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Abstract Background MB2 protein is a sporozoite surface antigen on the human malaria parasite Plasmodium falciparum. MB2 was identified by screening a P. falciparum sporozoite cDNA expression library using immune sera from a protected donor immunized via the bites of P. falciparum-infected irradiated mosquitoes. It is not known whether natural exposure to P. falciparum also induces the anti-MB2 response and if this response differs from that in protected individuals immunized via the bites of P. falciparum infected irradiated mosquitoes. The anti-MB2 antibody response may be part of a robust protective response against the sporozoite. Methods Fragments of polypeptide regions of MB2 were constructed as recombinant fusions sandwiched between glutathione S-transferase and a hexa histidine tag for bacterial expression. The hexa histidine tag affinity purified proteins were used to immunize rabbits and the polyclonal sera evaluated in an in vitro inhibition of sporozoite invasion assay. The proteins were also used in immunoblots with sera from a limited number of donors immunized via the bites of P. falciparum infected irradiated mosquitoes and plasma and serum obtained from naturally exposed individuals in Kenya. Results Rabbit polyclonal antibodies targeting the non-repeat region of the basic domain of MB2 inhibited sporozoites entry into HepG2-A16 cells in vitro. Analysis of serum from five human volunteers that were immunized via the bites of P. falciparum infected irradiated mosquitoes that developed immunity and were completely protected against subsequent challenge with non-irradiated parasite also had detectable levels of antibody against MB2 basic domain. In contrast, in three volunteers not protected, anti-MB2 antibodies were below the level of detection. Sera from protected volunteers preferentially recognized a non-repeat region of the basic domain of MB2, whereas plasma from naturally-infected individuals also had antibodies that recognize regions of MB2 that contain a repeat motif in immunoblots. Sequence analysis of eleven field isolates and four laboratory strains showed that these antigenic regions of the basic domain of the MB2 gene are highly conserved in parasites obtained from different parts of the world. Moreover, anti-MB2 antibodies also were detected in the plasma of 83% of the individuals living in a malaria endemic area of Kenya (n = 41). Conclusion A preliminary analysis of the human humoral response against MB2 indicates that it may be an additional highly conserved target for immune intervention at the pre-erythrocytic stage of P. falciparum life cycle.

Background: People with multiple sclerosis (pwMS) treated with certain disease-modifying therapies (DMTs) have attenuated IgG response following COVID-19 vaccination; however, the clinical consequences remain unclear. Objective: To report COVID-19 rates in pwMS according to vaccine serology. Methods: PwMS with available (1) serology 2–12 weeks following COVID-19 vaccine 2 and/or vaccine 3 and (2) clinical data on COVID-19 infection/hospitalisation were included. Logistic regression was performed to examine whether seroconversion following vaccination predicted risk of subsequent COVID-19 infection after adjusting for potential confounders. Rates of severe COVID-19 (requiring hospitalisation) were also calculated. Results: A total of 647 pwMS were included (mean age 48 years, 500 (77%) female, median Expanded Disability Status Scale (EDSS) 3.5% and 524 (81%) exposed to DMT at the time of vaccine 1). Overall, 472 out of 588 (73%) were seropositive after vaccines 1 and 2 and 222 out of 305 (73%) after vaccine 3. Seronegative status after vaccine 2 was associated with significantly higher odds of subsequent COVID-19 infection (odds ratio (OR): 2.35, 95% confidence interval (CI): 1.34–4.12, p = 0.0029), whereas seronegative status after vaccine 3 was not (OR: 1.05, 95% CI: 0.57–1.91). Five people (0.8%) experienced severe COVID-19, all of whom were seronegative after most recent vaccination. Conclusion: Attenuated humoral response to initial COVID-19 vaccination predicts increased risk of COVID-19 in pwMS, but overall low rates of severe COVID-19 were seen. [ABSTRACT FROM AUTHOR]

Although there is an ever-increasing number of disease-modifying treatments for relapsing multiple sclerosis (MS), few appear to influence coronavirus disease 2019 (COVID-19) severity. There is concern about the use of anti-CD20-depleting monoclonal antibodies, due to the apparent increased risk of severe disease following severe acute respiratory syndrome corona virus two (SARS-CoV-2) infection and inhibition of protective anti-COVID-19 vaccine responses. These antibodies are given as maintenance infusions/injections and cause persistent depletion of CD20+ B cells, notably memory B-cell populations that may be instrumental in the control of relapsing MS. However, they also continuously deplete immature and mature/naïve B cells that form the precursors for infection-protective antibody responses, thus blunting vaccine responses. Seroconversion and maintained SARS-CoV-2 neutralizing antibody levels provide protection from COVID-19. However, it is evident that poor seroconversion occurs in the majority of individuals following initial and booster COVID-19 vaccinations, based on standard 6 monthly dosing intervals. Seroconversion may be optimized in the anti-CD20-treated population by vaccinating prior to treatment onset or using extended/delayed interval dosing (3–6 month extension to dosing interval) in those established on therapy, with B-cell monitoring until (1–3%) B-cell repopulation occurs prior to vaccination. Some people will take more than a year to replete and therefore protection may depend on either the vaccine-induced T-cell responses that typically occur or may require prophylactic, or rapid post-infection therapeutic, antibody or small-molecule antiviral treatment to optimize protection against COVID-19. Further studies are warranted to demonstrate the safety and efficacy of such approaches and whether or not immunity wanes prematurely as has been observed in the other populations. We review emerging evidence indicating that differential rates of B-cell subset repopulation following CD20-depleting antibody treatments can be exploited, to maintain control of autoimmunity whilst allowing SARS-CoV-2 vaccination-induced seroconversion. Extended-interval antibody dosing, supported by use of antiviral antibodies or small molecules may help optimize protection against severe COVID-19. [ABSTRACT FROM AUTHOR]

Objective: The purpose of this study was to investigate the effect of disease modifying therapies on immune response to severe acute respiratory syndrome‐coronavirus 2 (SARS‐CoV‐2) vaccines in people with multiple sclerosis (MS). Methods: Four hundred seventy‐three people with MS provided one or more dried blood spot samples. Information about coronavirus disease 2019 (COVID‐19) and vaccine history, medical, and drug history were extracted from questionnaires and medical records. Dried blood spots were eluted and tested for antibodies to SARS‐CoV‐2. Antibody titers were partitioned into tertiles with people on no disease modifying therapy as a reference. We calculated the odds ratio of seroconversion (univariate logistic regression) and compared quantitative vaccine response (Kruskal Wallis) following the SARS‐CoV‐2 vaccine according to disease modifying therapy. We used regression modeling to explore the effect of vaccine timing, treatment duration, age, vaccine type, and lymphocyte count on vaccine response. Results: Compared to no disease modifying therapy, the use of anti‐CD20 monoclonal antibodies (odds ratio = 0.03, 95% confidence interval [CI] = 0.01–0.06, p < 0.001) and fingolimod (odds ratio = 0.04; 95% CI = 0.01–0.12) were associated with lower seroconversion following the SARS‐CoV‐2 vaccine. All other drugs did not differ significantly from the untreated cohort. Both time since last anti‐CD20 treatment and total time on treatment were significantly associated with the response to the vaccination. The vaccine type significantly predicted seroconversion, but not in those on anti‐CD20 medications. Preliminary data on cellular T‐cell immunity showed 40% of seronegative subjects had measurable anti‐SARS‐CoV‐2 T cell responses. Interpretation: Some disease modifying therapies convey risk of attenuated serological response to SARS‐CoV‐2 vaccination in people with MS. We provide recommendations for the practical management of this patient group. ANN NEUROL 20219999:n/a–n/a [ABSTRACT FROM AUTHOR]

Multiple sclerosis is the major demyelinating autoimmune disease of the central nervous system. Relapsing MS can be treated by a number of approved monoclonal antibodies that currently target: CD20, CD25 (withdrawn), CD49d and CD52. These all target potentially pathogenic memory B cell subsets and perhaps functionally inhibit pathogenic T cell function. These consist of chimeric, humanized and fully human antibodies. However, despite humanization it is evident that all of these monoclonal antibodies can induce binding and neutralizing antibodies ranging from < 1% to over 80% within a year of treatment. Importantly, it is evident that monitoring these allow prediction of future treatment-failure in some individuals and treatment cessation and switching therefore potentially limiting disease breakthrough and disability accumulation. In response to the COVID-19 pandemic and the need to avoid hospitals, shortened infusion times and extended dose intervals have been implemented, importantly, subcutaneous delivery of alternative treatments or formulations have been developed to allow for home treatment. Therefore, hospital-based and remote monitoring of ADA could therefore be advantageous to optimize patient responses in the future. [ABSTRACT FROM AUTHOR]

PURPOSE OF THE REVIEW: Here we critically evaluate the literature on immunotherapy failure in inflammatory bowel disease patients. In particular anti-drug antibody production, and subsequently loss of response as the primary cause of immunotherapy failure in IBD patients. The benefits of shifting from the "standard" empirical dose escalation approach to therapeutic drug monitoring with anti-TNF α therapy is explored. RECENT FINDINGS: The American Gastroenterology Association and British Society of Gastroenterology both currently recommend the use of reactive therapeutic drug monitoring to guide treatment, following loss of response in inflammatory bowel disease patients with active disease. However, further research is required to prove the efficacy of a proactive therapeutic drug monitoring approach alone in remitted IBD patients. SUMMARY: A combination of personalised monitoring approach for anti-drug antibodies and therapeutic drug monitoring could provide beneficial treatment outcome for people with inflammatory bowel disease by predicting drug failure prior to clinical symptoms and allowing timely switching to an alternative drug. [ABSTRACT FROM AUTHOR]

The number of biologic drugs available for the treatment of psoriasis continue to expand. However, being biological proteins and thus potentially immunogenic, there is evidence that anti-drug-antibodies develop against the various therapeutic proteins currently being utilised. Although chimeric antibodies that contain elements of the parental rodent monoclonal antibodies are immunogenic, anti-drug antibodies occur even if the biologic is a fully human protein and these can impact on clinical efficacy and safety. However, there is a wide variation in the reported level of anti-drug-antibodies for the same and different treatments that is highlighting issues with various assays used in anti-drug antibody detection. Here we review the available data on the occurrence of anti-drug antibodies in people with psoriasis treated with biologic agents. [ABSTRACT FROM AUTHOR]

Abstract Background Antibody-fluorophore conjugates are invaluable reagents used in contemporary molecular cell biology for imaging, cell sorting and tracking intracellular events. However they suffer in some cases from batch to batch variation, partial loss of binding and susceptibility to photo-bleaching. In theory, these issues can all be addressed by using recombinant antibody fused directly to genetically encoded fluorescent reporters. However, single-chain fragment variable domains linked by long flexible linkers are themselves prone to disassociation and aggregation, and in some cases with isoelectric points incompatible with use in physiologically relevant milieu. Here we describe a general approach that permits fully functional intracellular production of a range of coloured fluorescent recombinant antibodies with optimally orientated VH/VL interfaces and isoelectric points compatible for use in physiological solutions at pH 7.4 with a binding site to fluorophore stoichiometry of 1:1. Results Here we report the design, assembly, intracellular bacterial production and purification of a panel of novel antibody fluorescent protein fusion constructs. The insertion of monomeric fluorescent protein derived from either Discosoma or Aequorea in-between the variable regions of anti-p185HER2-ECD antibody 4D5-8 resulted in optimal VH/VL interface interactions to create soluble coloured antibodies each with a single binding site, with isoelectric points of 6.5- 6. The fluorescent antibodies used in cell staining studies with SK-BR-3 cells retained the fluorophore properties and antibody specificity functions, whereas the conventional 4D5-8 single chain antibody with a (Gly4Ser)3 linker precipitated at physiological pH 7.4. Conclusions This modular monomeric recombinant fluorescent antibody platform may be used to create a range of recombinant coloured antibody molecules for quantitative in situ, in vivo and ex vivo imaging, cell sorting and cell trafficking studies. Assembling the single chain antibody with monomeric fluorescent protein linker facilitates optimal variable domain pairing and alters the isoelectric point of the recombinant 4D5-8 protein conferring solubility at physiological pH 7.4. The efficient intracellular expression of these functional molecules opens up the possibility of developing an alternative approach for tagging intracellular targets with fluorescent proteins for a range of molecular cell biology imaging studies.

Abstract Background MB2 protein is a sporozoite surface antigen on the human malaria parasite Plasmodium falciparum. MB2 was identified by screening a P. falciparum sporozoite cDNA expression library using immune sera from a protected donor immunized via the bites of P. falciparum-infected irradiated mosquitoes. It is not known whether natural exposure to P. falciparum also induces the anti-MB2 response and if this response differs from that in protected individuals immunized via the bites of P. falciparum infected irradiated mosquitoes. The anti-MB2 antibody response may be part of a robust protective response against the sporozoite. Methods Fragments of polypeptide regions of MB2 were constructed as recombinant fusions sandwiched between glutathione S-transferase and a hexa histidine tag for bacterial expression. The hexa histidine tag affinity purified proteins were used to immunize rabbits and the polyclonal sera evaluated in an in vitro inhibition of sporozoite invasion assay. The proteins were also used in immunoblots with sera from a limited number of donors immunized via the bites of P. falciparum infected irradiated mosquitoes and plasma and serum obtained from naturally exposed individuals in Kenya. Results Rabbit polyclonal antibodies targeting the non-repeat region of the basic domain of MB2 inhibited sporozoites entry into HepG2-A16 cells in vitro. Analysis of serum from five human volunteers that were immunized via the bites of P. falciparum infected irradiated mosquitoes that developed immunity and were completely protected against subsequent challenge with non-irradiated parasite also had detectable levels of antibody against MB2 basic domain. In contrast, in three volunteers not protected, anti-MB2 antibodies were below the level of detection. Sera from protected volunteers preferentially recognized a non-repeat region of the basic domain of MB2, whereas plasma from naturally-infected individuals also had antibodies that recognize regions of MB2 that contain a repeat motif in immunoblots. Sequence analysis of eleven field isolates and four laboratory strains showed that these antigenic regions of the basic domain of the MB2 gene are highly conserved in parasites obtained from different parts of the world. Moreover, anti-MB2 antibodies also were detected in the plasma of 83% of the individuals living in a malaria endemic area of Kenya (n = 41). Conclusion A preliminary analysis of the human humoral response against MB2 indicates that it may be an additional highly conserved target for immune intervention at the pre-erythrocytic stage of P. falciparum life cycle.

Abstract Background A rapid phage display method for the elucidation of cognate peptide specific ligand for receptors is described. The approach may be readily integrated into the interface of genomic and proteomic studies to identify biologically relevant ligands. Methods A gene fragment library from influenza coat protein haemagglutinin (HA) gene was constructed by treating HA cDNA with DNAse I to create 50 – 100 bp fragments. These fragments were cloned into plasmid pORFES IV and in-frame inserts were selected. These in-frame fragment inserts were subsequently cloned into a filamentous phage display vector JC-M13-88 for surface display as fusions to a synthetic copy of gene VIII. Two well characterized antibodies, mAb 12CA5 and pAb 07431, directed against distinct known regions of HA were used to pan the library. Results Two linear epitopes, HA peptide 112 – 126 and 162–173, recognized by mAb 12CA5 and pAb 07431, respectively, were identified as the cognate epitopes. Conclusion This approach is a useful alternative to conventional methods such as screening of overlapping synthetic peptide libraries or gene fragment expression libraries when searching for precise peptide protein interactions, and may be applied to functional proteomics.

Abstract Background The circumsporozoite surface protein is the primary target of human antibodies against Plasmodium falciparum sporozoites, these antibodies are predominantly directed to the major repetitive epitope (Asn-Pro-Asn-Ala)n, (NPNA)n. In individuals immunized by the bites of irradiated Anopheles mosquitoes carrying P. falciparum sporozoites in their salivary glands, the anti-repeat response dominates and is thought by many to play a role in protective immunity. Methods The antibody repertoire from a protected individual immunized by the bites of irradiated P. falciparum infected Anopheles stephensi was recapitulated in a phage display library. Following affinity based selection against (NPNA)3 antibody fragments that recognized the PfCSP repeat epitope were rescued. Results Analysis of selected antibody fragments implied the response was restricted to a single antibody fragment consisting of VH3 and VκI families for heavy and light chain respectively with moderate affinity for the ligand. Conclusion The dissection of the protective antibody response against the repeat epitope revealed that the response was apparently restricted to a single VH/VL pairing (PfNPNA-1). The affinity for the ligand was in the μM range. If anti-repeat antibodies are involved in the protective immunity elicited by exposure to radiation attenuated P. falciparum sporozoites, then high circulating levels of antibodies against the repeat region may be more important than intrinsic high affinity for protection. The ability to attain and sustain high levels of anti-(NPNA)n will be one of the key determinants of efficacy for a vaccine that relies upon anti-PfCSP repeat antibodies as the primary mechanism of protective immunity against P. falciparum.

Alemtuzumab is a lymphocyte-depleting antibody and one of the most effective treatments for relapsing multiple sclerosis. However, it also causes loss of immune-tolerance leading to secondary autoimmunity and marked anti-drug antibody responses. Although these anti-drug responses have been reported to be of no significance, we hypothesized that they will affect the depleting capacity and treatment response in some individuals. This was found following analysis of the regulatory submission of the pivotal phase III trials, which was obtained from the European Medicines Agency. At the population level there was lack of influence of 'ever-positive' alemtuzumab-specific antibody responses on lymphocyte depletion, clinical efficacy and adverse effects during the 2-year trial. This was not surprising as no one before the first infusion, and only 0.6% of people before the second-infusion, had pre-infusion, neutralizing antibodies (NAbs). However, at the individual level, NAbs led to poor lymphocyte depletion. Importantly, it was evident that 31% of people had NAbs and 75% had binding antibodies at the end of treatment-cycle 2, which suggests that problems may occur in people requiring additional alemtuzumab cycles. In addition, we also identified individuals, following 'post-marketing' alemtuzumab use, whose lymphocyte level was never effectively depleted after the first infusion cycle. Hence, although alemtuzumab depletes lymphocytes in most individuals, some people fail to deplete/deplete poorly, probably due to biological-response variation and NAbs, and this may lead to treatment failure. Monitoring depletion following infusion and assessment of the neutralizing response before reinfusion may help inform the decision to retreat or switch therapy to limit treatment failure. [ABSTRACT FROM AUTHOR]

• Treatment with fingolimod is not associated with a worse prognosis from COVID-19. • Fingolimod inhibits antibody and measureable T cell responses due to SARS-COV-2 vaccination. • Fingolimod seems to reduce seroconversion compared to other S1PR modulators. • Vaccine antibody responses are probably controlled by S1PR1, S1PR2 and S1PR4. • Fingolimod/ozanimod/ponesimod/siponimod should not limit current anti-viral agents.+. Sphingosine-one phosphate receptor (S1PR) modulation inhibits S1PR1-mediated lymphocyte migration, lesion formation and positively-impacts on active multiple sclerosis (MS). These S1PR modulatory drugs have different: European Union use restrictions, pharmacokinetics, metabolic profiles and S1PR receptor affinities that may impact MS-management. Importantly, these confer useful properties in dealing with COVID-19, anti-viral drug responses and generating SARS-CoV-2 vaccine responses. To examine the biology and emerging data that potentially underpins immunity to the SARS-CoV-2 virus following natural infection and vaccination and determine how this impinges on the use of current sphingosine-one-phosphate modulators used in the treatment of MS. A literature review was performed, and data on infection, vaccination responses; S1PR distribution and functional activity was extracted from regulatory and academic information within the public domain. Most COVID-19 related information relates to the use of fingolimod. This indicates that continuous S1PR1, S1PR3, S1PR4 and S1PR5 modulation is not associated with a worse prognosis following SARS-CoV-2 infection. Whilst fingolimod use is associated with blunted seroconversion and reduced peripheral T-cell vaccine responses, it appears that people on siponimod, ozanimod and ponesimod exhibit stronger vaccine-responses, which could be related notably to a limited impact on S1PR4 activity. Whilst it is thought that S1PR3 controls B cell function in addition to actions by S1PR1 and S1PR2, this may be species-related effect in rodents that is not yet substantiated in humans, as seen with bradycardia issues. Blunted antibody responses can be related to actions on B and T-cell subsets, germinal centre function and innate-immune biology. Although S1P1R-related functions are seeming central to control of MS and the generation of a fully functional vaccination response; the relative lack of influence on S1PR4-mediated actions on dendritic cells may increase the rate of vaccine-induced seroconversion with the newer generation of S1PR modulators and improve the risk-benefit balance Although fingolimod is a useful asset in controlling MS, recently-approved S1PR modulators may have beneficial biology related to pharmacokinetics, metabolism and more-restricted targeting that make it easier to generate infection-control and effective anti-viral responses to SARS-COV-2 and other pathogens. Further studies are warranted. [Display omitted] [ABSTRACT FROM AUTHOR]

• PwMS on certain DMTs have attenuated response to initial COVID-19 vaccination. • Booster vaccinations result in seroconversion in one third. • Almost half of pwMS on fingolimod seroconverted after a booster vaccine. • COVID-19 T-cell responses are often present in people on ocrelizumab. People with MS treated with anti-CD20 therapies and fingolimod often have attenuated responses to initial COVID-19 vaccination. However, uncertainties remain about the benefit of a 3rd (booster) COVID-19 vaccine in this group. PwMS without a detectable IgG response following COVID-19 vaccines 1&2 were invited to participate. Participants provided a dried blood spot +/- venous blood sample 2–12 weeks following COVID-19 vaccine 3. Humoral and T cell responses to SARS-CoV-2 spike protein and nucleocapsid antigen were measured. Of 81 participants, 79 provided a dried blood spot sample, of whom 38 also provided a whole blood sample; 2 provided only whole blood. Anti-SARS-CoV-2-spike IgG seroconversion post-COVID-19 vaccine 3 occurred in 26/79 (33%) participants; 26/40 (65%) had positive T-cell responses. Overall, 31/40 (78%) demonstrated either humoral or cellular immune response post-COVID-19 vaccine 3. There was no association between laboratory evidence of prior COVID-19 and seroconversion following vaccine 3. Approximately one third of pwMS who were seronegative after initial COVID-19 vaccination seroconverted after booster (third) vaccination, supporting the use of boosters in this group. Almost 8 out of 10 had a measurable immune response following 3rd COVID-19 vaccine. [ABSTRACT FROM AUTHOR]

What are effective antibodies and when do they arise to prevent or delay disease onset during a natural infection or in the course of vaccination? To address these questions at a molecular level requires longitudinal studies, capturing and analyzing the antibody repertoire at regular intervals following exposure or sero-conversion. Such studies require a method that allows the rapid generation and evaluation of monoclonal antibodies from relatively small volumes of blood. Here we describe an approach for rapidly generating human monoclonal antibodies in vitro by directly screening single-chain antibody repertories derived from donor peripheral blood mononuclear cells using ribosome display. Two single-chain antibody libraries were constructed using RNA extracted from peripheral blood mononuclear cells of two HIV-1 long-term non-progressor donors (K530 and M325). Both libraries were subjected to a single round of in vitro ribosome display for enrichment of human monoclonal antibodies against recombinant gp120^{K530}, derived from virus isolated from donor K530. This study has validated a novel, in vitro method for the rapid generation of human monoclonal antibodies. An antibody library could be constructed from as little as 3 μg of total RNA, the equivalent of 3-5 mL of human blood. [ABSTRACT FROM AUTHOR]

• Clinical trial data was interrogated to determine the frequency of 1–3% B cell repopulation over 12–18 months. • Few people repopulate after standard 6 monthly ocrelizumab dosing, but an extended dosing interval could allow many more people to repopulate B cells. • CD19+ B cells rapidly repopulated after cladribine and alemtuzumab treatment. Ocrelizumab maintains B-cell depletion via six-monthly dosing. Whilst this controls relapsing multiple sclerosis, it also inhibits seroconversion following SARS-CoV-2 vaccination unlike that seen following alemtuzumab and cladribine treatment. Emerging reports suggest that 1–3% B-cell repopulation facilitates seroconversion after CD20-depletion. To determine the frequency of B-cell repopulation levels during and after ocrelizumab treatment. Relapse data, lymphocyte and CD19 B-cell numbers were obtained following requests to clinical trial data-repositories. Information was extracted from the phase II ocrelizumab extension (NCT00676715) trial and the phase III cladribine tablet (NCT00213135) and alemtuzumab (NCT00530348/NCT00548405) trials obtained clinical trial data requests Only 3–5% of people with MS exhibit 1% B-cells at 6 months after the last infusion following 3–4 cycles of ocrelizumab, compared to 50–55% at 9 months, and 85–90% at 12 months. During this time relapses occurred at consistent disease-breakthrough rates compared to people during standard therapy. In contrast most people (90–100%) exhibited more than 1% B-cells during treatment with either cladribine or alemtuzumab. Most people demonstrate B cell repletion within 3 months of the last treatment of alemtuzumab and cladribine. However, few people repopulate peripheral B-cells with standard ocrelizumab dosing. Controlled studies are warranted to examine a view that delaying the dosing interval by 3–6 months may allow more people to potentially seroconvert after vaccination. [ABSTRACT FROM AUTHOR]

A panel of human anti-anthrax protective antigen IgG1 monoclonal antibodies were evaluated to determine the mechanism of toxin neutralization. AVP-22G12, AVP-1C6 and AVP-21D9 bound to the protective antigen with picomolar affinities to distinct non-overlapping linear epitopes. Two of the antibodies neutralized the anthrax toxin by completely inhibiting the protective antigen oligomer assembly process in vitro. [ABSTRACT FROM AUTHOR]

Background: The circumsporozoite surface protein is the primary target of human antibodies against Plasmodium falciparum sporozoites, these antibodies are predominantly directed to the major repetitive epitope (Asn-Pro-Asn-Ala)n, (NPNA)n. In individuals immunized by the bites of irradiated Anopheles mosquitoes carrying P. falciparum sporozoites in their salivary glands, the antirepeat response dominates and is thought by many to play a role in protective immunity. Methods: The antibody repertoire from a protected individual immunized by the bites of irradiated P. falciparum infected Anopheles stephensi was recapitulated in a phage display library. Following affinity based selection against (NPNA)3 antibody fragments that recognized the PfCSP repeat epitope were rescued. Results: Analysis of selected antibody fragments implied the response was restricted to a single antibody fragment consisting of VH3 and VκI families for heavy and light chain respectively with moderate affinity for the ligand. Conclusion: The dissection of the protective antibody response against the repeat epitope revealed that the response was apparently restricted to a single VH/VL pairing (PfNPNA-1). The affinity for the ligand was in the μM range. If anti-repeat antibodies are involved in the protective immunity elicited by exposure to radiation attenuated P. falciparum sporozoites, then high circulating levels of antibodies against the repeat region may be more important than intrinsic high affinity for protection. The ability to attain and sustain high levels of anti-(NPNA)n will be one of the key determinants of efficacy for a vaccine that relies upon anti-PfCSP repeat antibodies as the primary mechanism of protective immunity against P. falciparum. [ABSTRACT FROM AUTHOR]

• COVID-19 is a pandemic, sometimes fatal disease caused by the SARS-Cov-2 coronavirus. • Disease modifying treatments are a perceived risk factor for COVID-19. • Immunity eliminates the virus, but in some individuals it causes severe morbidity. • The essential immune elements to control MS and the virus may not be the same. • Understanding COVID-19 pathobiology and the mechanism of drug action in multiple sclerosis, will help inform choices for treatment SARS-CoV-2 viral infection causes COVID-19 that can result in severe acute respiratory distress syndrome (ARDS), which can cause significant mortality, leading to concern that immunosuppressive treatments for multiple sclerosis and other disorders have significant risks for both infection and ARDS. To examine the biology that potentially underpins immunity to the SARS-Cov-2 virus and the immunity-induced pathology related to COVID-19 and determine how this impinges on the use of current disease modifying treatments in multiple sclerosis. Although information about the mechanisms of immunity are scant, it appears that monocyte/macrophages and then CD8 T cells are important in eliminating the SARS-CoV-2 virus. This may be facilitated via anti-viral antibody responses that may prevent re-infection. However, viral escape and infection of leucocytes to promote lymphopenia, apparent CD8 T cell exhaustion coupled with a cytokine storm and vascular pathology appears to contribute to the damage in ARDS. In contrast to ablative haematopoietic stem cell therapy, most multiple-sclerosis-related disease modifying therapies do not particularly target the innate immune system and few have any major long-term impact on CD8 T cells to limit protection against COVID-19. In addition, few block the formation of immature B cells within lymphoid tissue that will provide antibody-mediated protection from (re)infection. However, adjustments to dosing schedules may help de-risk the chance of infection further and reduce the concerns of people with MS being treated during the COVID-19 pandemic. [ABSTRACT FROM AUTHOR]

Abstract: The parasite Trypanasoma cruzi is responsible for Chagas disease and its triatomine vector, Rhodnius prolixus, has a symbiotic relationship with the soil bacterium, Rhodococcus rhodnii. R. rhodnii that was previously genetically engineered to produce the anti-microbial peptide, cecropin A was co-infected with T. cruzi into R. prolixus resulting in clearance of the infectious T. cruzi in 65% of the vectors. Similar anti-microbial peptides have been isolated elsewhere and were studied for differential toxicity against T. cruzi and R. rhodnii. Of the six anti-microbial peptides tested, apidaecin, magainin II, melittin, and cecropin A were deemed potential candidates for the Chagas paratransgenic system as they were capable of killing T. cruzi at concentrations that exhibit little or no toxic effects on R. rhodnii. Subsequent treatments of T. cruzi with these peptides in pair-wise combinations resulted in synergistic killing, indicating that improvement of the 65% parasite clearance seen in previous experiments may be possible utilizing combinations of different anti-microbial peptides. [Copyright &y& Elsevier]

Pierce's disease is a devastating lethal disease of Vitus vinifera grapevines caused by the bacterium Xylella fastidiosa. There is no cure for Pierce's disease, and control is achieved predominantly by suppressing transmission of the glassy-winged sharpshooter insect vector. We present a simple robust approach for the generation of panels of recombinant single-chain antibodies against the surface-exposed elements of X. fastidiosa that may have potential use in diagnosis and/or disease transmission blocking studies. In vitro combinatorial antibody ribosome display libraries were assembled from immunoglobulin transcripts rescued from the spleens of mice immunized with heat-killed X. fastidiosa. The libraries were used in a single round of selection against an outer membrane protein, MopB, resulting in the isolation of a panel of recombinant antibodies. The potential use of selected anti-MopB antibodies was demonstrated by the successful application of the 4XfMopB3 antibody in an enzyme-linked immunosorbent assay (ELISA), a Western blot assay, and an immunofluorescence assay (IFA). These immortalized in vitro recombinant single-chain antibody libraries generated against heat-killed X. fastidiosa are a resource for the Pierce's disease research community that may be readily accessed for the isolation of antibodies against a plethora of X. fastidiosa surface-exposed antigenic molecules. [ABSTRACT FROM AUTHOR]

Abstract: We describe the facile generation of a stable recombinant antibody with intrinsic red fluorescent properties for qualitative and potentially quantitative immunofluorescence analysis. The REDantibody based on the X-ray crystallographic structures of the anti-sialyl-Tn antibody B72.3 and 3D model of the monomeric red fluorescent protein was designed to retain optimal spatial geometry between the C- and N-termini of the VH and VL chains respectively to mimic the domains interface pairing in antibody Fab fragments and to incorporate the red fluorescent protein as a bridging scaffold. The model was further validated by assembling a REDantibody based on CA19.9 the anti-sialylated Lewis (Le)a blood group antigen and 4D5-8 the anti-p185HER2 antibodies. The chimeric heavy and light chains containing red fluorescent protein as a bridge were correctly processed and secreted into Escherichia coli periplasm for assembly and disulphide bond formation, further analysis revealed the molecules to be exclusively monomers. Purified anti-glycan proteins were used for an immunofluorescent analysis of Trypanosoma cruzi epimastigotes, and the anti-p185HER2 used to determine the binding properties. The REDantibody platform facilitates rapid generation of scFv chimeras that could be used for screening antibodies against cell surface markers. Furthermore, such modular assembly should permit the interchange of binding sites and of fluorophores to create robust panels of coloured antibodies. [ABSTRACT FROM AUTHOR]

Background: Potent anthrax toxin neutralizing human monoclonal antibodies were generated from peripheral blood lymphocytes obtained from Anthrax Vaccine Adsorbed (AVA) immune donors. The anti-anthrax toxin human monoclonal antibodies were evaluated for neutralization of anthrax lethal toxin in vivo in the Fisher 344 rat bolus toxin challenge model. Methods: Human peripheral blood lymphocytes from AVA immunized donors were engrafted into severe combined immunodeficient (SCID) mice. Vaccination with anthrax protective antigen and lethal factor produced a significant increase in antigen specific human IgG in the mouse serum. The antibody producing lymphocytes were immortalized by hybridoma formation. The genes encoding the protective antibodies were rescued and stable cell lines expressing full-length human immunoglobulin were established. The antibodies were characterized by; (1) surface plasmon resonance; (2) inhibition of toxin in an in vitro mouse macrophage cell line protection assay and (3) in vivo in a Fischer 344 bolus lethal toxin challenge model. Results: The range of antibodies generated were diverse with evidence of extensive hyper mutation, and all were of very high affinity for PA83~ 1 × 10-10-11M. Moreover all the antibodies were potent inhibitors of anthrax lethal toxin in vitro. A single IV dose of AVP-21D9 or AVP-22G12 was found to confer full protection with as little as 0.5× (AVP-21D9) and 1× (AVP-22G12) molar equivalence relative to the anthrax toxin in the rat challenge prophylaxis model. Conclusion: Here we describe a powerful technology to capture the recall antibody response to AVA vaccination and provide detailed molecular characterization of the protective human monoclonal antibodies. AVP- 21D9, AVP-22G12 and AVP-1C6 protect rats from anthrax lethal toxin at low dose. Aglycosylated versions of the most potent antibodies are also protective in vivo, suggesting that lethal toxin neutralization is not Fc effector mediated. The protective effect of AVP-21D9 persists for at least one week in rats. These potent fully human anti-PA toxin-neutralizing antibodies are attractive candidates for prophylaxis and/or treatment against Anthrax Class A bioterrorism toxins. [ABSTRACT FROM AUTHOR]

Background: People with multiple sclerosis (pwMS) treated with certain disease-modifying therapies (DMTs) have attenuated IgG response following COVID-19 vaccination; however, the clinical consequences remain unclear., Objective: To report COVID-19 rates in pwMS according to vaccine serology., Methods: PwMS with available (1) serology 2-12 weeks following COVID-19 vaccine 2 and/or vaccine 3 and (2) clinical data on COVID-19 infection/hospitalisation were included. Logistic regression was performed to examine whether seroconversion following vaccination predicted risk of subsequent COVID-19 infection after adjusting for potential confounders. Rates of severe COVID-19 (requiring hospitalisation) were also calculated., Results: A total of 647 pwMS were included (mean age 48 years, 500 (77%) female, median Expanded Disability Status Scale (EDSS) 3.5% and 524 (81%) exposed to DMT at the time of vaccine 1). Overall, 472 out of 588 (73%) were seropositive after vaccines 1 and 2 and 222 out of 305 (73%) after vaccine 3. Seronegative status after vaccine 2 was associated with significantly higher odds of subsequent COVID-19 infection (odds ratio (OR): 2.35, 95% confidence interval (CI): 1.34-4.12, p  = 0.0029), whereas seronegative status after vaccine 3 was not (OR: 1.05, 95% CI: 0.57-1.91). Five people (0.8%) experienced severe COVID-19, all of whom were seronegative after most recent vaccination., Conclusion: Attenuated humoral response to initial COVID-19 vaccination predicts increased risk of COVID-19 in pwMS, but overall low rates of severe COVID-19 were seen.

Aim: The humanized anti-CD52 monoclonal antibody alemtuzumab depletes lymphocytes and is currently used to treat relapsing multiple sclerosis. During treatment, anti-alemtuzumab antibodies may develop and reduce effective lymphocyte depletion in future treatment cycles. Results: Alemtuzumab-Alexa Fluor 488 conjugate binding to the CHO-CD52 cell surface was inhibited by anti-alemtuzumab antibodies. Conclusion: In this proof-of-concept study, a CHO-CD52 cell line has been developed and used to detect the presence of anti-alemtuzumab neutralizing antibodies. This platform provides the basis of an assay for routine screening of serum for neutralizing antibodies from patients treated with alemtuzumab.

Alemtuzumab was designed to reduce the immunogenicity of the parent CD52-specific rat immunoglobulin. Although originally marketed for use in cancer (Mabcampath®), alemtuzumab is currently licensed and formulated for the treatment of relapsing multiple sclerosis (Lemtrada®). Perhaps due to its history as the first humanized antibody, the potential of immunogenicity of the molecule has been considered inconsequential, and anti-drug antibodies (ADA) responses were similarly reported as being clinically insignificant. Nonetheless, despite humanization and depletion of peripheral T and B cells, alemtuzumab probably generates the highest frequency of binding and neutralizing ADA of all humanized antibodies currently in clinical use, and they occur rapidly in a large majority of people with MS (pwMS) on alemtuzumab treatment. These ADA appear to be an inherent issue of the biology of the molecule-and more importantly, the target-such that avoidance of immunogenicity-related effects has been facilitated by the dosing schedule used in clinical practice. At the population level this enables the drug to work in most pwMS, but in some individuals, as we show here, antibody neutralization appears to be sufficiently severe to reduce efficacy and allow disease breakthrough. It is therefore imperative that efficacy of lymphocyte depletion and the anti-drug response is monitored in people requiring additional cycles of treatment, notably following disease breakthrough. This may help inform whether to re-treat or to switch to another disease-modifying treatment., (Copyright © 2020 Baker, Ali, Saxena, Pryce, Jones, Schmierer, Giovannoni, Gnanapavan, Munger, Samkoff, Goodman and Kang.)

Prevention of inhalation anthrax requires early and extended antibiotic therapy, and therefore, alternative treatment strategies are needed. We investigated whether a human monoclonal antibody (AVP-21D9) to protective antigen (PA) would protect mice, guinea pigs, and rabbits against anthrax. Control animals challenged with Bacillus anthracis Ames spores by the intranasal route died within 3 to 7 days. AVP-21D9 alone provided minimal protection against anthrax in the murine model, but its efficacy was notably better in guinea pigs. When Swiss-Webster mice, challenged with five 50% lethal doses (LD50s) of anthrax spores, were given a single 16.7-mg/kg of body weight AVP-21D9 antibody dose combined with ciprofloxacin (30 mg/kg/day for 6 days) 24 h after challenge, 100% of the mice were protected for more than 30 days, while ciprofloxacin or AVP-21D9 alone showed minimal protection. Similarly, when AVP-21D9 antibody (10 to 50 mg/kg) was combined with a low, nonprotective dose of ciprofloxacin (3.7 mg/kg/day) and administered to guinea pigs for 6 days, synergistic protection against anthrax was observed. In contrast, a single dose of AVP-21D9 antibody (1, 5, 10, or 20 mg/kg) but not 0.2 mg/kg alone completely protected rabbits against challenge with 100 LD50s of B. anthracis Ames spores, and 100% of the rabbits survived rechallenge. Further, administration of AVP-21D9 (10 mg/kg) to rabbits at 0, 6, and 12 h after challenge with anthrax spores resulted in 100% survival; however, delay of antibody treatment by 24 and 48 h reduced survival to 80% and 60%, respectively. Serological analysis of sera from various surviving animals 30 days postprimary infection showed development of a species-specific PA enzyme-linked immunosorbent assay antibody titer that correlated with protection against reinfection. Taken together, the effectiveness of human anti-PA antibody alone or in combination with low ciprofloxacin levels may provide the basis for an improved strategy for prophylaxis or treatment following inhalation anthrax infection.

Malaria is one of the world's most devastating diseases, and Plasmodium falciparum (Pf) causes significant mortalities particularly in Sub-Saharan Africa. The rise and spread of multi-drug resistant strains of the parasite has coincided with an era of increased travel to malaria endemic regions. In the absence of an effective vaccine against malaria it may be possible to utilize human monoclonal antibodies against the stage transmitted by mosquito bites (sporozoites) as a prophylactic to prevent infection. We report the characterization of an engineered human IgG(4) monoclonal antibody against Pf sporozoite cloned from a protected individual recognized the sporozoite surface and inhibited sporozoite invasion of human hepatocytes in vitro. The fully human monoclonal antibody PfNPNA-1 IgG(4) against (NPNA)(3) specifically labels Plasmodium falciparum in an IFA. This antibody also inhibits Plasmodium falciparum sporozoite invasion of human hepatocytes HepG2-A16 in a dose dependent manner in an in vitro assay. PfNPNA-1 IgG(4) is a promising candidate for evaluation for the prevention of malaria.

A panel of human anti-anthrax protective antigen IgG1 monoclonal antibodies were evaluated to determine the mechanism of toxin neutralization. AVP-22G12, AVP-1C6 and AVP-21D9 bound to the protective antigen with picomolar affinities to distinct non-overlapping linear epitopes. Two of the antibodies neutralized the anthrax toxin by completely inhibiting the protective antigen oligomer assembly process in vitro.