Neutralization of SARS-CoV-2 Omicron XBB.1.5 and JN.1 variants after COVID-19 booster-vaccination and infection.

SARS-CoV-2 Omicron lineages continue to emerge and evolve into new sublineages, causing infection waves throughout 2022 and 2023, which has been attributed to immune escape. We examined neutralizing antibody responses to the recently emerged SARS-CoV-2 JN.1 variant in comparison to ancestral D614G and Omicron BA.1, BA.2, BA.5, and XBB.1.5 variants. We tested 79 human sera from cohorts with different combinations of vaccinations and infections, including 23 individuals who had been repeatedly exposed to Omicron. Individuals with a monovalent XBB.1.5 vaccine booster or XBB.1.5 breakthrough infection had robust antibody levels against all variants tested; however, JN.1 evaded antibodies in individuals after single Omicron BA.1, BA.2 or BA.5 breakthrough infections. Moreover, in the non-vaccinated cohort, serum antibodies demonstrated almost no cross-neutralization activities against D614G, XBB.1.5 and JN.1. after infections with earlier Omicron variants. These findings show that SARS-CoV-2-immunity is heterogeneous, depending on different combinations of vaccinations and infections, and emphasize the importance of considering different immune-backgrounds when evaluating novel variants.

Respiratory syncytial virus surge in 2022 caused by lineages already present before the COVID-19 pandemic.

In 2022, Austria experienced a severe respiratory syncytial virus (RSV) epidemic with an earlier-than-usual start (Weeks 35/2021-45/2022) and increased numbers of pediatric patients in emergency departments. This surge came 2 years after a season with no cases detected as a result of coronavirus disease 2019 nonpharmaceutical interventions. We analyzed epidemiologic patterns and the phylodynamics of RSV based on approximately 30 800 respiratory specimens collected year-round over 10 years from ambulatory and hospitalized patients from 248 locations in Austria. Genomic surveillance and phylogenetic analysis of 186 RSV-A and 187 RSV-B partial glycoprotein sequences collected from 2018 to 2022 revealed that the 2022/2023 surge was driven by RSV-B in contrast to the surge in the 2021/2022 season that was driven by RSV-A. Whole-genome sequencing and phylodynamic analysis indicated that the RSV-B strain GB5.0.6a was the predominant genotype in the 2022/2023 season and emerged in late 2019. The results provide insight into RSV evolution and epidemiology that will be applicable to future monitoring efforts with the advent of novel vaccines and therapeutics.

Breakthrough infections with SARS-CoV-2 omicron efficiently boost antibodies from previous BNT162b2 vaccinations.

Objective: To investigate whether SARS-CoV-2 omicron breakthrough infection in individuals after three doses of wildtype-based BNT162b2 increases antibody levels measured by a commercially available wildtype-based immunoassay. Methods: 16 of 21 individuals in a BNT162b2 vaccination cohort (recruited 129 [129-135] days after dose 3) experienced a breakthrough infection (BTI) between March and September 2022. Antibodies to the receptor binding domain (RBP) of the spike protein (Anti-S) were quantified using the wildtype-based Elecsys SARS-CoV-2 S assay (Roche). Antibody responses of triple vaccinated BTI cases were compared to triple vaccinated individuals without breakthrough infection and to 16 matched individuals after primary omicron infection. Results: In the 16 individuals with primary Omicron infection, the anti-S assay returned only very low results (2.25 [0.61-5.80] U/mL). However, in individuals with BTI, Anti-S levels rose from 7,135 [5,870-17,470] U/mL to 21,705 (7,750-46,137.5) U/mL. At the same time, Anti-S concentrations decreased from 9,120 [7,480-13,480] U/mL to 3,830 (2,390-4,220) U/mL in those 5 of 21 vaccinated only. Conclusions: Our data suggest that breakthrough infection with omicron can efficiently boost wild-type antibodies in individuals vaccinated with wild-type BNT162b2.

Prediction of humoral and cellular immune response to COVID-19 mRNA vaccination by TTV load in kidney transplant recipients and hemodialysis patients.

BACKGROUND: Immunosuppressed individuals such as kidney transplant recipients (KTR) and hemodialysis patients (DP) show impaired immune responses to COVID-19 vaccination. Plasma Torque Teno Virus (TTV) DNA load is used as surrogate for the individual degree of immunosuppression. We now assessed the association of TTV load at time of COVID-19 vaccination with humoral and cellular immune response rates to vaccination in KTR, DP, and healthy medical personnel (MP). METHODS: A total of 100 KTR, 115 DP and 54 MP were included. All were SARS-CoV-2 seronegative at the time of vaccination with either BNT162b2 or mRNA-1273. Plasma TTV loads were assessed at the time of first vaccination. After two-dose vaccination, seroconversion (de novo detection of SARS-CoV-2 S1-IgA and/or IgG) was determined. In addition, cellular responses as assessed by interferon γ release and neutralizing antibodies were assessed in a subset of participants. ROC analyses were performed to define TTV load cut-offs predicting specific immune responses to vaccination. RESULTS: Plasma TTV loads at the time of first vaccination were negatively associated with seroconversion after two-dose vaccination in KTR (OR 0.87, 95% CI 0.76-0.99). TTV loads were significantly lower in KTR who developed humoral and cellular immune responses to vaccination compared to non-responders (p = 0.0411 and 0.0030, respectively). Of patients with TTV loads above 106 copies/ml, none developed cellular immune responses against SARS-CoV-2, and only 2 of 17 (12%) seroconverted in response to vaccination. CONCLUSION: Plasma TTV loads at the time of first vaccination in immunosuppressed individuals may be useful to predict individual vaccine-specific immune responses.

Bivalent COVID-19 mRNA booster vaccination (BA.1 or BA.4/BA.5) increases neutralization of matched Omicron variants.

We report SARS-CoV-2 neutralizing antibody titers in sera of triple-vaccinated individuals who received a booster dose of an original monovalent or a bivalent BA.1- or BA.4/BA.5-adapted vaccine or had a breakthrough infection with Omicron variants BA.1, BA.2 or BA.4/BA.5. A bivalent BA.4/BA.5 booster or Omicron-breakthrough infection induced increased Omicron-neutralization titers compared with the monovalent booster. The XBB.1.5 variant effectively evaded neutralizing-antibody responses elicited by current vaccines and/or infection with previous variants.

Different Neutralization Profiles After Primary SARS-CoV-2 Omicron BA.1 and BA.2 Infections.

Background and Methods: The SARS-CoV-2 (severe acute respiratory syndrome coronavirus 2) Omicron (B.1.1.529) variant is the antigenically most distinct variant to date. As the heavily mutated spike protein enables neutralization escape, we studied serum-neutralizing activities of naïve and vaccinated individuals after Omicron BA.1 or BA.2 sub-lineage infections in live virus neutralization tests with Omicron BA.1, Omicron BA.2, wildtype (WT, B1.1), and Delta (B.1.617.2) strains. Serum samples obtained after WT infections and three-dose mRNA vaccinations with and without prior infection were included as controls. Results: Primary BA.1 infections yielded reduced neutralizing antibody levels against WT, Delta, and Omicron BA.2, while samples from BA.2-infected individuals showed almost no cross-neutralization against the other variants. Serum neutralization of Omicron BA.1 and BA.2 variants was detectable after three-dose mRNA vaccinations, but with reduced titers. Vaccination-breakthrough infections with either Omicron BA.1 or BA.2, however, generated equal cross-neutralizing antibody levels against all SARS-CoV-2 variants tested. Conclusions: Our study demonstrates that although Omicron variants are able to enhance cross-neutralizing antibody levels in pre-immune individuals, primary infections with BA.1 or BA.2 induced mostly variant-specific neutralizing antibodies, emphasizing the differently shaped humoral immunity induced by the two Omicron variants. These data thus contribute substantially to the understanding of antibody responses induced by primary Omicron infections or multiple exposures to different SARS-CoV-2 variants and are of particular importance for developing vaccination strategies in the light of future emerging variants.