The varying extent of humoral and cellular immune responses to either vector- or RNA-based SARS-CoV-2 vaccines persists for at least 18 months and is independent of infection.

The corona virus disease 2019 (COVID-19) pandemic caused by severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2) spurred a worldwide race for the development of an efficient vaccine. Various strategies were pursued; however, the first vaccines to be licensed presented the SARS-CoV-2 spike protein either in the context of a non-replicating adenoviral vector or as an mRNA construct. While short-term efficacies have extensively been characterized, the duration of protection, the need for repeated boosting, and reasonable vaccination intervals have yet to be defined. We here describe the adaptive immune response resulting from homologous and heterologous vaccination regimen at 18 months after primary vaccination. To that extent, we monitored 176 healthcare workers, the majority of whom had recovered from previous SARS-CoV-2 infection. In summary, we find that differences depending on primary immunization continue to exist 18 months after the first vaccination and these findings hold true irrespective of previous infection with the virus. Homologous primary immunization with BNT162b2 was repeatedly shown to produce higher antibody levels and slower antibody decline, leading to more effective in vitro neutralization capacities. Likewise, cellular responses resulting from in vitro re-stimulation were more pronounced after primary immunization involving BNT162b2. In contrast, IL-2 producing memory T helper and cytotoxic T cells appeared independent from the primary vaccination regimen. Despite these differences, comparable infection rates among all vaccination groups suggest comparable real-life protection.IMPORTANCEVaccination against the severe acute respiratory syndrome corona-virus 2 (SARS-CoV-2) was shown to avert severe courses of corona virus disease 2019 (COVID-19) and to mitigate spreading of the virus. However, the duration of protection and need for repeated boosting have yet to be defined. Monitoring and comparing the immune responses resulting from various vaccine strategies are therefore important to fill knowledge gaps and prepare for future pandemics.

PREVALENCE OF SARS-CoV-2 RNA AND ANTIBODY DETECTION, AND VACCINATION STATUS IN PATIENTS WITH OCULAR VASCULAR OCCLUSION.

PURPOSE: To analyze the annual prevalence of ocular vascular occlusion in relation to COVID-19 infection and vaccination status in a prospective study. METHODS: All patients were examined for an active severe acute respiratory syndrome coronavirus 2 infection by RNA detection and for a previous infection by virus-specific antibody detection, and their vaccination status was documented. Data from pandemic year 2020 and previous years, before COVID-19 (2019, 2018, 2017), were retrospectively analyzed. RESULTS: In 2021, a total of 103 patients with the first diagnosis of ocular vascular occlusion were treated. Most frequent subdiagnoses were central retinal vein occlusion (20.4%), nonarteritic anterior ischemic optic neuropathy (18.4%), central retinal artery occlusion (13.6%), and branch retinal artery occlusion (12.6%). Thereof, only three patients (2.9%) presented with virus-specific severe acute respiratory syndrome coronavirus 2 antibodies, and none was PCR positive. Patients with preceded severe acute respiratory syndrome coronavirus 2 vaccination (59.2%) presented with comparable characteristics as unvaccinated patients with vascular occlusion regarding age, gender distribution, systemic risk factors, duration of symptoms, visual acuity, and the present subdiagnoses ( P > 0.05). The total number of cases in 2021 (103 cases) was comparable with the pandemic year 2020, at which no vaccination was available (114 cases), and to earlier years 2017, 2018, and 2019 without COVID-19 pandemic (100, 120, and 119 cases). Furthermore, we did not reveal any differences between pandemic and reference years regarding patients' characteristics ( P > 0.05). CONCLUSION: Our study did not reveal an increased annual prevalence of ocular vascular occlusions during COVID-19 pandemic years 2020 and 2021. Patients with previous COVID-19 vaccination did not present differences regarding the risk profile nor symptoms, compared with unvaccinated individuals.

Single-dose SARS-CoV-2 vaccinations with either BNT162b2 or AZD1222 induce disparate Th1 responses and IgA production.

BACKGROUND: While vaccination programs against the severe acute respiratory syndrome virus 2 (SARS-CoV-2) are globally ongoing, disparate strategies for the deployment of spike antigen show varying effectiveness. METHODS: In order to explore this phenomenon, we sought to compare the early immune responses against AZD1222 and BNT162b2. SARS-CoV-2 seronegative participants received a single dose of either vaccine and were analyzed for immune cell, effector T cell, and antibody dynamics. RESULTS: AZD1222 induced transient leukopenia and major changes among innate and adaptive subpopulations. Both vaccines induced spike protein-specific effector T cells which were dominated by type 1 helper T cell responses following AZD1222 vaccination. A significant reduction of anti-inflammatory T cells upon re-stimulation was also restricted to AZD1222 vaccinees. While IgM and IgG were the dominant isotypes elicited by AZD1222, BNT162b2 led to a significant production of IgG and IgA. CONCLUSIONS: Our results suggest that the strategy for spike protein delivery impacts on how and to what extent immune priming against the main SARS-CoV-2 antigen proceeds.

Human serum activates the tegument of female schistosomes and supports recovery from Praziquantel.

Schistosomiasis is one of the most devastating parasitic disease in the world. Schistosoma spp. survive for decades within the vasculature of their human hosts. They have evolved a vast array of mechanisms to avoid the immune reaction of the host. Due to their sexual dimorphism, with the female worm lying within the gynecophoric canal of the male worm, it is the male that is exposed to the immediate environment and the soluble parts of the host's immune response. To understand how the worms are so successful in fending off the immune attacks of the host, comparative analyses of both worm sexes in human serum (with or without Praziquantel) were performed using scanning electron microscopy, transmission electron microscopy, and immunohistochemistry. Further, gene expression analyses of tegument-specific genes were performed. Following the incubation in human serum, males and females out of pairs show morphological changes such as an altered structure of the pits below the surface and an increased number of pits per area. In addition, female schistosomes presented a marked tuft-like repulsion of their opsonized surface. The observed resistance of females to Praziquantel seemed to depend on active proteins in the human serum. Moreover, different expression profiles of tegument-specific genes indicate different functions of female_single and male_single teguments in response to human serum. Our results indicate that female schistosomes developed different evasion strategies toward the host's immune system in comparison to males that might lead to more robustness and has to be taken into account for the development of new anti-schistosomal drugs.

[Challenges of the COVID-19 Pandemic for Schools in Mecklenburg-Vorpommern - First Results of a Prospective Case Study]. / Herausforderungen der COVID-19-Pandemie für Schulen in Mecklenburg-Vorpommern ­ erste Ergebnisse einer prospektiven Fallstudie.

BACKGROUND: The current risk of infection with SARS-CoV-2 in schools continues to be a subject of controversy. METHODOLOGY: "schugi-MV" collects data on the incidence of infection, hygiene management and other factors in structured inspections of schools in Mecklenburg-Western Pomerania. Recommendations for safe teaching are to be derived from the results. This article presents information on the first 10 schools visited between 18.12.2020 and 20.01.2021. RESULTS: At the schools visited, the ratio of the number of index cases among adults and children was 1:1.25. The inspections showed a great heterogeneity of schools and school buildings and the resulting possibilities for implementing infection control measures. CONCLUSION: Based on the present preliminary results, hygiene and infection control measures at schools in Mecklenburg-Western Pomerania cannot be standardised, but should leave room for design.

Immunogenicity, safety, and tolerability of the measles-vectored chikungunya virus vaccine MV-CHIK: a double-blind, randomised, placebo-controlled and active-controlled phase 2 trial.

BACKGROUND: Chikungunya fever is an emerging viral disease and substantial threat to public health. We aimed to assess the safety, tolerability, and immunogenicity of a live-attenuated, measles-vectored chikungunya vaccine (MV-CHIK). METHODS: In this double-blind, randomised, placebo-controlled and active-controlled phase 2 trial, we enrolled healthy volunteers aged 18-55 years at four study sites in Austria and Germany. Participants were randomly assigned to receive intramuscular injections with MV-CHIK (5 × 104 or 5 × 105 50% tissue culture infectious dose), control vaccine, or measles prime and MV-CHIK, in two different administration regimens. Randomisation was done by use of three-digit randomisation codes in envelopes provided by a data management service. The participants and investigators were masked to treatment assignment, which was maintained by use of sterile saline as a placebo injection. The primary endpoint was immunogenicity, defined as the presence of neutralising antibodies against chikungunya virus, at day 56, which is 28 days after one or two immunisations. The primary endpoint was assessed in all participants who completed the study without major protocol deviations (per-protocol population) and in all randomised participants who received at least one study treatment (modified intention-to-treat population). The safety analysis included all participants who received at least one study treatment. This trial is registered with ClinicalTrials.gov (NCT02861586) and EudraCT (2015-004037-26) and is completed. FINDINGS: Between Aug 17, 2016, and May 31, 2017, we randomly assigned 263 participants to receive control vaccine (n=34), MV-CHIK (n=195), or measles prime and MV-CHIK (n=34). 247 participants were included in the per-protocol population. Neutralising antibodies against chikungunya virus were detected in all MV-CHIK treatment groups after one or two immunisations, with geometric mean titres ranging from 12·87 (95% CI 8·75-18·93) to 174·80 (119·10-256·50) and seroconversion rates ranging from 50·0% to 95·9% depending on the dose and administration schedule. Adverse events were similar between groups, with solicited adverse events reported in 168 (73%) of 229 participants assigned to MV-CHIK and 24 (71%) of 34 assigned to control vaccine (p=0·84) and unsolicited adverse events in 116 (51%) participants assigned to MV-CHIK and 17 (50%) assigned to control vaccine (p=1·00). No serious adverse events related to the vaccine were reported. INTERPRETATION: MV-CHIK showed excellent safety and tolerability and good immunogenicity, independent of pre-existing immunity against the vector. MV-CHIK is a promising candidate vaccine for the prevention of chikungunya fever, an emerging disease of global concern. FUNDING: Themis.

[COVID-19: epidemiology and clinical facts]. / COVID-19: Epidemiologische und klinische Fakten.

Until July 31, 2020, about 17.6 million SARS-CoV­2 infections and 680,000 deaths from COVID-19 were reported. SARS-CoV­2 is most likely transmitted by droplets and probably by aerosols. Patients become infectious 2-3 days before the onset of symptoms, and persons with asymptomatic infections are also infectious. COVID-19 affects the upper respiratory tract, lungs (pneumonia, acute respiratory distress syndrome [ARDS]), heart, liver, gastrointestinal tract, and other organs. SARS-CoV­2 uses ACE2 a receptor to enter host cells. Vasculitis, endothelial damage, thromboembolic events and organ failure are accompanied by a massive cytokine response. Elderly people and those with pre-existing diseases are particularly vulnerable. An efficient antiviral therapy is not yet available. Severely ill patients may benefit from dexamethasone and early treatment of complications. Candidate vaccines are currently being tested in clinical studies.

Crimean-Congo Hemorrhagic Fever, Kosovo, 2013-2016.

During 2013-2016, a total of 32 patients were treated for Crimean-Congo hemorrhagic fever in Prishtina, Kosovo; 11 died. In the 11 patients who died, findings included viral loads >1 × 108.5/mL, lactate dehydrogenase >2,700 U/mL, bleeding, and impaired consciousness. Ribavirin therapy had no noticeable effect in this small patient sample.

A phase III, open-label, single-arm, study to evaluate the safety and immunogenicity of a trivalent, surface antigen inactivated subunit influenza virus vaccine produced in mammalian cell culture (Optaflu®) in healthy adults.

Vaccination is an essential tool in reducing the impact of seasonal influenza infections. The viral strains responsible for seasonal outbreaks vary annually, and preventive vaccines have to be adapted accordingly. The aim of this study was to evaluate the safety, clinical tolerability and the antibody response to each of the three influenza vaccine antigens after vaccination with a cell-derived, trivalent, surface antigen, inactivated influenza vaccine (TIVc), as measured by single radial haemolysis (SRH) or haemagglutination inhibition (HI) assay in accordance with European Union licensing guidelines in place for years 2013/2014. This phase 3, open-label, single-arm study enrolled 126 healthy adults divided into two age groups (63 subjects aged 18 to ≤ 60 years and 63 subjects aged ≥ 61 years). Antibody titres were measured before and 21 days after vaccination. Adverse events were determined using diary cards, interviews and reviews of the available medical records. One subject was lost to follow-up and three subjects had protocol deviations. Following vaccination, protective HI antibody titres (≥ 1:40) were detected in 100%, 97%, and 94% of the younger adults (18-≤ 60 years) and in 97%, 95%, and 80% of the older adults (≥ 61 years) against the A (H1N1), A (H3N2), and B influenza strains respectively. The antibody response licensing criteria were met in both age groups. Solicited adverse events were reported by 57% subjects 18 to ≤ 60 years and 35% subjects ≥ 61 years. Among the younger adults 51% had local and 27% had systemic adverse events, whereas of the older subjects 29% had local and 13% had systemic adverse events (mainly injection site pain or headache in both age groups). Unsolicited adverse events at least possibly related to the vaccine were mild and detected in 3% of the younger adults and none of the older adults. Overall, the trivalent, surface antigen, inactivated subunit influenza virus vaccine produced in mammalian cell culture proved to be safe and immunogenic in younger and older healthy adults.

Tuberculosis-associated hemophagocytic lymphohistiocytosis with subsequent unmasking cryptococcal immune reconstitution inflammatory syndrome (IRIS) in an HIV-negative man.

A 22-year-old HIV-negative man from Ghana was diagnosed with severe hemophagocytic lymphohistiocytosis (HLH) induced by multiorgan tuberculosis with peritoneal, hepatic, pericardial, myocardial, pleural, pulmonary, and bone manifestation. His body mass index was 12.9 m2/kg. Bioptic material of a peritoneal biopsy grew M. tuberculosis, sensitive to all first-line antituberculous drugs. HLH resolved with antituberculous therapy, without additional anti-inflammatory therapy being given. The initial CT scan of his brain was normal. After 5 months of antituberculous treatment, he developed a paralysis of the left arm. A cerebral MRT showed ring-enhanced lesions. Blood cultures and lumbar puncture revealed Cryptococcus neoformans var. grubi. The HIV test was repeatedly negative. Antituberculous treatment was continued for a total of 9 months, and additional treatment with antifungal therapy was established. He recovered fully after 14 months of antifungal treatment.

Tuberculosis and Takayasu arteritis: case-based review.

This report presents a case of co-occurrence of Takayasu arteritis (TA) and multiorgan tuberculosis (TB) in a 20-year-old female and provides a review of 18 previously reported cases of co-occurring TA and TB. All patients were between 9 and 24 years of age. Most reports describe a concomitant diagnosis of active TB and TA. TB lymphadenitis was described in 11 cases (57.9%), and microbiologically confirmed in 4 of these. All patients received antituberculous therapy and most received corticosteroids (89.5%). In our and two other cases, TA relapses necessitating additional immunosuppressive therapy were observed.

24-nor-ursodeoxycholic acid ameliorates inflammatory response and liver fibrosis in a murine model of hepatic schistosomiasis.

BACKGROUND & AIMS: Intrahepatic granuloma formation and fibrosis characterize the pathological features of Schistosoma mansoni infection. Based on previously observed substantial anti-fibrotic effects of 24-nor-ursodeoxycholic acid (norUDCA) in Abcb4/Mdr2(-/-) mice with cholestatic liver injury and biliary fibrosis, we hypothesized that norUDCA improves inflammation-driven liver fibrosis in S. mansoni infection. METHODS: Adult NMRI mice were infected with 50 S. mansoni cercariae and after 12 weeks received either norUDCA- or ursodeoxycholic acid (UDCA)-enriched diet (0.5% wt/wt) for 4 weeks. Bile acid effects on liver histology, serum biochemistry, key regulatory cytokines, hepatic hydroxyproline content as well as granuloma formation were compared to naive mice and infected controls. In addition, effects of norUDCA on primary T-cell activation/proliferation and maturation of the antigen-presenting-cells (dendritic cells, macrophages) were determined in vitro. RESULTS: UDCA as well as norUDCA attenuated the inflammatory response in livers of S. mansoni infected mice, but exclusively norUDCA changed cellular composition and reduced size of hepatic granulomas as well as TH2-mediated hepatic fibrosis in vivo. Moreover, norUDCA affected surface expression level of major histocompatibility complex (MHC) class II of macrophages and dendritic cells as well as activation/proliferation of T-lymphocytes in vitro, whereas UDCA had no effect. CONCLUSIONS: This study demonstrates pronounced anti-inflammatory and anti-fibrotic effects of norUDCA compared to UDCA in S. mansoni induced liver injury, and indicates that norUDCA directly represses antigen presentation of antigen presenting cells and subsequent T-cell activation in vitro. Therefore, norUDCA represents a promising drug for the treatment of this important cause of liver fibrosis.

NVX-CoV2373 induces humoral and cellular immune responses that are functionally comparable to vector and mRNA-based vaccines.

Background: After licensing of the protein-based vaccine NVX-CoV2373, three technically different vaccines against the SARS-CoV-2 became available for application to the human population - and for comparison of efficacies. Methods: We here recruited 42 study participants who had obtained one initial dose of NVX-CoV2373 and analyzed their immune responses in contrast to 37 study participants who had obtained either the vector vaccine AZD1222 or the mRNA vaccine BNT162b2 a year earlier. 32 participants also donated blood before first vaccination to serve as a vaccine-naive control. In detail, we investigated and quantified at day 21 and approximately six months after primary immunization the amounts of vaccine-specific antibodies produced, their neutralization capacity, their quality in terms of binding different epitopes and their efficiency in inducing various isotypes. Cellular immunity and intracellular cytokine production following in vitro re-stimulation with BNT162b2 vaccine was analyzed via ELISpot or via flow cytometry. Results: Our results show that even though vaccination including the mRNA vaccine yielded best results in almost any aspect of antibody levels and binding efficiency, the neutralization capacities against the wild-type Wuhan strain and the Omicron BA.1 variant early and at six months were comparable among all three vaccination groups. As for the T cells, we observed a prevailing CD8 response at three weeks which turned into a predominant CD4 memory at six months which has not yet been observed for AZD1222 and BNT162b2. While additional infection with SARS-CoV-2 resulted in a boost for the humoral response, T cell memory appeared rather unaffected. Conclusion: Whether any of these differences translate into real world protection from infection, mitigation of severe disease courses and prevention of long/post COVID will need to be investigated in the future.

Utilization of a highly adaptable murine air pouch model for minimally invasive testing of the inflammatory potential of biomaterials.

Introduction: The biocompatibility of an implanted material strongly determines the subsequent host immune response. After insertion into the body, each medical device causes tissue reactions. How intense and long-lasting these are is defined by the material properties. The so-called foreign body reaction is a reaction leading to the inflammation and wound healing process after implantation. The constantly expanding field of implant technology and the growing areas of application make optimization and adaptation of the materials used inevitable. Methods: In this study, modified liquid silicone rubber (LSR) and two of the most commonly used thermoplastic polyurethanes (TPU) were compared in terms of induced inflammatory response in the body. We evaluated the production of inflammatory cytokines, infiltration of inflammatory cells and encapsulation of foreign bodies in a subcutaneous air-pouch model in mice. In this model, the material is applied in a minimally invasive procedure via a cannula and in one piece, which allows material testing without destroying or crushing the material and thus studying an intact implant surface. The study design includes short-term (6 h) and long-term (10 days) analysis of the host response to the implanted materials. Air-pouch-infiltrating cells were determined by flow cytometry after 6 h and 10 days. Inflammation, fibrosis and angiogenesis markers were analyzed in the capsular tissue by qPCR after 10 days. Results: The foreign body reaction was investigated by macroscopic evaluation and scanning electron microscopy (SEM). Increased leukocyte infiltration was observed in the air-pouch after 6 h, but it markedly diminished after 10 days. After 10 days, capsule formations were observed around the materials without visible inflammatory cells. Discussion: For biocompatibility testing materials are often implanted in muscle tissue. These test methods are not sufficiently conclusive, especially for materials that are intended to come into contact with blood. Our study primarily shows that the presented model is a highly adaptable and minimally invasive test system to test the inflammatory potential of and foreign body reaction to candidate materials and offers more precise analysis options by means of flow cytometry.

Safety and immunogenicity of Ad26.COV2.S in adults: A randomised, double-blind, placebo-controlled Phase 2a dose-finding study.

BACKGROUND: A single dose of Ad26.COV2.S is well-tolerated and effective in preventing moderate-to-severe disease outcomes due to COVID-19. We evaluated the impact of dose level, number of doses, and dose interval on immunogenicity, reactogenicity, and safety of Ad26.COV2.S in adults. Anamnestic responses were also explored. METHODS: This randomised, double-blind, placebo-controlled, Phase 2a study was conducted in adults aged 18-55 years and ≥ 65 years (NCT04535453). Four dose levels (1.25 × 1010, 2.5 × 1010, 5 × 1010, and 1 × 1011 viral particles [vp], single and 2-dose schedules, and dose intervals of 56 and 84 days, were assessed. Four or 6 months post-primary vaccination, Ad26.COV2.S 1.25 × 1010 vp was given to evaluate anamnestic responses. Humoral and cell-mediated immune responses were measured. Reactogenicity and safety were assessed in all participants. RESULTS: All Ad26.COV2.S schedules induced humoral responses with evidence of a dose response relationship. A single dose of Ad26.COV2.S (5 × 1010 vp) induced antibody and cellular immune responses that persisted for up to at least 6 months. In the 2-dose regimens, antibody responses were higher than 1-dose regimens at comparable dose levels, and the magnitude of the immune response increased when the interval between doses was increased (84 days vs 56 days). Rapid, marked immune responses were observed in all groups after vaccine antigen exposure indicating immune memory. Durable immune responses were observed in all groups for up to at least 6 months post-antigen exposure. Strong and consistent correlations between neutralising and binding antibodies were observed CD4 + and CD8 + T cell responses were similar after all regimens. Reactogenicity within 7 days post-vaccination tended to be dose-related. CONCLUSION: The study supports the primary, single dose schedule with Ad26.COV2.S at 5 × 1010 vp and homologous booster vaccination after a 6 month interval. Rapid and marked responses to vaccine antigen exposure indicate induction of immune memory by 1- and 2-dose primary vaccination.

Pneumocystis jirovecii colonization among renal transplant recipients.

AIM: Renal transplant recipients are at risk of developing Pneumocystis pneumonia (PcP), especially in the first 2 years after transplantation, with a mortality rate of up to 50%. No data are available on pulmonary colonization with Pneumocystis jirovecii in renal transplant recipients. The aim of this study was to determine the prevalence of pulmonary colonization with Pneumocystis jirovecii in renal transplant recipients and to find related risk factors. METHODS: We investigated the induced sputa of 70 renal transplant recipients for the presence of Pneumocystis jirovecii using nested polymerase chain reaction. RESULTS: Thirteen of 70 patients (18.6%) were colonized with Pneumocystis jirovecii. There was no significant correlation between colonization and immunosuppressive medication or regimens. However, colonized subjects had undergone transplantation longer ago than non-colonized subjects. 30.8% of those whose transplantation had taken place more than 8 years previously were colonized, in contrast to 11.4% of those whose transplantation had taken place less than 8 years ago (P = 0.059; odds ratio = 3.467, 95% confidence interval = 0.99-12.09). CONCLUSION: Most cases of Pneumocystis colonization were detected in those patients where renal transplantion had taken place more than 2 years previously. As most PcP cases occur within the first 2 years of transplantation, colonization does not seem to play a role in the development of acute PcP in this period. Though Pneumocystis pneumonia is likely to be a newly acquired infection in the first 2 years after transplantation, colonized patients remain a potential source of transmission of Pneumocystis jirovecii.

A linear B-cell epitope close to the furin cleavage site within the S1 domain of SARS-CoV-2 Spike protein discriminates the humoral immune response of nucleic acid- and protein-based vaccine cohorts.

Background: Understanding the humoral immune response towards viral infection and vaccination is instrumental in developing therapeutic tools to fight and restrict the viral spread of global pandemics. Of particular interest are the specificity and breadth of antibody reactivity in order to pinpoint immune dominant epitopes that remain immutable in viral variants. Methods: We used profiling with peptides derived from the Spike surface glycoprotein of SARS-CoV-2 to compare the antibody reactivity landscapes between patients and different vaccine cohorts. Initial screening was done with peptide microarrays while detailed results and validation data were obtained using peptide ELISA. Results: Overall, antibody patterns turned out to be individually distinct. However, plasma samples of patients conspicuously recognized epitopes covering the fusion peptide region and the connector domain of Spike S2. Both regions are evolutionarily conserved and are targets of antibodies that were shown to inhibit viral infection. Among vaccinees, we discovered an invariant Spike region (amino acids 657-671) N-terminal to the furin cleavage site that elicited a significantly stronger antibody response in AZD1222- and BNT162b2- compared to NVX-CoV2373-vaccinees. Conclusions: Understanding the exact function of antibodies recognizing amino acid region 657-671 of SARS-CoV-2 Spike glycoprotein and why nucleic acid-based vaccines elicit different responses from protein-based ones will be helpful for future vaccine design.

Unisexual infection with Schistosoma mansoni in mice has the potential to boost the immune response against eggs after challenge infection.

Introduction: The complexity of the Schistosoma spp. life cycle and their effective immune evasion strategies, makes vaccine development challenging. Unisexual infection models, that excludes any immunomodulatory effects of the parasite eggs, may contribute to a better understanding of complex immunological processes and identification of new targets for vaccine research. We have recently shown that long-term unisexual infection with schistosomes in mice results in an unpolarized Th1/Th2 response associated with an abnormally enlarged spleen and diffuse liver inflammation. Herein, we investigated whether (i) unisexual worms can mate after three months of single sex infection and (ii) thus the Th2 response induced by oviposition can reverse or heal the described systemic inflammation. Methods: Therefore, we infected 6-8 weeks old female C57BL/6j mice with 100 male or female cercariae and reinfected with the opposite sex for the same period after 12 weeks. At 24 weeks after initial infection, we histologically examined worm mating, as evidenced by the presence of parasite eggs, infection-related pathology associated with eggs, and characterization of fibrosis in the livers. Results: Single worms are able to mate months after unisexual infection and start oviposition. Egg deposition has been associated with a typical Th2 immune response in the liver after unisexual reinfection, accompanied by increased recruitment of CD4+ T cells. Hepatic collagen levels were significantly increased in the reinfected groups compared to the naive and unisexually infected group. Discussion: Our results indicate that the eggs are able to restore the Th1/Th2 immune balance of a previous unisexual infection. However, the organ damage caused by the unisexual worms does not subside, but rather provides the baseline for the emerging egg-triggered inflammation and fibrosis. Since single schistosomes can mate even several weeks after unisexual infection and then accumulate worm- and egg-related organ damage, infection status without positive egg detection is very important, especially in areas with low prevalence.

Individually or as a Team-The Immunological Milieu in the Lung Caused by Migrating Single-Sex or Mixed-Sex Larvae of Schistosoma mansoni.

While the lung is considered an efficient site for stopping the larvae of the acute Schistosoma spp. infection phase from migrating through extensive inflammatory responses in the surrounding tissues, little is known about these processes. To date, the highest resistance to infection has been achieved in experimental studies with radiation-attenuated cercariae immunization, which elicits a strong Th1/Th2 response in the lung and results in up to 80% protection. Based on our own studies demonstrating a systemic, unpolarized Th1/Th2 response resulting from infection with male or female Schistosoma mansoni, we hypothesize that this atypical immune response is already detectable during the pulmonary passage of parasite larvae. Therefore, we examined the immune milieu in the lungs of mice caused by migrating schistosome larvae, either male or female (single-sex groups) or male + female (bisexual control), 4 and 16 days after infection in bronchoalveolar lavage and lung tissue by flow cytometry, qPCR, and multiplex analyzes. Our results show only minor differences in the inflammatory profile between the single-sex groups but significant differences compared with the bisexual control group. Both single-sex infected groups have increased expression of inflammatory markers in lung tissue, higher numbers of cytotoxic T cells (day 4 post-infection) and more T helper cells (day 16 post-infection), compared with the bisexual control group. A single-sex infection, regardless of whether it is an infection with male or female cercariae, causes an immune milieu in the lung that is clearly different from an infection with both sexes. In terms of identifying therapeutic targets to achieve resistance to re-infection, it is of great scientific interest to identify the differences in the inflammatory potential of male or female and male + female parasites.