Papers by Ranawaka A.P.M Perera - Dr
Vaccines, 2020
The stalk domain of the hemagglutinin has been identified as a target for induction of protective... more The stalk domain of the hemagglutinin has been identified as a target for induction of protective antibody responses due to its high degree of conservation among numerous influenza subtypes and strains. However, current assays to measure stalk-based immunity are not standardized. Hence, harmonization of assay readouts would help to compare experiments conducted in different laboratories and increase confidence in results. Here, serum samples from healthy individuals (n = 110) were screened using a chimeric cH6/1 hemagglutinin enzyme-linked immunosorbent assay (ELISA) that measures stalk-reactive antibodies. We identified samples with moderate to high IgG anti-stalk antibody levels. Likewise, screening of the samples using the mini-hemagglutinin (HA) headless construct #4900 and analysis of the correlation between the two assays confirmed the presence and specificity of anti-stalk antibodies. Additionally, samples were characterized by a cH6/1N5 virus-based neutralization assay, an a...
Background: Many serologic studies were done during and after the 2009 influenza pandemic, to est... more Background: Many serologic studies were done during and after the 2009 influenza pandemic, to estimate the cumulative incidence of influenza A(H1N1)pdm09 virus infections, but there are few comparative estimates of the incidence of influenza A(H3N2) virus infections during epidemics. Methods: We conducted a longitudinal serologic study in Hong Kong. We collected sera annually and tested samples from 2009-13 by HAI against the A/Perth/16/2009(H3N2) virus, and samples from 2013-15 against the A/Victoria/361/2011(H3N2) virus using the hemagglutination inhibition (HAI) assay. We estimated the cumulative incidence of infections based on 4-fold or greater rises in HAI titers in consecutive sera. Results: There were four major H3N2 epidemics: (1) Aug-Oct 2010; (2) Mar-Jun 2012; (3) Jul-Oct 2013; and (4) Jun-Jul 2014. Between 514 516 and 614 619 relevant pairs of sera were available for each epidemic. We estimated that 98%, 2019%, 57% and 7% of the population were infected in each epidemic, respectively, with higher incidence in children in epidemics 1 and 4. Conclusions: We estimatedfound that around 5% to 20% of the Hong Kong population were infectedre-infections in each of the four H3N2 epidemics that occurred from 2010 through 2014 were rare. The largest H3N2 epidemic occurred with the lowest level of pre-epidemic immunity
Viruses, 2022
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have spilled over from hu... more Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections have spilled over from humans to companion and wild animals since the inception of the global COVID-19 pandemic. However, whole genome sequencing data of the viral genomes that infect non-human animal species have been scant. Here, we detected and sequenced a SARS-CoV-2 delta variant (AY.3) in fecal samples from an 11-year-old domestic house cat previously exposed to an owner who tested positive for SARS-CoV-2. Molecular testing of two fecal samples collected 7 days apart yielded relatively high levels of viral RNA. Sequencing of the feline-derived viral genomes showed the two to be identical, and differing by between 4 and 14 single nucleotide polymorphisms in pairwise comparisons to human-derived lineage AY.3 sequences collected in the same geographic area and time period. However, several mutations unique to the feline samples reveal their divergence from this cohort on phylogenetic analysis. These results de...
The file that are used by [indirect_benefit_main.r]
The mcmc result for the manuscript
This is the long format that each row is a participant
This data file contains data from the kiddivax study at 2009-2010. This is in a wide format that ... more This data file contains data from the kiddivax study at 2009-2010. This is in a wide format that each row is a household
R syntax to condcut prediction based on the posterior distribution of model parameter [mcmc_resul... more R syntax to condcut prediction based on the posterior distribution of model parameter [mcmc_result.csv]
We identified the near-full-genome sequence (29,908 nt, >99%) of Middle East respiratory syndr... more We identified the near-full-genome sequence (29,908 nt, >99%) of Middle East respiratory syndrome coronavirus (MERS-CoV) from a nasal swab specimen from a drome-dary camel in Egypt. We found that viruses genetically very similar to human MERS-CoV are infecting dromedaries beyond the Arabian Peninsula, where human MERS-CoV infections have not yet been detected. Middle East respiratory syndrome (MERS) is a pneu-monic illness caused by a novel lineage C beta-coronavirus (CoV). During September 2012–January 20, 2014, a total of 178 confirmed cases in humans resulted in 76 deaths (1). Primary infections have originated from countries within the Arabian Peninsula, although travel-associated cases and some secondary transmission have been reported in other countries. Limited human-to-human transmission has resulted in clusters of cases, some associ-ated with multiple rounds of human-to-human transmission (2); the remaining sporadic cases in humans are presumed to be of zoonotic origin. ...
Nature Communications, 2021
The SARS-CoV-2 pandemic poses the greatest global public health challenge in a century. Neutraliz... more The SARS-CoV-2 pandemic poses the greatest global public health challenge in a century. Neutralizing antibody is a correlate of protection and data on kinetics of virus neutralizing antibody responses are needed. We tested 293 sera from an observational cohort of 195 reverse transcription polymerase chain reaction (RT-PCR) confirmed SARS-CoV-2 infections collected from 0 to 209 days after onset of symptoms. Of 115 sera collected ≥61 days after onset of illness tested using plaque reduction neutralization (PRNT) assays, 99.1% remained seropositive for both 90% (PRNT90) and 50% (PRNT50) neutralization endpoints. We estimate that it takes at least 372, 416 and 133 days for PRNT50 titres to drop to the detection limit of a titre of 1:10 for severe, mild and asymptomatic patients, respectively. At day 90 after onset of symptoms (or initial RT-PCR detection in asymptomatic infections), it took 69, 87 and 31 days for PRNT50 antibody titres to decrease by half (T1/2) in severe, mild and asy...
The Journal of Infectious Diseases, 2019
Background Immune responses to influenza vaccination can be weaker in older adults than in other ... more Background Immune responses to influenza vaccination can be weaker in older adults than in other age groups. We hypothesized that antibody responses would be particularly weak among repeat vaccinees when the current and prior season vaccine components are the same. Methods An observational study was conducted among 827 older adults aged ≥75 years in Hong Kong. Sera were collected immediately before and one month after receipt of the 2015/16 quadrivalent inactivated influenza vaccine. We measured antibody titers with the hemagglutination inhibition assay, and compared mean fold rise in titers from pre- to post-vaccination, and the proportion with post-vaccination titers ≥40 and ≥160. Results Participants who reported receipt of vaccination during either of the previous two years had lower mean fold rise against all strains compared to those who were not. Mean fold rises for A(H3N2) and B/Yamagata were particularly weak following repeated vaccination with the same vaccine strain, but ...
Emerging Infectious Diseases, 2016
Euro surveillance : bulletin Européen sur les maladies transmissibles = European communicable disease bulletin, Jan 15, 2015
Plaque reduction neutralisation tests (PRNT), microneutralisation (MN), Middle East respiratory s... more Plaque reduction neutralisation tests (PRNT), microneutralisation (MN), Middle East respiratory syndrome (MERS)-spike pseudoparticle neutralisation (ppNT) and MERS S1-enzyme-linked immunosorbent assay (ELISA) antibody titres were compared using 95 sera from 17 patients with MERS, collected two to 46 days after symptom onset. Neutralisation tests correlated well with each other and moderately well with S1 ELISA. Moreover to compare antigenic similarity of genetically diverse MERS-CoV clades, the response of four sera from two patients sampled at two time periods during the course of illness were tested by 90% PRNT. Genetically diverse MERS-CoV clades were antigenically homogenous.
Emerging Infectious Diseases, 2015
Emerging Infectious Diseases, 2015
British Journal of Nutrition, 2015
Vitamin D plays an important role in skeletal health throughout life. Some studies have hypothesi... more Vitamin D plays an important role in skeletal health throughout life. Some studies have hypothesised that vitamin D may reduce the risk of other diseases. Our study aimed to estimate age-specific and sex-specific serum 25-hydroxyvitamin D (25(OH)D) status and to identify the determinants of serum 25(OH)D status in Hong Kong, a subtropical city in southern China. In 2009–2010, households in Hong Kong were followed up to identify acute respiratory illnesses, and sera from 2694 subjects were collected in three to four different study phases to permit measurement of 25(OH)D levels at different times of the year. A questionnaire survey on diet and lifestyle was conducted among children, with simultaneous serum collection in April and May 2010. The mean of serum 25(OH)D levels in age groups ranged from 39 to 63 nmol/l throughout the year with the mean values in all age groups in spring below 50 nmol/l. Children aged 6–17 years, and girls and women had significantly lower serum 25(OH)D lev...
Clinical chemistry, Jan 31, 2015
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Papers by Ranawaka A.P.M Perera - Dr