This paper corresponds to the first study of aetiology description in Colombian patients with end-stage liver diseases and the molecular characterization of HBV and HCV strains detected in this group of patients.
One of forty deaths around the world is due to end-stage liver disease. In the present study, 71% of the patients correspond to cirrhosis cases and 29% to HCC, a similar result to other descriptions reported in countries of the region [
1,
30,
31]. Among these 131 patients, alcohol intake abuse was the most frequent risk factor observed (37.4%), followed by viral infections (17.6%). Although this epidemiological pattern is usually found in developed countries, the high proportion of males (in general males have a higher alcohol intake than females) in the present study and the HBV vaccination status in Colombia could be contributing to the risk factors' pattern of the population study [
32]. On the other hand, the prevalence of cryptogenic cirrhosis and autoimmune liver disease is according to previous reports [
1,
30].
As previously mentioned, the frequency of cirrhosis and HCC cases associated to viral etiology in the present study was low (17.6%; 23/131). Only 10.7% (14/131) and 6.9% (9/131) of these patients were positive for serological markers of HBV (HBsAg) or HCV (anti-HCV) infection, respectively.
The HCV-related HCC has increased in several countries; 80% of infected patients with HCV progress to chronic infection, while 20% of them develop cirrhosis, and at least 5% of these evolve to HCC [
33]. In Latin America, the world health organization (WHO) estimates an intermediate prevalence of HCV infection (1–2.5%); moreover, a low prevalence (0.5–1%) has been reported among Colombian blood donor population [
34–
36].
As previously mentioned, Medellin is the second largest city in the country and the capital of Antioquia State (Department of Antioquia). Health authorities in Antioquia have reported a similar HCV prevalence since 2004 (0.2–0.3/100.000 inhabitants) (Indicadores Básicos 2004–2007).
Contrary to general population, studies in some Latin American countries show a high HCV prevalence in severe liver disease. Indeed, HCV infection is the predominant HCC risk factor in Argentina, Chile, and southeastern states of Brazil. Furthermore, in a recently prospective multicenter study of HCC cases from 9 Latin American countries, the main HCC risk factor was HCV infection (30.8%), followed by alcohol (20.4%), HBV infection (10.8%), and then HCV plus alcohol (5.8%) [
37–
39]. A similar tendency was observed in Mexican cirrhotic patients, where 39.5% of recruited patients presented alcohol intake abuse, followed by HCV infection (36.6%) [
40].
Considering the analysis of HCV sequences included in the phylogenetic analysis, the prototypes clustered according to the genotypes described in the literature (HCV/1-6), obtaining similar results with all methods conducted. Inside the main cluster of genotype HCV/1 was clearly observed clades assigned to subtype HCV/1a and HCV/1b; Colombian strains were grouping into these subtypes. Indeed, one isolate belongs to HCV/1a and three strains to HCV/1b. This result is consistent with previous reports of HCV geographic distribution in Latin American countries where different genotypes are present (HCV/1, HCV/2, HCV/3, and HCV/4); however, genotype HCV/1 is the prevalent in most countries of the region including Colombia [
41]. Indeed, HCV/1 has been described in some studies performed by different approaches in Colombian multitransfused patients, individuals with elevated aminotransferases, general population, and kidney transplant patients [
42–
45]. This is the first report based on sequence analysis and developed in samples of patients with severe liver disease in Colombia. Secondly, most of research findings agree that HCV/1b is related with higher risk of severe liver disease [
23,
46–
48]. It is important for health authorities in Colombia and other Latin American countries to develop studies that contribute to knowing the impact of genotype HCV/1b over the hepatitis C natural history in the region.
According to WHO, Colombia has a moderate endemicity for hepatitis B, although there are several epidemiological patterns given the geographic, ethnic, cultural, and socioeconomic status of the population. Actually, Sierra Nevada de Santa Marta, Orinoquian and Amazon basins, and southeastern part of the country corresponded to high-prevalence regions for hepatitis B infection in this country. However Antioquia state holds a different behavior [
49]; in fact, the general incidence of HBV infection in this state in the last years range was 2.7–4.4 per 100.000 inhabitants, while the prevalence in blood donors was 0.3% [
49,
50]. As mentioned above, HBV infection was observed in 10.7% of the patients analyzed. The study population was recruited in Medellin, the second largest city in Colombia, in one of the most important units of hepatology in the country; even if it is possible that this hospital receives patients from rural area of Antioquia state and other Colombian states, most of the cases corresponded to people living in urban area and not from high-prevalence regions of hepatitis B infection.
This heterogeneity of hepatitis B situation is also described in Brazil; indeed, higher frequency of HBV infection than other risk factors has been described in HCC patients from states of northeastern and northern regions of Brazil but not in patients from southeastern states [
51,
52].
The low HBV prevalence described in the present study contrasts with some studies conducted in Peru and Brazil, where HBV was reported in 42–63% of end-stage liver disease cases [
51–
56]. Contrary to these reports, a low HBV prevalence has been described among HCC patients from Chile (6.8%) and Puerto Rico (4%) [
57,
58], similar to other works carried out in the United States, Japan, and western Europe [
1]. On the other hand, on Ecuador a study conducted in 770 cirrhotic patients linked viral etiology to 2.8% of the cases, while alcohol intake was the most frequent risk factor associated (48.3%) [
59]. Whereas differences among studied populations (gender, age, origin), diagnosis, and viral markers are described above, additional studies will be necessary for clarifying the real statement of hepatotropic viruses in cases of cirrhosis and HCC/Ci* in Colombia and the region.
On the other hand, the phylogenetic analysis of HBV showed that HBV/F and subgenotype HBV/F3 were presented in serum and tissue samples of the Colombian population analyzed; subgenotypes HBV/F1a and HBV/F3 were also detected in two cases from El Salvador and Venezuela, respectively. These results are consistent with previously published reports about molecular diversity of these hepatotropic viruses, geographic distribution in Latin America, and their prevalence in severe forms of hepatic disease. In addition, the A1762T/G1764A double mutant, associated according to some authors with a poor clinical outcome, was described in strains isolated from Colombian patients with diagnosis of HCC/Ci*. As mentioned before all isolates of HBV sequenced belonged to HBV/F. It has been proposed that HBV/F is autochthonous to America due to its predominance in different ethnic groups, in particular Amerindian [
60]. In Colombia, few studies about HBV molecular characterization have been published. Two of them included samples from blood donor populations, showing a predominance of genotype HBV/F (77–87.23%) [
21,
22]. This result is in agreement with our study and previous findings of genetic population founder carried out in the state of Antioquia [
61,
62], which revealed that 90% of the genetic pool (mitochondrial DNA) corresponded to Amerindian origin. More recently, in Colombia was detected the genotype HBV/E in nine pregnant women, being the first description of an exclusively African HBV genotype circulating in South America [
63]; this result also coincides with high frequency of African haplotypes in population from Choco state, at the pacific coast of Colombia [
64]. The subgenotypes HBV/F1-F4 have a specific geographic distribution in America. Indeed, subgenotype HBV/F1a is predominant in Alaska, Nicaragua, Costa Rica, and El Salvador, while subgenotype HBV/F1b in Peru and Argentina. Subgenotype HBV/F2 is prevalent in Venezuela and Brazil and subgenotype HBV/F3 in Panama, Venezuela, and Colombia. Finally, subgenotype HBV/F4 is present in Bolivia and Argentina [
20,
65]. Devesa et al. and Alvarado et al. have characterized the HBV subgenotypes in samples from Colombian blood donor isolates; most of the isolates corresponded to HBV/F3. Genotype HBV/F was also recently characterized in samples from blood donor population from Medellin by our group (unpublished data). In the present study, the complete genome analysis in 4 out of 6 HBV isolates from patients with cirrhosis or HCC/Ci* made it possible to classify 3 of them into subgenotype HBV/F3, and one strain into subgenotype HBV/F1a, while partial analysis (small S gene sequence) of two others showed grouping with HBV/F3 prototypes.
The BCP and pre-C/C mutations have been associated with clinical outcome severity. One frequent mutation corresponds to G1896A in the pre-C/C region which leads to a premature stop codon preventing HBeAg synthesis [
4,
8,
20,
66]. When this region was analyzed, the G1896A mutation was characterized only in one isolate (UdeA-054), presenting in addition T
1858, while the isolates UdeA-083 and UdeA-089 carry C
1858. According to several studies, G1896A is frequent in genotype HBV/F isolates that carry T
1858. A hypothesis for this coevolution pattern is that hydrogen binding between nucleotides 1858–1896 is necessary to maintain the low stem secondary structure of
ε signal [
67]. The presence of G1896A in isolate UdeA-054 correlated with no detection of HBeAg by ELISA in serum sample ().
When BCP was analyzed, it was demonstrated that isolates UdeA-083 and UdeA-089 carried the double mutation A1762T/G1764A; these isolates corresponded to two Colombian patients with diagnosis of HCC/Ci*.
Regarding the prevalence of double mutation in BCP in isolates of genotype HBV/F, there are different results. In fact, in Brazilian patients with chronic infection, the BCP double mutation was described in 90% of HBV/F isolates; this double mutation was not identified in any other samples of these studies [
68,
69].
Several authors have proposed that HBV genotype and BCP mutants could be related with liver disease severity. Although HBV/B and HBV/C circulate in Asia, patients with diagnosis of HBV-related HCC present a higher prevalence of HBV/C infection [
9,
12,
13]. Similar findings have been reported for HBV/F, in a prospective study of 258 patients with chronic HBV infection; after a mean followup of 94 months, the mortality rate related to liver disease was more frequent in cases of genotype HBV/F than HBV/ A and HBV/D infection [
14]. Livingston et al. also described an association of HBV/F and liver disease severity, in particular HCC risk. They compared the frequency of HBV/F in Alaska natives with chronic hepatitis B infection with or without HCC; the frequency of genotype HBV/F was 68% and 18%, respectively [
15]. This finding suggested a higher risk of HCC development in HBV/F cases [
15,
60]. Sanchez-Tapias et al. and Livingston et al. described that genotype HBV/F, autochthonous to America, could be related with poor clinical outcome and higher HCC risk development; however, a higher number of studies should be developed for a stronger support of these findings.
In addition, the present study is the first report of A1762T/G1764A in Colombian HBV isolates. Recent studies assign a more important role to A1762T/G1764A in hepatocarcinogenesis than the HBV genotype itself. It has been demonstrated that the BCP double mutation generates a new binding site for the transcription factor HNF1, regulating pgRNA transcription and promoting an enhancement of HBV replicative activity [
70]. In patients with HCC due to HBV infection, isolates belonging to genotype HBV/C carry a higher frequency of A1762T/G1764A compared to HBV/B strains [
4,
9,
71,
72]. In our study, the presence of BCP double mutation correlates with HCC diagnosis in those patients.
This study corresponds to the first description of end-stage liver diseases and the molecular characterization of HBV and HCV in cirrhosis and HCC/Ci* cases in Colombia. Genotype HCV/1 and genotype HBV/F (subgenotype F3) were detected in samples belonging to Colombian patients. This result agrees with previous studies and in the case of HBV with genetic founder populations in Colombia. Additionally, HBV/F3 and HBV/F1a were characterized in isolates from patients from Venezuela and El Salvador, respectively. The HBV and HCV subgenotyping/subtyping results obtained in the present study are according to the geographic pattern and predominance described for these hepatotropic viruses, especially subgenotypes HBV/F1a and HBV/F3 in Central and South America, respectively.
On the other hand, mutation of A1762T/G1764A was characterized in isolates from patients with HCC. Although the double mutant has been related with higher risk of HCC development, the descriptive design of our study and limited sample size do not allow us to assess any type of statistical association between BCP mutant, genotype, and clinical outcome. Additionally studies will be necessary to determine whether HCV/1b, HBV/F, and pre-C/C variants are associated with a higher risk of cirrhosis and HCC development.
Moreover, the statement of viral etiology and alcohol intake abuse in end-stage liver disease cases in Colombia and Latin America should be explored in further case-control studies.
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