CBR - Contribuições em Revistas Científicas / Contribution to Journals
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- Correction: IgG antibodies to SARS-CoV-2 in asymptomatic blood donors at two time points in KarachiPublication . Hasan, Muhammad; Moiz, Bushra; Qaiser, Shama; Masood, Kiran Iqbal; Ghous, Zara; Hussain, Areeba; Ali, Natasha; Simas, J. Pedro; Veldhoen, Marc; Alves, Paula; Abidi, Syed Hani; Ghias, Kulsoom; Khan, Erum; Hasan, Zahra
- Humoral and T cell responses to SARS-CoV-2 reveal insights into immunity during the early pandemic period in PakistanPublication . Masood, Kiran Iqbal; Qaiser, Shama; Abidi, Syed Hani; Khan, Erum; Mahmood, Syed Faisal; Hussain, Areeba; Ghous, Zara; Imtiaz, Khekahsan; Ali, Natasha; Hasan, Muhammad; Memon, Haris Ali; Yameen, Maliha; Ali, Shiza; Baloch, Sadaf; Lakhani, Gulzar; Alves, Paula M.; Iqbal, Najeeha Talat; Ahmed, Kumail; Iqbal, Junaid; Bhutta, Zulfiqar A.; Hussain, Rabia; Rottenberg, Martin; Simas, J. Pedro; Veldhoen, Marc; Ghias, Kulsoom; Hasan, ZahraBackground: Protection against SARS-CoV-2 is mediated by humoral and T cell responses. Pakistan faced relatively low morbidity and mortality from COVID-19 through the pandemic. To examine the role of prior immunity in the population, we studied IgG antibody response levels, virus neutralizing activity and T cell reactivity to Spike protein in a healthy control group (HG) as compared with COVID-19 cases and individuals from the pre-pandemic period (PP). Methods: HG and COVID-19 participants were recruited between October 2020 and May 2021. Pre-pandemic sera was collected before 2018. IgG antibodies against Spike and its Receptor Binding Domain (RBD) were determined by ELISA. Virus neutralization activity was determined using a PCR-based micro-neutralization assay. T cell – IFN-γ activation was assessed by ELISpot. Results: Overall, the magnitude of anti-Spike IgG antibody levels as well as seropositivity was greatest in COVID-19 cases (90%) as compared with HG (39.8%) and PP (12.2%). During the study period, Pakistan experienced three COVID-19 waves. We observed that IgG seropositivity to Spike in HG increased from 10.3 to 83.5% during the study, whilst seropositivity to RBD increased from 7.5 to 33.3%. IgG antibodies to Spike and RBD were correlated positively in all three study groups. Virus neutralizing activity was identified in sera of COVID-19, HG and PP. Spike reactive T cells were present in COVID-19, HG and PP groups. Individuals with reactive T cells included those with and without IgG antibodies to Spike. Conclusions: Antibody and T cell responses to Spike protein in individuals from the pre-pandemic period suggest prior immunity against SARS-CoV-2, most likely from cross-reactive responses. The rising seroprevalence observed in healthy individuals through the pandemic without known COVID-19 may be due to the activation of adaptive immunity from cross-reactive memory B and T cells. This may explain the more favourable COVID-19 outcomes observed in this population.
- A rapid real-time polymerase chain reaction-based live virus microneutralization assay for detection of neutralizing antibodies against SARS-CoV-2 in blood/serumPublication . Abidi, Syed Hani; Imtiaz, Kehkashan; Kanji, Akbar; Qaiser, Shama; Khan, Erum; Iqbal, Kiran; Veldhoen, Marc; Ghias, Kulsoom; Simas, J. Pedro; Hasan, ZahraBackground Individuals recovering from COVID-19 are known to have antibodies against the Spike and other structural proteins. Antibodies against Spike have been shown to display viral neutralization. However, not all antibodies against Spike have neutralizing ability although they may be cross-reactive. There is a need for easy-to-use SARS-CoV-2 neutralizing assays for the determination of virus-neutralizing activity in sera of individuals. Here we describe a PCR-based micro-neutralization assay that can be used to evaluate the viral neutralization titers of serum from SARS-CoV-2 infected individuals. Methods The SARS-CoV-2 strain used was isolated from a nasopharyngeal specimen of a COVID-19 case. The limiting dilution method was used to obtain a 50% tissue culture infective dose (TCID50) of Vero cells. For the micro-neutralization assay, 19 serum samples, with positive IgG titers against Spike Receptor-Binding Domain (RBD) were tested. After 24 hours, infected cells were inspected for the presence of a cytopathic effect, lysed and RNA RT-PCR conducted for SARS-CoV-2. PCR target Ct values were used to calculate percent neutralization/inhibition of SARS-CoV-2. Results Out of 19 samples, 13 samples gave 100% neutralization at all dilutions, 1 sample showed neutralization at the first dilution, 4 samples showed neutralization at lower dilutions, while one sample did not demonstrate any neutralization. The RBD ODs and neutralization potential percentages were found to be positively correlated. Conclusion We describe a rapid RT-PCR-based SARS-CoV-2 microneutralization assay for the detection of neutralizing antibodies. This can effectively be used to test the antiviral activity of serum antibodies for the investigation of both disease-driven and vaccine-induced responses.