Ioannis Sitaras

Ioannis Sitaras
Johns Hopkins Bloomberg School of Public Health | JHSPH · W. Harry Feinstone Department of Molecular Microbiology and Immunology

PhD

About

19
Publications
1,042
Reads
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135
Citations
Additional affiliations
January 2020 - present
Centers for Disease Control and Prevention
Position
  • Research Associate
June 2017 - January 2020
United States Department of Agriculture
Position
  • PostDoc Position
September 2008 - November 2017
Wageningen University & Research
Position
  • PhD Student
Education
September 2008 - November 2017
Wageningen University & Research
Field of study
  • Ph.D. Virology and Epidemiology
September 2003 - September 2004
The University of York
Field of study
  • M.Res. Biomolecular Science
September 1998 - September 2002
University of the West of England, Bristol
Field of study
  • B.Sc. (Honours) Biomedical Sciences

Publications

Publications (19)
Preprint
Background: The emergence of the Omicron variant (B.1.1.529) which correlated with dramatic losses in cross-neutralization capacity of post-vaccination sera raised concerns about the effectiveness of COVID-19 vaccines against infection and disease. Clinically relevant sub-variants (BA.1, BA.1.1, BA.2, BA.2.12.1, BA.3, and BA.4/5) subsequently emerg...
Article
Full-text available
In late 2021, the omicron variant of SARS Coronavirus 2 (SARS-CoV-2) emerged and replaced the previously dominant delta strain. Effectiveness of COVID-19 vaccines against omicron has been challenging to estimate in clinical studies or is not available for all vaccines or populations of interest. T cell function can be predictive of vaccine longevit...
Preprint
Neutralizing antibody responses are attenuated in many solid organ transplant recipients (SOTRs) despite SARS-CoV-2 vaccination. Pre-exposure prophylaxis (PrEP) with the monoclonal antibody combination Tixagevimab and Cilgavimab (T+C) might augment immunoprotection, yet activity against Omicron sublineages in vaccinated SOTRs is unknown. Vaccinated...
Article
Full-text available
Assessing COVID-19 vaccine effectiveness against emerging SARS-CoV-2 variants is crucial for determining future vaccination strategies and other public health strategies. When clinical effectiveness data are unavailable, a common method of assessing vaccine performance is to utilize neutralization assays using post-vaccination sera. Neutralization...
Article
Full-text available
Background: Male sex and old age are risk factors for severe COVID-19, but the intersection of sex and aging on antibody responses to SARS-CoV-2 vaccines has not been characterized. Methods: Plasma samples were collected from older adults (75-98 years) before and after three doses of SARS-CoV-2 mRNA vaccination, and from younger adults (18-74 ye...
Article
Full-text available
Several vaccines have been introduced to combat the coronavirus infectious disease‐2019 (COVID‐19) pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2). Current SARS‐CoV‐2 vaccines include mRNA‐containing lipid nanoparticles or adenoviral vectors that encode the SARS‐CoV‐2 Spike (S) protein of SARS‐CoV‐2, inactivated vir...
Article
Full-text available
Benchmarks for protective immunity from infection or severe disease after SARS-CoV-2 vaccination are still being defined. Here we characterized virus neutralizing and ELISA antibody levels, cellular immune responses, and viral variants in 4 separate groups: Healthy control participants weeks (early) or months (late) following vaccination in compari...
Article
Vaccine-induced SARS-CoV-2 antibody responses are attenuated in solid organ transplant recipients (SOTRs) and breakthrough infections are more common. Additional SARS-CoV-2 vaccine doses increase anti-spike IgG in some SOTRs, but it is uncertain whether neutralization of variants of concern (VOCs) is enhanced. We tested 47 SOTRs for clinical and re...
Article
Full-text available
Understanding the dynamics of the selection of influenza A immune escape variants by serum antibody is critical for designing effective vaccination programs for animals, especially poultry where large populations have a short generation time and may be vaccinated with high frequency. In this report, immune-escape mutants of A/turkey/New York/4450/...
Article
Five vaccines, including four inactivated, whole-virus water-in-oil adjuvanted vaccines and a commercial non-replicating alphavirus vectored RNA particle (RP) vaccine were evaluated in chickens for their ability to provide protection against challenge with a recent H7 highly pathogenic avian influenza virus (AIV) from the US (A/turkey/IN/1403-1/201...
Chapter
The hemagglutination inhibition (HI) assay for influenza A virus has been used since the 1940s. The assay may be utilized to detect or quantify antibodies to influenza A viruses and can be used to characterize differences in antigenic reactivity between influenza isolates. In addition, data from HI assays are routinely used for antigenic cartograph...
Chapter
Antigenic cartography is a powerful method that allows for the calculation of antigenic distances between influenza viruses or sera and their positioning on a map, by quantifying raw data from hemagglutination inhibition assays. As a consequence, the antigenic drift of influenza viruses over time can be visualized in a straightforward manner. Antig...
Article
Background: Transmission of highly pathogenic avian influenza (HPAI) viruses in poultry flocks is associated with huge economic losses, culling of millions of birds, as well as human infections and deaths. In the cases where vaccination against avian influenza is used as a control measure, it has been found to be ineffective in preventing transmis...
Article
Full-text available
Highly pathogenic avian influenza (HPAI) H5N1 epidemics in poultry cause huge economic losses as well as sporadic human morbidity and mortality. Vaccination in poultry has often been reported as being ineffective in preventing transmission and as a potential driving force in the selection of immune escape mutants.We conducted transmission experimen...
Poster
Full-text available
Selection of immune escape mutants of HPAI H5N1 virus using homologous polyclonal sera. Investigation into the role of vaccine dose (and vaccination-induced immunity) and antigenic distance in the transmission of HPAI H5N1 escape mutants to vaccinated animals. We demonstrate through the use of novel mathematical models that the effect of antigenic...
Article
Full-text available
Evolution of Avian Influenza (AI) viruses - especially of the Highly Pathogenic Avian Influenza (HPAI) H5N1 subtype - is a major issue for the poultry industry. HPAI H5N1 epidemics are associated with huge economic losses and are sometimes connected to human morbidity and mortality. Vaccination (either as a preventive measure or as a means to contr...

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Projects

Project (1)
Project
Research on HPAI and LPAI evolution and escape mutant selection (in ovo and in vivo) under immune pressure from homologous polyclonal sera or vaccines. Research on the effect of LPAI virus infections in egg production and transmission of viruses to egg surfaces and embryos. The post-doctoral projects involve in ovo and in vivo work (vaccination, swabbing, intra-venous and intra-cardiac bleeding, temperature taking, euthanasia, etc.), preparation of vaccines, EID50, haemagglutination, and haemagglutination inhibition assays, RNA isolation, PCR, qPCR, agarose gel electrophoresis, sequencing, preparation of sera, use of sequencing software, mathematical analysis, antigenic cartography.