Impaired immunity and high attack rates caused by SARS-CoV-2 variants among vaccinated long-term care facility residents

Introduction: Long-term care facilities (LTCF) residents are at high risk for severe coronavirus disease 2019 (COVID-19), and therefore, COVID-19 vaccinations were prioritized for residents and personnel in Finland at the beginning of 2021. Methods: We investigated COVID-19 outbreaks in two LTCFs, where residents were once or twice vaccinated. After the outbreaks we measured immunoglobulin G (IgG) antibodies to severe acute respiratory syndrome coronavirus 2 spike glycoprotein, neutralizing antibody (NAb) titers, and cell-mediated immunity markers from residents and healthcare workers (HCWs). Results: In LTFC-1, the outbreak was caused by an Alpha variant (B.1.1.7) and the attack rate (AR) among once vaccinated residents was 23%. In LTCF-2 the outbreak was caused by a Beta variant (B.1.351). Its AR was 47% although all residents had received their second dose 1 month before the outbreak. We observed that vaccination had induced lower IgG concentrations, NAb titers and cell-mediated immune responses in residents compared to HCWs. Only 1/8 residents had NAb to the Beta variant after two vaccine doses. Conclusions: The vaccinated elderly remain susceptible to breakthrough infections caused by Alpha and Beta variants. The weaker vaccine response in the elderly needs to be addressed in vaccination protocols, while new variants capable of evading vaccine-induced immunity continue to emerge.Peer reviewe

Long-Lasting T Cell Responses in BNT162b2 COVID-19 mRNA Vaccinees and COVID-19 Convalescent Patients

Peer reviewe

Long-Lasting T Cell Responses in BNT162b2 COVID-19 mRNA Vaccinees and COVID-19 Convalescent Patients

The emergence of novel variants of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has made it more difficult to prevent the virus from spreading despite available vaccines. Reports of breakthrough infections and decreased capacity of antibodies to neutralize variants raise the question whether current vaccines can still protect against COVID-19 disease. We studied the dynamics and persistence of T cell responses using activation induced marker (AIM) assay and Th1 type cytokine production in peripheral blood mononuclear cells obtained from BNT162b2 COVID-19 mRNA vaccinated health care workers and COVID-19 patients. We demonstrate that equally high T cell responses following vaccination and infection persist at least for 6 months against Alpha, Beta, Gamma, and Delta variants despite the decline in antibody levels.</p

Persistent T cell-mediated immune responses against Omicron variants after the third COVID-19 mRNA vaccine dose

IntroductionThe prime-boost COVID-19 mRNA vaccination strategy has proven to be effective against severe COVID-19 disease and death. However, concerns have been raised due to decreasing neutralizing antibody levels after COVID-19 vaccination and due to the emergence of new immuno-evasive SARS-CoV-2 variants that may require additional booster vaccinations.MethodsIn this study, we analyzed the humoral and cell-mediated immune responses against the Omicron BA.1 and BA.2 subvariants in Finnish healthcare workers (HCWs) vaccinated with three doses of COVID-19 mRNA vaccines. We used enzyme immunoassay and microneutralization test to analyze the levels of SARS-CoV-2 specific IgG antibodies in the sera of the vaccinees and the in vitro neutralization capacity of the sera. Activation induced marker assay together with flow cytometry and extracellular cytokine analysis was used to determine responses in SARS-CoV-2 spike protein stimulated PBMCs.ResultsHere we show that within the HCWs, the third mRNA vaccine dose recalls both humoral and T cell-mediated immune responses and induces high levels of neutralizing antibodies against Omicron BA.1 and BA.2 variants. Three weeks after the third vaccine dose, SARS-CoV-2 wild type spike protein-specific CD4+ and CD8+ T cells are observed in 82% and 71% of HCWs, respectively, and the T cells cross-recognize both Omicron BA.1 and BA.2 spike peptides. Although the levels of neutralizing antibodies against Omicron BA.1 and BA.2 decline 2.5 to 3.8-fold three months after the third dose, memory CD4+ T cell responses are maintained for at least eight months post the second dose and three months post the third vaccine dose.DiscussionWe show that after the administration of the third mRNA vaccine dose the levels of both humoral and cell-mediated immune responses are effectively activated, and the levels of the spike-specific antibodies are further elevated compared to the levels after the second vaccine dose. Even though at three months after the third vaccine dose antibody levels in sera decrease at a similar rate as after the second vaccine dose, the levels of spike-specific CD4+ and CD8+ T cells remain relatively stable. Additionally, the T cells retain efficiency in cross-recognizing spike protein peptide pools derived from Omicron BA.1 and BA.2 subvariants. Altogether our results suggest durable cellmediated immunity and protection against SARS-CoV-2

Rokotteen ja infektion tuottama soluvälitteinen immuniteetti SARS-CoV-2 virusta vastaan ihmisillä

Tässä maisterintutkielmassa tutkittiin T-soluvasteita SARS-CoV-2:n rakenneproteiineille. T-solu vasteita tutkittiin rokotetuilla ja tartunnan saaneilla (n=30), vain tartunnan saaneilla (n=22) sekä henkilöillä, joilla ei ollut aiempaa tartuntaa eikä rokotteita (n = 6). Lisäksi vertailin T-solu vasteita ryhmien välillä, jotka olivat saaneet joko villityypin- (WT), Alfa- (B.1.1.7) tai Beta -infektion (B.1.351). Ennen tutkittavien näytteiden analysointia optimoin solustimulaatio olosuhteet. Perifeerisen veren mononukleaarisolut (PBMC) kerättiin tartunnan henkilöiltä kuusi kuukautta tartunnan jälkeen. Mononukleaarisoluja stimuloitiin SARS-CoV-2 villityypin nukleo-, piikki-, vaippa- ja kalvoproteiini- peptidi pooleilla. Tässä työssä määritin mononukleaaristensolujen erittämät sytokiinit ja efektorimolekyylit, jotka olivat perforiini, tuumorinekroositekijä alfa (TNF-a), grantsyymi B, interferoni gamma (IFN-y), interleukiini 2 (IL-2) ja interleukiini 4 (IL-4). Nämä sytokiinit ja efektorimolekyylit kertovat CD4+- ja CD8+ solu vasteista. Löysin että tutkittavilla, joilla oli pelkästään infektio tai infektion ja rokotuksen yhdistelmä, oli voimakkaampi soluvälitteinen immuunivaste verrattuna terveisiin kontrolli henkilöihin. Infektio sai aikaan suurempaa grantsyymi B:n, IFN-y:n ja IL-2:n eritystä. Infektion ja rokotuksen yhdistelmä sai aikaan suurempaa grantsyymi B:n, perforiinin, IFN-y:n, IL-2:n ja IL-4:n eritystä. Huomasin, että henkilöillä, joilla oli rokotteen sekä infektion tuottamaa hybridi-immuniteettiä SARS-CoV-2 vastaan, oli keskimäärin suurempi IL-4:n eritys verrattuna henkilöihin, jotka olivat saaneet vain tartunnan. Tässä tutkielmassa havaitsin, että nukleo-, piikki- ja kalvoproteiini stimuloivat T-soluvasteita, kun taas vaippaproteiini ei saanut aikaan T-soluvasteita. Löysin, että WT-, Alfa- tai Beeta-infektiot tuottivat yhtä hyviä T-soluvasteita villityypin piikkiproteiinille. Löysin tässä tutkielmassa, että COVID-19-potilaille syntyy pitkäkestoinen T-soluvaste. Löysin myös, että T-solut tunnistavat erilaisia SARS-CoV-2-variantteja. Eri varianttien piikkiproteiineissa esiintyvät mutaatiot eivät vaikuta T-solujen kykyyn tunnistaa näitä antigeenejä. T-soluihin perustuva immuniteetti ei ole siis yhtä herkkä antigeeni muutoksille kuin vasta-aine välitteinen immuniteetti on. T-soluilla on tärkeä rooli uusia variantteja vastaan suojautumisessa, kun uudet SARS-CoV-2-variantit väistävät vasta-aine välitteistä immuniteettia.In this thesis, I studied T cell responses to SARS-CoV-2 structural proteins in subjects who had been both vaccinated and infected (n=30), who had only been infected (n=22), and as controls, in subjects who had been neither vaccinated nor infected (n=6). In addition, I compared cellular responses between groups of subjects who had been infected with either wild-type (WT) SARS-CoV-2, Alpha (B.1.1.7), or Beta (B.1.351) variants. Before analyzing the samples to be studied, I optimized the conditions for the cell stimulations. Peripheral blood mononuclear cells (PBMCs) were collected from infected subjects six months after infection. PBMCs were stimulated with SARS-CoV-2 wild-type nucleoprotein, spike-, envelope-, and membrane protein peptide pools. I quantified cytokines and effector molecules characteristic of CD4+ and CD8+ cell responses; perforin, tumor necrosis factor alpha (TNF-a), granzyme B, interferon gamma (IFN-γ), interleukin 2 (IL-2) and interleukin 4 (IL-4) secreted by PBMCs were quantified. In this study, I found that subjects with infection, or combination of infection and vaccination had higher cellular immune responses compared to uninfected controls. Infection induced higher granzyme B, IFN-y, and IL-2 secretion, and the combination of infection and vaccination induced higher granzyme B, perforin, IFN-y, IL-2 and IL-4 secretion. I found that subjects with hybrid immunity, defined as immunity acquired from combined vaccination and infection, had on average higher IL-4 responses compared to those who had been infected only. In this study, I found that nucleoprotein, spike-, and membrane proteins stimulated T cell responses whereas envelope protein did not stimulate T cell responses. I found that WT, Alpha or Beta infection produced equally good T cell responses to WT spike peptide. In conclusion, I found that COVID-19 patients have long-lasting T cell responses. I found that T cells recognize different SARS-CoV-2 variants. Mutations present in the spike proteins of the different variants do not affect T-cell ability to recognize these antigens. Immunity based on T cells is not as susceptible to antigenic changes as the humoral immunity. T cells have a vital role in protection against variants, when new SARS-CoV-2 variants evaded antibody-based immunity

Hybrid Immunity Improves the Immune Response after the Fourth COVID-19 Vaccine Dose in Individuals with Medical Conditions Predisposing to Severe COVID-19

Data on immune responses following COVID-19 booster vaccinations and subsequent infections in the immunocompromised are limited. We studied antibody responses after the fourth dose and subsequent infections to define patient groups benefiting most from boosters. Fourth vaccine (booster) doses were, in Finland, first recommended for severely immunocompromised individuals, whom we invited to participate in our study in 2022. We assessed spike protein-specific IgG and neutralizing antibodies (NAb) against the ancestral and Omicron BA.1 strains one month after the fourth dose from 488 adult participants and compared them to the levels of 35 healthy controls after three doses. We used Bayesian generalized linear modeling to assess factors explaining antibody levels and assessed vaccine-induced and hybrid immunity six months after the last vaccine dose. Chronic kidney disease (CKD) and immunosuppressive therapy (IT) were identified as factors explaining sub-optimal antibody responses. The proportion of participants with a normal antibody response and NAbs was significantly lower regarding CKD patients compared to the controls. By the 6-month sampling point, one-third of the participants became infected (documented by serology and/or molecular tests), which notably enhanced antibody levels in most immunocompromised participants. Impaired antibody responses, especially NAbs against the Omicron lineage, suggest limited protection in individuals with CKD and highlight the need for alternative pharmaceutical preventive strategies. Vaccination strategies should take into account the development of robust hybrid immunity responses also among the immunocompromised