Nanobodies (Nbs) serve as powerful tools in immunoassays. However, their small size and monovalent properties pose challenges for practical application. Multimerization emerges as a significant strategy to address these limitations, enhancing the utilization of nanobodies in immunoassays. Herein, we report the construction of a Salmonella-specific fenobody (Fb) through the fusion of a nanobody to ferritin, resulting in a self-assembled 24-valent nanocage-like structure. The fenobody exhibits a 35-fold increase in avidity compared to the conventional nanobody while retaining good thermostability and specificity. Leveraging this advancement, three ELISA modes were designed using Fb as the capture antibody, along with unmodified Nb422 (FbNb-ELISA), biotinylated Nb422 (FbBio-ELISA), and phage-displayed Nb422 (FbP-ELISA) as the detection antibody, respectively. Notably, the FbNb-ELISA demonstrates a detection limit (LOD) of 3.56 × 104 CFU/mL, which is 16-fold lower than that of FbBio-ELISA and similar to FbP-ELISA. Moreover, a fenobody and nanobody sandwich chemiluminescent enzyme immunoassay (FbNb-CLISA) was developed by replacing the TMB chromogenic substrate with luminal, resulting in a 12-fold reduction in the LOD. Overall, the ferritin-displayed technology represents a promising methodology for enhancing the detection performance of nanobody-based sandwich ELISAs, thereby expanding the applicability of Nbs in food detection and other fields requiring multivalent modification.

Yersinia pestis, the causative agent of plague and a biological threat agent, presents an urgent need for novel medical countermeasures due to documented cases of naturally acquired antibiotic resistance and potential person-to-person spread during a pneumonic infection. Immunotherapy has been proposed as a way to circumvent current and future antibiotic resistance. Here, we describe the development and characterization of two affinity matured human antibodies (αF1Ig AM2 and αF1Ig AM8) that promote survival of mice after exposure to aerosolized Y. pestis. We share details of the error prone PCR and yeast display technology-based affinity maturation process that we used. The resultant matured antibodies have nanomolar affinity for Y. pestis F1 antigen, are produced in high yield, and are resilient to 37°C stress for up to 6 months. Importantly, in vitro assays using a murine macrophage cell line demonstrated that αF1Ig AM2 and αF1Ig AM8 are opsonic. Even more importantly, in vivo studies using pneumonic plague mouse models showed that 100% of the mice receiving 500 μg of IgGs αF1Ig AM2 and αF1Ig AM8 survived lethal challenge with aerosolized Y. pestis CO92. Combined, these results provide evidence of the quality and robustness of αF1Ig AM2 and αF1Ig AM8 and support their development as potential medical countermeasures against plague.

BACKGROUND: Antibodies have been proven effective as diagnostic agents for detecting zoonotic diseases. The variable domain of camel heavy chain antibody (VHH), as an antibody derivative, may be used as an alternative for traditional antibodies in existing immunodiagnostic reagents for detecting rapidly spreading infectious diseases.
OBJECTIVE: To expedite the isolation of specific antibodies for diagnostic purposes, we constructed a semi-synthetic camel single domain antibody library based on the phage display technique platform (PDT) and verified the validity of this study.
METHODS: The semi-synthetic single domain antibody sequences consist of two parts: one is the FR1-FR3 region amplified by RT-PCR from healthy camel peripheral blood lymphocytes (PBLs), and the other part is the CDR3-FR4 region synthesised as an oligonucleotide containing CDR3 randomised region. The two parts were fused by overlapping PCR, resulting in the rearranged variable domain of heavy-chain antibodies (VHHs). Y. pestis low-calcium response V protein (LcrV) is an optional biomarker to detect the Y. pestis infection. The semi-synthetic library herein was screened using recombinant (LcrV) as a target antigen.
RESULTS: After four cycles of panning the library, four VHH binders targeting 1-270 aa residues of LcrV were isolated. The four VHH genes with unique sequences were recloned into an expression vector and expressed as VHH-hFc chimeric antibodies. The purified antibodies were identified and used to develop a lateral flow immunoassay (LFA) test strip using latex microspheres (LM) for the rapid and visual detection of Y. pestis infection.
CONCLUSIONS: These data demonstrate the great potential of the semi-synthetic library for use in isolation of antigen-specific nanobodies and the isolated specific VHHs can be used in antigen-capture immunoassays.

A maternal vaccine to protect newborns against invasive Streptococcus agalactiae infection is a developing medical need. The vaccine should be offered during the third trimester of pregnancy and induce strong immune responses and placental transfer of protective antibodies. Polysaccharide vaccines against S. agalactiae conjugated to protein carriers are in advanced stages of development. Additionally, protein-based vaccines are also in development, showing great promise as they can provide protection regardless of serotype. Furthermore, safety concerns regarding a new vaccine are the main barriers identified. Here, we present vaccines in development and identified safety, cost, and efficacy concerns, especially in high-need, low-income countries.

IgA nephropathy (IgAN) is one of the most common primary glomerulonephritis, and serum Helicobacter pylori (H. pylori) antibody levels are increased in patients with IgA N, but the role of H. pylori infection in the pathogenesis of IgAN is unclear. In this study, we investigated whether there is a causal relationship and reverse causality between IgAN and H. pylori infection by using a bidirectional two-sample Mendelian randomization (MR) analysis. This study was estimated using inverse variance weighted (IVW), MR-Egger and weighted median methods, with the IVW method having the strongest statistical efficacy. Seven common serum H. pylori antibodies were selected as exposure factors for positive MR analysis. The results showed that there was no evidence of a causal relationship between H. pylori infection and IgAN. Reverse MR analysis showed that there was also no evidence that the occurrence of IgAN leads to an increased risk of H. pylori infection.

BACKGROUND: The \"hygiene hypothesis\" states that reduced exposure to microbial antigens due to an excessively hygienic environment can increase the risk of developing autoimmune diseases, including atopic disorders and asthma. In recent decades, there has been a progressive decline in the prevalence of numerous microorganisms following improved hygienic-sanitary conditions. More specifically, several studies reported an inverse association between the reduction in Helicobacter pylori infection and the rise of asthma and allergic disorders.
OBJECTIVE: To evaluate the prevalence of atopic disorders in a pediatric population in relation to seropositivity against H. pylori.
METHODS: Children from Northern Sardinia, Italy, referred to the local Children\'s Hospital for any reason, were investigated to identify risk factors, especially H. pylori infection, associated with atopic disorders. A validated questionnaire, including demographics, house size, history of breastfeeding, residence, school or daycare center attendance, exposure to animals, and a defined diagnosis of atopy-including asthma-was filled out by a trained pediatrician according to parents\' answers and child records. A blood sample was collected from each participant and immunoglobulin G against H. pylori was assessed by a locally validated ELISA test.
RESULTS: The seroprevalence of H. pylori infection was 11.7% among 492 children (240 females). Thirty-two children had a confirmed diagnosis of asthma and 12 of allergy. No one child showed both conditions. Statistically significant differences in H. pylori seropositivity were not detected between children with or without atopy (8.4% vs. 12.6; p = 0.233). Although atopic disorders were more frequent in children exposed to traditional atopic risk factors, none of them showed to be significant after adjusting for all covariates.
CONCLUSIONS: Serologically assessed H. pylori infection was not significantly associated with a reduced risk of atopic diseases in children.

Helicobacter pylori causes globally prevalent infections that are highly related to chronic gastritis and even development of gastric carcinomas. With the increase of antibiotic resistance, scientists have begun to search for better vaccine design strategies to eradicate H. pylori colonization. However, while current strategies prefer to formulate vaccines with a single H. pylori antigen, their potential has not yet been fully realized. Outer membrane vesicles (OMVs) are a potential platform since they could deliver multiple antigens. In this study, we engineered three crucial H. pylori antigen proteins (UreB, CagA, and VacA) onto the surface of OMVs derived from Salmonella enterica serovar Typhimurium (S. Typhimurium) mutant strains using the hemoglobin protease (Hbp) autotransporter system. In various knockout strategies, we found that OMVs isolated from the ΔrfbP ΔfliC ΔfljB ΔompA mutants could cause distinct increases in immunoglobulin G (IgG) and A (IgA) levels and effectively trigger T helper 1- and 17-biased cellular immune responses, which perform a vital role in protecting against H. pylori. Next, OMVs derived from ΔrfbP ΔfliC ΔfljB ΔompA mutants were used as a vector to deliver different combinations of H. pylori antigens. The antibody and cytokine levels and challenge experiments in mice model indicated that co-delivering UreB and CagA could protect against H. pylori and antigen-specific T cell responses. In summary, OMVs derived from the S. Typhimurium ΔrfbP ΔfliC ΔfljB ΔompA mutant strain as the vector while importing H. pylori UreB and CagA as antigenic proteins using the Hbp autotransporter system would greatly benefit controlling H. pylori infection.
Outer membrane vesicles (OMVs), as a novel antigen delivery platform, has been used in vaccine design for various pathogens and even tumors. Salmonella enterica serovar Typhimurium (S. Typhimurium), as a bacterium that is easy to engineer and has both adjuvant efficacy and immune stimulation capacity, has become the preferred bacterial vector for purifying OMVs after Escherichia coli. This study focuses on the design of Helicobacter pylori ;(H. pylori) vaccines, utilizing genetically modified Salmonella OMVs to present several major antigens of H. pylori, including UreB, VacA and CagA. The optimal Salmonella OMV delivery vector and antigen combinations are screened and identified, providing new ideas for the development of H. pylori vaccines and an integrated antigen delivery platform for other difficult to develop vaccines for bacteria, viruses, and even tumors.

BACKGROUND: Refractory Helicobacter pylori (H. pylori) infection inevitably increase the difficulty of drug selection. Here, we described our experience with the use of a novel tetravalent IgY against H. pylori for the treatment of patients with refractory H. pylori infection.
METHODS: Patients were randomly assigned to receive the standard quadruple therapy (amoxicillin, clarithromycin, omeprazole and bismuth potassium citrate ) for 2 weeks or 250 mg of avian polyclonal IgY orally twice a day for 4 weeks. The binding efficacy of IgY to H. pylori antigens was detected by western blotting13. C-urea breath test was performed to evaluate the eradication therap\'s efficacy. The side effects of IgY were evaluated via various routine tests. The questionnaire was used to gather clinical symptoms and adverse reactions.
RESULTS: Western blot analysis showed that tetravalent IgY simultaneously bind to VacA, HpaA, CagA and UreB of H. pylori. Tetravalent IgY had an eradication rate of 50.74% in patients with refractory H. pylori and an inhibition rate of 50.04% against DOB (delta over baseline) of 13C-urea. The symptom relief rate was 61.76% in thirty-four patients with clinical symptoms, and no adverse reactions were observed during tetravalent IgY treatment period.
CONCLUSIONS: Polyclonal avian tetravalent IgY reduced H. pylori infection, and showed good efficacy and safety in the treatment of refractory H. pylori infection patients, which represented an effective therapeutic option of choice for patients with refractory H. pylori infection.

Tetanus toxin (TeNT) is one of the most toxic proteins. Neutralizing antibodies against TeNT are effective in prevention and treatment. In this study, 14 anti-tetanus nanobodies were obtained from a phage display nanobody library by immunizing a camel with the C-terminal receptor-binding domain of TeNT (TeNT-Hc) as the antigen. After fusion with the human Fc fragment, 11 chimeric heavy-chain antibodies demonstrated nanomolar binding toward TeNT-Hc. The results of toxin neutralization experiments showed that T83-7, T83-8, and T83-13 completely protected mice against 20 × the median lethal dose (LD50) at a low concentration. The neutralizing potency of T83-7, T83-8, and T83-13 against TeNT is 0.4 IU/mg, 0.4 IU/mg and 0.2 IU/mg, respectively. In the prophylactic setting, we found that 5 mg/kg of T83-13 provided the mice with full protection from tetanus, even when they were injected 14 days before exposure to 20 × LD50 TeNT. T83-7 and T83-8 were less effective, being fully protective only when challenged 7 or 10 days before exposure, respectively. In the therapeutic setting, 12 h after exposure to TeNT, 1 ~ 5 mg/kg of T83-7, and T83-8 could provide complete protection for mice against 5 × LD50 TeNT, while 1 mg/kg T83-13 could provide complete protection 24 h after exposure to 5 × LD50 TeNT. Our results suggested that these antibodies represent prophylactic and therapeutic activities against TeNT in a mouse model. The T83-7, T83-8, and T83-13 could form the basis for the subsequent development of drugs to treat TeNT toxicity.

UNASSIGNED: Non-typhoidal Salmonella (NTS) generally causes self-limiting gastroenteritis. However, older adults (≥65 years) can experience more severe outcomes from NTS infection. We have previously shown that a live attenuated S. Typhimurium vaccine, CVD 1926 (I77 ΔguaBA ΔclpP ΔpipA ΔhtrA), was immunogenic in adult but not aged mice. Here we describe modification of CVD 1926 through deletion of steD, a Salmonella effector responsible for host immune escape, which we hypothesized would increase immunogenicity in aged mice.
UNASSIGNED: Mel Juso and/or mutuDC cells were infected with S. Typhimurium I77, CVD 1926, and their respective steD mutants, and the MHC-II levels were evaluated. Aged (18-month-old) C57BL/6 mice received two doses of PBS, CVD 1926, or CVD 1926 ΔsteD perorally (109 CFU) and the number of FliC-specific CD4+ T cells were determined. Lastly, aged C57BL/6 mice received three doses of PBS, CVD 1926, or CVD 1926 ΔsteD perorally (109 CFU) and then were challenged perorally with wild-type S. Typhimurium SL1344 (108 CFU). These animals were also evaluated for antibody responses.
UNASSIGNED: MHC-II induction was higher in cells treated with steD mutants, compared to their respective parental strains. Compared to PBS-vaccinated mice, CVD 1926 ΔsteD elicited significantly more FliC-specific CD4+ T cells in the Peyer\'s Patches. There were no significant differences in FliC-specific CD4+ T cells in the Peyer\'s patches or spleen of CVD 1926- versus PBS-immunized mice. CVD 1926 and CVD 1926 ΔsteD induced similar serum and fecal anti-core and O polysaccharide antibody titers after three doses. After two immunizations, the proportion of seroconverters for CVD 1926 ΔsteD was 83% (10/12) compared to 42% (5/12) for CVD 1926. Compared to PBS-immunized mice, mice immunized with CVD 1926 ΔsteD had significantly lower S. Typhimurium counts in the spleen, cecum, and small intestine upon challenge. In contrast, there were no differences in bacterial loads in the tissues of PBS-vaccinated and CVD 1926-immunized animals.
UNASSIGNED: These data suggest that the steD deletion enhanced the immunogenicity of our live attenuated S. Typhimurium vaccine. Deletion of immune evasion genes could be a potential strategy to improve the immunogenicity of live attenuated vaccines in older adults.