Effect of previous heterologous flavivirus vaccinations on human antibody responses in tick-borne encephalitis and dengue virus infections

Arthropod-borne flaviviruses include a number of medically relevant human pathogens such as the mosquito-borne dengue (DEN), Zika, and yellow fever (YF) viruses as well as tick-borne encephalitis virus (TBEV). All flaviviruses are antigenically related and anamnestic responses due to prior immunity can modulate antibody specificities in subsequent infections or vaccinations. In our study, we analyzed the induction of broadly flavivirus cross-reactive antibodies in tick-borne encephalitis (TBE) and DEN patients without or with prior flavivirus exposure through TBE and/or YF vaccination, and determined the contribution of these antibodies to TBE and dengue virus (DENV) neutralization. In addition, we investigated the formation of cross-reactive antibodies in TBE-vaccination breakthroughs (VBTs). A TBEV infection without prior YF or TBE vaccination induced predominantly type-specific antibodies. In contrast, high levels of broadly cross-reactive antibodies were found in samples from TBE patients prevaccinated against YF as well as in DEN patients prevaccinated against TBE and/or YF. While these cross-reactive antibodies did not neutralize TBEV, they were effective in neutralizing DENV. This discrepancy points to structural differences between the two viruses and indicates that broadly cross-reactive epitopes are less accessible in TBEV than in DENV. In TBE VBT infections, type-specific antibodies dominated the antibody response, thus revealing no difference from that of unvaccinated TBE patients. Our results emphasize significant differences in the structural properties of different flaviviruses that have an impact on the induction of broadly cross-reactive antibodies and their functional activities in virus neutralization.

Structural Framework for Analysis of CD4+ T-Cell Epitope Dominance in Viral Fusion Proteins

Antigen conformation shapes CD4+ T-cell specificity through mechanisms of antigen processing, and the consequences for immunity may rival those from conformational effects on antibody specificity. CD4+ T cells initiate and control immunity to pathogens and cancer and are at least partly responsible for immunopathology associated with infection, autoimmunity, and allergy. The primary trigger for CD4+ T-cell maturation is the presentation of an epitope peptide in the MHC class II antigen-presenting protein (MHCII), most commonly on an activated dendritic cell, and then the T-cell responses are recalled by subsequent presentations of the epitope peptide by the same or other antigen-presenting cells. Peptide presentation depends on the proteolytic fragmentation of the antigen in an endosomal/lysosomal compartment and concomitant loading of the fragments into the MHCII, a multistep mechanism called antigen processing and presentation. Although the role of peptide affinity for MHCII has been well studied, the role of proteolytic fragmentation has received less attention. In this Perspective, we will briefly summarize evidence that antigen resistance to unfolding and proteolytic fragmentation shapes the specificity of the CD4+ T-cell response to selected viral envelope proteins, identify several remarkable examples in which the immunodominant CD4+ epitopes most likely depend on the interaction of processing machinery with antigen conformation, and outline how knowledge of antigen conformation can inform future efforts to design vaccines.

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.

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.

Safety and immunogenicity of a third COVID-19 vaccination in patients with immune-mediated inflammatory diseases compared with healthy controls

OBJECTIVES

A third COVID-19 vaccination is recommended for immunosuppressed patients. However, data on immunogenicity and safety of a third COVID-19 vaccination in patients with immune-mediated inflammatory diseases (IMIDs) are sparse and therefore addressed within this clinical trial.

METHODS

60 immunosuppressed patients and 48 healthy controls (HCs) received a third vaccination with an mRNA vaccine. The primary endpoint was defined as the presence of antibody levels against the receptor-binding domain (RBD)>1500 BAU/mL in patients with IMIDs versus HCs. Further endpoints included differences in neutralising antibodies and cellular immune responses after the third vaccination. Reactogenicity was recorded for 7 days, and safety was evaluated until week 4.

RESULTS

Rate of individuals with anti-RBD antibodies>1500 BAU/mL was not significantly different after the third vaccination between patients with IMIDs and HCs (91% vs 100% p=0.101). Anti-RBD and neutralising antibody levels were significantly lower in patients with IMIDs after the third vaccination than in HCs (p=0.002 and p=0.016, respectively). In contrast, fold increase in antibody levels between week 0 and 4 was higher in patients with IMIDs. Treatment with biological (b) disease-modifying anti-rheumatic drugs (DMARD) or combination of bDMARDs and conventional synthetic DMARDs was associated with reduced antibody levels. Enhanced cellular immune response to wild type and Omicron peptide stimulation was observed after the third vaccination. No serious adverse event was attributed to the third vaccination.

CONCLUSION

Our clinical trial data support the immunogenicity and safety of a third COVID-19 vaccination in patients with IMIDs. However, effects of DMARD therapy on immunogenicity should be considered.

TRIAL REGISTRATION NUMBER

EudraCT No: 2021-002693-10.

Heterologous vector versus homologous mRNA COVID-19 booster vaccination in non-seroconverted immunosuppressed patients: a randomized controlled trial

Impaired response to COVID-19 vaccination is of particular concern in immunosuppressed patients. To determine the best vaccination strategy for this vulnerable group we performed a single center, 1:1 randomized blinded clinical trial. Patients who failed to seroconvert upon two mRNA vaccinations (BNT162b2 or mRNA-1273) are randomized to receive either a third dose of the same mRNA or the vector vaccine ChAdOx1 nCoV-19. Primary endpoint is the difference in SARS-CoV-2 spike antibody seroconversion rate between vector and mRNA vaccinated patients four weeks after the third dose. Secondary outcomes include cellular immune responses. Seroconversion rates at week four are significantly higher in the mRNA (homologous vaccination, 15/24, 63%) as compared to the vector vaccine group (heterologous vaccination, 4/22, 18%). SARS-CoV-2-specific T-cell responses are reduced but could be increased after a third dose of either vector or mRNA vaccine. In a multivariable logistic regression analysis, patient age and vaccine type are associated with seroconversion. No serious adverse event is attributed to COVID-19 booster vaccination. Efficacy and safety data underline the importance of a booster vaccination and support the use of a homologous mRNA booster vaccination in immunosuppressed patients.Trial registration: EudraCT No.: 2021-002693-10.

Immunogenicity and safety of a fourth COVID-19 vaccination in rituximab-treated patients: an open-label extension study

OBJECTIVES

Patients under rituximab therapy are at high risk for a severe COVID-19 disease course. Humoral immune responses to SARS-CoV-2 vaccination are vastly diminished in B-cell-depleted patients, even after a third vaccine dose. However, it remains unclear whether these patients benefit from a fourth vaccination and whether continued rituximab therapy affects antibody development.

METHODS

In this open-label extension trial, 37 rituximab-treated patients who received a third dose with either a vector or mRNA-based vaccine were vaccinated a fourth time with an mRNA-based vaccine (mRNA-1273 or BNT162b2). Key endpoints included the humoral and cellular immune response as well as safety after a fourth vaccination.

RESULTS

The number of patients who seroconverted increased from 12/36 (33%) to 21/36 (58%) following the fourth COVID-19 vaccination. In patients with detectable antibodies to the spike protein's receptor-binding domain (median: 8.0 binding antibody units (BAU)/mL (quartiles: 0.4; 13.8)), elevated levels were observed after the fourth vaccination (134.0 BAU/mL (quartiles: 25.5; 1026.0)). Seroconversion and antibody increase were strongly diminished in patients who received rituximab treatment between the third and the fourth vaccination. The cellular immune response declined 12 weeks after the third vaccination, but could only be slightly enhanced by a fourth vaccination. No unexpected safety signals were detected, one serious adverse event not related to vaccination occurred.

CONCLUSIONS

A fourth vaccine dose is immunogenic in a fraction of rituximab-treated patients. Continuation of rituximab treatment reduced humoral immune response, suggesting that rituximab affects a second booster vaccination. It might therefore be considered to postpone rituximab treatment in clinically stable patients.

TRIAL REGISTRATION NUMBER

2021-002348-57.

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.

Immune Response after mRNA COVID-19 Vaccination in Lung Transplant Recipients: A 6-Month Follow-Up

Background and objective: This prospective cohort study analyzed the immune response to COVID-19 mRNA vaccines in lung transplant recipients (LuTRs) compared to healthy controls (HCs) at a 6-month follow-up. Methods: After the first two doses of either BNT162b2 or mRNA-1273, SARS-CoV-2 antibodies were measured in LuTRs (n = 57) and sex- and age-matched HCs (n = 57). Antibody kinetics during a 6-month follow-up and the effect of a third vaccine dose were evaluated. Humoral responses were assessed using the Elecsys^® Anti-SARS-CoV-2 S immunoassay. In 16 LuTRs, SARS-CoV-2-specific T cell responses were quantified using IFN-γ ELISpot assays. Results: Seroconversion rates were 94% and 100% after the first and second vaccine dose, respectively, in HCs, while only 19% and 56% of LuTRs developed antibodies. Furthermore, 22 of 24 LuTRs who received the third vaccine dose showed seroconversion (five of seven primary non-responders and 17 of 17 primary responders). A T cell response against SARS-CoV-2-spike S1 and/or S2 was detected in 100% (16/16) of HCs and 50% (8/16) of LuTRs. Conclusions: The data suggest that LuTRs have reduced humoral and cellular immune responses after two doses of COVID-19 mRNA vaccination when compared to HCs. A third dose may be of substantial benefit.

Heterogeneous SARS-CoV-2-Neutralizing Activities After Infection and Vaccination

Background

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) variants of concern (VOCs) with different resistance levels to existing immunity have recently emerged. Antibodies that recognize the SARS-CoV-2 spike (S) protein and exhibit neutralizing activities are considered the best correlate of protection and an understanding of humoral immunity is crucial for controlling the pandemic. We thus analyzed such antibodies in individuals recovered from infection in 2020 as well as vaccinees after two doses of an mRNA vaccine.

Methods

Neutralizing antibody responses against three SARS-CoV-2 variants (D614G, VOCs Beta and Delta) were determined in serum samples from 54 infected individuals (24 non-hospitalized, 30 hospitalized) and 34 vaccinees shortly after symptom onset or second vaccination, respectively, as well as six months later. In addition, the effect of the S sequence of the infecting strain on neutralization was studied.

Results

Non-hospitalized patients had the lowest neutralization titers against all variants, while those of hospitalized patients equaled or exceeded those of vaccinees. Neutralizing activity was lower against the two VOCs and declined significantly in all cohorts after six months. This decrease was more pronounced in hospitalized and vaccinated individuals than in non-hospitalized patients. Of note, the specific neutralizing activity (NT titer/ELISA value ratio) was higher in the infected cohorts than in vaccinees and did not differ between non-hospitalized and hospitalized patients. Patients infected with viral strains carrying mutations in the N-terminal domain of the spike protein were impaired in Beta VOC neutralization.

Conclusions

Specific neutralizing activities were higher in infected than in vaccinated individuals, and no difference in the quality of these antibodies was observed between hospitalized and non-hospitalized patients, despite significantly lower titers in the latter group. Additionally, antibody responses of infected individuals showed greater heterogeneity than those of vaccinees, which was associated with mutations in the spike protein of the infecting strain. Overall, our findings yielded novel insights into SARS-CoV-2-specific neutralizing antibodies, evolving differently after virus infection and COVID-19 vaccination, which is an important issue to consider in ongoing vaccine strategy improvements.

Long-Lived Immunity in SARS-CoV-2-Recovered Children and Its Neutralizing Capacity Against Omicron

SARS-CoV-2 infection is effectively controlled by humoral and cellular immune responses. However, the durability of immunity in children as well as the ability to neutralize variants of concern are unclear. Here, we assessed T cell and antibody responses in a longitudinal cohort of children after asymptomatic or mild COVID-19 over a 12-month period. Antigen-specific CD4 T cells remained stable over time, while CD8 T cells declined. SARS-CoV-2 infection induced long-lived neutralizing antibodies against ancestral SARS-CoV-2 (D614G isolate), but with poor cross-neutralization of omicron. Importantly, recall responses to vaccination in children with pre-existing immunity yielded neutralizing antibody activities against D614G and omicron BA.1 and BA.2 variants that were 3.9-fold, 9.9-fold and 14-fold higher than primary vaccine responses in seronegative children. Together, our findings demonstrate that SARS-CoV-2 infection in children induces robust memory T cells and antibodies that persist for more than 12 months, but lack neutralizing activity against omicron. Vaccination of pre-immune children, however, substantially improves the omicron-neutralizing capacity.

The first case of Usutu virus neuroinvasive disease in Austria, 2021

Usutu virus (USUV) is a mosquito-borne flavivirus closely related to West Nile virus (WNV) that is endemic in many European countries. We report the first case of USUV neuroinvasive disease in Austria and discuss challenges in differentiating USUV from WNV infections in areas where both viruses are endemic.

Additional heterologous versus homologous booster vaccination in immunosuppressed patients without SARS-CoV-2 antibody seroconversion after primary mRNA vaccination: a randomised controlled trial

OBJECTIVES

SARS-CoV-2-induced COVID-19 has led to exponentially rising mortality, particularly in immunosuppressed patients, who inadequately respond to conventional COVID-19 vaccination.

METHODS

In this blinded randomised clinical trial, we compare the efficacy and safety of an additional booster vaccination with a vector versus mRNA vaccine in non-seroconverted patients. We assigned 60 patients under rituximab treatment, who did not seroconvert after their primary mRNA vaccination with either BNT162b2 (Pfizer-BioNTech) or mRNA-1273 (Moderna), to receive a third dose, either using the same mRNA or the vector vaccine ChAdOx1 nCoV-19 (Oxford-AstraZeneca). Patients were stratified according to the presence of peripheral B cells. The primary efficacy endpoint was the difference in the SARS-CoV-2 antibody seroconversion rate between vector (heterologous) and mRNA (homologous) vaccinated patients by week 4. Key secondary endpoints included the overall seroconversion and cellular immune response; safety was assessed at week 1 and week 4.

RESULTS

Seroconversion rates at week 4 were comparable between vector (6/27 patients, 22%) and mRNA (9/28, 32%) vaccines (p=0.6). Overall, 27% of patients seroconverted; specific T cell responses were observed in 20/20 (100%) vector versus 13/16 (81%) mRNA vaccinated patients. Newly induced humoral and/or cellular responses occurred in 9/11 (82%) patients. 3/37 (8%) of patients without and 12/18 (67%) of the patients with detectable peripheral B cells seroconverted. No serious adverse events, related to immunisation, were observed.

CONCLUSIONS

This enhanced humoral and/or cellular immune response supports an additional booster vaccination in non-seroconverted patients irrespective of a heterologous or homologous vaccination regimen.

B Cell Depletion and SARS-CoV-2 Vaccine Responses in Neuroimmunologic Patients

OBJECTIVE

The study was undertaken to assess the impact of B cell depletion on humoral and cellular immune responses to severe acute respiratory syndrome-coronavirus 2 (SARS-CoV-2) vaccination in patients with various neuroimmunologic disorders on anti-CD20 therapy. This included an analysis of the T cell vaccine response to the SARS-CoV-2 Delta variant.

METHODS

We investigated prospectively humoral and cellular responses to SARS-CoV-2 mRNA vaccination in 82 patients with neuroimmunologic disorders on anti-CD20 therapy and 82 age- and sex-matched healthy controls. For quantification of antibodies, the Elecsys anti-SARS-CoV-2 viral spike (S) immunoassay against the receptor-binding domain (RBD) was used. IFN-gamma enzyme-linked immunosorbent spot assays were performed to assess T cell responses against the SARS-CoV-2 Wuhan strain and the Delta variant.

RESULTS

SARS-CoV-2-specific antibodies were found less frequently in patients (70% [57/82]) compared with controls (82/82 [100%], p < 0.001). In patients without detectable B cells (<1 B cell/mcl), seroconversion rates and antibody levels were lower compared to nondepleted (≥1 B cell/mcl) patients (p < 0.001). B cell levels ≥1 cell/mcl were sufficient to induce seroconversion in our cohort of anti-CD20 treated patients. In contrast to the antibody response, the T-cell response against the Wuhan strain and the Delta variant was more pronounced in frequency (p < 0.05) and magnitude (p < 0.01) in B-cell depleted compared to nondepleted patients.

INTERPRETATION

Antibody responses to SARS-CoV-2 mRNA vaccinnation can be attained in patients on anti-CD20 therapy by the onset of B cell repopulation. In the absence of B cells, a strong T cell response is generated which may help to protect against severe coronavirus disease 2019 (COVID-19) in this high-risk population. ANN NEUROL 2022;91:342-352.

Comparison of SARS-CoV-2 Antibody Response 4 Weeks After Homologous vs Heterologous Third Vaccine Dose in Kidney Transplant Recipients: A Randomized Clinical Trial

IMPORTANCE

Fewer than 50% of kidney transplant recipients (KTRs) develop antibodies against the SARS-CoV-2 spike protein after 2 doses of an mRNA vaccine. Preliminary data suggest that a heterologous vaccination, combining mRNA and viral vector vaccines, may increase immunogenicity.

OBJECTIVE

To assess the effectiveness of a third dose of an mRNA vs a vector vaccine in KTRs who did not have antibodies against the SARS-CoV-2 spike protein after 2 doses of an mRNA vaccine.

DESIGN, SETTING, AND PARTICIPANTS

This was a single center, single-blinded, 1:1 randomized clinical trial of a third dose of vaccine against SARS-CoV-2, conducted from June 15 to August 16, 2021, in 201 KTRs who had not developed SARS-CoV-2 spike protein antibodies after 2 doses of an mRNA vaccine. Data analyses were performed from August 17 to August 31, 2021.

INTERVENTIONS

mRNA (BNT162b2 or mRNA-1273) or vector (Ad26COVS1) as a third dose of a SARS-CoV-2 vaccine.

MAIN OUTCOMES AND MEASURES

The primary study end point was seroconversion after 4 weeks (29-42 days) following the third vaccine dose. Secondary end points included neutralizing antibodies and T-cell response assessed by interferon-γ release assays (IGRA). In addition, the association of patient characteristics and vaccine response was assessed using logistic regression, and the reactogenicity of the vaccines was compared.

RESULTS

Among the study population of 197 kidney transplant recipients (mean [SD] age, 61.2 [12.4] years; 82 [42%] women), 39% developed SARS-CoV-2 antibodies after the third vaccine. There was no statistically significant difference between groups, with an antibody response rate of 35% and 42% for the mRNA and vector vaccines, respectively. Only 22% of seroconverted patients had neutralizing antibodies. Similarly, T-cell response assessed by IGRA was low with only 17 patients showing a positive response after the third vaccination. Receiving nontriple immunosuppression (odds ratio [OR], 3.59; 95% CI, 1.33-10.75), longer time after kidney transplant (OR, 1.44; 95% CI, 1.15-1.83, per doubling of years), and torque teno virus plasma levels (OR, 0.92; 95% CI, 0.88-0.96, per doubling of levels) were associated with vaccine response. The third dose of an mRNA vaccine was associated with a higher frequency of local pain at the injection site compared with the vector vaccine, while systemic symptoms were comparable between groups.

CONCLUSIONS AND RELEVANCE

This randomized clinical trial found that 39% of KTRs without an immune response against SARS-CoV-2 after 2 doses of an mRNA vaccine developed antibodies against the SARS-CoV-2 spike protein 4 weeks after a third dose of an mRNA or a vector vaccine. The heterologous vaccination strategy with a vector-based vaccine was well tolerated and safe but not significantly better than the homologous mRNA-based strategy.

TRIAL REGISTRATION

EudraCT Identifier: 2021-002927-39.

SARS-CoV-2 vaccination in rituximab-treated patients: B cells promote humoral immune responses in the presence of T-cell-mediated immunity

OBJECTIVES

Evidence suggests that B cell-depleting therapy with rituximab (RTX) affects humoral immune response after vaccination. It remains unclear whether RTX-treated patients can develop a humoral and T-cell-mediated immune response against SARS-CoV-2 after immunisation.

METHODS

Patients under RTX treatment (n=74) were vaccinated twice with either mRNA-1273 or BNT162b2. Antibodies were quantified using the Elecsys Anti-SARS-CoV-2 S immunoassay against the receptor-binding domain (RBD) of the spike protein and neutralisation tests. SARS-CoV-2-specific T-cell responses were quantified by IFN-γ enzyme-linked immunosorbent spot assays. Prepandemic healthy individuals (n=5), as well as healthy individuals (n=10) vaccinated with BNT162b2, served as controls.

RESULTS

All healthy controls developed antibodies against the SARS-CoV-2 RBD of the spike protein, but only 39% of the patients under RTX treatment seroconverted. Antibodies against SARS-CoV-2 RBD significantly correlated with neutralising antibodies (τ=0.74, p<0.001). Patients without detectable CD19+ peripheral B cells (n=36) did not develop specific antibodies, except for one patient. Circulating B cells correlated with the levels of antibodies (τ=0.4, p<0.001). However, even patients with a low number of B cells (<1%) mounted detectable SARS-CoV-2-specific antibody responses. SARS-CoV-2-specific T cells were detected in 58% of the patients, independent of a humoral immune response.

CONCLUSIONS

The data suggest that vaccination can induce SARS-CoV-2-specific antibodies in RTX-treated patients, once peripheral B cells at least partially repopulate. Moreover, SARS-CoV-2-specific T cells that evolved in more than half of the vaccinated patients may exert protective effects independent of humoral immune responses.

Tick-Borne Encephalitis Specific Lymphocyte Response after Allogeneic Hematopoietic Stem Cell Transplantation Predicts Humoral Immunity after Vaccination

The aim of this prospective study was to assess lymphocyte proliferative and cytokine response prior to and following tick-borne encephalitis (TBE) immunization among patients after allogeneic hematopoietic stem cell transplantation (HSCT). Seventeen adult patients 11–13 months after HSCT and eight unvaccinated healthy adults received up to three TBE vaccinations. Following in vitro stimulation with TBE-antigen, lymphocyte proliferation and cytokine secretion (IL-2, IL-10, IL-13, TNF-alpha, IFN-gamma, GM-CSF) were analyzed by thymidine incorporation assay and the Luminex system. Ten patients (59%) showed significant baseline TBE-specific lymphocyte proliferation (stimulation index (SI) > 3) prior to vaccination, but none of the unvaccinated controls (p = 0.002). All patients with a TBE-specific antibody response after two vaccinations (at least 2-fold increase of neutralization test titers) exhibited a strong TBE-specific lymphocyte proliferative response at baseline (SI > 10). Patients with sibling donors had a significantly stronger baseline TBE-specific lymphocyte proliferative and IL-13 cytokine response than patients with unrelated donors (p < 0.05). In conclusion, a relevant proportion of patients showed TBE-specific lymphocyte proliferative and cytokine responses prior to vaccination after HSCT, which predicted the humoral response to the vaccine. Patients with vaccinated sibling donors were more likely to elicit a cellular immune response than patients with unrelated donors of unknown vaccination status.

Different Cross-Reactivities of IgM Responses in Dengue, Zika and Tick-Borne Encephalitis Virus Infections

Flaviviruses circulate worldwide and cause a number of medically relevant human diseases, such as dengue, Zika, yellow fever, and tick-borne encephalitis (TBE). Serology plays an important role in the diagnosis of flavivirus infections, but can be impeded by antigenic cross-reactivities among flaviviruses. Therefore, serological diagnosis of a recent infection can be insufficiently specific, especially in areas where flaviviruses co-circulate and/or vaccination coverage against certain flaviviruses is high. In this study, we developed a new IgM assay format, which is well suited for the specific diagnosis of TBE, Zika and dengue virus infections. In the case of TBE and Zika, the IgM response proved to be highly specific for the infecting virus. In contrast, primary dengue virus infections induced substantial amounts of cross-reactive IgM antibodies, which is most likely explained by structural peculiarities of dengue virus particles. Despite the presence of cross-reactive IgM, the standardized nature and the quantitative read-out of the assay even allowed the serotype-specific diagnosis of recent dengue virus infections in most instances.

SARS-CoV-2 mutations in MHC-I-restricted epitopes evade CD8+ T cell responses

CD8⁺ T cell immunity to SARS-CoV-2 has been implicated in COVID-19 severity and virus control. Here, we identified nonsynonymous mutations in MHC-I-restricted CD8⁺ T cell epitopes after deep sequencing of 747 SARS-CoV-2 virus isolates. Mutant peptides exhibited diminished or abrogated MHC-I binding in a cell-free in vitro assay. Reduced MHC-I binding of mutant peptides was associated with decreased proliferation, IFN-γ production and cytotoxic activity of CD8⁺ T cells isolated from HLA-matched COVID-19 patients. Single cell RNA sequencing of ex vivo expanded, tetramer-sorted CD8⁺ T cells from COVID-19 patients further revealed qualitative differences in the transcriptional response to mutant peptides. Our findings highlight the capacity of SARS-CoV-2 to subvert CD8⁺ T cell surveillance through point mutations in MHC-I-restricted viral epitopes.

Genomic epidemiology of superspreading events in Austria reveals mutational dynamics and transmission properties of SARS-CoV-2

Superspreading events shaped the coronavirus disease 2019 (COVID-19) pandemic, and their rapid identification and containment are essential for disease control. Here, we provide a national-scale analysis of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) superspreading during the first wave of infections in Austria, a country that played a major role in initial virus transmissions in Europe. Capitalizing on Austria's well-developed epidemiological surveillance system, we identified major SARS-CoV-2 clusters during the first wave of infections and performed deep whole-genome sequencing of more than 500 virus samples. Phylogenetic-epidemiological analysis enabled the reconstruction of superspreading events and charts a map of tourism-related viral spread originating from Austria in spring 2020. Moreover, we exploited epidemiologically well-defined clusters to quantify SARS-CoV-2 mutational dynamics, including the observation of low-frequency mutations that progressed to fixation within the infection chain. Time-resolved virus sequencing unveiled viral mutation dynamics within individuals with COVID-19, and epidemiologically validated infector-infectee pairs enabled us to determine an average transmission bottleneck size of 103 SARS-CoV-2 particles. In conclusion, this study illustrates the power of combining epidemiological analysis with deep viral genome sequencing to unravel the spread of SARS-CoV-2 and to gain fundamental insights into mutational dynamics and transmission properties.

Dynamics of CD4 T Cell and Antibody Responses in COVID-19 Patients With Different Disease Severity

Disease caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) ranges from mild illness to severe respiratory disease and death. In this study, we determined the kinetics of viral loads, antibody responses (IgM, IgG, neutralization) and SARS-CoV-2-specific CD4 T cells by quantifying these parameters in 435 serial respiratory and blood samples collected from a cohort of 29 COVID-19 patients with either moderate or severe disease during the whole period of hospitalization or until death. Remarkably, there was no significant difference in the kinetics and plateau levels of neutralizing antibodies among the groups with different disease severity. In contrast, the dynamics of specific CD4 T cell responses differed considerably, but all patients with moderate or severe disease developed robust SARS-CoV-2-specific responses. Of note, none of the patients had detectable cross-reactive CD4 T cells in the first week after symptom onset, which have been described in 20–50% of unexposed individuals. Our data thus provide novel insights into the kinetics of antibody and CD4 T cell responses as well as viral loads that are key to understanding the role of adaptive immunity in combating the virus during acute infection and provide leads for the timing of immune therapies for COVID-19.

Impact of flavivirus vaccine-induced immunity on primary Zika virus antibody response in humans

Background

Zika virus has recently spread to South- and Central America, causing congenital birth defects and neurological complications. Many people at risk are flavivirus pre-immune due to prior infections with other flaviviruses (e.g. dengue virus) or flavivirus vaccinations. Since pre-existing cross-reactive immunity can potentially modulate antibody responses to Zika virus infection and may affect the outcome of disease, we analyzed fine-specificity as well as virus-neutralizing and infection-enhancing activities of antibodies induced by a primary Zika virus infection in flavivirus-naïve as well as yellow fever- and/or tick-borne encephalitis-vaccinated individuals.

Methodology

Antibodies in sera from convalescent Zika patients with and without vaccine-induced immunity were assessed by ELISA with respect to Zika virus-specificity and flavivirus cross-reactivity. Functional analyses included virus neutralization and infection-enhancement. The contribution of IgM and cross-reactive antibodies to these properties was determined by depletion experiments.

Principal findings

Pre-existing flavivirus immunity had a strong influence on the antibody response in primary Zika virus infections, resulting in higher titers of broadly flavivirus cross-reactive antibodies and slightly lower levels of Zika virus-specific IgM. Antibody-dependent enhancement (ADE) of Zika virus was mediated by sub-neutralizing concentrations of specific IgG but not by cross-reactive antibodies. This effect was potently counteracted by the presence of neutralizing IgM. Broadly cross-reactive antibodies were able to both neutralize and enhance infection of dengue virus but not Zika virus, indicating a different exposure of conserved sequence elements in the two viruses.

Conclusions

Our data point to an important role of flavivirus-specific IgM during the transient early stages of infection, by contributing substantially to neutralization and by counteracting ADE. In addition, our results highlight structural differences between strains of Zika and dengue viruses that are used for analyzing infection-enhancement by cross-reactive antibodies. These findings underscore the possible impact of specific antibody patterns on flavivirus disease and vaccination efficacy.

The explosive spread of Zika virus, a flavivirus, to South- and Central America underscores the potential threat of newly emerging arthropod-borne viruses. Zika virus infection can cause congenital birth defects and neurological complications. Many people at risk are flavivirus pre-immune because of prior infections with other flaviviruses (e.g. dengue virus, which co-circulates in Zika outbreak regions) or vaccinations (e.g. against yellow fever or tick-borne encephalitis) and have non-protective cross-reactive antibodies at the time of infection. Since pre-existing immunity can modulate the specificity and functional activity of antibody responses, and cross-reactive antibodies have been implicated in disease enhancement, we compared the specificities of serum samples from flavivirus-naïve and vaccinated individuals after primary Zika virus infections. Prior immunity led to a strong booster of cross-reactive antibodies that did not neutralize Zika virus. Importantly, we could also show that newly formed IgM antibodies contributed significantly to virus neutralization and prevented infection enhancement by other antibodies. Our data thus show how pre-existing cross-reactive immunities can alter the specificities and functional activities of antibody responses in flavivirus infections, which may affect flavivirus-induced disease and the efficacy of vaccinations.

CD4 T Cell Determinants in West Nile Virus Disease and Asymptomatic Infection

West Nile (WN) virus infection of humans is frequently asymptomatic, but can also lead to WN fever or neuroinvasive disease. CD4 T cells and B cells are critical in the defense against WN virus, and neutralizing antibodies, which are directed against the viral glycoprotein E, are an accepted correlate of protection. For the efficient production of these antibodies, B cells interact directly with CD4 helper T cells that recognize peptides from E or the two other structural proteins (capsid-C and membrane-prM/M) of the virus. However, the specific protein sites yielding such helper epitopes remain unknown. Here, we explored the CD4 T cell response in humans after WN virus infection using a comprehensive library of overlapping peptides covering all three structural proteins. By measuring T cell responses in 29 individuals with either WN virus disease or asymptomatic infection, we showed that CD4 T cells focus on peptides in specific structural elements of C and at the exposed surface of the pre- and postfusion forms of the E protein. Our data indicate that these immunodominant epitopes are recognized in the context of multiple different HLA molecules. Furthermore, we observed that immunodominant antigen regions are structurally conserved and similarly targeted in other mosquito-borne flaviviruses, including dengue, yellow fever, and Zika viruses. Together, these findings indicate a strong impact of virion protein structure on epitope selection and antigenicity, which is an important issue to consider in future vaccine design.

Increase in human West Nile and Usutu virus infections, Austria, 2018

Between 28 June and 17 September 2018, 27 cases of human West Nile virus infections were recorded in Austria; four cases of West Nile neuroinvasive disease, 11 cases of West Nile fever, six infections detected by blood donation screening and six imported cases. In addition, 18 cases of human Usutu virus infections (all blood donors) were recorded. This is the highest number of annual infections recorded in Austria since the introduction of both viruses.

CD4 T cell responses to flaviviruses

Flaviviruses pose an increasing threat to global health with their potential to cause severe disease in millions of people. Protective and long-lived immunity is closely linked to the generation of CD4 T cells, which provide B cell help and support high affinity neutralizing antibody responses. Research performed during the last years revealed important new insights into the antigen specificities and diverse effector functions of CD4 T cell responses to flaviviruses. Moreover, the identification of mechanisms involved in the regulation of T cell specificity and function provides significant advances in our understanding of how durable protective immunity is established. Here, we summarize what is known about human CD4 T cell responses to flaviviruses, with a special emphasis on CD4 T cells that provide direct help to B cells producing neutralizing and protective antibodies. We review recent progress in the identification of epitope sites in the context of the atomic structures of flavivirus proteins and highlight specific influences that shape the human CD4 T cell response in the context of infection or vaccination. Finally, we discuss challenges facing vaccine efforts to generate appropriate CD4 T cell responses, as well as recent strategies to enhance T cell-mediated antibody responses.

Corrigendum: Structural Influence on the Dominance of Virus-Specific CD4 T Cell Epitopes in Zika Virus Infection

[This corrects the article DOI: 10.3389/fimmu.2018.01196.].

Structural Influence on the Dominance of Virus-Specific CD4 T Cell Epitopes in Zika Virus Infection

Zika virus (ZIKV) has recently caused explosive outbreaks in Pacific islands, South- and Central America. Like with other flaviviruses, protective immunity is strongly dependent on potently neutralizing antibodies (Abs) directed against the viral envelope protein E. Such Ab formation is promoted by CD4 T cells through direct interaction with B cells that present epitopes derived from E or other structural proteins of the virus. Here, we examined the extent and epitope dominance of CD4 T cell responses to capsid (C) and envelope proteins in Zika patients. All patients developed ZIKV-specific CD4 T cell responses, with substantial contributions of C and E. In both proteins, immunodominant epitopes clustered at sites that are structurally conserved among flaviviruses but have highly variable sequences, suggesting a strong impact of protein structural features on immunodominant CD4 T cell responses. Our data are particularly relevant for designing flavivirus vaccines and their evaluation in T cell assays and provide insights into the importance of viral protein structure for epitope selection and antigenicity.

Protein structure shapes immunodominance in the CD4 T cell response to yellow fever vaccination

The live attenuated yellow fever (YF) vaccine is a highly effective human vaccine and induces long-term protective neutralizing antibodies directed against the viral envelope protein E. The generation of such antibodies requires the help of CD4 T cells which recognize peptides derived from proteins in virus particles internalized and processed by E-specific B cells. The CD4 T helper cell response is restricted to few immunodominant epitopes, but the mechanisms of their selection are largely unknown. Here, we report that CD4 T cell responses elicited by the YF-17D vaccine are focused to hotspots of two helices of the viral capsid protein and to exposed strands and loops of E. We found that the locations of immunodominant epitopes within three-dimensional protein structures exhibit a high degree of overlap between YF virus and the structurally homologous flavivirus tick-borne encephalitis virus, although amino acid sequence identity of the epitope regions is only 15-45%. The restriction of epitopes to exposed E protein surfaces and their strikingly similar positioning within proteins of distantly related flaviviruses are consistent with a strong influence of protein structure that shapes CD4 T cell responses and provide leads for a rational design of immunogens for vaccination.

The Chemokine CXCL-10 Is a Marker of Infection Stage in Individuals With DNAemia Due to Parvovirus B19

Background

Accurate diagnosis of parvovirus B19 (B19V) infection requires the differentiation between acute and past infection, which is especially important when DNAemia due to B19V (hereafter, "B19V DNAemia") is detected in pregnancy. Here, we explored whether the level of the chemokine CXCL-10, in combination with findings of molecular and serological assays, can discriminate between acute and past B19V infection.

Methods

B19V DNA-positive serum samples from 222 immunocompetent individuals were analyzed for (1) viral DNA loads, (2) anti-B19V immunoglobulin M (IgM) and immunoglobulin G (IgG), (3) anti-VP1 IgG avidity, (4) anti-VP-2 epitope type specificity (ETS), and (5) CXCL-10 serum levels.

Results

Anti-B19V IgM and IgG, avidity, and ETS assays were used to categorize individuals with B19V DNAemia as having acute or past B19V infection. Acute B19V infection caused a significant increase in the serum concentration of CXCL-10, compared with the concentration at baseline, before infection. Higher CXCL-10 serum levels were furthermore detected in acute B19V infection as compared to past infection. As a marker, CXCL-10 serum levels could discriminate between acute and past B19V infection, with an excellent discriminatory capacity when CXCL-10 and B19V DNA levels were used as combined parameters.

Conclusion

Acute B19V infection is associated with increased CXCL-10 production, and measurement of CXCL-10 serum levels thus allows for the staging of B19V infection in individuals with B19V DNAemia.

Human CD4+ T Helper Cell Responses after Tick-Borne Encephalitis Vaccination and Infection

Tick-borne encephalitis virus (TBEV) is a human-pathogenic flavivirus that is endemic in large parts of Europe and Asia and causes severe neuroinvasive illness. A formalin-inactivated vaccine induces strong neutralizing antibody responses and confers protection from TBE disease. CD4⁺ T cell responses are essential for neutralizing antibody production, but data on the functionalities of TBEV-specific CD4⁺ T cells in response to vaccination or infection are lacking. This study provides a comprehensive analysis of the cytokine patterns of CD4⁺ T cell responses in 20 humans after TBE vaccination in comparison to those in 18 patients with TBEV infection. Specifically, Th1-specific cytokines (IFN-γ, IL-2, TNF-α), CD40 ligand and the Th1 lineage-specifying transcription factor Tbet were determined upon stimulation with peptides covering the TBEV structural proteins contained in the vaccine (C-capsid, prM/M-membrane and E-envelope). We show that TBEV-specific CD4⁺ T cell responses are polyfunctional, but the cytokine patterns after vaccination differed from those after infection. TBE vaccine responses were characterized by lower IFN-γ responses and high proportions of TNF-α⁺IL-2⁺ cells. In vaccine-induced responses—consistent with the reduced IFN-γ expression patterns—less than 50% of TBEV peptides were detected by IFN-γ⁺ cells as compared to 96% detected by IL-2⁺ cells, indicating that the single use of IFN-γ as a read-out strongly underestimates the magnitude and breadth of such responses. The results provide important insights into the functionalities of CD4⁺ T cells that coordinate vaccine responses and have direct implications for future studies that address epitope specificity and breadth of these responses.

Approaches for monitoring of non virus-specific and virus-specific T-cell response in solid organ transplantation and their clinical applications

Opportunistic viral infections are still a major complication following solid organ transplantation. Immune monitoring may allow the identification of patients at risk of infection and, eventually, the modulation of immunosuppressive strategies. Immune monitoring can be performed using virus-specific and non virus-specific assays. This article describes and summarizes the pros and cons of the different technical approaches. Among the assays based on non virus-specific antigens, the enumeration of T-cell subsets, the quantification of cytokines and chemokines and the quantification of intracellular adenosine triphosphate following mitogen stimulation are described and their clinical applications to determine the risk for viral infection are discussed. In addition, current specific methods available for monitoring viral-specific T-cell responses are summarized, such as peptide-MHC multimer staining, intracellular cytokine staining, enzyme-linked immunospot and virus-specific IFN-γ ELISA assays, and their clinical applications to determine the individual risk for opportunistic viral infections with human cytomegalovirus, Epstein-Barr virus and polyoma BK virus are discussed. The standardization of the procedure, the choice of the antigen(s) and the criteria to define cut-off values for positive responses are needed for some of these approaches before their implementation in the clinic. Nevertheless, immune monitoring combined with virological monitoring in transplant recipients is increasingly regarded as a helpful tool to identify patients at risk of infection as well as to assess treatment efficacy.

A diagnostic score for the prediction of spontaneous resolution of acute hepatitis C virus infection

BACKGROUND & AIMS

IL28B polymorphisms, jaundice, decline in HCV-RNA, IP-10, and gender have been proposed to be indicative of spontaneous clearance of acute hepatitis C virus infection. The aim of this study was to define a score enabling the discrimination of patients with spontaneous clearance of HCV from those with development of viral persistence and need for early antiviral treatment.

METHODS

136 patients (74 male; 35 ± 15 years) were analyzed. From variables predictive of spontaneous clearance, calculated by univariate analysis, three scores were built. Analogous cut-offs were evaluated by computing area under the receiver operating characteristic curves. Candidate variables and cut-offs were: (I) presence of IL28B C/C (p=0.027), (II) age (p=0.031; cut-off: 35 years), (III) peak-bilirubin (p=0.018; cut-off: 6 mg/dl), (IV) HCV-RNA decline within 4 weeks (p<0.001;cut-off: >2.5 log), (V) serum IP-10 (p=0.003; cut-off: 546 pg/ml), (VI) presence of CD4(+) Th1 cells (p=0.024). Each variable was allocated to 0 or 1 point, an HCV-RNA decline of ≥ 1 log 10 but <2.5 log 10 to 1 point, a decline of ≥ 2.5 log 10 to 2 points. Three scores were evaluated (Score 1: I-IV; Score 2: I-V; Score 3: I-VI).

RESULTS

A cut-off of ≥ 3 points out of 5 in Score 1 (AUROC: 0.82; DeLong 95% CI: 0.76-0.93) predicted spontaneous clearance with a sensitivity of 71% (95% CI: 0.53-0.86) and specificity of 87% (95% CI: 0.73-0.95). PPV and NPV were 79% and 82%. Corresponding findings for Score 2 including IP-10 (AUROC: 0.93; DeLong 95% CI: 0.86-0.93) at a cut-off of ≥ 4 were: sensitivity 81%, specificity 95% (PPV: 100%; NPV: 77%). A cut-off of ≥ 5 in Score 3 (AUROC: 0.98; DeLong 95% CI: 0.95-1.0) predicted spontaneous resolution with a sensitivity of 75% and specificity of 100% (PPV: 100%; NPV: 88%).

CONCLUSIONS

The scores enable a reliable discrimination between AHC-patients with high potential for spontaneous clearance from candidates for early therapeutic intervention due to marginal chance of spontaneous resolution.

Mechanistic insights into the impairment of memory B cells and antibody production in the elderly

It is well established that immunologic memory generated early in life can be maintained into old age and mediate robust anamnestic antibody responses. Little is known, however, about the initiation of memory B cells in the elderly. We have conducted a prospective analysis of the quantities and functionalities of antigen-specific B cell responses and its association with the functional helper CD4(+)T cell responses. The ability of naïve B cells from old (60-80 years) and young (20-31 years) humans to establish functional memory was examined following primary and booster vaccination with an inactivated-virus vaccine against tick-borne encephalitis. Our data show that the number of antigen-specific memory B cells generated during primary vaccination was ~3-fold lower in old than in young individuals. The maintenance and booster responsiveness of these memory B cells were not compromised, as evidenced by similar increases in specific memory B cell frequencies upon revaccination in old and young adults. In contrast, the Ab response mediated per memory B cell after revaccination was dramatically diminished in the elderly. Also, antigen-specific IL-2-positive CD4(+)T cell responses were strongly reduced in the elderly and displayed an excellent correlation with Ab titres. The data suggest that the dramatically lower antibody response in the elderly could only partially be accounted for by the reduced B cell numbers and was strongly correlated with profound functional defects in CD4 help.

Age-dependent increase of memory B cell response to cytomegalovirus in healthy adults

Human cytomegalovirus (HCMV) may play an important role in immune system aging, due to its ability to modulate the host immune system. A significant age-related increase has been demonstrated for HCMV-specific serum antibody levels but so far, no information exists whether and to which extent the magnitude of the HCMV-specific memory B cell response develops with increasing age. We examined the size of the HCMV-specific memory B cell response and assessed whether there are quantitative differences in HCMV-specific memory B cell numbers and serum antibody titers against HCMV in young and older persons. The quantities of HCMV-specific memory B cells were determined in 20 young (20-31 years) and 21 older (60-80 years) healthy volunteers by limiting dilution analysis. HCMV-specific antibody levels were analyzed by ELISA. Our study demonstrates that higher HCMV-specific plasma antibody levels correlated well with the numbers of circulating HCMV-specific memory B cells and were not due to a generally higher antibody production in these individuals. The magnitude of HCMV-specific memory B cell responses was significantly higher in the group of older as compared to young subjects, but showed a high degree of individual variation in elderly persons. Together, the results of the present study indicate that the circulating memory B cell pool against HCMV increases during aging in humans. The expansion of HCMV-specific memory B cells and antibody titers possibly contribute to the sustained control of HCMV infection during old age.

Age affects quantity but not quality of antibody responses after vaccination with an inactivated flavivirus vaccine against tick-borne encephalitis

The impairment of immune functions in the elderly (immunosenescence) results in post-vaccination antibody titers that are significantly lower than in young individuals. It is, however, a controversial question whether also the quality of antibodies declines with age. In this study, we have therefore investigated the age-dependence of functional characteristics of antibody responses induced by vaccination with an inactivated flavivirus vaccine against tick-borne encephalitis (TBE). For this purpose, we quantified TBE virus-specific IgG and neutralizing antibody titers in post-vaccination sera from groups of young and elderly healthy adults and determined antibody avidities and NT/ELISA titer ratios (functional activity). In contrast to the quantitative impairment of antibody production in the elderly, we found no age-related differences in the avidity and functional activity of antibodies induced by vaccination, which also appeared to be independent of the age at primary immunization. There was no correlation between antibody avidity and NT/ELISA ratios suggesting that additional factors affect the quality of polyclonal responses, independent of age. Our work indicates that healthy elderly people are able to produce antibodies in response to vaccination with similar avidity and functional activity as young individuals, albeit at lower titers.

Serum level of IP-10 increases predictive value of IL28B polymorphisms for spontaneous clearance of acute HCV infection

BACKGROUND & AIMS

Single nucleotide polymorphisms (SNPs) in IL28B and serum levels of interferon γ inducible protein 10 (IP-10) predict outcomes of antiviral therapy in patients with chronic hepatitis C. We associated IL28B SNPs rs12979860 and rs8099917, along with serum levels of IP-10, with outcomes of patients with acute hepatitis C (AHC).

METHODS

We studied 120 patients with AHC (64 male; 37 ± 16 years old) and 96 healthy individuals (controls). The IL28B SNPs rs12979860 and rs8099917 were detected using real-time polymerase chain reaction; serum concentrations of IP-10 were measured by enzyme-linked immunosorbent assays of 62 patients with AHC.

RESULTS

Hepatitis C virus was cleared spontaneously from 59 patients (49.2%). The IL28B rs12979860 C/C genotype was more frequent among patients with AHC than controls (62.5% vs 39.6%; P < .001) and among patients with spontaneous clearance than those without (74.6% vs 51.7%; P = .02) (positive predictive value, 60.3%). Patients with IL28B rs12979860 C/C more frequently developed jaundice (53.2% vs 27.6%; P = .022) than carriers of the T allele. The median level of IP-10 was lower among patients with AHC and spontaneous clearance (764 [113-2470] pg/mL) than those without spontaneous clearance (1481 [141-4412] pg/mL; P = .006). Based on receiver operating characteristic analysis, 540 pg/mL IP-10 was set as the cutoff for patients most likely to have spontaneous clearance (positive predictive value, 71.4%; negative predictive value, 65.9%). Including data on IP-10 levels increased the ability of the IL28B rs12979860 C/C to identify patients most likely to have spontaneous clearance (83% of those who had an IP-10 level <540 pg/mL and 32% who had an IP-10 level >540 pg/mL) (P < .01).

CONCLUSIONS

The combination of serum level of IP-10 and SNPs in IL28B can identify patients with AHC who are most likely to undergo spontaneous clearance and those in need of early antiviral therapy.

Diagnosis of respiratory syncytial virus infection

Respiratory syncytial virus (RSV) is one of the most important pathogen causing severe lower respiratory tract infections in all age groups often requiring hospitalization. Rapid laboratory diagnosis of RSV infection significantly decreases the use of antibiotics, additional laboratory testing and is associated with shorter hospitalization periods. The specific diagnosis of RSV infection is based on the detection of virus or viral antigens or virus specific nucleic acid sequences in respiratory secretions. The kind and quality of the clinical specimen exerts a considerable influence on the results of all currently used viral detection assays. Antigen based tests are widely available, easy to perform and the results are available in a short time but their reduced sensitivity and specificity represent a considerable shortcoming. Among the methods available isolation in cell culture was considered the gold standard for the sensitive identification of RSV but is gradually replaced by highly sensitive and specific nucleic acid amplification assays that provide more rapid results. Of these reverse transcription polymerase chain reaction (PCR) was the first and is still the most frequently used nucleic acid-based assay. New methodologies, as for example the real-time PCR methods allow the quantification of viral nucleic acids in the clinical sample. Disadvantages of the nucleic acid based assays are their high costs and their limited standardization.

Future research on new methodologies for the diagnosis of viral respiratory tract infections should focus on the development of sensitive, rapid and cost effective test systems allowing the screening for all probable causative agents. In addition varying testing protocols for summer and winter months based on epidemiologic data are needed to direct their practical use.

Human cytomegalovirus infection in lung transplant recipients triggers a CXCL-10 response

Human cytomegalovirus (HCMV) causes significant morbidity in lung transplant recipients (LTRs). The clinical effects of HCMV replication are determined partly by a type 1 T-helper cell (Th1) response. Because the chemokine interferon-inducible protein of 10 kilodaltons (IP-10, CXCL-10) induces a Th1 response, we investigated whether HCMV triggers IP-10 in LTRs. The IP-10 concentration and HCMV DNA load were determined in 107 plasma and 46 bronchoalveolar lavage fluid (BALF) samples from 36 LTRs. Initial HCMV detection posttransplantation was significantly associated with increased plasma IP-10, regardless of whether the patients showed HCMV DNAemia (p = 0.001) or HCMV replication only in the allograft (p < 0.0001). In subsequent episodes of HCMV detection, plasma IP-10 increased regardless of whether HCMV was detected in blood (p = 0.0078) or only in BALF (p < 0.0001) and decreased after successful antiviral therapy (p = 0.0005). Furthermore, levels of HCMV DNA and IP-10 correlated statistically (p = 0.0033). Increased IP-10 levels in HCMV-positive BALF samples were significantly associated with severe airflow obstruction, as indicated by a decrease in forced expiratory volume in one second (FEV1). Our data indicate that HCMV replication in LTRs evokes a plasma IP-10 response and that, when an IP-10 response is observed in BALF, it is associated with inflammatory airway obstruction in the allograft.

Dynamic coinfection with multiple viral subtypes in acute hepatitis C

INTRODUCTION

Acute hepatitis C virus (HCV) infection is rarely studied, but virus sequence evolution and host-virus dynamics during this early stage may influence the outcome of infection. Hypervariable region 1 (HVR1) is genetically diverse and under selective pressure from the host immune response. We analyzed HVR1 evolution by frequent sampling of an acutely infected HCV cohort.

METHODS

Three or more pretreatment samples were obtained from each of 10 acutely infected subjects. Polymerase chain reaction amplification was performed with multiple primer combinations to identify the full range of sequences present. Positive samples were cloned and sequenced. Phylogenetic analyses were used to assess viral diversity.

RESULTS

Eight of the 10 subjects were coinfected with at least 2 HCV subtypes. Multiple subtypes were detected in individual samples, and their relative proportions changed through acute infection. The subjects with the most complex subtype structure also had a dynamic viral load; however, changes in viral load were not directly linked to changes in subtype.

CONCLUSIONS

This well-sampled cohort with acute HCV infection was characterized by dynamic coinfection with multiple viral subtypes, representing a highly complex virologic landscape extremely early in infection.

Genetic analysis of Puumala hantavirus strains from Austria

Sequences of the Small (S) and the Medium (M) genome segments of Puumala hantavirus (PUUV) were recovered from bank voles Clethrionomys glareolus trapped at 2 locations, Klippitztörl (Carinthia) and Ernstbrunn (Lower Austria). Lung tissue samples from 12 rodents earlier found hantavirus antibody-positive were further screened for the presence of hantaviral N-antigen using immunoblotting. RNA purified from 7 N-Ag-positive samples was subjected to the reverse transcription-polymerase chain reaction with primers designed to recover the complete S segment sequence of PUUV. The amplicons of expected size (approximately 1800 bp) have been recovered from 2 samples, 1 from Klippitztörl and another from Ernstbrunn. From the same 2 samples, PCR amplicons corresponding to the partial M segment sequence (nt 2140 to 2594), have been prepared. The S and M amplicons were sequenced and subjected to genetic analyses. Recovered hantavirus genome sequences undoubtedly belonged to PUUV genotype and the corresponding wild-type hantavirus strains were designated as PUU/Klippitztörl/Cg9/1995 and PUU/Ernstbrunn/Cg641/1995. Phylogenetic analysis placed 2 Austrian PUUV strains within a distinct genetic lineage that also included strains from the neighbouring Slovenia and Croatia. This Alpe-Adrian lineage, previously designated as 'Balkan lineage', was well supported on both S and M phylogenetic trees.

IP-10 correlates with hepatitis C viral load, hepatic inflammation and fibrosis and predicts hepatitis C virus relapse or non-response in HIV-HCV coinfection

BACKGROUND

Interferon (IFN)-gamma inducible protein 10 (IP-10) is increased in hepatitis C virus (HCV) monoinfection, correlates with hepatic inflammation and predicts non-response (NR) to antiviral therapy. We aimed to clarify the role of IP-10 in HIV-HCV coinfection.

METHODS

Serum IP-10 levels of 30 HIV-HCV-coinfected patients treated with pegylated (PEG)-IFN-alpha2a (180 microg/week) and ribavirin (800-1,200 mg/day) were measured at baseline and 24 h after first IFN dose. The predictive value of IP-10 was compared with established markers of treatment outcome by applying a multivariate logistic regression model.

RESULTS

Patients with NR (476 +/- 156 pg/ml) or virological relapse (508 +/- 298 pg/ml) had significantly higher baseline IP-10 levels compared with patients who had a sustained virological response (SVR; 293 +/- 97 pg/ml, P = 0.001). The IFN-induced increase of IP-10 was significantly stronger in patients with an SVR (P = 0.017). IP-10 levels were associated with HCV viral load, alanine aminotransferase (ALT) levels, hepatic inflammatory activity and fibrosis stage. Advanced fibrosis, high HCV viral load, hepatovenous pressure gradient and pretreatment IP-10 > 400 pg/ml predicted NR to antiviral therapy. In the multivariate analysis, IP-10 was identified as the strongest baseline predictor of SVR with a specificity and sensitivity of 83.4% and 92.9%, respectively.

CONCLUSIONS

Pretreatment IP-10 levels correlated with HCV viral load, ALT levels, hepatic inflammation and fibrosis. An IP-10 cutoff level of 400 pg/ml might serve as a useful predictive marker for anti-HCV therapy in HIV-HCV-coinfected patients because it could discriminate patients with expected NR or HCV relapse after therapy from patients with an SVR before starting antiviral treatment.

CD4+ T cell responses in patients with chronic hepatitis C undergoing peginterferon/ribavirin therapy correlate with faster, but not sustained, viral clearance

T cell immune responses may be important for the elimination of chronic hepatitis C virus (HCV) infection during antiviral treatment. In the present study, the kinetics of T cell responses to HCV antigens (NS3-4 and core) were prospectively assessed and were correlated with virologic outcome in 31 patients with chronic HCV infection undergoing peginterferon- alpha 2a/ribavirin therapy. NS3-4--directed T helper cell type 1 (Th1) responses were detected in 77% of patients with a significant decline in viremia at treatment week 4 but were not detected not in those with a slower viral decline. The detectability of NS3-4--directed Th1 responses was associated with faster viremia clearance, was short-lived, and did not seem to be associated with the final treatment outcome.

Humoral and cellular immune response to RNA immunization with flavivirus replicons derived from tick-borne encephalitis virus

A new vaccination principle against flaviviruses, based on a tick-borne encephalitis virus (TBEV) self-replicating noninfectious RNA vaccine that produces subviral particles, has recently been introduced (R. M. Kofler, J. H. Aberle, S. W. Aberle, S. L. Allison, F. X. Heinz, and C. W. Mandl, Proc. Natl. Acad. Sci. USA 7:1951-1956, 2004). In this study, we evaluated the potential of the self-replicating RNA vaccine in mice in comparison to those of live, attenuated vaccines and a formalin-inactivated whole-virus vaccine (ImmunInject). For this purpose, mice were immunized using gene gun-mediated application of the RNA vaccine and tested for CD8+ T-cell responses, long-term duration, neutralizing capacity, and isotype profile of specific antibodies and protection against lethal virus challenge. We demonstrate that the self-replicating RNA vaccine induced a broad-based, humoral and cellular (Th1 and CD8+ T-cell response) immune response comparable to that induced by live vaccines and that it protected mice from challenge. Even a single immunization with 1 microg of the replicon induced a long-lasting antibody response, characterized by high neutralizing antibody titers, which were sustained for at least 1 year. Nevertheless, it was possible to boost this response further by a second injection with the RNA vaccine, even in the presence of a concomitant CD8+ T-cell response. In this way it was possible to induce a balanced humoral and cellular immune response, similar to infection-induced immunity but without the safety hazards of infectious agents. The results also demonstrate the value of TBEV replicon RNA for inducing protective long-lasting antiviral responses.

Prospective study of viral clearance and CD4(+) T-cell response in acute hepatitis C primary infection and reinfection

BACKGROUND

The outcome of acute hepatitis C is determined by early host-virus interactions, particularly involving the antiviral T-cell response.

OBJECTIVES

To identify early prognostic markers of spontaneous resolution of acute hepatitis C by performing a comprehensive analysis of viral and immunological factors during the natural course of acute HCV infection and reinfection.

STUDY DESIGN

20 patients were investigated prospectively during acute HC or confirmed reinfection and 18 of them during follow up after spontaneous or treatment-induced elimination of the virus and resolution of the disease. Multiparameter flow cytometry was used to functionally characterize virus-specific CD4(+) T-cell responses relative to the virologic outcome.

RESULTS

Parallel immunologic and virologic monitoring of patients with acute HC identified distinct patterns of host-virus interaction related to HCV persistence or clearance. The highest frequency of antiviral Th1 cytokine-producing CD4(+) T-cells was observed in patients with HCV reinfection, preceding rapid viral clearance within 3 weeks after disease onset. In all patients who subsequently cleared viremia, CD4(+) T-cells produced Th1 cytokines following stimulation with non-structural HCV antigens (NS3 and NS4). In contrast, a chronic course of disease was associated with the absence of antiviral Th1 cytokine producing cells from the first weeks after onset of disease (acute persistent HC), or with fluctuating RNA levels (yo-yo pattern) and gradual waning of antiviral Th1 cells.

CONCLUSIONS

The results highlight the variability of immune response pattern in acute hepatitis C. Most importantly, "acute persistent hepatitis C" and a lack of TH1 effector cells within the first months of acute hepatitis C represent efficacious predictors of viral persistence and could thus be used as criteria in selecting candidates for early antiviral treatment.