Study maps primary resistance among carriers of hepatitis B

Analysis conducted on 702 patient samples from seven Brazilian states indicated that 1.6% were infected with treatment-resistant forms of the virus.

By Karina Toledo

Agência FAPESP – Hepatitis B is considered to be a chronic disease that can be controlled by medications. Over time, however, the therapy tends to select for virus strains that are resistant to the drugs used. The problem becomes even more serious when the treatment is not performed regularly or according to the most appropriate protocols.

To investigate the frequency of transmission of these resistant strains in the Brazilian population, researchers at the University of São Paulo’s Institute of Tropical Medicine (IMT-USP) and School of Medicine (FMUSP) analyzed blood samples from 702 carriers of hepatitis B, who had never been treated, from seven Brazilian states.

The study was conducted with funding from FAPESP during the doctoral studies of Michele Soares Gomes Gouvêa. Fortunately, the findings revealed the presence of resistant strains in only 11 patients, corresponding to 1.6% of the population studied.

“Although the prevalence of primary resistance [when the patient is infected by an already-resistant form of the virus] has been low, the problem still exists. This factor should be taken into consideration if the patient fails to immediately respond to treatment. To know if this is in fact occurring, frequent analyses of the viral load are needed. In the event that the viral load does not diminish, the ideal would be to conduct genome sequencing of the virus to study the resistance mutations and the proper handling of the treatment,” Gouvêa said.

According to Gouvêa, nearly 80% of patients treated with the drug lamivudine acquire resistance within a treatment period of approximately five years. Other drugs take slightly longer, but because treatment is lifelong, the problem eventually appears.

“Certain mutations increase the replication capacity of the virus, and the patient could end up with a resistant virus overload. We would like to know if these strains are being disseminated,” Gouvêa explained.

The problem of primary resistance is significant in certain regions of Africa. According to the scientific literature, the problem affects 20% of carriers of hepatitis B in South Africa. The rate jumps to 50% when considering patients who are co-infected with the AIDS virus.

“The findings of our study show that the Brazilian situation is relatively good. This gives us a certain amount of tranquility with regard to the circulation of resistant strains in the country, but we have to keep doing careful patient follow-up,” said IMT-USP/FMUSP physician Maria Cássia Jacintho Mendes Corrêa, coordinator of the project “Prevalence of primary resistance to antiviral therapy against hepatitis B in patients with chronic hepatitis B virus infection and not submitted to treatment.” She, along with João Renato Rebello Pinho of the Gastroenterology and Tropical Hepatology Laboratory of the FMUSP/IMT-USP Department of Gastroenterology, is an advisor to Gouvêa.

“Drugs that treat hepatitis B need to be used with a lot of attention and care, so as not to increase the problem of primary resistance. South Africa is one example of what can happen if we’re not careful,” Pinho stated.

According to the researchers, medications to treat hepatitis B are offered at no charge under the Unified Health System (SUS). However, there are places in Brazil where inadequate treatment plans are being adopted, either because of difficulty in gaining access to the necessary drugs or because of a lack of continuing medical education.

“An example is monotherapy with lamivudine, which was used frequently in the past but today is outlawed all over the world because it promotes the emergence of resistant strains,” Corrêa commented.

According to the physician, another factor that contributes to the exacerbation of viral resistance is patients abandoning treatment. “In most cases, hepatitis B is an asymptomatic disease. Treatment is for life, but the patient feels fine. Some people stop taking the drugs altogether, or at least on a regular basis. In some areas, access to the drugs is difficult,” she said.

If not properly treated, the inflammation in the liver caused by the hepatitis B virus (HBV) can lead to chronic hepatitis, cirrhosis of the liver or cancer of the liver. Infection – which occurs through sexual contact or contact with contaminated blood or fluids or during birth or nursing – can be prevented by a vaccine that is also available through the public health network.

Partner institutions

The work conducted as part of Gouvêa’s doctoral studies included partnerships with researchers from the Evandro Chagas Institute (state of Pará), the Pará Santa Casa de Misericórdia, the Clinical Research Center of the University Hospital of the Federal University of Maranhão (UFMA), the Gastro-Hepatology Department of the Professor Edgard Santos University Hospital at the Federal University of Bahia (UFBA), the Internal Medicine Department of the School of Medicine at the Federal University of Minas Gerais (UFMG), the Infectious and Preventive Disease Treatment Center of the School of Medicine at the Federal University of the ABC (UFABC), the Department of Infectious and Parasitic Diseases at the USP School of Medicine, the Hepatitis Clinic of the Municipal Health Department of Ribeirão Preto, the 15th Regional Health Center (state of Paraná), the Santa Casa de Porto Alegre Hospital (state of Rio Grande do Sul) and the Municipal Department of Infectology at the Caxias do Sul Specialized Health Center (state of Rio Grande do Sul).

The samples collected at each of the centers were sent for analysis at the Gastroenterology and Tropical Hepatology Laboratory of the IMT-USP. “A total of 779 samples were collected, and we found a detectable viral load and/or were able to magnify the appropriate region of interest of the viral genome in 702 samples. We then conducted genome sequencing of HBV and analyzed the region that encoded the polymerase protein [an enzyme used in the process of viral replication] because that is where the resistance mutations occur,” Gouvêa explained.

According to Gouvêa, resistance mutations that are already known were found in patients from the states of Pará, Maranhão, São Paulo and Minas Gerais. Evidence of hepatitis D, which is believed to exist only in the Amazon region, was also found in five patients from Maranhão. Of these five patients, three presented with active replication of the virus, detected based on the presence of the viral genome in the blood. These findings were published in an article that appeared in the journal Virus Research.

“The hepatitis D virus infects only carriers of hepatitis B. When this coinfection occurs, the results are disastrous. The evolution of the disease is very bad, and treatment has little effect. The patient ends up quickly developing cancer or advanced liver disease,” explained Corrêa, the project coordinator.

According to Gouvêa, one of the five cases of hepatitis D detected in Maranhão was imported from the Amazon region, a fact determined based on epidemiological data and phylogenetic analyses. “The other two with detectable viral loads presented a virus with a genotype more similar to that found in Africa. We believe that it was introduced long ago, at the time of slave trafficking. Our theory is that there are more cases in the state, and this gave rise to another study that is underway to assess the epidemiological situation of Maranhão,” she said.

Genetic diversity

Genetic sequencing of HBV has allowed researchers to also investigate the interactions among different lines (or genotypes) of the virus circulating in Brazil.

“We know of ten different genotypes of HBV – A, B, C, D, E, F, G, H, I and J – and some of these genotypes are divided into sub-genotypes. With this mapping, we have shown that there are also various sub-genotypes in Brazil and that the diversity is much higher than imagined. This is a significant finding at a time when there is a lot of discussion about the importance of considering the genotype of the virus for patient follow-up because it could influence the development of the disease and the response to certain drugs,” Gouvêa stated.

Several of the findings regarding the genetic diversity of HBV were published in an article that appeared in the journal Infection, Genetics and Evolution.

Hepatitis B affects more than 400,000,000 people in the world. In Brazil, it generally affects less than 1% of the population, but there are regions in which the disease prevalence reaches 20%, such as Amazônia, the state of Espírito Santo and western Paraná state.