Karena Burkin

National Institute for Biological Standards and Control

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Trends

Author Order

Document Type

Co-Authors

Barbara Bolgiano

National Institute for Biological Standards and Control

Peter Rigsby

National Institute for Biological Standards and Control

Fang Gao

National Institute for Biological Standards and Control

Kay Lockyer

National Institute for Biological Standards and Control

Dennis Crane

National Institute for Biological Standards and Control

Fatme Mawas

National Institute for Biological Standards and Control

Manolya Saydam

National Institute for Biological Standards and Control

Nicola J. Beresford

National Institute for Biological Standards and Control

Caroline Vipond

National Institute for Biological Standards and Control

Gianluigi De Benedetto

National Institute for Biological Standards and Control

Cooperative Institutions

National Institute for Biological Standards and Control

University of Hertfordshire

Government of the United Kingdom

Potters Bar Community Hospital

Imperial College London

University of Manchester

King's College London

World Health Organization - Lyon Office

Charité - Universitätsmedizin Berlin

Centers for Disease Control and Prevention

Author Statistics

Papers

Citation

H-Index

i-10 index

Research Field

Further Insights into the Measurement of Free Polysaccharide in Meningococcal Conjugate Vaccines

Vaccines (2025)

Nicola J. Beresford Gianluigi De Benedetto Kay Lockyer Fang Gao Karena Burkin

Objectives: The purpose of this study was to further characterize the ultrafiltration (UF) method for determining free saccharide levels in glycoconjugate vaccines and compare it with other methods used for the determination of free saccharide levels in meningococcal glycoconjugate vaccines. Methods: We performed experiments on both meningococcal glycoconjugates and capsular polysaccharides, and compared UF, deoxycholate (DOC) precipitation, and solid-phase extraction (SPE) methods. Meningococcal capsular polysaccharides from groups A (MenA), C (MenC), and W (MenW) were depolymerized and characterized using SEC-MALS (size-exclusion chromatography with multi-angle laser light scattering) to determine the molecular weight and hydrodynamic size and then subjected to UF. The free saccharide content was quantified using HPAEC-PAD (high-performance anion-exchange chromatography with pulsed amperometric detection). Results: The characterization of size-reduced group C polysaccharide revealed weight-average molecular mass (Mw) ranging from 22,200 g/mol to 287,300 g/mol and hydrodynamic radii of 3.7 to 19.5 nm. Pore size studies confirmed that polysaccharides with diameters up to 15 nm filtered through the 100 kDa cellulose membrane. The smallest PS fragment tested (22,200 g/mol, 7.4 nm diameter) was partially recovered from the 30 kDa membrane. For MenC-CRM197, DOC yielded the lowest free saccharide content (<1%), UF gave moderate results (7–8%), and SPE showed the highest and most variable values (up to 15%). For MenA- and MenW-CRM197, UF and DOC consistently provided low free saccharide levels (<2% and 3–11%, respectively). Conclusions: The upper limits on the size of free group C meningococcal polysaccharides that can be ultrafiltered were assessed. Differences in the relative amount of free saccharide were observed between various methods used to control meningococcal conjugate vaccines.

Ultrafiltration (renal)

Glycoconjugate

Solid phase extraction

10.3390/vaccines13020167

Cite

Citations (0)

A physico-chemical assessment of the thermal stability of pneumococcal conjugate vaccine components

Human Vaccines & Immunotherapeutics (2014)

Fang Gao Kay Lockyer Karena Burkin Dennis Crane Barbara Bolgiano

Physico-chemical analysis of pneumococcal polysaccharide (PS)-protein conjugate vaccine components used for two commercially licensed vaccines was performed to compare the serotype- and carrier protein-specific stabilities of these vaccines. Nineteen different monovalent pneumococcal conjugates from commercial vaccines utilizing CRM197, diphtheria toxoid (DT), Protein D (PD) or tetanus toxoid (TT) as carrier proteins were incubated at temperatures up to 56°C for up to eight weeks or were subjected to freeze-thawing (F/T). Structural stability was evaluated by monitoring their size, integrity and carrier protein conformation. The molecular size of the vaccine components was well maintained for Protein D, TT and DT conjugates at -20°C, 4°C and F/T, and for CRM197 conjugates at 4°C and F/T. It was observed that four of the eight serotypes of Protein D conjugates tended to form high molecular weight complexes at 37°C or above. The other conjugated carrier proteins also appeared to form oligomers or 'aggregates' at elevated temperatures, but rarely when frozen and thawed. There was evidence of degradation in some of the conjugates as evidenced by the formation of lower molecular weight materials which correlated with measured free saccharide. In conclusion, pneumococcal-Protein D/TT/DT and most CRM197 bulk conjugate vaccines were stable when stored at 2–8°C, the recommended temperature. In common between the conjugates produced by the two manufacturers, serotypes 1, 5, and 19F were relatively less stable and 6B was the most stable, with types 7F and 23F also showing good stability.

Conjugate

Diphtheria Toxin

Toxoid

Molecular mass

10.4161/hv.29696

Cite

Citations (20)

Evaluation of candidate International Standards for meningococcal capsular polysaccharide groups W and Y

Biologicals (2024)

Hannah Chan Nicola J. Beresford Timothy R. Rudd Peter Rigsby Caroline Vipond

Two candidate International Standards for meningococcal capsular group W and Y (MenW and MenY, respectively) polysaccharides were assessed for their suitability as quantitative standards in various physicochemical assays. The study was designed to evaluate the intended purpose of these standards, namely, to standardize the quantification of the respective polysaccharide content in meningococcal polysaccharide and conjugate vaccines and their intermediate components. Twelve laboratories from eleven different countries participated in the collaborative study of candidate preparations for International Standards for MenW and MenY polysaccharide (coded 16/152 and 16/206, respectively). Unitage was assigned using the Resorcinol assay. Our proposals, on the basis of data from the Resorcinol assay were: 1) candidate standard for MenW polysaccharide (16/152) to be assigned a content of 1.015 ± 0.071 mg MenW polysaccharide per ampoule (expanded uncertainty with coverage factor k = 2.13, corresponding to a 95 % level of confidence) and 2) candidate standard for MenY polysaccharide (16/206) be assigned a content of 0.958 ± 0.076 mg MenY polysaccharide per ampoule (expanded uncertainty with coverage factor k = 2.26, corresponding to a 95 % level of confidence). The amount of polysaccharide per ampoule remained consistent under all stability conditions over a 36-month period.

Ampoule

Meningococcal vaccine

10.1016/j.biologicals.2024.101780

Cite

Citations (0)

A Retrospective Study on the Quality of Haemophilus Influenzae Type B Vaccines Used in the U.K. Between 1996 and 2004

Human Vaccines (2007)

Barbara Bolgiano Fatme Mawas Karena Burkin Dennis Crane Manolya Saydam

Following the reduction in efficacy of Hib-TT vaccines in the primary immunization schedule observed in the U.K. between 1999 and 2003, batches of vaccine manufactured by two different companies were retrospectively examined by the National Institute for Biological Standards and Control. The study evaluated 41 batches of the Hib-TT vaccines manufactured between 1994 and 2003, assaying potency (total PRP saccharide content), integrity (% free saccharide), consistency (molecular sizing), and immunogenicity, as well as reviewing data previously obtained at the time of release. The study indicated the stability of the lyophilized final fill vaccines to extend well past their assigned shelf-lives, and found no trends in the endotoxin content, total saccharide or % free saccharide content. A trend towards slightly larger conjugates was observed over time in Hib-TT A, evidenced in both the manufacturer’s data obtained at the time that samples were submitted for testing and in data obtained from the retrospective analysis. The study confirmed that that there had been no significant change in the quality of the Hib vaccines that could possibly account for the change reported in their protective efficacy in the U.K. The study also demonstrated the value of independent testing of vaccines from the time of licensure and in the ongoing monitoring and re-examination of selected batches, as necessary, to assure their continuing quality, safety and consistency.

10.4161/hv.3.5.4352

Cite

Citations (13)

Saccharide dosage content of meningococcal polysaccharide conjugate vaccines determined using WHO International Standards for serogroup A, C, W, Y and X polysaccharides

Biologicals (2021)

Fang Gao Nicola J. Beresford Kay Lockyer Karena Burkin Peter Rigsby

Potency of meningococcal polysaccharide-protein conjugate vaccines relies on the polysaccharide content to prevent meningitis. NIBSC, as the official national control laboratory in UK, analysed ten different mono- and multi-meningococcal conjugate vaccines, using established International Standards for meningococcal serogroups A, C, W, Y and X, by resorcinol or HPAEC-PAD assay. Most saccharide contents were within ±20% of their claimed content for licensure with taking different O-acetylation levels into consideration, with only MenC content in two vaccines below (by 60% and 54%) the labelled value, however, previous study showed different dosage was not necessarily correlated to the immunogenicity of those vaccines. This study demonstrated the use of International Standards to quantify saccharide content in polysaccharide-based vaccines with different percentage of O-acetylation. These International Standards are suitable to serve as either quantitative standard or calibrator of in-house standards, with supplied stability data.

Meningococcal vaccine

Conjugate

10.1016/j.biologicals.2021.01.001

Cite

Citations (4)

Evaluation of a candidate International Standard for Meningococcal Group C polysaccharide

Biologicals (2012)

Caroline Vipond Barbara Mulloy Peter Rigsby Karena Burkin Barbara Bolgiano

Meningococcal vaccine

10.1016/j.biologicals.2012.03.003

Cite

Citations (17)

Immunogenicity and thermal stability of a combined vaccine against Haemophilus influenzae type b and Neisseria meningitidis serogroup C diseases

Vaccine (2010)

Manolya Saydam Karena Burkin Rory Care Peter Rigsby Barbara Bolgiano

Neisseriaceae

Meningococcal vaccine

Neisseria

10.1016/j.vaccine.2010.07.005

Cite

Citations (7)

International collaborative study for establishment of the 2nd WHO International Standard for Haemophilus influenzae type b polysaccharide

Biologicals (2015)

Fatme Mawas Karena Burkin Thomas Dougall Manolya Saydam Peter Rigsby

Ribitol

10.1016/j.biologicals.2015.07.006

Cite

Citations (1)

Patterns of binding of aluminum-containing adjuvants to Haemophilus influenzae type b and meningococcal group C conjugate vaccines and components

Biologicals (2015)

Robert B D Otto Karena Burkin Saba Erum Amir Dennis Crane Barbara Bolgiano

The basis of Haemophilus influenzae type b (Hib) and Neisseria meningitidis serogroup C (MenC) glycoconjugates binding to aluminum-containing adjuvants was studied. By measuring the amount of polysaccharide and protein in the non-adsorbed supernatant, the adjuvant, aluminum phosphate, AlPO4, was found to be less efficient than aluminum hydroxide, Al(OH)3 at binding to the conjugates, at concentrations relevant to licensed vaccine formulations and when equimolar. At neutral pH, binding of TT conjugates to AlPO4 was facilitated through the carrier protein, with only weak binding of AlPO4 to CRM197 being observed. There was slightly higher binding of either adjuvant to tetanus toxoid conjugates, than to CRM197 conjugates. This was verified in AlPO4 formulations containing DTwP-Hib, where the adsorption of TT-conjugated Hib was higher than CRM197-conjugated Hib. At neutral pH, the anionic Hib and MenC polysaccharides did not appreciably bind to AlPO4, but did bind to Al(OH)3, due to electrostatic interactions. Phosphate ions reduced the binding of the conjugates to the adjuvants. These patterns of adjuvant adsorption can form the basis for future formulation studies with individual and combination vaccines containing saccharide-protein conjugates.

Conjugate

Toxoid

Glycoconjugate

10.1016/j.biologicals.2015.06.008

Cite

Citations (12)