Laboratory experiments conducted at the State University of Campinas (Unicamp) indicate that antibodies present in the blood plasma of people who have had COVID-19 and recovered are about six times less efficient in neutralizing the Brazilian variant of SARS-CoV-2, called P .1., Than the so-called lineage B, which circulated in the country in the first months of the pandemic.
The study also shows that the plasma collected from individuals who received the second dose of CoronaVac about five months ago has a low amount of antibodies capable of neutralizing the new coronavirus – both strain B and variant P.1. The data were released Monday (01/03) on the platform Preprints with The Lancet and are still in the process of peer review.
“What these preliminary results suggest is that both people who have had COVID-19 and those who have been vaccinated can be infected with the new P.1 variant. and therefore, they should not be neglected ”, warns José Luiz Proença Modena, professor at the Institute of Biology (IB-Unicamp) and research coordinator.-
According to the researcher, this phenomenon is common and also occurs with other vaccines, causing some viruses to continue to circulate even after a population is immunized. “Under no circumstances does he suggest that the vaccine does not work,” he says.
The experiments described in the article were carried out with support from FAPESP (projects 16/00194-8 e 20/04558-0) at the IB-Unicamp Laboratory for Emerging Virus Studies (Light), which has biosafety level 3 (NB3) and is administered by Modena.
The group received from collaborators of the Brazil-United Kingdom Center for Discovery, Diagnosis, Genomics and Arbovirus Epidemiology (CADDE) 20 samples of nasopharyngeal secretion from patients infected with the Brazilian variant, which were inoculated in cell cultures susceptible to SARS-CoV-2. The presence of P.1. in patient samples it was confirmed by sequencing the viral genome.
Two isolates of the P.1 variant. obtained from infected cultures in vitro were used in the neutralization tests carried out with both convalescent and vaccinated plasma.
“We already had a collection of plasma donated by people who recovered from COVID-19 – all samples with high amounts of neutralizing antibodies. This material was originally collected and analyzed for the treatment of critically ill patients [método conhecido como transfusão passiva de imunidade ou terapia com plasma convalescente]”, Modena tells Agência FAPESP.
Convalescent plasma samples – collected between two and three months after infection – were tested in parallel against strain B and variant P.1. The results indicate that the neutralization potential against the new strain was, on average, six times lower.
“This is a value that draws attention,” says Modena. “In the case of the influenza virus [causador da gripe], for example, when from year to year a new variant appears that is six times less neutralized by antibodies, it is already considered that there is an immune escape and that it is necessary to update the vaccine. ”
Further studies are needed
The neutralization experiments with the plasma of vaccinees were carried out with samples collected from eight volunteers who participated in the CoronaVac phase 3 clinical trial – an immunizer developed by the Chinese company Sinovac Biotech in partnership with the Butantan Institute. Immunization took place between the months of August and September 2020.
As phase 2 clinical tests have already indicated, the amount of neutralizing antibodies in the blood of vaccinees drops sharply after approximately six months. So, in the tests in vitro made at Unicamp, the effect of neutralizing blood plasma was small both against P.1. as against strain B. However, the researchers emphasize that these results need to be interpreted with caution, since neutralizing antibodies are only one component of the immune system.
“Other protective elements that can be strongly induced by the vaccine, such as cellular immunity, are probably still able to prevent those immunized from developing the disease – especially the most severe forms. However, everything indicates that the vaccinees are not free to become infected and to transmit the virus ”, evaluates Modena.
According to the researcher, the number of individuals evaluated in the study is small and the results are not robust enough to conclude something related to the effectiveness of CoronaVac against the Brazilian variant of the new coronavirus. “More in-depth studies are needed to assess both the effectiveness of CoronaVac and other vaccines against P.1.”, He says.
The authors also point out that hygiene and social distance measures remain essential to control the spread of the virus, even among people previously infected or already vaccinated. “These measures are important to avoid possible cases of reinfection, especially due to the new emerging strains”, they state.
* Article published by Agência Fapesp
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