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Now showing 1 - 4 of 4
  • PublicationOpen Access
    Discordance between Serum Neutralizing Antibody Titers and the Recovery from COVID-19
    (2020-09-25T00:00:00Z) Koç, Mm; Kalkan, Yazıcı; Çetin, Nesibe Selma; Doymaz, Mz; Sümbül, B; Durdu, B; YAZICI, MERVE; MERİÇ KOÇ, MELİHA; ÇETİN, NESİBE SELMA; KARAASLAN, ELİF; OKAY, GÜLAY; DURDU, BÜLENT; SÜMBÜL, BİLGE; DOYMAZ, MEHMET ZIYA
    The recent pandemic of COVID-19 has caused a tremendous alarm around the world. Details of the infection process in the host have significant bearings on both recovery from the disease and on the correlates of the protection from the future exposures. One of these factors is the presence and titers of neutralizing Abs (NAbs) in infected people. In the current study, we set out to investigate NAbs in the recovered subjects discharged from the hospital in full health. Serum samples from a total of 49 documented consecutive COVID-19 subjects were included in the study. All the subjects were adults, and serum samples collected during the discharge were tested in viral neutralization, enzyme immunoassay (EIA), and Western immunoblot tests against viral Ags. Even though a majority of the recovered subjects had raised significant NAb titers, there is a substantial number of recovered patients (10 out of 49) with no or low titers of NAbs against the virus. In these cohorts as well as in patients with high NAb titers, viral Ag binding Abs were detectable in EIA tests. Both NAb titers and EIA detectable Abs are increased in patients experiencing a severe form of the disease, and in older patients the Ab titers were heightened. The main conclusion is that the recovery from SARS-CoV-2 infection is not solely dependent on high NAb titers in affected subjects, and this recovery process is probably produced by a complex interplay between many factors, including immune response, age of the subjects, and viral pathology.
  • PublicationOpen Access
    An Attenuated HSV-1-Derived Malaria Vaccine Expressing Liver-Stage Exported Proteins Induces Sterilizing Protection against Infectious Sporozoite Challenge
    (2022-02-01T00:00:00Z) Rider, Paul J. F.; KAMIL, MOHD; Yilmaz, Ilknur; Atmaca, Habibe N.; Kalkan-Yazici, Merve; Ziya Doymaz, Mehmet; Kousoulas, Konstantin G.; ALY, Ahmed Sayed Ibrahım; KAMIL, MOHD; YAZICI, MERVE; ALY, AHMED SAYED IBRAHıM
    Here, we present the construction of an attenuated herpes simplex virus type-1 (HSV-1)-vectored vaccine, expressing three liver-stage (LS) malaria parasite exported proteins (EXP1, UIS3 and TMP21) as fusion proteins with the VP26 viral capsid protein. Intramuscular and subcutaneous immunizations of mice with a pooled vaccine, composed of the three attenuated virus strains expressing each LS antigen, induced sterile protection against the intravenous challenge of Plasmodium yoelii 17X-NL salivary gland sporozoites. Our data suggest that this malaria vaccine may be effective in preventing malaria parasite infection using practical routes of immunization in humans.
  • PublicationOpen Access
    Cross-Reactive anti-Nucleocapsid Protein Immunity against Crimean-Congo Hemorrhagic Fever Virus and Hazara Virus in Multiple Species.
    (2021-01-13T00:00:00Z) Kalkan-Yazıcı, Merve; Karaaslan, Elif; Çetin, Nesibe Selma; Hasanoğlu, Sevde; Güney, Filiz; Zeybek, Ümit; Doymaz, Mehmet Ziya; YAZICI, MERVE; ÇETİN, NESİBE SELMA; DOYMAZ, MEHMET ZIYA
    The World Health Organization estimates that there may be three billion people at risk of infection by Crimean-Congo Hemorrhagic Fever Virus (CCHFV), a highly lethal, emerging orthonairovirus carried by ticks. On the other hand, the closely related Hazara virus (HAZV), a member of the same serogroup, has not been reported as a pathogen for humans. Given the structural and phylogenetic similarities between these two viruses, we evaluated the immunological similarities of the nucleocapsid protein (NP) of these two viruses in multiple species. Strong antigenic similarities were demonstrated in anti-NP humoral immune responses against HAZV and CCHFV in multiple species using convalescent human CCHF sera, rabbit and mouse polyclonal antiserum raised against CCHFV, and mouse polyclonal antiserum against CCHFV-NP in enzyme immunoassays. We also report a convincing cross-reactivity between NPs in Western blots using HAZV-infected cell lysate as antigen and inactivated CCHFV and CCHFV-NP-immunized mice sera. These results suggest that NPs of HAZV and CCHFV share significant similarities in humoral responses across species and underline the potential utility of HAZV as a surrogate model for CCHFV.IMPORTANCE CCHFV and HAZV, members of the Nairoviridae family, are transmitted to mammals by tick bites. CCHFV is considered to be a severe threat to public health and causes hemorrhagic diseases with a high mortality rate, and there are neither preventative nor therapeutic medications against CCHFV disease. HAZV, on the other hand, is not a pathogen to humans and can be studied under BSL-2 conditions. The antigenic relationship between these viruses is of interest for vaccines and for preventative investigations. Here, we demonstrate cross-reactivity in anti-NP humoral immune response between NPs of HAZV and CCHFV in multiple species. These results underline the utility of HAZV as a surrogate model to study CCHFV infection.
  • PublicationMetadata only
    A case-control study on effects of the ATM, RAD51 and TP73 genetic variants on colorectal cancer risk
    (2019-12-01T00:00:00Z) Yazici, Merve; Yilmaz, Umit; Yilmaz, Nesibe; Celik, Faruk; Isikoren, Ece Gizem; Celikel, Burcu; Ergen, Arzu; Keskin, Metin; Zeybek, Şakir Ümit; YAZICI, MERVE
    Aim: ATM, RAD51 and TP73 are genes that take part in DNA repair pathways. The aim of this prospective case-control study was to determine the genotype and allele distributions of the ATM 5--UTR G/A, RAD51 135 G/C and TP73 GC/AT polymorphisms and their relationship with clinical parameters in Turkish colorectal cancer (CRC) patients.