between 1- and 2-weeks post-infection. Remarkably, a robust signal was seen in the male genital tract (MGT) of all three animals studied. Infection of the MGT was validated by immunofluorescence imaging of infected cells in the testicular and penile tissue and severe pathology was observed in the testes of one animal at 2-weeks post-infection. The results presented here underscore the utility of using immunoPET to study the dynamics of SARS-CoV-2 infection to understand its pathogenicity and discover new anatomical sites of viral replication. We provide direct evidence for SARS-CoV-2 infection of the MGT in rhesus macaques revealing the possible pathologic outcomes of viral replication at these sites.

An immunoPET probe to SARS-CoV-2 reveals early infection of the male genital tract in rhesus macaques

The systemic nature of SARS-CoV-2 infection is highly recognized, but poorly characterized. A non-invasive and unbiased method is needed to clarify whole body spatiotemporal dynamics of SARS-CoV-2 infection after transmission. We recently developed a probe based on the anti-SARS-CoV-2 spike antibody CR3022 to study SARS-CoV-2 pathogenesis in vivo. Herein, we describe its use in immunoPET to investigate SARS-CoV-2 infection of three rhesus macaques. Using PET/CT imaging of macaques at different times post-SARS-CoV-2 inoculation, we track the 64Cu-labelled CR3022-F(ab')2 probe targeting the spike protein of SARS-CoV-2 to study the dynamics of infection within the respiratory tract and uncover novel sites of infection. Using this method, we uncovered differences in lung pathology between infection with the WA1 isolate and the delta variant, which were readily corroborated through computed tomography scans. The 64Cu-CR3022-probe also demonstrated dynamic changes occurring between 1- and 2-weeks post-infection. Remarkably, a robust signal was seen in the male genital tract (MGT) of all three animals studied. Infection of the MGT was validated by immunofluorescence imaging of infected cells in the testicular and penile tissue and severe pathology was observed in the testes of one animal at 2-weeks post-infection. The results presented here underscore the utility of using immunoPET to study the dynamics of SARS-CoV-2 infection to understand its pathogenicity and discover new anatomical sites of viral replication. We provide direct evidence for SARS-CoV-2 infection of the MGT in rhesus macaques revealing the possible pathologic outcomes of viral replication at these sites.

Multiorgan and Vascular Tropism of SARS-CoV-2

Although the respiratory tract is the main target of SARS-CoV-2, other tissues and organs are permissive to the infection. In this report, we investigated this wide-spectrum tropism by studying the SARS-CoV-2 genetic intra-host variability in multiple tissues. The virological and histological investigation of multiple specimens from a post-mortem COVID-19 patient was performed. SARS-CoV-2 genome was detected in several tissues, including the lower respiratory system, cardio-vascular biopsies, stomach, pancreas, adrenal gland, mediastinal ganglion and testicles. Subgenomic RNA transcripts were also detected, in favor of an active viral replication, especially in testicles. Ultra-deep sequencing allowed us to highlight several SARS-CoV-2 mutations according to tissue distribution. More specifically, mutations of the spike protein, i.e., V341A (18.3%), E654 (44%) and H655R (30.8%), were detected in the inferior vena cava. SARS-CoV-2 variability can contribute to heterogeneous distributions of viral quasispecies, which may affect the COVID-19 pathogeny.

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infection by Intranasal or Intratesticular Route Induces Testicular Damage

BACKGROUND

The role of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in the pathogenesis of testicular damage is uncertain.

METHODS

We investigated the virological, pathological, and immunological changes in testes of hamsters challenged by wild-type SARS-CoV-2 and its variants with intranasal or direct testicular inoculation using influenza virus A(H1N1)pdm09 as control.

RESULTS

Besides self-limiting respiratory tract infection, intranasal SARS-CoV-2 challenge caused acute decrease in sperm count, serum testosterone and inhibin B at 4-7 days after infection; and chronic reduction in testicular size and weight, and serum sex hormone at 42-120 days after infection. Acute histopathological damage with worsening degree of testicular inflammation, hemorrhage, necrosis, degeneration of seminiferous tubules, and disruption of orderly spermatogenesis were seen with increasing virus inoculum. Degeneration and death of Sertoli and Leydig cells were found. Although viral loads and SARS-CoV-2 nucleocapsid protein expression were markedly lower in testicular than in lung tissues, direct intratesticular injection of SARS-CoV-2 demonstrated nucleocapsid expressing interstitial cells and epididymal epithelial cells, While intranasal or intratesticular challenge by A(H1N1)pdm09 control showed no testicular infection or damage. From 7 to 120 days after infection, degeneration and apoptosis of seminiferous tubules, immune complex deposition, and depletion of spermatogenic cell and spermatozoa persisted. Intranasal challenge with Omicron and Delta variants could also induce similar testicular changes. This testicular damage can be prevented by vaccination.

CONCLUSIONS

SARS-CoV-2 can cause acute testicular damage with subsequent chronic asymmetric testicular atrophy and associated hormonal changes despite a self-limiting pneumonia in hamsters. Awareness of possible hypogonadism and subfertility is important in managing convalescent coronavirus disease 2019 in men.

Implications of testicular ACE2 and the renin-angiotensin system for SARS-CoV-2 on testis function

Although many studies have focused on SARS-CoV-2 infection in the lungs, comparatively little is known about the potential effects of the virus on male fertility. SARS-CoV-2 infection of target cells requires the presence of furin, angiotensin-converting enzyme 2 (ACE2) receptors, and transmembrane protease serine 2 (TMPRSS2). Thus, cells in the body that express these proteins might be highly susceptible to viral entry and downstream effects. Currently, reports regarding the expression of the viral entry proteins in the testes are conflicting; however, other members of the SARS-CoV family of viruses - such as SARS-CoV - have been suspected to cause testicular dysfunction and/or orchitis. SARS-CoV-2, which displays many similarities to SARS-CoV, could potentially cause similar adverse effects. Commonalities between SARS family members, taken in combination with sparse reports of testicular discomfort and altered hormone levels in patients with SARS-CoV-2, might indicate possible testicular dysfunction. Thus, SARS-CoV-2 infection has the potential for effects on testis somatic and germline cells and experimental approaches might be required to help identify potential short-term and long-term effects of SARS-CoV-2 on male fertility.

Golden Syrian Hamsters as a Model for Revisiting the Role of Biological Sex Differences in SARS-CoV-2 Infection

There is growing evidence that coronavirus disease 2019 (COVID-19) affects males more severely than females, including compelling evidence indicating that biological sex is an important clinical factor influencing disease pathology and outcomes. In their recent article in mBio, S. Dhakal, C. A. Ruiz-Bedoya, R. Zhou, P. S. Creisher, et al. (mBio 12:e00974-21, 2021, https://doi.org/10.1128/mBio.00974-21) find further evidence to support this hypothesis as they interrogate biological sex differences in the pathogenesis and clinical features of COVID-19 in the golden Syrian hamster model. Their study probes SARS-CoV-2 infection in terms of loss of body mass, recovery, lung compromise, viral replication, inflammatory response, immune response, and, most importantly, the role of estrogen. They also demonstrate the value of a novel unbiased, quantitative chest computed tomography (CT) imaging approach. The golden Syrian hamster model holds a promising opportunity to further investigate how biological sex acts as a primary determinant in SARS-CoV-2 pathogenesis, as also demonstrated in this study.