Acute tubulointerstitial nephritis with or without uveitis: a novel form of post-acute COVID-19 syndrome in children (preprint)

Background COVID-19 is a complex multisystem disease, frequently associated with kidney injury. Since the beginning of the COVID-19 pandemic, we observed a striking increase in the incidence of acute tubulointerstitial nephritis (aTIN) without or with uveitis (TINUs) among children. This prompted us to examine whether SARS-CoV-2 might be the underlying trigger. Methods We conducted a French nationwide retrospective cohort study. We included all consecutive children diagnosed with aTIN or TINUs of undetermined cause between April-2020 and March-2021. SARS-CoV-2 antibody responses were tested by a luciferase immunoprecipitation system and compared to age-matched controls. Immunohistochemistry, immunofluorescence and molecular microbiology analyses were performed on kidney biopsies. Results Forty-eight children were included with a median age at diagnosis of 14.7 years (9.4-17.6). aTIN and TINUs incidence rates increased 3-fold and 12-fold, respectively, compared to pre-pandemic years. All patients had impaired kidney function with a median eGFR of 31.9 ml/min/1.73m2 at diagnosis. Kidney biopsies showed lesions of acute tubulointerstitial nephritis and 25% of patients had fibrosis. No patient had concomitant acute COVID-19. All 16 children tested had high anti-N IgG titers and one had anti-S IgGs. Next-generation sequencing failed to detect any infectious agents in kidney biopsies. However, SARS-CoV-2 RNA was detected by PCR in two kidney samples supporting a potential direct link between SARS-CoV-2 and aTIN/TINUs. Conclusions We describe a novel form of post-acute COVID-19 syndrome in children, unique in its exclusive kidney and eye involvement, and its distinctive anti-SARS-CoV-2 N+/S- serological profile. Our results support a causal association linking SARS-CoV-2 infection to this newly-reported burst of renal/eye inflammation.

SARS-CoV-2-Related Bat Virus in Human Relevant Models Sheds Light on the Proximal Origin of COVID-19 (preprint)

Bat sarbecovirus BANAL-236 is highly related to SARS-CoV-2 and infects human cells, albeit lacking the furin cleavage site in its spike protein. To inform on the origin of SARS-CoV-2, we evaluated the clinical, epidemiological and evolutionary consequences of a potential BANAL-236 spillover into humans using animal models. The virus replicates efficiently and pauci-symptomatically in humanized mice and in macaques, where its tropism is enteric, strongly differing from that of SARS-CoV-2. BANAL-236 infection leads to protection against superinfection by a more virulent strain like Wuhan SARS-CoV-2. Yet we found no evidence of antibodies recognizing bat sarbecoviruses in populations highly exposed to bats, indicating that such infections, if they occur, are rare. Six passages in mice or in human intestinal cells, mimicking putative early spillover events, selected adaptive mutations without appearance of a furin cleavage site and not change in virulence. We thus conclude that the hypothesis of the SARS-CoV-2 pandemic being preceded by silent circulation in humans of BANAL-236-like strains leading to the acquisition of a furin cleavage site is unlikely. Our studies suggest that a specific search for a furin cleavage site in sarbecoviruses in the wild should be pursued to understand the origin of the SARS-CoV-2 pandemics.

Humoral Immunity to SARS-CoV-2 and Inferred Protection from Infection in a French Longitudinal Community Cohort (preprint)

Population-level immunity to SARS-CoV-2 is growing through vaccination as well as ongoing circulation. Given waning immunity and emergence of new variants, it is important to dynamically determine the risk of re-infection in the population. For estimating immune protection, neutralization titers are most informative, but these assays are difficult to conduct at a population level. Measurement of antibody levels can be implemented at high throughput, but has not been robustly validated as a correlate of protection. Here, we have developed a method that predicts neutralization and protection based on variant-specific antibody measurements to SARS-CoV-2 antigens. This approach allowed us to estimate population-immunity in a longitudinal cohort from France followed for up to 2 years. Participants with a single vaccination or immunity caused by infection only are especially vulnerable to COVID-19 or hospitalization due to SARS-CoV-2. While the median reduced risk to COVID-19 in participants with 3 vaccinations was 96%, the median reduced risk among participants with infection-acquired immunity only was 42%. The results presented here are consistent with data from vaccine-effectiveness studies indicating robustness of our approach. Our multiplex serological assay can be readily optimized and employed to study any new variant and provides a framework for development of an assay that would include protection estimates.

SARS-CoV-2 Omicron neutralization and risk of infection among elderly after a booster dose of Pfizer vaccine (preprint)

Background: The protective immunity against Omicron following a BNT162b2 Pfizer booster dose among elderly is not well characterized. Methods: Thirty-eight residents from three nursing homes were recruited for the study. Antibodies targeting the Spike protein of SARS-CoV-2 were measured with the S-Flow assay. Neutralizing activities in sera were measured as effective dilution 50% (ED50) with the S-Fuse assay using authentic isolates of Delta and Omicron. Results: Among the 38 elderly included in the study, with median (inter-quartile range, IQR) age of 88 (81-92) years, 30 (78.9%) had been previously infected. The ED50 of neutralization were lower against Omicron than Delta, and higher among convalescent compared to naive residents. During an Omicron epidemic affecting two of the three nursing homes in December 2021-January 2022, 75% (6/8) of naive residents got infected, compared to 25% (6/24) of convalescents (P=0.03). Antibody levels to Spike and ED50 of neutralization against Omicron after the BNT162b2 booster dose were lower in those with breakthrough infection (n=12) compared to those without (n=20): median of 1256 vs 2523 BAU/mL (P=0.02) and median ED50 of 234 vs 1298 (P=0.0004), respectively. Conclusion: This study confirmed the importance of receiving at least three antigenic exposures to the SARS-CoV-2 Spike protein for achieving satisfactory neutralizing antibody levels. In this population, protection against Omicron infection was increased in individuals who had been previously infected in addition to the three vaccine doses. Thus, a fourth antigenic exposure may be useful in the elderly population to prevent infection with Omicron, a variant known for its high escape immunity properties.

Rapid characterization of a Delta-Omicron SARS-CoV-2 recombinant detected in Europe (preprint)

Recombination is a crucial process in the evolution of many organisms. Although the evolutionary reasons behind its occurrence in RNA viruses are debated, this phenomenon has been associated with major epidemiological events such as virus host range expansion, antigenic shift or variation in virulence 1,2, and this process occurs frequently in positive strand RNA viruses such as coronaviruses. The SARS-CoV-2 pandemic has been associated with the repeated emergence of variants of concern presenting increased transmissibility, severity or immune escape 3. The recent extensive circulation of Delta worldwide and its subsequent replacement by viruses of the Omicron lineage 4 (BA.1 then BA.2), have created conditions for genetic exchanges between viruses with both genetic diversity and phenotypic specificities 5-7. Here we report the identification and in vitro and in vivo characterization of a Delta-Omicron recombinant in Europe. This recombinant exhibits immune escape properties similar to Omicron, while its behavior in mice expressing the human ACE2 receptor is more similar to Delta. This recombinant provides a unique and natural opportunity to better understand the genotype to phenotype links in SARS-CoV-2.