Kinetics and durability of humoral responses to SARS-CoV-2 infection and vaccination (preprint)

We analyzed the kinetics and durability of the humoral responses to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and vaccination using >8,000 longitudinal samples collected over a three-year period (April 2020 to April 2023) in the New York City metropolitan area. Upon primary immunization, participants with pre-existing immunity mounted higher antibody responses faster and achieved higher steady-state levels compared to naive individuals. Antibody durability was characterized by two phases: an initial rapid decay, followed by a phase of stabilization with very slow decay resulting in an individual spike binding antibody steady state. Booster vaccination equalized the differences in antibody levels between participants with and without hybrid immunity, but the antibody titers reached decreased with each successive antigen exposure. Break-through infections increased antibody titers to similar levels as an additional vaccine dose in naive individuals. Our study provides strong evidence for the fact that SARS-CoV-2 antibody responses are long lasting, with an initial waning phase followed by a stabilization phase.

Cellular and molecular heterogeneities and signatures, and pathological trajectories of fatal COVID-19 lungs defined by spatial single-cell transcriptome analysis (preprint)

Despite intensive studies during the last 3 years, the pathology and underlying molecular mechanism of coronavirus disease 2019 (COVID-19) remain poorly defined. Here, we examined postmortem COVID-19 lung tissues by spatial single-cell transcriptome analysis (SSCTA). We identified 18 major parenchymal and immune cell types, all of which are infected by SARS-CoV-2. Compared to the non-COVID-19 control, COVID-19 lungs have reduced alveolar cells (ACs), and increased innate and adaptive immune cells. Additionally, 19 differentially expressed genes in both infected and uninfected cells across the tissues mirror the altered cellular compositions. Spatial analysis of local infection rates revealed regions with high infection rates that are correlated with high cell densities (HIHD). The HIHD regions express high levels of SARS-CoV-2 entry-related factors including ACE2, FURIN, TMPRSS2, and NRP1, and co-localized with organizing pneumonia (OP) and lymphocytic and immune infiltration that have increased ACs and fibroblasts but decreased vascular endothelial cells and epithelial cells, echoing the tissue damage and wound healing processes. Sparse non-negative matrix factorization (SNMF) analysis of neighborhood cell type composition (NCTC) features identified 7 signatures that capture structure and immune niches in COVID-19 tissues. Trajectory inference based on immune niche signatures defined two pathological routes. Trajectory A progresses with primarily increased NK cells and granulocytes, likely reflecting the complication of microbial infections. Trajectory B is marked by increased HIHD and OP, possibly accounting for the increased immune infiltration. The OP regions are marked by high numbers of fibroblasts expressing extremely high levels of COL1A1 and COL1A2. Examination of single-cell RNA-seq data (scRNA-seq) from COVID-19 lung tissues and idiopathic pulmonary fibrosis (IPF) identified similar cell populations primarily consisting of myofibroblasts. Immunofluorescence staining revealed the activation of IL6-STAT3 and TGF-{beta}-SMAD2/3 pathways in these cells, which likely mediate the upregulation of COL1A1 and COL1A2, and excessive fibrosis in the lung tissues. Together, this study provides an SSCTA atlas of cellular and molecular signatures of fatal COVID-19 lungs, revealing the complex spatial cellular heterogeneity, organization, and interactions that characterized the COVID-19 lung pathology.

Intrahost evolution and forward transmission of a novel SARS-CoV-2 Omicron BA.1 subvariant (preprint)

AO_SCPLOWBSTRACTC_SCPLOWPersistent SARS-CoV-2 infections have been reported in immune-compromised individuals and people undergoing immune-modulatory treatments. It has been speculated that the emergence of antigenically diverse SARS-CoV-2 variants such as the Omicron variant may be the result of intra-host viral evolution driven by suboptimal immune responses, which must be followed by forward transmission. However, while intrahost evolution has been documented, to our knowledge no direct evidence of subsequent forward transmission is available to date. Here we describe the emergence of an Omicron BA.1 sub-lineage with 8 additional amino acid substitutions within the spike (E96D, L167T, R346T, L455W, K458M, A484V, H681R, A688V) in an immune-compromised host along with evidence of 5 forward transmission cases. Our findings show that the Omicron BA.1 lineage can further diverge from its exceptionally mutated genome during prolonged SARS-CoV-2 infection; highlighting an urgent need to employ therapeutic strategies to limit duration of infection and spread in vulnerable patients.

Nirmatrelvir, Molnupiravir, and Remdesivir maintain potent in vitro activity against the SARS-CoV-2 Omicron variant (preprint)

Variants of SARS-CoV-2 have become a major public health concern due to increased transmissibility, and escape from natural immunity, vaccine protection, and monoclonal antibody therapeutics. The highly transmissible Omicron variant has up to 32 mutations within the spike protein, many more than previous variants, heightening these concerns of immune escape. There are now multiple antiviral therapeutics that have received approval for emergency use by the FDA and target both the SARS-CoV-2 RNA-dependent RNA polymerase (RdRp) and the main protease (Mpro), which have accumulated fewer mutations in known SARS-CoV-2 variants. Here we test nirmatrelvir (PF-07321332), and other clinically relevant SARS-CoV-2 antivirals, against a panel of SARS-CoV-2 variants, including the novel Omicron variant, in live-virus antiviral assays. We confirm that nirmatrelvir and other clinically relevant antivirals all maintain activity against all variants tested, including Omicron.

SARS-CoV-2 variants of concern have acquired mutations associated with an increased spike cleavage (preprint)

For efficient cell entry and membrane fusion, SARS-CoV-2 spike (S) protein needs to be cleaved at two different sites, S1/S2 and S2 by different cellular proteases such as furin and TMPRSS2. Polymorphisms in the S protein can affect cleavage, viral transmission, and pathogenesis. Here, we investigated the role of arising S polymorphisms in vitro and in vivo to understand the emergence of SARS-CoV-2 variants. First, we showed that the S:655Y is selected after in vivo replication in the mink model. This mutation is present in the Gamma Variant Of Concern (VOC) but it also occurred sporadically in early SARS-CoV-2 human isolates. To better understand the impact of this polymorphism, we analyzed the in vitro properties of a panel of SARS-CoV-2 isolates containing S:655Y in different lineage backgrounds. Results demonstrated that this mutation enhances viral replication and spike protein cleavage. Viral competition experiments using hamsters infected with WA1 and WA1-655Y isolates showed that the variant with 655Y became dominant in both direct infected and direct contact animals. Finally, we investigated the cleavage efficiency and fusogenic properties of the spike protein of selected VOCs containing different mutations in their spike proteins. Results showed that all VOCs have evolved to acquire an increased spike cleavage and fusogenic capacity despite having different sets of mutations in the S protein. Our study demonstrates that the S:655Y is an important adaptative mutation that increases viral cell entry, transmission, and host susceptibility. Moreover, SARS-COV-2 VOCs showed a convergent evolution that promotes the S protein processing.

The plasmablast response to SARS-CoV-2 mRNA vaccination is dominated by non-neutralizing antibodies that target both the NTD and the RBD (preprint)

In this study we profiled vaccine-induced polyclonal antibodies as well as plasmablast derived mAbs from subjects who received SARS-CoV-2 spike mRNA vaccine. Polyclonal antibody responses in vaccinees were robust and comparable to or exceeded those seen after natural infection. However, that the ratio of binding to neutralizing antibodies after vaccination was greater than that after natural infection and, at the monoclonal level, we found that the majority of vaccine-induced antibodies did not have neutralizing activity. We also found a co-dominance of mAbs targeting the NTD and RBD of SARS-CoV-2 spike and an original antigenic-sin like backboost to seasonal human coronaviruses OC43 and HKU1 spike proteins. Neutralizing activity of NTD mAbs but not RBD mAbs against a clinical viral isolate carrying E484K as well as extensive changes in the NTD was abolished, suggesting that a proportion of vaccine induced RBD binding antibodies may provide substantial protection against viral variants carrying E484K.

Introductions and early spread of SARS-CoV-2 in the New York City area (preprint)

New York City (NYC) has emerged as one of the epicenters of the current SARS-CoV2 pandemic. To identify the early events underlying the rapid spread of the virus in the NYC metropolitan area, we sequenced the virus causing COVID19 in patients seeking care at the Mount Sinai Health System. Phylogenetic analysis of 84 distinct SARS-CoV2 genomes indicates multiple, independent but isolated introductions mainly from Europe and other parts of the United States. Moreover, we find evidence for community transmission of SARS-CoV2 as suggested by clusters of related viruses found in patients living in different neighborhoods of the city.