RESPIRATORY SYNCYTIAL VIRUS NEUTRALIZING ANTIBODIES IN PERSONS RESIDING IN CHICAGO, ILLINOIS

The R.S. virus neutralization test was examined in terms of several factors bearing on the consistency and specificity of antibody response to a single strain (Randall) of this virus. It was found that this virus detected significant rises in antibody titer in 90% of 30 patients over 6 months of age who were infected with wild strains of R.S. virus between the years 1958 and 1962. Heterologous neutralizing antibodies to R.S. virus did not occur following human infections with various myxoviruses, adenoviruses, enteroviruses and herpesvirus. Indirect evidence was presented indicating that tile neutralizing activity of human serums is due to specific antibody and not due to non-specific, heat stable neutralizing substance. The titer of R.S. neutralizing antibodies was determined in the serums of 26 parturient mothers, and their 27 newborn babies, and 186 other individuals between the ages of 6 months and 69 years. Longitudinal observations of antibody titer were also conducted on 12 other infants. Neutralizing antibodies to R.S. virus were found to reach the term fetus at undiminished titer. In the longitudinal observations, serum neutralizing antibody titers were found to fall during the first months of life, decreasing by half in an average time of 43 days. Neutralizing antibodies, actively formed in response to R.S. virus infection, were observed to occur with rapidly increasing frequency in relation to age in subjects older than 6 months. These serologic findings indicated that among individuals residing in the metropolitan Chicago area, R.S. virus infection has been experienced by many during the first 2 years of life, most by school age, and all by 7 years of age. Geometric mean antibody titers were found to show a small, but probably significant, increase with age. The restriction of low titer reactors to pre-school children was noted. These serologic findings were interpreted as evidence that re-infections with R.S. virus occur, perhaps quite commonly.

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Antibody titers measured by commercial assays are correlated with neutralizing antibody titers calibrated by international standards

10.1101/2021.07.16.21260618 ◽

2021 ◽

Author(s):

Yu-An Kung ◽

Chung-Guei Huang ◽

Sheng-Yu Huang ◽

Kuan-Ting Liu ◽

Peng-Nien Huang ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Vaccine Development ◽

Geometric Mean ◽

Neutralizing Antibody ◽

Diagnostic Techniques ◽

International Standards ◽

World Health ◽

Serum Samples ◽

Antibody Titers ◽

Health Organization

The World Health Organization (WHO) has highlighted the importance of an international standard (IS) for SARS-CoV-2 neutralizing antibody titer detection, with the aim of calibrating different diagnostic techniques. In this study, IS was applied to calibrate neutralizing antibody titers (IU/mL) and binding antibody titers (BAU/mL) in response to SARS-CoV-2 vaccines. Serum samples were collected from participants receiving the Moderna (n = 20) and Pfizer (n = 20) vaccines at three time points: pre-vaccination, after one dose, and after two doses. We obtained geometric mean titers of 1404.16 and 928.75 IU/mL for neutralizing antibodies after two doses of the Moderna and Pfizer vaccines, respectively. These values provide an important baseline for vaccine development and the implementation of non-inferiority trials. We also compared three commercially available kits from Roche, Abbott, and MeDiPro for the detection of COVID-19 antibodies based on binding affinity to S1 and/or RBD. Our results demonstrated that antibody titers measured by commercial assays are highly correlated with neutralizing antibody titers calibrated by IS.

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Prevalence and Persistence of Maternal Dengue Neutralizing Antibodies in Infants From Central and Southern Thailand: A Retrospective Cohort Study

Asia Pacific Journal of Public Health ◽

10.1177/1010539519853396 ◽

2019 ◽

Vol 31 (4) ◽

pp. 288-295 ◽

Cited By ~ 1

Author(s):

Adrienne Guignard ◽

François Haguinet ◽

Stéphanie Wéry ◽

Phirangkul Kerdpanich

Keyword(s):

Neutralizing Antibodies ◽

Vaccine Development ◽

Geometric Mean ◽

Neutralizing Antibody ◽

Maternal Antibodies ◽

Childhood Immunization ◽

Serum Samples ◽

Denv Serotypes ◽

Antibody Titers ◽

Antibody Kinetics

Understanding maternal dengue virus (DENV) neutralizing antibody kinetics in infants remains timely to develop a safe and effective childhood immunization. This retrospective study evaluated the prevalence and persistence of maternal antibody titers against DENV serotypes 1 to 4 in 139 Thai infants at 2, 6, and 7 months of age, using serum samples collected in a vaccination trial ( http://clinicaltrials.gov ; NCT00197275). Neutralizing antibodies against all 4 DENV serotypes were detected in 87.8% and 22.9% of infants at 2 and 7 months, respectively. At 2 months, DENV-4 neutralizing antibody geometric mean titers were notably lower (80) compared with DENV-1 to DENV-3 (277-471). Our results corroborate previous findings that DENV-1 to DENV-4 maternal antibodies persist at 7 months despite titers decrease from 2 months onwards. As persisting maternal antibodies may inhibit immune responses in DENV-vaccinated infants, a comprehensive understanding of DENV antibody kinetics is required in the perspective of vaccine development for infants.

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2855. Respiratory Syncytial Virus Neutralizing Antibodies in Cord Blood and Serum from Infants up to 2 Years of Age in a Multinational Prospective Study

Open Forum Infectious Diseases ◽

10.1093/ofid/ofz359.160 ◽

2019 ◽

Vol 6 (Supplement_2) ◽

pp. S74-S75

Author(s):

Joseph B Domachowske ◽

Veronique Bianco ◽

Ana Ceballos ◽

Luis Cousin ◽

Ulises D’Andrea ◽

...

Keyword(s):

Respiratory Syncytial Virus ◽

Cord Blood ◽

Neutralizing Antibodies ◽

Geometric Mean ◽

Neutralizing Antibody ◽

Neutralization Assay ◽

Entire Cohort ◽

Syncytial Virus ◽

Tract Infections

Abstract Background Respiratory syncytial virus (RSV) is the most common cause of lower respiratory tract infections (LRTI) during infancy worldwide. High cord blood (CB) concentrations of anti-RSV neutralizing antibody (nAb) may attenuate, delay, or prevent infant infection. We report RSV A and B nAb concentrations in CB and serum from a birth cohort at different time points through 2 years of age. Methods Between 2013 and 2017, newborns from 8 countries were studied prospectively from birth to 2 years of age (NCT01995175). CB was collected at birth for the entire cohort. A subcohort of children was randomly assigned to have one blood sample collected again at either 2, 4, 6, 12, 18, or 24 months of age. Sera were analyzed for RSV A and B nAb concentrations by serum neutralization assay. Active surveillance was used to identify LRTIs during the 2-year follow-up as previously reported. Results In total, 2,401 newborns were enrolled and followed up. >99% of infants had detectable CB RSV A and B nAb. Geometric mean antibody titers (GMTs) varied by country, but were overall higher for RSV B than for RSV A (327 vs. 251; Figure 1). The lowest GMTs were seen from CB sera collected from South African newborns (197 RSV A, 255 RSV B); Canadian newborns had the highest RSV A GMT (383), while Hondurans had the highest RSV B GMT (460). 1380 infants provided follow-up serum nAb results as part of the subcohort (Figure 2). Dramatic waning of GMTs was evident, with a ~3-fold drop in GMTs at 2 months of age, and an additional ~2-fold drop between 2 and 4 months of age. At 6 and 12 months of age, 71% and 50% of infants had RSV A nAb and GMTs were at a nadir of 14. At 6, 12, and 18 months of age, RSV B nAb was detected in 98%, 69%, and 63% of infants, respectively. The RSV B nAb nadir GMT of 20 was observed at 12 months of age, while the 6- and 18-month RSV B nAb GMTs were 30 and 31, respectively. A total of 1,017 LRTIs were identified during the 2-year study period; of which, 94 (9%) were caused by RSV A and 132 (13%) by RSV B. Associations between CB nAb levels and RSV infection will be presented. Conclusion Neutralizing Ab to RSV A and B was present at birth in infants from 8 countries, and waned over time. GMTs were at a nadir at 6 to 12 months of age. Funding. GlaxoSmithKline Biologicals SA. Disclosures All Authors: No reported Disclosures.

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Immunogenicity and Safety of 3 Formulations of a Respiratory Syncytial Virus Candidate Vaccine in Nonpregnant Women: A Phase 2, Randomized Trial

The Journal of Infectious Diseases ◽

10.1093/infdis/jiz395 ◽

2019 ◽

Vol 220 (11) ◽

pp. 1816-1825 ◽

Cited By ~ 1

Author(s):

Tino F Schwarz ◽

Roderick A McPhee ◽

Odile Launay ◽

Geert Leroux-Roels ◽

Jaak Talli ◽

...

Keyword(s):

Respiratory Syncytial Virus ◽

Neutralizing Antibodies ◽

Geometric Mean ◽

Neutralizing Antibody ◽

Candidate Vaccine ◽

Phase 2 ◽

Serious Adverse Events ◽

Intramuscular Dose ◽

Syncytial Virus ◽

Neonates And Infants

Abstract Background Respiratory syncytial virus (RSV) is a common cause of respiratory tract illness and hospitalization in neonates and infants. RSV vaccination during pregnancy may protect offspring in their first months of life. Methods This randomized, observer-blind, multicenter, phase 2 study evaluated the immunogenicity and safety of an RSV candidate vaccine in healthy nonpregnant women aged 18–45 years. Four hundred participants were randomized (1:1:1:1) to receive a single intramuscular dose of vaccine containing 30 µg, 60 µg, or 120 µg of RSV fusion protein engineered to preferentially maintain a prefusion conformation (RSV-PreF vaccine) or placebo. Results Thirty days postvaccination, RSV-A neutralizing antibody geometric mean titers (GMTs) increased 3.75-, 4.42- and 4.36-fold; RSV-B neutralizing antibody GMTs 2.36-, 2.54- and 2.76-fold; and palivizumab competing antibody (PCA) concentrations 11.69-, 14.38- and 14.24-fold compared with baseline levels in the 30 µg, 60 µg, and 120 µg RSV-PreF groups, respectively. Antibody titers and PCA concentrations at day 30 were significantly higher with the 120 µg compared to the 30 µg RSV-PreF vaccine. All RSV-PreF vaccine formulations and the placebo had similar reactogenicity profiles. No serious adverse events were considered to be related to the RSV-PreF vaccine. Conclusions The 3 formulations of the investigational RSV-PreF vaccine were well-tolerated and induced RSV-A and RSV-B neutralizing antibodies and PCAs in healthy, nonpregnant women. Clinical Trials Registration NCT02956837.

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Neutralization of SARS-CoV-2 Omicron variant by sera from BNT162b2 or Coronavac vaccine recipients

10.1101/2021.12.13.21267668 ◽

2021 ◽

Author(s):

Lu Lu ◽

Bobo Mok ◽

Linlei Chen ◽

Jacky Chan ◽

Owen Tsang ◽

...

Keyword(s):

Neutralizing Antibodies ◽

Geometric Mean ◽

Neutralizing Antibody ◽

World Health ◽

Whole Genome Sequence ◽

Live Virus ◽

Significant Difference ◽

Antibody Titers ◽

Ancestral Virus ◽

Health Organization

Background The SARS-CoV-2 Omicron variant, designated as a Variant of Concern(VOC) by the World Health Organization, carries numerous spike protein mutations which have been found to evade neutralizing antibodies elicited by COVID-19 vaccines. The susceptibility of Omicron variant by vaccine-induced neutralizing antibodies are urgently needed for risk assessment. Methods Omicron variant strains HKU691 and HKU344-R346K were isolated from patients using TMPRSS2-overexpressing VeroE6 cells. Whole genome sequence was determined using nanopore sequencing. Neutralization susceptibility of ancestral lineage A virus and the Omicron, Delta and Beta variants to sera from 25 BNT162b2 and 25 Coronavac vaccine recipients was determined using a live virus microneutralization assay. Results The Omicron variant strain HKU344-R346K has an additional spike R346K mutation, which is present in 8.5% of strains in GISAID database. Only 20% and 24% of BNT162b2 recipients had detectable neutralizing antibody against the Omicron variant HKU691 and HKU344-R346K, respectively, while none of the Coronavac recipients had detectable neutralizing antibody titer against either Omicron isolates. For BNT162b2 recipients, the geometric mean neutralization antibody titers(GMT) of the Omicron variant isolates(5.43 and 6.42) were 35.7-39.9-fold lower than that of the ancestral virus(229.4), and the GMT of both omicron isolates were significantly lower than those of the beta and delta variants. There was no significant difference in the GMT between HKU691 and HKU344-R346K. Conclusions Omicron variant escapes neutralizing antibodies elicited by BNT162b2 or CoronaVac. The additional R346K mutation did not affect the neutralization susceptibility. Our data suggest that the Omicron variant may be associated with lower COVID-19 vaccine effectiveness.

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COVID-19 Repeated Convalescent Plasma Collection: Analysis of 149 Donations from 88 French Military Health Workers

Transfusion Medicine and Hemotherapy ◽

10.1159/000515843 ◽

2021 ◽

pp. 1-6

Author(s):

Pierre-Louis Conan ◽

Cécile Ficko ◽

Marine Chueca ◽

Carole Rolland ◽

Olivier Javaudin ◽

...

Keyword(s):

Antibody Titer ◽

Neutralizing Antibodies ◽

Health Workers ◽

Young Patients ◽

Neutralizing Antibody ◽

Military Health ◽

Service Workers ◽

The Third ◽

Significant Difference ◽

Antibody Titers

Background: Passive therapy with convalescent plasma (CP) could be an effective and safe treatment option in COVID-19 patients. Neutralizing antibodies present in CP generated in response to SARS-CoV-2 infection and directed against the receptor-binding domain of the spike protein are considered to play a major role in the viral clearance. CP infusion may also contribute to the modulation of the immune response through its immunomodulatory effect. We describe for the first time the effectiveness of a CP collection protocol from repeated donations in young patients. Materials and Methods: We enrolled health service workers who experienced mild to moderate COVID-19 and from whom several donations have been collected. No minimal severity threshold and no biological cure criteria were required. Donors could return to a second plasma donation 14 days after the first donation. A minimal neutralizing antibody titer of 1:40 was considered for clinical use. Results: Eighty-eight donors were included (median age 35 [28–48] years, 41 women), and 149 plasma products were collected. COVID-19 were mainly WHO stage 2 infections (96%). Among the 88 first donations, 76% had neutralizing antibody titers higher than or equal to 1:40. Eighty-eight percent of donors who came for a second donation had a neutralizing antibody titer of 1:40. Median durations were 15 (15–19) and 38 (33–46) days from the first to the second donation and from recovery to the second donation, respectively. Sixty-nine percent of donors who came for a third donation had a neutralizing antibody titer of 1:40. Median durations were 16 (13–37) and 54 (49–61) days from the second to the third donation and from recovery to the third donation, respectively. No significant difference was observed between the IgG ratio and the age of the donors or the time between recovery and donation. The average IgG ratio did not significantly vary between donations. When focused on repeated blood donors, no significant differences were observed either. Conclusion: The recruitment of young patients with a mild to moderate COVID-19 course is an efficient possibility to collect CP with a satisfactory level of neutralizing antibodies. Repeated donations are a well-tolerated and effective way of CP collection.

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Search for Correlates of Protective Immunity Conferred by Anthrax Vaccine

Infection and Immunity ◽

10.1128/iai.69.5.2888-2893.2001 ◽

2001 ◽

Vol 69 (5) ◽

pp. 2888-2893 ◽

Cited By ~ 175

Author(s):

Shaul Reuveny ◽

Moshe D. White ◽

Yaakov Y. Adar ◽

Yaron Kafri ◽

Zeev Altboum ◽

...

Keyword(s):

Antibody Titer ◽

Neutralizing Antibodies ◽

Protective Immunity ◽

Protective Antigen ◽

Surrogate Marker ◽

Neutralizing Antibody ◽

Enzyme Linked Immunosorbent Assay ◽

Lethal Challenge ◽

Anthrax Spores ◽

Antibody Titers

ABSTRACT Vaccination by anthrax protective antigen (PA)-based vaccines requires multiple immunization, underlying the need to develop more efficacious vaccines or alternative vaccination regimens. In spite of the vast use of PA-based vaccines, the definition of a marker for protective immunity is still lacking. Here we describe studies designed to help define such markers. To this end we have immunized guinea pigs by different methods and monitored the immune response and the corresponding extent of protection against a lethal challenge with anthrax spores. Active immunization was performed by a single injection using one of two methods: (i) vaccination with decreasing amounts of PA and (ii) vaccination with constant amounts of PA that had been thermally inactivated for increasing periods. In both studies a direct correlation between survival and neutralizing-antibody titer was found (r 2 = 0.92 and 0.95, respectively). Most significantly, in the two protocols a similar neutralizing-antibody titer range provided 50% protection. Furthermore, in a complementary study involving passive transfer of PA hyperimmune sera to naive animals, a similar correlation between neutralizing-antibody titers and protection was found. In all three immunization studies, neutralization titers of at least 300 were sufficient to confer protection against a dose of 40 50% lethal doses (LD50) of virulent anthrax spores of the Vollum strain. Such consistency in the correlation of protective immunity with anti-PA antibody titers was not observed for antibody titers determined by an enzyme-linked immunosorbent assay. Taken together, these results clearly demonstrate that neutralizing antibodies to PA constitute a major component of the protective immunity against anthrax and suggest that this parameter could be used as a surrogate marker for protection.

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Immunogenicity in sheep of Uruguayan commercial vaccines against bovine alphaherpesvirus 1, 5 and bovine pestiviruses

Ciência Rural ◽

10.1590/0103-8478cr20190465 ◽

2020 ◽

Vol 50 (4) ◽

Author(s):

Ingryd Merchioratto ◽

Alana de Almeida Aurélio ◽

Janice Machado Villela ◽

Nicole Vieira Stone ◽

Isac Junior Roman ◽

...

Keyword(s):

Antibody Response ◽

Neutralizing Antibodies ◽

Geometric Mean ◽

Neutralizing Antibody ◽

Serological Response ◽

Serum Samples ◽

Post Vaccination ◽

Immunological Responses ◽

Antibody Titers ◽

Low Levels

ABSTRACT: The serological responses induced by four commercial inactivated Uruguayan vaccines against bovine alphaherpesviruses (BoHV)-1 and -5 and bovine pestiviruses (BVDV-1, BVDV-2, and HoBiPeV) were evaluated in sheep. Thirty-seven sheep were immunized twice (day 0 and 25) and their serum samples were tested at different intervals (days 0, 25, 40, 60, and 90) post-vaccination (PV). Among the four vaccines tested, only one (G4) could induce the production of moderate neutralizing antibody titers against BoHV-1 and -5 and BVDV-1 and -2. The G3 vaccine showed a neutralizing serological response against the bovine alphaherpesviruses only. The G1 and G2 vaccines produced extremely low levels of antibodies in a few vaccinated animals only (geometric mean titers (GMT) 2.2). Similar levels of immunological responses were induced by the G4 vaccine against BoHV-1 and -5, and titers of neutralizing antibodies induced in approximately 70% of the animals are known to confer protection (GMT > 8). For bovine pestiviruses, the vaccine stimulated response of G4 against BVDV-2 was higher compared to that against BVDV-1, and extremely low for HoBiPeV. The peak of neutralizing antibodies to BoHV-1 and BVDV-1 was observed on days 40 and 60 PV, respectively. Thereafter, a remarkably decrease in neutralizing antibody response was observed at day 90 PV. These results demonstrated that tested commercial Uruguayan vaccines did not induce a serological response of adequate magnitude and duration. Thus, it is important to periodically review formulations and compositions of commercial vaccines against bovine alphaherpesviruses and pestiviruses.

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Neutralizing Antibody Response to Pseudotype SARS-CoV-2 Differs between mRNA-1273 and BNT162b2 COVID-19 Vaccines and by History of SARS-CoV-2 Infection

10.1101/2021.10.20.21265171 ◽

2021 ◽

Author(s):

Harmony L. Tyner ◽

Mark G. Thompson ◽

Jefferey L. Burgess ◽

Lauren Grant ◽

Manjusha Gaglani ◽

...

Keyword(s):

Antibody Response ◽

Messenger Rna ◽

Neutralizing Antibodies ◽

Geometric Mean ◽

Vaccine Dose ◽

Neutralizing Antibody ◽

Frontline Workers ◽

History Of ◽

Antibody Titers ◽

Polymerase Chain

Background: Data on the development of neutralizing antibodies against SARS-CoV-2 after SARS-CoV-2 infection and after vaccination with messenger RNA (mRNA) COVID-19 vaccines are limited. Methods: From a prospective cohort of 3,975 adult essential and frontline workers tested weekly from August, 2020 to March, 2021 for SARS-CoV-2 infection by Reverse Transcription-Polymerase Chain Reaction (RT-PCR) assay irrespective of symptoms, 497 participants had sera drawn after infection (170), vaccination (327), and after both infection and vaccination (50 from the infection population). Serum was collected after infection and each vaccine dose. Serum-neutralizing antibody titers against USA-WA1/2020-spike pseudotype virus were determined by the 50% inhibitory dilution. Geometric mean titers (GMTs) and corresponding fold increases were calculated using t-tests and linear mixed effects models. Results: Among 170 unvaccinated participants with SARS-CoV-2 infection, 158 (93%) developed neutralizing antibodies (nAb) with a GMT of 1,003 (95% CI=766-1,315). Among 139 previously uninfected participants, 138 (99%) developed nAb after mRNA vaccine dose-2 with a GMT of 3,257 (95% CI = 2,596-4,052). GMT was higher among those receiving mRNA-1273 vaccine (GMT =4,698, 95%CI= 3,186-6,926) compared to BNT162b2 vaccine (GMT=2,309, 95%CI=1,825-2,919). Among 32 participants with prior SARS-CoV-2 infection, GMT was 21,655 (95%CI=14,766-31,756) after mRNA vaccine dose-1, without further increase after dose-2. Conclusions: A single dose of mRNA vaccine after SARS-CoV-2 infection resulted in the highest observed nAb response. Two doses of mRNA vaccine in previously uninfected participants resulted in higher nAb to SARS-CoV-2 than after one dose of vaccine or SARS-CoV-2 infection alone. Neutralizing antibody response also differed by mRNA vaccine product.

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Early fulminant BK polyomavirus-associated nephropathy in two kidney transplant patients with low neutralizing antibody titers receiving allografts from the same donor

Virology Journal ◽

10.1186/s12985-019-1275-9 ◽

2020 ◽

Vol 17 (1) ◽

Cited By ~ 2

Author(s):

Elias Myrvoll Lorentzen ◽

Stian Henriksen ◽

Amandeep Kaur ◽

Grete Birkeland Kro ◽

Clara Hammarström ◽

...

Keyword(s):

Renal Function ◽

Mycophenolate Mofetil ◽

Kidney Transplant ◽

Antibody Titer ◽

Neutralizing Antibodies ◽

Neutralizing Antibody ◽

Genotype I ◽

Post Transplant ◽

Bk Polyomavirus ◽

Antibody Titers

Abstract Background BK Polyomavirus (BKPyV) causes premature graft failure in 1 to 15% of kidney transplant (KT) recipients. High-level BKPyV-viruria and BKPyV-DNAemia precede polyomavirus-associated nephropathy (PyVAN), and guide clinical management decisions. In most cases, BKPyV appears to come from the donor kidney, but data from biopsy-proven PyVAN cases are lacking. Here, we report the early fulminant course of biopsy-proven PyVAN in two male KT recipients in their sixties, receiving kidneys from the same deceased male donor. Case presentations Both recipients received intravenous basiliximab induction, and maintenance therapy consisting of tacrolimus (trough levels 3–7 ng/mL from time of engraftment), mycophenolate mofetil 750 mg bid, and prednisolone. At 4 weeks post-transplant, renal function was satisfactory with serum creatinine concentrations of 106 and 72 μmol/L in recipient #1 and recipient #2, respectively. Plasma BKPyV-DNAemia was first investigated at 5 and 8 weeks post-transplant being 8.58 × 104 and 1.12 × 106 copies/mL in recipient #1 and recipient #2, respectively. Renal function declined and biopsy-proven PyVAN was diagnosed in both recipients at 12 weeks post-transplant. Mycophenolate mofetil levels were reduced from 750 mg to 250 mg bid while tacrolimus levels were kept below 5 ng/mL. Recipient #2 cleared BKPyV-DNAemia at 5.5 months post-transplant, while recipient #1 had persistent BKPyV-DNAemia of 1.07 × 105 copies/mL at the last follow-up 52 weeks post-transplant. DNA sequencing of viral DNA from early plasma samples revealed apparently identical viruses in both recipients, belonging to genotype Ib-2 with archetype non-coding control region. Retrospective serological work-up, demonstrated that the donor had high BKPyV-IgG-virus-like particle ELISA activity and a high BKPyV-genotype I neutralizing antibody titer, whereas both KT recipients only had low neutralizing antibody titers pre-transplantation. By 20 weeks post-transplant, the neutralizing antibody titer had increased by > 1000-fold in both recipients, but only recipient #2 cleared BKPyV-DNAemia. Conclusions Low titers of genotype-specific neutralizing antibodies in recipients pre-transplant, may identify patients at high risk for early fulminant donor-derived BKPyV-DNAemia and PyVAN, but development of high neutralizing antibody titers may not be sufficient for clearance.

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