Abstract
Neutralizing monoclonal antibodies are being found to be increasingly useful in viral infections. In hepatitis B infection, antibodies are proven to be useful for passive prophylaxis. The preS1 region (21–47a.a.) of HBV contains the viral hepatocyte-binding domain crucial for its attachment and infection of hepatocytes. Antibodies against this region are neutralizing and are best suited for immune-based neutralization of HBV, especially in view of their not recognizing decoy particles. Anti-preS1 (21–47a.a.) antibodies are present in serum of spontaneously recovered individuals. We generated a phage-displayed scFv library using circulating lymphocytes from these individuals and selected four preS1-peptide specific scFvs with markedly distinct sequences from this library. All the antibodies recognized the blood-derived and recombinant preS1 containing antigens. Each scFv showed a discrete binding signature, interacting with different amino acids within the preS1-peptide region. Ability to prevent binding of the preS1 protein (N-terminus 60a.a.) to HepG2 cells stably expressing hNTCP (HepG2-hNTCP-C4 cells), the HBV receptor on human hepatocytes was taken as a surrogate marker for neutralizing capacity. These antibodies inhibited preS1-hepatocyte interaction individually and even better in combination. Such a combination of potentially neutralizing recombinant antibodies with defined specificities could be used for preventing/managing HBV infections, including those by possible escape mutants.
Highlights
Transplantation and immune-compromised individuals accompanied with an increase in ‘viral escape mutants’ are responsible for the high global prevalence of this disease[2,4]
We report the generation of potentially neutralizing preS1-specific recombinant human monoclonal scFvs from the peripheral blood lymphocytes of individuals spontaneously recovered from hepatitis B
We reasoned that individuals who have recovered naturally from hepatitis B infection would have clonally selected circulating memory B cells/plasma cells secreting highly specific neutralizing antibody against HBV
Summary
Transplantation and immune-compromised individuals accompanied with an increase in ‘viral escape mutants’ are responsible for the high global prevalence of this disease[2,4]. The viral hepatocyte binding domain has shown that anti-preS1(21–47 a.a.) agents such as antibodies are quite effective in neutralizing the virus by blocking its attachment, endocytosis and possibly membrane penetration into the hepatocyte[9,10,11,24]. A number of highly specific murine and humanized preS1-specific monoclonal antibodies that effectively neutralize HBV infection in non-human primates have been generated[9,10]. Phage-displayed recombinant antibody libraries from human source (naïve, infected or recovered individuals), containing > 108–1010 antibody sequences can be generated and high affinity monoclonal antibodies can be screened from them against specific target antigens[29,30]. We report the generation of potentially neutralizing preS1-specific recombinant human monoclonal scFvs from the peripheral blood lymphocytes of individuals spontaneously recovered from hepatitis B. We suggest that the combined usage of these recombinant human antibodies may achieve broad spectrum neutralization and in addition provide better post-exposure prophylactic interventions for HBV infection
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