Virus World

COVID-19 vaccines have recently been updated with the spike protein of SARS-Co-V-2 XBB.1.5 subvariant alone, but their immunogenicity in humans has yet to be fully evaluated and reported, particularly against emergent viruses that are rapidly expanding. We now report that administration of an updated monovalent mRNA vaccine (XBB.1.5 MV) to uninfected individuals boosted serum virus-neutralization antibodies significantly against not only XBB.1.5 (27.0-fold) and the currently dominant EG.5.1 (27.6-fold) but also key emergent viruses like HV.1, HK.3, JD.1.1, and JN.1 (13.3-to-27.4-fold). In individuals previously infected by an Omicron subvariant, serum neutralizing titers were boosted to highest levels (1,764-to-22,978) against all viral variants tested. While immunological imprinting was still evident with the updated vaccines, it was not nearly as severe as the previously authorized bivalent BA.5 vaccine. Our findings strongly support the official recommendation to widely apply the updated COVID-19 vaccines to further protect the public.

Preprint in bioRxiv (Nov. 27, 2023): 

 https://doi.org/10.1101/2023.11.26.568730 

It’s not yet clear whether the antibody levels produced will lead to immunity to the virus. To prove that, the companies will need to conduct large studies. An experimental Covid-19 vaccine being developed by the drug giant Pfizer and the biotech firm BioNTech spurred immune responses in healthy patients, but also caused fever and other side effects, especially at higher doses. The first clinical data on the vaccine were disclosed Wednesday in a paper released on medRXiv, a preprint server, meaning it has not yet been peer-reviewed or published in a journal. “We still have a ways to go and we’re testing other candidates as well,” said Philip Dormitzer, the chief scientific officer for viral vaccines at Pfizer’s research laboratories. “However, what we can say at this point is there is a viable candidate based on immunogenicity and early tolerability safety data.” 

The study randomly assigned 45 patients to get one of three doses of the vaccine or placebo. Twelve received a 10-microgram dose, 12 a 30-microgram dose, 12 a 100-microgram dose, and nine a placebo. The 100-microgram dose caused fevers in half of patients; a second dose was not given at that level. Following a second injection three weeks later of the other doses, 8.3% of the participants in the 10-microgram group and 75% of those in the 30-microgram group developed fevers. More than 50% of the patients who received one of those doses reported some kind of adverse event, including fever and sleep disturbances. None of these side effects was deemed serious, meaning they did not result in hospitalization or disability and were not life-threatening.

The vaccine generated antibodies against SARS-CoV-2, the virus that causes Covid-19, and some of these antibodies were neutralizing, meaning that they appear to prevent the virus from functioning. Levels of neutralizing antibodies were 1.8 to 2.8 times the level of that in the recovered patients. It’s not certain that higher antibody levels will lead to immunity to the virus. To prove that, Pfizer will need to conduct large studies that aim to prove that people who have received the vaccine are at least 50% less likely to become infected. Those studies are expected to begin this summer, mostly in the United States. Pfizer and BioNTech are testing four different versions of the vaccine, but only one will advance to larger studies....

Preprint available at medRxiv (July 1, 2020):

https://doi.org/10.1101/2020.06.30.20142570

In this study, by characterizing several human monoclonal antibodies (mAbs) isolated from single B cells of the COVID-19–recovered individuals in India who experienced ancestral Wuhan strain (WA.1) of SARS-CoV-2 during early stages of the pandemic, we found a receptor binding domain (RBD)–specific mAb 002-S21F2 that has rare gene usage and potently neutralized live viral isolates of SARS-CoV-2 variants including Alpha, Beta, Gamma, Delta, and Omicron sublineages (BA.1, BA.2, BA.2.12.1, BA.4, and BA.5) with IC50 ranging from 0.02 to 0.13 μg/ml. Structural studies of 002-S21F2 in complex with spike trimers of Omicron and WA.1 showed that it targets a conformationally conserved epitope on the outer face of RBD (class 3 surface) outside the ACE2-binding motif, thereby providing a mechanistic insights for its broad neutralization activity. The discovery of 002-S21F2 and the broadly neutralizing epitope it targets have timely implications for developing a broad range of therapeutic and vaccine interventions against SARS-CoV-2 variants including Omicron sublineages.

Published in Science Advances (October 5, 2022):

https://doi.org/10.1126/sciadv.add2032 

Scientists in Shanghai say some recovered patients show no signs of the neutralising proteins.  Researchers in Shanghai hope to determine whether some recovered coronavirus patients  have a higher risk of reinfection after finding surprisingly low levels of Covid-19 antibodies in a number of people discharged from hospital. A team from Fudan University analysed blood samples from 175 patients discharged from the Shanghai Public Health Clinical Centre and found that nearly a third had unexpectedly low levels of antibodies. In some cases, antibodies could not be detected at all.