If someone were infected with genotype A of HBV, cleared the infection and then became chronically infected with genotype B, what would his patterns of HBs antigen & antibody look like assuming he had detectable HBV viremia?
Dear Dr Cosmina,
If I could understand your question properly, then two scenarios come to my mind. First, since the patient had a prior exposure to genotype A, I assume that the second infection with genotype B will be cured by the cross-reacting neutralizing antibodies (predominantly IgG) generated against genotype A (secondary response). This is also the working principle of the currently available HBV Vaccine, which contains recombinant small HBsAg corresponding to HBV genotype A (subgenotype Ae/A2) and is reported to provide protection against other genoypes too. Alternatively, if the patient had a detectable viremia, and has progressed to chronic infection (HBsAg is positive for more than 6 months), it suggests a breakthrough infection (similar to vaccine escape infections), and the antigen antibody responses will be similar to new infection.
SD
This is very unusual case where a previously infected person who cleared the virus would become chronically infected with a new genotype. Most of the well documented HBV breakthrough infections are in vaccinated blood donors. As a rule they are always asymptomatic, may or may not have a positive HBsAg, the viremia is short lived and they clear the virus within couple of months at most. The only consistent pattern is the sharp rise in anti-HBs. When you mentioned that the person cleared the first episode of HBV what were his anti-HBs levels? Hypothetically it is possible (if no anti-HBs response was observed) that the patient's infection may have eventually become "occult" HBV, in which case a second infection with a different genotype may eventually become chronic. So to sum-up while it is possible to get re-infected it is almost impossible for someone who has been previously infected, cleared the virus and mounted a proper immune response to develop a CHRONIC HBV infection.
Thank you for your answers. My question was hypothetical. But I was confronted with the following situation: detectable viremia, negative HBs antigen and positive antiHBs antibodies. Assuming there was no mix-up in the lab, I was wondering what other explanation there could be so I invented the above scenario to see if it seemed plausible to any experts out there:)
In that scenario the most plausible answer is OBI (occult HBV infection).