Natural selection and genetic diversity of domain I of Plasmodium falciparum apical membrane antigen-1 on Bioko Island.

BACKGROUND: Plasmodium falciparum apical membrane antigen-1 (PfAMA-1) is a promising candidate antigen for a blood-stage malaria vaccine. However, antigenic variation and diversity of PfAMA-1 are still major problems to design a universal malaria vaccine based on this antigen, especially against domain I (DI). Detail understanding of the PfAMA-1 gene polymorphism can provide useful information on this potential vaccine component. Here, general characteristics of genetic structure and the effect of natural selection of DIs among Bioko P. falciparum isolates were analysed. METHODS: 214 blood samples were collected from Bioko Island patients with P. falciparum malaria between 2011 and 2017. A fragment spanning DI of PfAMA-1 was amplified by nested polymerase chain reaction and sequenced. Polymorphic characteristics and the effect of natural selection were analysed using MEGA 5.0, DnaSP 6.0 and Popart programs. Genetic diversity in 576 global PfAMA-1 DIs were also analysed. Protein function prediction of new amino acid mutation sites was performed using PolyPhen-2 program. RESULTS: 131 different haplotypes of PfAMA-1 were identified in 214 Bioko Island P. falciparum isolates. Most amino acid changes identified on Bioko Island were found in C1L. 32 amino acid changes identified in PfAMA-1 sequences from Bioko Island were found in predicted RBC-binding sites, B cell epitopes or IUR regions. Overall patterns of amino acid changes of Bioko PfAMA-1 DIs were similar to those in global PfAMA-1 isolates. Differential amino acid substitution frequencies were observed for samples from different geographical regions. Eight new amino acid changes of Bioko island isolates were also identified and their three-dimensional protein structural consequences were predicted. Evidence for natural selection and recombination event were observed in global isolates. CONCLUSIONS: Patterns of nucleotide diversity and amino acid polymorphisms of Bioko Island isolates were similar to those of global PfAMA-1 DIs. Balancing natural selection across DIs might play a major role in generating genetic diversity in global isolates. Most amino acid changes in DIs occurred in predicted B-cell epitopes. Novel sites mapped on a three dimensional structure of PfAMA-1 showed that these regions were located at the corner. These results may provide significant value in the design of a malaria vaccine based on this antigen.

[Factors associated with response to lamivudine: retrospective study of 233 patients with chronic hepatitis B].

OBJECTIVE: To identify factors associated with response to lamivudine in chronic hepatitis B patients. METHODS: Clinical data of 233 chronic hepatitis B patients treated with lamivudine 100mg daily (91 patients were switched to Adefovir 10mg daily or Adefovir 10mg in combination with lamivudine 100mg daily) were retrospective. HBV DNA level and serum HBV markers were detected by polymerase chain reaction and enzyme-linked immunosorbent assay. Kaplan-Meier, long-rank, t test were conducted to evaluate the data. RESULTS: (1) The rates of HBV DNA loss, ALT normalization, viral breakthrough(VB), HBeAg loss and seroconversion were 63.4% , 83.8%, 30.9%, 30.9%, and 14.3%, respectively, in HBeAg(+) patients; and these were 84.6%, 81.3%, 14.3%, respectively in HBeAg(-) patients.(2) The rates of HBV DNA loss, HBeAg loss, HBeAg seroconversion, viral breakthrough (VB) were 55% and 66.7% (P more than 0.05), 55.0%, and 66.7% (P less than 0.05), 17.5% and 33.3% (P less than 0.05), 50% and 34.3% (P less than 0.05) in HBeAg(+) patients with baseline ALT less than 2.5 ULN and HBeAg(+) patients with baseline ALT is more than or equal to 2.5 ULN, respectively. (3) For HBeAg(+) patients, viral breakthrough rate was significantly lower in patients with baseline HBV DNA less than 10(6) copies/ml than that in patients with baseline HBV DNA more than 10(6) copies/ml patients (23.4% VS 46.3%, P less than 0.05) among HBeAg(+) patients. (4) The rate of HBV DNA loss, HBeAg loss, HBeAg seroconversion and viral breakthrough for the patients with IVR at week 24 were 76.3%, 72.3%, 40.8% and 28.9% compared to 47.6% (P less than 0.01), 46% (P less than 0.01), 12.7% (P less than 0.01) and 47.6% (P less than 0.05) for those without IVR. (4) For the 44 patients with viral breakthrough, 32 were switched to Adefovir monotherapy or adefovir in combination with lamivudine therapy, and 12 continued to receive lamivudine monotherapy. HBV DNA loss, HBeAg seroconversion were 40.6%, 21.9% for those switch/add group compare to 16.7%, 16.7% for the lamivudine monotherapy group. There were no significant differences in the background factors (sex, diagnosis, antiviral period, pre-tx ALT, pre-tx HBV DNA) between these two groups. CONCLUSION: Both the baseline ALT and HBV DNA are associated with the efficacy of lamivudine in chronic hepatitis B patients. Patients with baseline ALT is more than or equal to 2.5*ULN and (or) HBV DNA level of less than 1*10(6) copies/ml have better efficacy and lower rate of breakthrough rate. IVR at week 24 is an important predictive factor of a favorable response to lamivudine therapy. For the patients with viral breakthrough, those switched to/added on Adefovir have a favorable result.

[A long-term observation and follow-up for patients with HBeAg/Anti-HBe seroconversion after lamivudine treatment].

OBJECTIVE: To observe the resulting change in patients who achieved HBeAg/Anti-HBe seroconversion after lamivudine treatment. METHODS: 68 patients were observed for over 24 months. They were HBeAg/Anti-HBe with a seroconversion time > or = 6 months and the course of lamivudine treatment was > or = 18 months. RESULTS: After lamivudine treatment, the rate of HBeAg/Anti-HBe seroconversion was 25.19%, the rate of YMDD mutations was 20.59%, and the rate of relapse was 27.94% for these patients that achieved HBeAg/Anti-HBe seroconversion in observation and in the follow-up period. Lamivudine was still an effective drug for these patients with relapses. The rate of relapse was in correlation to the patients' age and the ALT level before treatment. The rate of relapse was not correlated to the HBV DNA level before the course of treatment. YMDD mutations were not correlated to the relapses. CONCLUSION: Even with a HBeAg/Anti-HBe seroconversion time > or = 6 months, the rate of relapse was still higher in patients with chronic hepatitis B that received lamivudine. The patients with long-term lamivudine treatment should be observed and have frequent follow-up visits.

[Relation of serological markers of hepatitis B virus and alanine transaminase to hepatic tissue pathology in patients with chronic hepatitis B].

OBJECTIVE: To investigate the association of serological markers of hepatitis B virus (HBV) and alanine transaminase (ALT) with hepatic tissue pathology in patients with chronic hepatitis B. METHODS: The serological marker of HBV, liver function and liver biopsy of 133 patients with chronic hepatitis B were measured and evaluated. The patients were divided into 4 groups according to HBeAg and HBV DNA positivity. Hepatic necrosis/inflammation grade and hepatic fibrosis were compared between the groups. RESULTS: Hepatic histological examination of all these patients showed inflammation, necrosis and different degrees of fibrosis. In patients with normal serum ALT, liver biopsy showed different degrees of inflammation, hepatic fibrosis, and even hepatocirrhosis. In patients with abnormal serum ALT negative for HBeAg, hepatic tissue inflammation and fibrosis were more serious. Hepatic tissue pathology was not paralleled with the level of HBV replication. CONCLUSION: Evaluation of the liver disease can not depend solely on serum ALT and viral loading in these patients. Hepatic tissue pathology in patients with chronic hepatitis B should be served as the most reliable evidence for evaluating hepatitis conditions and making the decision on antiviral therapy.