Just as Brazil surpassed 200,000 deaths from COVID-19 on Jan. 7, news from Bahia added another layer of concern: A platform case report in a preprint detailed the first case of reinfection in that state, apparently caused by a new strain, one having the E484K mutation.
That variant, now called Brazil P.1, has migrated to the United States. The Minnesota Department of Health announced on Jan. 25 the nation’s first known COVID-19 case associated with it.
The mutation is located in the protein gene of the virus’ spike, which forms the crown structure of coronaviruses and is responsible for the virus’ binding to human cells. The E484K mutation is now the focus because it’s associated with mutations that escape the immune system’s neutralizing antibodies.
“This mutation is at the center of worldwide concern, and it is the first time that it has appeared in a reinfection,” the study’s first author, Bruno Solano de Freitas Souza, MD, a researcher at the Salvador regional unit of Instituto D’Or of Teaching and Research, based at Hospital São Rafael, Salvador, Brazil, explained in an interview.
“We will wait for the sample from Bahia to confirm the case from the perspective of the Ministry of Health’s surveillance network,” said Fernando Motta, PhD, deputy head of the Laboratory for Respiratory Virus and Measles at the Oswaldo Cruz Institute in Rio de Janeiro, which acts as a national reference center for respiratory viruses with the Brazilian Ministry of Health (MS) and as a reference for the World Health Organization.
A case of reinfection
The case patient that led to the alarm was a 45-year-old woman who is a health care executive. She had no comorbidities. The team had been following health care professionals and patients who had tested positive on reverse transcription–polymerase chain reaction (RT-PCR) testing more than once to understand whether they represented cases of prolonged viral persistence or new infections.
The woman had symptoms of viral infection on two occasions (May 26 and Oct. 26). On both occasions, results of RT-PCR testing for SARS-CoV-2 on nasopharyngeal samples were positive. In the first episode, the patient had diarrhea, myalgia, asthenia, and odynophagia for about 7 days. She returned to activities 21 days later. In the second episode, she had more severe symptoms that lasted longer, but she still did not require hospitalization.
“It was the first confirmed case of reinfection in Bahia, and in the second episode, we observed a mutation that could have an impact on the ability of antibodies to neutralize the virus,” Dr. Souza said. “The research continues with the investigation of cases in which the patient has a positive SARS-CoV-2 RT-PCR more than once in an interval greater than 45 days, to have a higher level of evidence.”
He stressed that “it is very important to reinforce measures to control the pandemic, social distance, use of masks, and speed up vaccination to be able to control the circulation of the virus, while monitoring the evolution of it.”
On alert for more cases
A person who twice tests positive for SARS-CoV-2 on real-time RT-PCR is suspected of having been reinfected, provided 90 or more days have elapsed between the two episodes, regardless of the condition observed. To confirm the suspected case, the samples must be sent to reference laboratories according to a plan established by the Ministry of Health in Brazil.
A health professional living in the Brazilian city of Natal represented the first confirmed case of reinfection by the new coronavirus in Brazil. That case was announced on Dec. 10, 2020.
“We communicated this case of reinfection to the MS in early December 2020. And the second sample already had the E484K mutation on the spike, as in the case of Bahia,” said Dr. Motta.
The first step in differentiating reinfection from persistence is to observe differences in the genotyping of the virus. For the technique to be successful, Dr. Souza said, researchers need a large amount of viral genetic material, which usually cannot be obtained.
“That is why there are many more suspected than confirmed cases,” Dr. Souza explained. He admitted that, although there are few cases, “it is increasingly clear that reinfection is a reality.”
Markers of mutations
What worried the researchers most was not only the possibility of reinfection but also the fact that preliminary analyses showed a specific mutation.
“The E484K mutation is present in a group of variants identified in South Africa that have been associated with increased infectivity and has been observed in a strain recently described in Brazil,” Dr. Souza said.
Mutations are expected, appear spontaneously, and in most cases have no effects on transmission or clinical outcome – they are simply used as markers and are useful for contact tracing or studying transmission routes. But some mutations can last because they provide an advantage for the pathogen, even if only momentary. In the case of SARS-CoV-2, mutations in the protein spike gene (S) are relevant because they may give clues to that advantage – as well as to changes in infectivity, transmission potential, antibodies, and response to vaccines.
A variant of the virus that has eight changes that affect the protein S gene – and several others in different genes – is behind the increase in the number of cases in London and southeastern England. Researchers from the University of São Paulo identified one of the factors that made this new variant – classified as B.1.1.7 – more infectious.
With bioinformatics tools, they found that the protein S gene in the new viral strain has a stronger molecular interaction with the ACE2 receptor, which is on the surface of human cells and to which the virus binds, making infection possible. The variant has already spread to the rest of the world, and the first two cases have been confirmed in Brazil by the Adolf Lutz Institute.
The alert for a new variant in Africa – similar to B.1.1.7 in the United Kingdom in that it carries nine changes in protein S at position 501 – was made by the Brazilian virologist Tulio de Oliveira, PhD.
“We found that this strain seems to be spreading much faster,” Dr. Oliveira, who is with the University of KwaZulu Natal, told the journal Science. His work first alerted British scientists to the importance of the position N501Y.
“The new variants just described in the United Kingdom and South Africa are slightly more transmissible and have already been identified in cases imported into Brazil,” Dr. Motta said. “Unfortunately, we believe it is only a matter of time before it becomes indigenous.”