Analysis of 52 240 source plasma donors of convalescent COVID-19 plasma: Sex, ethnicity, and age association with initial antibody levels and rate of dissipation.

BACKGROUND: COVID-19 convalescent plasma (CCP) was approved under emergency authorization to treat critically ill patients with COVID-19 in the United States in 2020. We explored the demographics of donors contributing plasma for a hyperimmune, plasma-derived therapy to evaluate factors that may be associated with anti-SARS-CoV-2 antibody response variability and, subsequently, antibody titers. STUDY DESIGN: An electronic search of CCP donors was performed across 282 US plasma donation centers. Donations were screened for nucleocapsid protein-binding-IgG using the Abbott SARS-CoV-2 IgG assay. RESULTS: Overall, 52 240 donors donated 418 046 units of CCP. Donors were of various ethnicities: 43% Caucasian, 34% Hispanic, 17% African American, 2% Native American, 1% Asian, and 3% other. Females had higher initial mean anti-SARS-CoV-2 antibody titers but an overall faster rate of decline (P < .0001). Initial antibody titers increased with age: individuals aged 55 to 66 years had elevated anti-SARS-CoV-2 titers for longer periods compared with other ages (P = .0004). African American donors had the lowest initial antibody titers but a slower rate of decline (P < .0001), while Caucasian (P = .0088) and Hispanic (P = .0193) groups had the fastest rates of decline. Most donor antibody levels decreased below the inclusion criteria (≥1.50) within 30 to 100 days of first donation, but donation frequency did not appear to be associated with rate of decline. CONCLUSION: Several factors may be associated with anti-SARS-CoV-2 antibody response including donor age and sex. Evaluating these factors during development of future hyperimmune globulin products may help generation of therapies with optimal efficacy.

Hepatitis A Virus Incidence Rates and Biomarker Dynamics for Plasma Donors, United States.

The United States is currently affected by widespread hepatitis A virus (HAV) outbreaks. We investigated HAV incidence rates among source plasma donors in the United States since 2016. Serial donations from HAV-positive frequent donors were analyzed for common biologic markers to obtain a detailed picture of the course of infection. We found a considerable increase in incidence rates with shifting outbreak hotspots over time. Although individual biomarker profiles were highly variable, HAV RNA typically had a high peak and a biphasic decrease and often remained detectable for several months. One donor had a biomarker pattern indicative of previous exposure. Our findings show that current HAV outbreaks have been spilling over into the plasma donor population. The detailed results presented improve our comprehension of HAV infection and related public health aspects. In addition, the capture of full RNA curves enables estimation of HAV doubling time.

Determination of neutralising anti-SARS-CoV-2 antibody half-life in COVID-19 convalescent donors.

Despite the burgeoning field of coronavirus disease-19 (COVID-19) research, the persistence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) neutralising antibodies remains unclear. This study validated two high-throughput immunological methods for use as surrogate live virus neutralisation assays and employed them to examine the half-life of SARS-CoV-2 neutralising antibodies in convalescent plasma donations made by 42 repeat donors between April and September 2020. SARS-CoV-2 neutralising antibody titres decreased over time but typically remained above the methods' diagnostic cut-offs. Using this longitudinal data, the average half-life of SARS-CoV-2 neutralising antibodies was determined to be 20.4 days. SARS-CoV-2 neutralising antibody titres appear to persist in the majority of donors for several months. Whether these titres confer protection against re-infection requires further study and is of particular relevance as COVID-19 vaccines become widely available.

Hepatitis E virus: Efficacy of pasteurization of plasma-derived VWF/FVIII concentrate determined by pig bioassay.

BACKGROUND: Hepatitis E virus (HEV) is the leading cause of acute hepatitis throughout the world. Increasing blood component transfusion-associated HEV infections highlight the need for reliable virus inactivation procedures for plasma derivatives from pooled plasma donations. STUDY DESIGN AND METHODS: An animal infection study was conducted to evaluate the efficiency of HEV inactivation by pasteurization during the manufacturing process of the von Willebrand Factor/Factor VIII (VWF/FVIII) concentrate Haemate P/Humate-P (CSL Behring, Marburg, Germany). For this purpose, groups of pigs were inoculated with stabilized VWF/FVIII intermediate spiked with HEV-positive liver homogenate and exposed to increasing incubation times of 0, 3, 6, and 10 h at 60°C. Animals were evaluated for virus replication over 27 days and in a subsequent trial over 92 days. RESULTS: Virus replication was detected in animals up to the 6-h pasteurization group. In contrast, pasteurization for 10 h did not reveal virus detection when the observation period was 27 days. In an additional experiment using the 10-h pasteurized material, two individuals started virus excretion and seroconverted when the observation period was extended to 92 days. Based on the total infection rate (2 of 12) of the animals inoculated with the sample pasteurized for 10 h, a virus reduction factor of at least 4.7 log10 is calculated. CONCLUSION: This study demonstrates that pasteurization at 60°C for 10 h of an HEV-positive plasma derivative leads to the effective reduction of infectivity, resulting in a VWF/FVIII product with an appropriate margin of safety for HEV.

Impact of the isoelectric point of model parvoviruses on viral retention in anion-exchange chromatography.

Anion-exchange chromatography (AEX) is used in the downstream purification of monoclonal antibodies to remove impurities and potential viral contamination based on electrostatic interactions. Although the isoelectric point (pI) of viruses is considered a key factor predicting the virus adsorption to the resin, the precise molecular mechanisms involved remain unclear. To address this question, we compared structurally homologous parvoviruses that only differ in their surface charge distribution. A single charged amino acid substitution on the capsid surface of minute virus of mice (MVM) provoked an increased apparent pI (pIapp ) 6.2 compared to wild-type MVM (pIapp = 4.5), as determined by chromatofocusing. Despite their radically different pIapp , both viruses displayed the same interaction profile in Mono Q AEX at different pH conditions. In contrast, the closely related canine parvovirus (pIapp = 5.3) displayed a significantly different interaction at pH 5. The detailed structural analysis of the intricate three-dimensional structure of the capsids suggests that the charge distribution is critical, and more relevant than the pI, in controlling the interaction of a virus with the chromatographic resin. This study contributes to a better understanding of the molecular mechanisms governing virus clearance by AEX, which is crucial to enable robust process design and maximize safety.

Nanofiltration as a robust method contributing to viral safety of plasma-derived therapeutics: 20 years' experience of the plasma protein manufacturers.

BACKGROUND: Nanofiltration entails the filtering of protein solutions through membranes with pores of nanometric sizes that have the capability to effectively retain a wide range of viruses. STUDY DESIGN AND METHODS: Data were collected from 754 virus validation studies (individual data points) by Plasma Protein Therapeutics Association member companies and analyzed for the capacity of a range of nanofilters to remove viruses with different physicochemical properties and sizes. Different plasma product intermediates were spiked with viruses and filtered through nanofilters with different pore sizes using either tangential or dead-end mode under constant pressure or constant flow. Filtration was performed according to validated scaled-down laboratory conditions reflecting manufacturing processes. Effectiveness of viral removal was assessed using cell culture infectivity assays or polymerase chain reaction (PCR). RESULTS: The nanofiltration process demonstrated a high efficacy and robustness for virus removal. The main factors affecting nanofiltration efficacy are nanofilter pore size and virus size. The capacity of nanofilters to remove smaller, nonenveloped viruses was dependent on filter pore size and whether the nanofiltration process was integrated and designed with the intention to provide effective parvovirus retention. Volume filtered, operating pressure, and total protein concentration did not have a significant impact on the effectiveness of virus removal capacity within the investigated ranges. CONCLUSIONS: The largest and most diverse nanofiltration data collection to date substantiates the effectiveness and robustness of nanofiltration in virus removal under manufacturing conditions of different plasma-derived proteins. Nanofiltration can enhance product safety by providing very high removal capacity of viruses including small non-enveloped viruses.

Manufacturing of plasma-derived C1-inhibitor concentrate for treatment of patients with hereditary angioedema.

Background: Replacement therapy with plasma-derived C1-inhibitor (C1-INH) has been used for decades to treat patients with hereditary angioedema (HAE) with C1-INH deficiency. Objective: This article reviewed the rationale for using C1-INH replacement therapy in patients with HAE and the process of manufacturing plasma-derived C1-INH. Methods: The manufacture of C1-INH is an involved and carefully monitored process that includes screening and selection of prospective donors, the collection of source plasma, and purification with dedicated pathogen reduction steps. Donor eligibility is determined by restrictive criteria established and monitored by regulatory agencies as well as voluntary standards implemented by plasma collection centers that exceed government regulations. Individual and pooled donations are tested for transfusion-transmissible infections, including hepatitis B virus, hepatitis C virus, human immunodeficiency virus, parvovirus B19, and hepatitis A virus, by using enzyme-linked immunosorbent assays or nucleic acid amplification technologies. Frozen plasma that is cleared for manufacturing undergoes controlled thawing and centrifugation, and the resulting supernatant (i.e., cryoprecipitate-depleted plasma) is used to manufacture several plasma-derived therapies, including C1-INH. In addition to chromatography steps, the manufacturing process consists of dedicated and effective pathogen reduction steps, including pasteurization, hydrophobic interaction chromatography or polyethylene glycol precipitation, and virus filtration. Manufacturers continuously monitor the safety profile of C1-INH products by robust pharmacovigilance processes that enable systematic collection and evaluation of all suspected adverse drug reaction reports as well as evaluation of safety information from all other sources. Results and Conclusion: These procedures used in donor screening, donation and manufacturing pool testing, manufacturing, and pharmacovigilance ensure that plasma-derived C1-INH products have the safety, quality, identity, potency, and purity that is necessary to provide the intended therapeutic effect.

Choice of parvovirus model for validation studies influences the interpretation of the effectiveness of a virus filtration step.

Different parvoviruses are used interchangeably as models in validation studies to demonstrate effective clearance of small viruses by filtration in the manufacturing of biotherapeutics. The aim of these experiments was to determine if filtration of different parvoviruses (canine parvovirus [CPV], minute virus of mice [MVM], and porcine parvovirus [PPV]) results in similar virus retention. While filtration with a Planova™ 20 N filter (mean pore size: 19 ±â€¯2 nm) completely removed PPV and MVM from the filtrate (mean log reduction factors [LRFs] ≥5.8 to ≥7.3 log10), CPV was only partly retained (3.6 log10) in a series of single and co-spike experiments. Additional co-spike experiments in 2 different feedstreams using 10 commercially available small pore filters confirmed these results; the LRF for CPV was around 2 log10 lower than for MVM and PPV. A sizing study using filters with mean pore sizes between 16.5 and 19 nm resulted in complete removal of CPV only with smaller pore sizes (17 and 16.5 nm). CPV behaves differently to MVM and PPV in viral filtration due to its apparent smaller size, suggesting CPV represents a worst-case model for other parvoviruses. Interpretation of efficacy and robustness of virus filtration thus depends on the choice of model virus.

Effective inactivation of a wide range of viruses by pasteurization.

BACKGROUND: Careful selection and testing of plasma reduces the risk of blood-borne viruses in the starting material for plasma-derived products. Furthermore, effective measures such as pasteurization at 60°C for 10 hours have been implemented in the manufacturing process of therapeutic plasma proteins such as human albumin, coagulation factors, immunoglobulins, and enzyme inhibitors to inactivate blood-borne viruses of concern. A comprehensive compilation of the virus reduction capacity of pasteurization is presented including the effect of stabilizers used to protect the therapeutic protein from modifications during heat treatment. STUDY DESIGN AND METHODS: The virus inactivation kinetics of pasteurization for a broad range of viruses were evaluated in the relevant intermediates from more than 15 different plasma manufacturing processes. Studies were carried out under the routine manufacturing target variables, such as temperature and product-specific stabilizer composition. Additional studies were also performed under robustness conditions, that is, outside production specifications. RESULTS: The data demonstrate that pasteurization inactivates a wide range of enveloped and nonenveloped viruses of diverse physicochemical characteristics. After a maximum of 6 hours' incubation, no residual infectivity could be detected for the majority of enveloped viruses. Effective inactivation of a range of nonenveloped viruses, with the exception of nonhuman parvoviruses, was documented. CONCLUSION: Pasteurization is a very robust and reliable virus inactivation method with a broad effectiveness against known blood-borne pathogens and emerging or potentially emerging viruses. Pasteurization has proven itself to be a highly effective step, in combination with other complementary safety measures, toward assuring the virus safety of final product.

Pathogen safety of a pasteurized four-factor human prothrombin complex concentrate preparation using serial 20N virus filtration.

BACKGROUND: Beriplex P/N/Kcentra/Coaplex/Confidex is a four-factor human prothrombin complex concentrate (PCC). Here, we describe the pathogen safety profile and biochemical characteristics of an improved manufacturing process that further enhances the virus safety of Beriplex P/N. STUDY DESIGN AND METHODS: Samples of product intermediates were spiked with test viruses, and prions were evaluated under routine production and robustness conditions of the scale-down version of the commercial manufacturing process for their capacity to inactivate or remove pathogens. The PCC was characterized by determining the activity of Factor (F)II, FVII, FIX, FX, protein C, and protein S and the concentration of heparin and antithrombin III in nine product lots. RESULTS: The manufacturing process had a very high virus reduction capacity for a broad variety of virus challenges (overall reduction factors ≥15.5 to ≥18.4 log for enveloped viruses and 11.5 to ≥11.9 log for nonenveloped viruses). The high virus clearance capacity was provided by two dedicated virus reduction steps (pasteurization and serial 20N virus filtration) that provided effective inactivation and removal of viruses and a purification step (ammonium sulfate precipitation and adsorption to calcium phosphate) that contributed to the overall virus removal capacity. The diethylaminoethyl (DEAE) chromatography and ammonium sulfate precipitation steps removed prions to below the limit of detection. The levels of different clotting factors in the final product were well balanced. CONCLUSION: The improved manufacturing process of Beriplex P/N further enhances the margin of pathogen safety based on its capacity to remove and inactivate a wide range of virus challenges.

Low hepatitis E virus RNA prevalence in a large-scale survey of United States source plasma donors.

BACKGROUND: Hepatitis E virus (HEV) is a small, nonenveloped, single-stranded, RNA virus of emerging concern in industrialized countries. HEV transmission through transfusion of blood components has been reported, but not via plasma-derived medicinal products (PDMPs) manufactured with virus inactivation and/or removal steps. This study aimed to determine the prevalence of HEV among US source plasma donors. STUDY DESIGN AND METHODS: Samples were collected from US source plasma donors at centers across the United States and were initially screened for HEV RNA in 96-sample minipools using the Roche cobas HEV test on the cobas 8800 system. Assuming a sensitivity of 18.6 IU/mL, the minipool screening strategy allowed for reliable detection of individual donations with HEV RNA titers of more than 2 × 103 IU/mL. Reactive minipools were resolved to individual donations, which were further analyzed to quantify viral RNA concentration, determine HEV genotype, and immunoglobulin (Ig)G and IgM HEV antibody status. RESULTS: A total of 128,020 samples were collected from 96 CSL Plasma centers in the United States, representing 27 states. The prevalence of HEV RNA-positive samples was 0.002% with three unique HEV-positive donors identified, all HEV Subgenotype 3a. Virus titers of HEV-positive samples were relatively low (103 -104 IU HEV RNA/mL). One positive donation was HEV IgG seropositive. CONCLUSION: Routine screening of US source plasma donations for HEV would not substantially improve the safety of most PDMPs. The low prevalence and potential viral load of HEV, together with effective virus reduction steps in manufacturing processes, results in a low residual risk and acceptable safety margins for PDMPs derived from US plasma donors.

Pathogen safety and characterisation of a highly purified human alpha1-proteinase inhibitor preparation.

Alpha1-proteinase inhibitor (A1PI) deficiency is a genetic condition predisposing to emphysema. Respreeza/Zemaira, a therapeutic preparation of A1PI, is prepared from human plasma. This article describes the purity and stability of Respreeza/Zemaira and the capacity of virus and prion reduction steps incorporated into its manufacturing process. Purity and stability of Respreeza/Zemaira were analysed using established methods. To test pathogen clearance capacity, high levels of test viruses/prions were spiked into aliquots of production intermediates and clearance studies were performed for selected manufacturing steps, under production and robustness conditions, using validated scale-down models. Respreeza/Zemaira had a purity of 99% A1PI and consisted of 96% monomers. It remained stable after storage for 3 years at 25 °C. Specific activity was 0.895 mg active A1PI/mg protein. Pasteurisation inactivated enveloped viruses and the non-enveloped hepatitis A virus. 20 N/20 N virus filtration was highly effective and robust at removing all tested viruses, including parvoviruses, to below the limit of detection. Cold ethanol fractionation provided substantial reduction of prions. The manufacturing process of Respreeza/Zemaira ensures the production of a stable and pure product. Taking into consideration the donor selection process, the testing of donations, and the highly effective virus and prion reduction, Respreeza/Zemaira has a high safety margin.

Therapeutic Angiogenesis by Ultrasound-Mediated MicroRNA-126-3p Delivery.

OBJECTIVE: MicroRNAs are involved in many critical functions, including angiogenesis. Ultrasound-targeted microbubble destruction (UTMD) is a noninvasive technique for targeted vascular transfection of plasmid DNA and may be well suited for proangiogenic microRNA delivery. We aimed to investigate UTMD of miR-126-3p for therapeutic angiogenesis in chronic ischemia. APPROACH AND RESULTS: The angiogenic potential of miR-126-3p was tested in human umbilical vein endothelial cells in vitro. UTMD of miR-126-3p was tested in vivo in Fischer-344 rats before and after chronic left femoral artery ligation, evaluating target knockdown, miR-126-3p and miR-126-5p expression, phosphorylated Tie2 levels, microvascular perfusion, and vessel density. In vitro, miR-126-3p-transfected human umbilical vein endothelial cells showed repression of sprouty-related protein-1 and phosphatidylinositol-3-kinase regulatory subunit 2, negative regulators of vascular endothelial growth factor and angiopoietin-1 signaling, increased phosphorylated Tie2 mediated by knockdown of phosphatidylinositol-3-kinase regulatory subunit 2 and greater angiogenic potential mediated by both vascular endothelial growth factor/vascular endothelial growth factor R2 and angiopoietin-1 /Tie2 effects. UTMD of miR-126-3p resulted in targeted vascular transfection, peaking early after delivery and lasting for >3 days, and resulting in inhibition of sprouty-related protein-1 and phosphatidylinositol-3-kinase regulatory subunit 2, with minimal uptake in remote organs. Finally, UTMD of miR-126-3p to chronic ischemic hindlimb muscle resulted in improved perfusion, vessel density, enhanced arteriolar formation, pericyte coverage, and phosphorylated Tie2 levels, without affecting miR-126-5p or delta-like 1 homolog levels. CONCLUSIONS: UTMD of miR-126 results in improved tissue perfusion and vascular density in the setting of chronic ischemia by repressing sprouty-related protein-1 and phosphatidylinositol-3-kinase regulatory subunit 2 and enhancing vascular endothelial growth factor and angiopoietin-1 signaling, with no effect on miR-126-5p. UTMD is a promising platform for microRNA delivery, with applications for therapeutic angiogenesis.

Characterization of Thrombate III®, a pasteurized and nanofiltered therapeutic human antithrombin concentrate.

Thrombate III(®) is a highly purified antithrombin concentrate that has been used by clinicians worldwide for more than two decades for the treatment of hereditary antithrombin deficiency. The manufacturing process is based on heparin-affinity chromatography and pasteurization. To modernize the process and to further enhance the pathogen safety profile of the final product, despite the absence of infectious disease transmission, a nanofiltration step was added. The biochemical characterization and pathogen safety evaluation of Thrombate III(®) manufactured using the modernized process are presented. Bioanalytical data demonstrate that the incorporation of nanofiltration has no impact on the antithrombin content, potency, and purity of the product. Scaledown models of the manufacturing process were used to assess virus and prion clearance under manufacturing setpoint conditions. Additionally, robustness of virus clearance was evaluated at or slightly outside the manufacturing operating limits. The results demonstrate that pasteurization inactivated both enveloped and non-enveloped viruses. The addition of nanofiltration substantially increased clearance capacities for both enveloped and non-enveloped viruses by approximately 4-6 log10. In addition, the process achieves 6.0 log10 ID50 prion infectivity clearance. Thus, the introduction of nanofiltration increased the pathogen safety margin of the manufacturing process without impacting the key biochemical characteristics of the product.

Robustness of nanofiltration for increasing the viral safety margin of biological products.

In this study, the virus-removal capacity of nanofiltration was assessed using validated laboratory scale models on a wide range of viruses (pseudorabies virus; human immunodeficiency virus; bovine viral diarrhea virus; West Nile virus; hepatitis A virus; murine encephalomyocarditis virus; and porcine parvovirus) with sizes from 18 nm to 200 nm and applying the different process conditions existing in a number of Grifols' plasma-derived manufacturing processes (thrombin, α1-proteinase inhibitor, Factor IX, antithrombin, plasmin, intravenous immunoglobulin, and fibrinogen). Spiking experiments (n = 133) were performed in process intermediate products, and removal was subsequently determined by infectivity titration. Reduction Factor (RF) was calculated by comparing the virus load before and after nanofiltration under each product purification condition. In all experiments, the RFs were close to or greater than 4 log10 (>99.99% of virus elimination). RF values were not significantly affected by the process conditions within the limits assayed (pH, ionic strength, temperature, filtration ratio, and protein concentration). The virus-removal capacity of nanofiltration correlated only with the size of the removed agent. In conclusion, nanofiltration, as used in the manufacturing of several Grifols' products, is consistent, robust, and not significantly affected by process conditions.

Prion removal capacity of plasma protein manufacturing processes: a data collection from PPTA member companies.

BACKGROUND: The variant Creutzfeldt-Jakob disease incidence peaked a decade ago and has since declined. Based on epidemiologic evidence, the causative agent, pathogenic prion, has not constituted a tangible contamination threat to large-scale manufacturing of human plasma-derived proteins. Nonetheless, manufacturers have studied the prion removal capabilities of various manufacturing steps to better understand product safety. Collectively analyzing the results could reveal experimental reproducibility and detect trends and mechanisms driving prion removal. STUDY DESIGN AND METHODS: Plasma Protein Therapeutics Association member companies collected more than 200 prion removal studies on plasma protein manufacturing steps, including precipitation, adsorption, chromatography, and filtration, as well as combined steps. The studies used a range of model spiking agents and bench-scale process replicas. The results were grouped based on key manufacturing variables to identify factors impacting removal. The log reduction values of a group are presented for comparison. RESULTS: Overall prion removal capacities evaluated by independent groups were in good agreement. The removal capacity evaluated using biochemical assays was consistent with prion infectivity removal measured by animal bioassays. Similar reduction values were observed for a given step using various spiking agents, except highly purified prion protein in some circumstances. Comparison between combined and single-step studies revealed complementary or overlapping removal mechanisms. Steps with high removal capacities represent the conditions where the physiochemical differences between prions and therapeutic proteins are most significant. CONCLUSION: The results support the intrinsic ability of certain plasma protein manufacturing steps to remove prions in case of an unlikely contamination, providing a safeguard to products.

Emergence and antibody evasion of BQ, BA.2.75 and SARS-CoV-2 recombinant sub-lineages in the face of maturing antibody breadth at the population level.

BACKGROUND: The Omicron era of the COVID-19 pandemic commenced at the beginning of 2022 and whilst it started with primarily BA.1, it was latter dominated by BA.2 and the related sub-lineage BA.5. Following resolution of the global BA.5 wave, a diverse grouping of Omicron sub-lineages emerged derived from BA.2, BA.5 and recombinants thereof. Whilst emerging from distinct lineages, all shared similar changes in the Spike glycoprotein affording them an outgrowth advantage through evasion of neutralising antibodies. METHODS: Over the course of 2022, we monitored the potency and breadth of antibody neutralization responses to many emerging variants in the Australian community at three levels: (i) we tracked over 420,000 U.S. plasma donors over time through various vaccine booster roll outs and Omicron waves using sequentially collected IgG pools; (ii) we mapped the antibody response in individuals using blood from stringently curated vaccine and convalescent cohorts. (iii) finally we determine the in vitro efficacy of clinically approved therapies Evusheld and Sotrovimab. FINDINGS: In pooled IgG samples, we observed the maturation of neutralization breadth to Omicron variants over time through continuing vaccine and infection waves. Importantly, in many cases, we observed increased antibody breadth to variants that were yet to be in circulation. Determination of viral neutralization at the cohort level supported equivalent coverage across prior and emerging variants with isolates BQ.1.1, XBB.1, BR.2.1 and XBF the most evasive. Further, these emerging variants were resistant to Evusheld, whilst increasing neutralization resistance to Sotrovimab was restricted to BQ.1.1 and XBF. We conclude at this current point in time that dominant variants can evade antibodies at levels equivalent to their most evasive lineage counterparts but sustain an entry phenotype that continues to promote an additional outgrowth advantage. In Australia, BR.2.1 and XBF share this phenotype and, in contrast to global variants, are uniquely dominant in this region in the later months of 2022. INTERPRETATION: Whilst the appearance of a diverse range of omicron lineages has led to primary or partial resistance to clinically approved monoclonal antibodies, the maturation of the antibody response across both cohorts and a large donor pools importantly observes increasing breadth in the antibody neutralisation responses over time with a trajectory that covers both current and known emerging variants. FUNDING: This work was primarily supported by Australian Medical Foundation research grants MRF2005760 (SGT, GM & WDR), Medical Research Future Fund Antiviral Development Call grant (WDR), the New South Wales Health COVID-19 Research Grants Round 2 (SGT & FB) and the NSW Vaccine Infection and Immunology Collaborative (VIIM) (ALC). Variant modeling was supported by funding from SciLifeLab's Pandemic Laboratory Preparedness program to B.M. (VC-2022-0028) and by the European Union's Horizon 2020 research and innovation programme under grant agreement no. 101003653 (CoroNAb) to B.M.

Inactivation and neutralization of parvovirus B19 Genotype 3.

BACKGROUND: Parvovirus B19 (B19V) is a common contaminant of human plasma donations. Three B19V genotypes have been defined based on their DNA sequence. Reliable detection of Genotype 3 DNA has proved problematic because of unexpected sequence variability. B19V Genotype 3 is found primarily in West Africa, but was recently detected in plasma from a North American donor. The safety of plasma-derived medicinal products, with respect to B19V, relies on exclusion of high-titer donations, combined with virus clearance at specific manufacturing steps. Studies on inactivation of B19V are difficult to perform and inactivation of Genotype 3 has not yet been investigated. STUDY DESIGN AND METHODS: Inactivation of B19V Genotypes 3 and 1 by pasteurization of human serum albumin and incubation at low pH was studied using a cell culture assay for infectious virus particles. Infected cells were detected by reverse transcription-polymerase chain reaction analysis of virus capsid mRNA. Neutralization of B19V Genotype 3 was investigated using human immunoglobulin preparations. RESULTS: Genotypes 1 and 3 displayed comparable inactivation kinetics during pasteurization of albumin at 56°C, as well as by incubation at various low-pH conditions (pH 4.2 at 37°C and pH 4.5 at 23°C, respectively) used in immunoglobulin manufacturing. Both Genotypes were readily neutralized by pooled immunoglobulin preparations of North American or European origin. CONCLUSION: Pasteurization and low-pH treatment were equally effective in inactivating B19V Genotypes 1 and 3. Neutralization experiments indicated that pooled immunoglobulin of North American or European origin is likely to be equally effective in treatment of disease induced by both genotypes.