The protective effect of neutralizing antibodies in SARS-CoV-2 infected individuals is not yet well defined. To address this issue, we have analyzed the kinetics of neutralizing antibody responses ...and their association with disease severity. Between March and May 2020, the prospective KING study enrolled 72 COVID-19+ participants grouped according to disease severity. SARS-CoV-2 infection was diagnosed by serological and virological tests. Plasma neutralizing responses were assessed against replicative virus and pseudoviral particles. Multiple regression and non-parametric tests were used to analyze dependence of parameters. The magnitude of neutralizing titers significantly increased with disease severity. Hospitalized individuals developed higher titers compared to mild-symptomatic and asymptomatic individuals, which together showed titers below the detection limit in 50% of cases. Longitudinal analysis confirmed the strong differences in neutralizing titers between non-hospitalized and hospitalized participants and showed rapid kinetics of appearance of neutralizing antibodies (50% and 80% of maximal activity reached after 11 and 17 days after symptoms onset, respectively) in hospitalized patients. No significant impact of age, gender or treatment on the neutralizing titers was observed in this limited cohort. These data identify a clear association of humoral immunity with disease severity and point to immune mechanisms other than antibodies as relevant players in COVID-19 protection.
Limited data exists on SARS-CoV-2 sustained-response to vaccine in patients with rheumatic diseases. This study aims to evaluate neutralizing antibodies (nAB) induced by SARS-CoV-2 vaccine after 3 to ...6 months from administration in Systemic Lupus Erythematosus (SLE) patients, as a surrogate of sustained-immunological response. This cross-sectional study compared nAB titre of 39 SLE patients and 37 Healthy individuals with no previous SARS-CoV-2 infection, who had all received a complete regimen of a mRNA SARS-CoV-2 vaccine within the last 3 to 6 months. We included four lines of SLE treatment including Not-treated, Hydroxychloroquine, immunosuppressive drugs and biological therapy. Glucocorticoids were allowed in all groups. Healthy and Not-treated individuals showed the highest levels of nAB. Treated patients presented lower nAB titres compared to Healthy: a 73% decrease for First-Line patients, 56% for Second-Line treatment and 72% for Third-Line. A multivariate analysis pointed to Glucocorticoids as the most associated factor with declining nAB levels (75% decrease) in treated SLE. Furthermore, a significant reduction in nAB titres was observed for Rituximab-users compared to Healthy subjects (89% decrease). Medium-term response of SLE patients to SARS-CoV-2 mRNA vaccines is negatively impacted in Glucocorticoids and Rituximab users. These findings might help to inform recommendations in vaccination protocols for SLE patients.
The understanding of HIV-1 pathogenesis and clinical progression is incomplete due to the variable contribution of host, immune, and viral factors. The involvement of viral factors has been ...investigated in extreme clinical phenotypes from rapid progressors to long-term non-progressors (LTNPs). Among HIV-1 proteins, the envelope glycoprotein complex (Env) has been concentrated on in many studies for its important role in the immune response and in the first steps of viral replication. In this study, we analyzed the contribution of 41 Envs from 24 patients with different clinical progression rates and viral loads (VLs), LTNP-Elite Controllers (LTNP-ECs); Viremic LTNPs (vLTNPs), and non-controller individuals contemporary to LTNPs or recent, named Old and Modern progressors. We studied the Env expression, the fusion and cell-to-cell transfer capacities, as well as viral infectivity. The sequence and phylogenetic analysis of Envs were also performed. In every functional characteristic, the Envs from subjects with viral control (LTNP-ECs and vLTNPs) showed significant lower performance compared to those from the progressor individuals (Old and Modern). Regarding sequence analysis, the variable loops of the gp120 subunit of the Env (i.e., V2, V4, and mainly V5) of the progressor individuals showed longer and more glycosylated sequences than controller subjects. Therefore, HIV-1 Envs from virus of patients presenting viremic control and the non-progressor clinical phenotype showed poor viral functions and shorter sequences, whereas functional Envs were associated with virus of patients lacking virological control and with progressor clinical phenotypes. These correlations support the role of Env genotypic and phenotypic characteristics in the
HIV-1 infection and pathogenesis.
Key message
Rice-produced SD1 retains its physicochemical properties and provides efficient pre-exposure HIV-1 prophylaxis against infection in vitro.
Scytovirin (SVN) is an HIV-neutralizing lectin ...that features two structural domains (SD1 and SD2) that bind to HIV-1 envelope glycoproteins. We expressed SD1 in rice seeds as a potential large-scale production platform and confirmed that rice-derived SD1 binds the HIV-1 envelope glycoprotein gp120 in vitro. We analyzed the thermodynamic properties of SD1 compared to full-size SVN (produced in
E. coli
) by isothermal titration and differential scanning calorimetry to characterize the specific interactions between SVN/SD1 and gp120 as well as to high-mannose oligosaccharides. SVN bound with moderate affinity (K
d
= 1.5 µM) to recombinant gp120, with 2.5-fold weaker affinity to nonamannoside (K
d
of 3.9 µM), and with tenfold weaker affinity to tetramannoside (13.8 µM). The melting temperature (T
m
) of full-size SVN was 59.1 °C and the enthalpy of unfolding (ΔH
unf
) was 16.4 kcal/mol, but the T
m
fell when SVN bound to nonamannoside (56.5 °C) and twice as much energy was required for unfolding (ΔH
unf
= 33.5 kcal/mol). Interestingly, binding to tetramannoside destabilized the structure of SD1 (ΔT
m
~ 11.5 °C) and doubled the enthalpy of unfolding, suggesting a dimerization event. The similar melting phenomenon shared by SVN and SD1 in the presence of oligomannose confirmed their conserved oligosaccharide-binding mechanisms. SD1 expressed in transgenic rice was able to neutralize HIV-1 in vitro. SD1 expressed in rice, therefore, is suitable as a microbicide component.
Patients with solid tumors have been a risk group since the beginning of the SARS‐CoV‐2 pandemic due to more significant complications, hospitalizations or deaths. The immunosuppressive state of ...cancer treatments or the tumor itself could influence the development of post‐vaccination antibodies. This study prospectively analyzed 89 patients under chemotherapy and/or immunotherapy, who received two doses of the mRNA‐1237 vaccine, and were compared with a group of 26 non‐cancer individuals. Information on adverse events and neutralizing antibodies against the ancestral strain of SARS‐CoV‐2 (WH1) have been analyzed. Local reactions accounted for 65%, while systemic reactions accounted for 46% of oncologic individuals/cancer patients. Regarding the response to vaccination, 6.7% of cancer patients developed low neutralizing antibody levels. Lower levels of neutralizing antibodies between cancer and non‐cancer groups were significant in individuals without previous SARS‐CoV‐2 infection, but not in previously infected individuals. We also observed that patients receiving chemotherapy or chemoimmunotherapy have significantly lower levels of neutralizing antibodies than non‐cancer individuals. In conclusion, our study confirms the importance of prioritizing cancer patients receiving anticancer treatment in SARS‐CoV‐2 vaccination programs.
Cancer patients are a risk group for SARS‐CoV‐2 infection. We determined the levels of anti‐SARS‐CoV‐2 plasma neutralizing antibodies post mRNA‐1273 vaccination and observed that cancer patients exhibit lower titers compared to non‐cancer individuals, particularly in individuals not previously infected by SARS‐CoV‐2. Additionally, we found an association between low levels of neutralizing antibodies and chemotherapy‐containing treatments, highlighting their prioritization in SARS‐CoV‐2 vaccination programs.
Several cases of naturally infected dogs with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been reported despite the apparently low susceptibility of this species. Here, we ...document the first reported case of infection caused by the Delta (B.1.617.2) variant of concern (VOC) in a dog in Spain that lived with several household members suffering from Coronavirus Infectious Disease 2019 (COVID-19). The animal displayed mild digestive and respiratory clinical signs and had a low viral load in the oropharyngeal swab collected at the first sampling. Whole-genome sequencing indicated infection with the Delta variant, coinciding with the predominant variant during the fifth pandemic wave in Spain. The dog seroconverted, as detected 21 days after the first sampling, and developed neutralizing antibodies that cross-neutralized different SARS-CoV-2 variants. This study further emphasizes the importance of studying the susceptibility of animal species to different VOCs and their potential role as reservoirs in the context of COVID-19.
In untreated HIV-1-infected individuals, viremia is positively associated with disease progression. However, some viremic non progressors (VNPs) individuals show paradoxical high CD4
T cell counts. ...HIV-1 envelope glycoprotein complex (Env) is a major cytopathic determinant in viral replication; therefore, we have deeply characterized Env function in this rare clinical phenotype. Full-length Env clones isolated from individuals with Viral Load (VL) > 10,000 copies/mL classified as VNPs (n = 15) or rapid progressors (RPs, n = 17) were geno- and phenotypically analyzed by determining diversity, expression, CD4 binding/signaling, fusogenicity, infectivity and autophagy induction. Selected Env clones from VNPs and RPs (n = 32) showed similar expression, fusion and infection abilities. Env clones from both groups showed similar affinity for CD4 during cell-to-cell transmission and consistently induced similar levels of CD4 signaling, measured by α-tubulin acetylation. Moreover, we demonstrate for the first time that primary Env clones from VNP and RP induce autophagy in uninfected cells and that this feature correlated with fusogenic capacity but was unrelated to disease progression. In conclusion, our data suggest that Env clones from VNP individuals are fully functional. Therefore, the paradoxical CD4
T cell count stability coexisting with high levels of viral replication is unrelated to Env function.
Evidence on the determinants of the magnitude of humoral responses and neutralizing titers in individuals with mild COVID-19 is scarce.
In this cohort study of mild COVID-19 patients, we assessed ...viral load (VL) by RT-qPCR at two/three time points during acute infection, and anti-SARS-CoV-2 antibodies by ELISA and plasma neutralizing responses using a pseudovirus assay at day 60.
Seventy-one individuals (65% female, median 42 years old) were recruited and grouped into high viral load (VL) >7.5 Log
copies/mL (n=20), low, VL ≤7.5 Log
copies/mL (n=22), or as Non-early seroconverters with a positive PCR (n=20), and healthy individuals with a negative PCR (n=9). Individuals with high or low VL showed similar titers of total neutralizing antibodies at day 60, irrespective of maximal VL or viral dynamics. Non-early seroconverters had lower antibody titers on day 60, albeit similar neutralizing activity as the groups with high or low VL. Longer symptom duration and older age were independently associated with increased humoral responses.
In mild SARS-CoV-2-infected individuals, the duration of symptoms and age (but not VL) contribute to higher humoral responses.
Antigen display on the surface of Virus-Like Particles (VLPs) improves immunogenicity compared to soluble proteins. We hypothesised that immune responses can be further improved by increasing the ...antigen density on the surface of VLPs. In this work, we report an HIV-1 Gag-based VLP platform engineered to maximise the presence of antigen on the VLP surface. An HIV-1 gp41-derived protein (Min), including the C-terminal part of gp41 and the transmembrane domain, was fused to HIV-1 Gag. This resulted in high-density MinGag-VLPs. These VLPs demonstrated to be highly immunogenic in animal models using either a homologous (VLP) or heterologous (DNA/VLP) vaccination regimen, with the latter yielding 10-fold higher anti-Gag and anti-Min antibody titres. Despite these strong humoral responses, immunisation with MinGag-VLPs did not induce neutralising antibodies. Nevertheless, antibodies were predominantly of an IgG2b/IgG2c profile and could efficiently bind CD16-2. Furthermore, we demonstrated that MinGag-VLP vaccination could mediate a functional effect and halt the progression of a Min-expressing tumour cell line in an in vivo mouse model.
With the spread of new variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), there is a need to assess the protection conferred by both previous infections and current ...vaccination. Here we tested the neutralizing activity of infected and/or vaccinated individuals against pseudoviruses expressing the spike of the original SARS-CoV-2 isolate Wuhan-Hu-1 (WH1), the D614G mutant and the B.1.1.7 variant. Our data show that parameters of natural infection (time from infection and nature of the infecting variant) determined cross-neutralization. Uninfected vaccinees showed a small reduction in neutralization against the B.1.1.7 variant compared to both the WH1 strain and the D614G mutant. Interestingly, upon vaccination, previously infected individuals developed more robust neutralizing responses against B.1.1.7, suggesting that vaccines can boost the neutralization breadth conferred by natural infection.
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