Researchers monitor rapid rise of plasma SARS-CoV-2 antibodies over the course of a pandemic

The researchers found that neutralization of antibodies against acute respiratory respiratory syndrome coronavirus 2 (SARS-CoV-2) can increase over time. They maintained that samples taken from convalescent plasma in September 2020 by July 2021 were likely to have high enough values ​​to protect immunocompromised patients receiving intravenous immunoglobulins as part of their treatment.

Plasma from healthy donors is used for the preparation of immunoglobulin (IG) containing antibodies for patients with primary and secondary immunodeficiencies requiring primary treatment. A large proportion of the plasma collected comes from the USA, which also has a large number of COVID-19 cases. Therefore, it is also expected that antibodies collected from donors will now contain antibodies against SARS-CoV-2, the causative agent of coronavirus disease 2019 (COVID-19).

Researchers from Baxter AG in Vienna, Austria, report the results of their study of seroconversion of U.S. plasma supply by testing intravenous immunoglobulins (IVIG) for SARS-CoV-2 neutralization. They reported their findings in a paper published on the bioRxiv * preprint server.

Monitoring for neutral antibodies

The team analyzed 176 IVIG lots collected between March 2020 and January 2021. They also collected convalescent plasma samples, 300 from Austria and 138 from the USA. The team tested the plasma for the presence of antibodies neutralized to SARS-CoV-2 and human coronavirus (HCoV-229E) using standard methods.

They did not detect antibodies to SARS-CoV-2 in the lots released to the market between March 2020 and August 2020. For lots released in September 2020, 46% had antibodies to SARS -CoV-2. In subsequently released lots, the proportion of seropositive SARS-CoV-2 lots and density of antibodies increased steadily, with about 93% of seropositive lots in January 2021. The antibody titers increased from 1.8 IU / ml for September 2020 lot to 36.7 IU / ml in January 2021.

HCoV-229E antibody neutralizing titers remained present during the test period and were similar to previously observed domains.

Plasma was usually collected about six months before the IVIG lots were released, so plasma for the lots released in January 2021 would have been collected about six months ago, in July 2020. The seroprevalence reveals COVID-19 cases in the US population, with plasma collected in March 2020 (lesion released in September 2020) showing levels low of antibody and subsequently increases with the increase in the number of cases in the US.

The neutralizing antibody concentrations in the accumulated convalescent plasma were, on average, about 300 IU / ml. The majority of donors had moderate or asymptomatic COVID-19, with 9% having recovered from severe infection.

From the data for the concentrations of SARS-CoV-2 neutral antibodies in the plasma released to January 2021, the team estimates that the level of antibodies will be around 400 IU / ml in lots. which will be released in July 2021.

Protecting patients with immunity

However, these estimates appear to be conservative, in particular, with vaccines rapidly advancing in the US. By the end of January 2021, approximately 9.6% of the U.S. population has already been vaccinated. The COVID-19 mRNA vaccines stimulate higher antibody titers, in addition to the natural disease, they increase the anti-SARS-CoV-2 potential of IG products in the future, possibly higher than previously estimated in the study.

In a tested sample of convalescent plasma, the team found a means to neutralize antibody titers of 516 IU / ml, corresponding to 103,200 IU in 200 ml. Improved results have been reported using a higher dose of 945 IU / ml (189,000 IU in 200 ml).

Releasing to July 2021, the authors estimate that IGs will contain approximately 400 IU / ml of neutral SARS-CoV-2 antibodies. If a person receives 70 kg of a dose of about 350 ml, the dose will be about 140,000 IU of antibodies.

Studies have shown that convalescent plasma administration works best if given early after SARS-CoV-2 infection. For people with immunodeficiencies, plasma is administered as part of their general treatment, and therefore susceptible before the onset of a virus, so they will have better results if they get the infection. This will be very helpful for patients with primary immunodeficiency, who are reported to have a 10-fold higher COVID-19 mortality.

Therefore, the protection of immunocompromised patients who receive IG on a regular basis is quite possible as the number of people receiving the vaccine in the U.S. continues to grow, along with growing cases. of natural diseases. The team is also evaluating hyper-IVIG performed exclusively from the plasma of COVID-19 patients recovered as a potential treatment for COVID-19.

* Important message

bioRxiv publish preliminary scientific reports that are not peer-reviewed and, therefore, should not be seen as final, guiding health-related clinical practice / behavior, or be treated as information established.