RESUMO
@#Abstract: Objective To clarify the long-term evolution of hepatitis B virus (HBV) quasi-species in HBsAg asymptomatic carriers in Long'an county, Guangxi. Methods ELISA was used to detect serological markers of HBV. Viral loads were measured by real time PCR. HBV DNA was extracted from serum by kits. The whole HBV genome was amplified using nested PCR and amplicons were sequenced by next-generation sequencing (NGS). These sequences from NGS were analyzed by the software like Mega. Results Serum samples were collected from 9 HBsAg asymptomatic carriers in Longan County，Guangxi at 4 different time points in 2004, 2007, 2013, 2019 or 2020. A total of 23 serum samples and 309 full-length gene quasi-species sequences were obtained, with an average amount of (0.18±0.07) G sequencing data for each sample. Genotype of 55.54%(5/9) the studied subjects underwent genotype conversion during the long-term evolution process of HBV quasi-species, and the genotyping results of the phylogenetic tree in the PreS/S region are in perfect agreement with the results of the whole genome analysis; recombinant B/C, I/C were found; the Sn ranged from 0 to 0.37 and the genetic diversity ranged from 0 to 0.11, respectively. A total of 21 special single nucleotide/amino acid mutations (7 in the S region, 2 in the X region, 3 in the PreC region and 9 in the BCP region) and 6 deletion mutations were detected, multiple mutations were found and no drug resistant mutations were found; 77.8%(7/9) of the HBV strains carried by the subjects in 2004 had double mutations at nt1 762(A→T) and 1 764(G→A) and a stop mutation at nt1 896(G→A); HBV mutations can be restored from the mutant type to the wild type and (or) vice versa without antiviral drug pressure, and The evolution rate of HBV genome was 2.03×10-5~3.50×10-3.Conclusion HBV genotype, recombinants, genetic complexity and diversity of HBV quasi-species can change over time during in natural infection. The transformation between HBV mutation type and wild type reduces the value of predicting clinical outcomes by genetic types and related mutations to some extent. The HBV genome evolution rate of asymptomatic carriers of HBsAg in Long'an County is very high.
RESUMO
The spike protein of SARS-CoV-2 is arranged as a trimer on the virus surface, composed of three S1 and three S2 subunits. Infected and vaccinated individuals generate antibodies against spike, which can neutralize the virus. Most antibodies target the receptor-binding domain (RBD) and N-terminal domain (NTD) of S1; however, antibodies against other regions of spike have also been isolated. The variation between infected individuals in domain specificity of the antibodies and in their relative neutralization efficacy is still poorly characterized. To this end, we tested serum and plasma samples from 85 COVID-19 convalescent subjects using 7 immunoassays that employ different domains, subunits and oligomeric forms of spike to capture the antibodies. Samples were also tested for their neutralization of pseudovirus containing SARS-CoV-2 spike and of replication-competent SARS-CoV-2. We observed strong correlations between the levels of NTD- and RBD-specific antibodies, with a fixed ratio of each type to all anti-spike antibodies. The relative potency of the response (defined as the measured neutralization efficacy relative to the total level of spike-targeting antibodies) also exhibited limited variation between subjects, and was not associated with the overall amount of anti-spike antibodies produced. Accordingly, the ability of immunoassays that use RBD, NTD and different forms of S1 or S1/S2 as capture antigens to estimate the neutralizing efficacy of convalescent samples was largely similar. These studies suggest that host-to-host variation in the polyclonal response elicited against SARS-CoV-2 spike is primarily limited to the quantity of antibodies generated rather than their domain specificity or relative neutralization potency. IMPORTANCEInfection by SARS-CoV-2 elicits antibodies against various domains of the spike protein, including the RBD, NTD and S2. Different infected individuals generate vastly different amounts of anti-spike antibodies. By contrast, as we show here, there is a remarkable similarity in the properties of the antibodies produced. Different individuals generate the same proportions of antibodies against each domain of the spike protein. Furthermore, the relationship between the amount of anti-spike antibodies produced and their neutralization efficacy of SARS-CoV-2 is highly conserved. Therefore, the observed variation in the neutralizing activity of the antibody response in COVID-19 convalescent subjects is caused by differences in the amounts of antibodies rather than their recognition properties or relative antiviral activity. These findings suggest that COVID-19 vaccine strategies that focus on enhancing the overall level of the antibodies will likely elicit a more uniformly efficacious protective response.
