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Journal of Clinical Microbiology, July 1999, p. 2371-2372, Vol. 37, No. 7
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Molecular Epidemiology of Hepatitis C Virus
Infection in an Area of Hyperendemicity in Southern Italy: a
Population-Based Study
Alberto R.
Osella,1,*
Laura
Sonzogni,2
Aldo
Cavallini,3
Luciana
Foti,2
Vito
Guerra,1
Alfredo
Di
Leo,3
Mario U.
Mondelli,4
Giovanni
Misciagna,1 and
Enrico
M.
Silini2,5
Laboratory of Epidemiology and
Biostatistics1 and Laboratory of
Biochemistry,3 IRCCS "Saverio De
Bellis," 70013 Castellana Grotte (BA), Associazione Studio Avanzato
Epatiti Virali (A.S.A.E.V.), 24040 Bonate Sotto
(BG),2 Departments of
Pathology5 and Infectious
Diseases,4 University and IRCCS "S. Matteo,"
27100 Pavia, Italy
Received 23 November 1998/Returned for modification 4 March
1999/Accepted 16 April 1999
 |
ABSTRACT |
In a cohort of subjects from Italy, anti-hepatitis C virus (HCV)
and HCV RNA [HCV(+) subgroup] prevalences were 24.6 and 79.6%, respectively. HCV types 1b and 2a/c accounted for 95% of infections. Adjusted alanine aminotransferase levels were higher in males than in
females and in RNA-positive subjects than in RNA-negative subjects
regardless of HCV type. Genotype distribution was unrelated to
demographic variables.
| |
TEXT |
Population-based surveys performed
in different areas of Italy have shown a high prevalence of antibodies
to hepatitis C virus (HCV), which can reach 40% among older subjects
of southern regions (3, 8, 11, 23). It is controversial
whether this burden of infections is paralleled by high disease
prevalence, as most anti-HCV-positive subjects have normal alanine
aminotransferase (ALT) levels and no evidence of liver damage (3,
8, 23). Several variables can influence the expression of
HCV-related liver disease: alcohol abuse (7, 12), associated
liver disorders (21), immunogenetic factors (1,
9), and levels of replication and genetic variability of HCV
(17, 19). Virus genotypes, in particular, have raised
considerable interest (20), given the association of type 1b
with resistance to interferon treatment and advanced stages of disease
(6).
This paper describes the molecular epidemiology of HCV infection in a
large population-based cohort of anti-HCV-positive subjects enrolled in
Castellana, a small municipality in Apulia characterized by a high
prevalence of anti-HCV antibody among older subjects and a moderate
incidence. For this investigation serum HCV RNA and HCV genotypes were
studied for over 400 unselected individuals.
The cohort was assembled in 1985 by systematic sampling from electoral
registers and followed up in 1992 (11). Physical, ultrasound, and laboratory examinations were performed on both occasions, and serum samples were collected. A structured
interview on sociodemographic status, health history, behavioral
variables, and alcohol intake was also conducted. Variables considered
in the analysis were (i) type of job, (ii) history of hepatitis, (iii)
ALT elevation (at least twice the reference values), (iv) daily alcohol
intake, and (v) past surgery. The study was originally designed to
investigate the prevalence of gallstones (10); therefore, no
systematic effort was made to record risk factors for parenterally transmitted infections. While HCV sexual transmission is presumably low
and drug abuse is irrelevant in our cohort, transfusional risk might
have contributed significantly to HCV spread, as transmission through
transfusion has been previously reported in 6.2 to 12.5% of anti-HCV-
positive subjects (3, 8, 23). To overcome this
limitation, we derived a proxy variable, past surgery, from the
history, which expresses the parenteral transmission risk linked to
medical procedures. Follow-up sera from 2,158 subjects were
considered for the study, as samples collected from the cohort in 1985 had not been appropriately processed for molecular testing.
Anti-HCV serology was established by second-generation enzyme-linked
immunosorbent assay and confirmed by using RIBA 2.0 (Ortho Diagnostic
Systems, Raritan, N.J.) for 2,116 available sera. Anti-HCV antibody
prevalence was 24.6% (521 subjects, including 287 males); the mean
age ± standard deviation of anti-HCV antibody-positive patients
was 58.9 ± 9.3 years (males, 59.6 ± 8.9 years; females, 58.1 ± 9.8 years). Four hundred seventeen anti-HCV-positive sera of 521 sera were available for molecular testing. Serum HCV RNA was
extracted by using the QIAamp Viral RNA kit (QIAGEN Inc., Hilden,
Germany) and tested by nested PCR by using primers from the 5'
untranslated region of HCV. Genotyping was performed by the method of
Okamoto with subsequent modifications (17).
Serum HCV RNA was detected in 332 (79.6%) of 417 available
anti-HCV-positive samples, indicating that active replication was present in the majority of subjects. This figure should be considered conservative, since the analysis was performed at a single time point
and on sera stored frozen for 5 years. The HCV type distribution was as
follows: 1 serum of type 1a (0.3%), 119 sera of type 1b (35.8%), 196 sera of type 2a (59.0%), 1 serum of type 2a/2b (0.3%), 1 serum of
type 2a/c (0.3%) and 14 untypeable sera (4.2%).
Analysis of covariance was performed to estimate the effect of viral
factors on ALT levels controlled for sex, age, and daily alcohol
intake. Four subject categories, i.e., type 1 infected, type 2 infected, untypeable, and HCV RNA negative, were considered (Table
1). Mean ALT levels were higher in HCV
RNA-positive subjects than in RNA-negative subjects regardless of HCV
type (P < 0.05) and in males than in females
(P < 0.05). The prevalence of ALT elevation among
HCV-infected subjects was 35% overall and 43% among those with HCV
RNA positivity. This is in contrast to findings reported by another
group of authors, who, studying a cohort of subjects from southern
Italy with similar socioeconomic status, found ALT elevation of any
degree in 4.1% of the subjects (8). However, our findings
are consistent with those acquired in other population-based studies
(3) and with the accepted view of the natural history of HCV
infection (2). Normal ALT levels were more frequent for
subjects with HCV type 2a/c infections than for those with type 1b
infections (58.1 and 52.5%, respectively), although this difference
did not reach the statistical significance reported by other groups who
found an excess of HCV type 2a/c infections in selected HCV carriers
with persistently normal ALT levels (15-17). A detailed
assessment of disease severity was not performed during the survey,
which included ultrasonography of the upper abdominal region as the
only means of assessment; nonetheless, it is likely that a significant
proportion of HCV-infected subjects had liver disease, since
liver-related disease accounts for 40% of the mortality among
anti-HCV-positive subjects in Castellana (14).
View this table:
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TABLE 1.
Age- and daily alcohol intake-adjusted ALT (natural log
transformed) levels of subjects classified by HCV type and sex
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|
Correlations of HCV types with demographic and epidemiological
variables were explored by using contingency tables and by grouping
patients as described above. HCV types 1b and 2a/c were equally
distributed among the variables analyzed, indicating that they had been
present in our community for at least 60 to 70 years and had circulated
together, likely through similar routes of transmission (4, 8,
22). This contention is strengthened by the high prevalence of
anti-HCV in the population (11), the old mean age of
infected subjects, the homogeneous socioeconomic structure of the
community, which lacks relevant immigration, and the absence of
infections by "new" HCV types, such as types 1a and 3a, which were
not introduced into Italy, through drug abuse, until the 1960s
(13, 18). Both type 1b and type 2a/c are endemic in Italy
and show remarkably similar prevalence rates in southern regions other
than Apulia.
In light of these considerations, the Castellana cohort provides an
excellent model for the study of the differential pathogenicity of HCV
types in the general population allowing for minimized biases due to
differences in infection duration and cohort effects on genotype
distribution. In this regard, it is interesting that in Apulia, the HCV
type distribution among patients with chronic liver disease differs
significantly from that observed in our cohort, most patients (55%)
being infected with genotype 1b, consistent with the presumed higher
degree of pathogenicity of this genotype (5).
| |
ACKNOWLEDGMENTS |
This work was supported in part by grant 030RFM93/01 from the
Italian Ministry of Health to the IRCCS Policlinico S. Matteo di Pavia.
We thank Maria Bianco (Laboratory Technician).
| |
FOOTNOTES |
*
Corresponding author. Mailing address: Laboratory of
Epidemiology and Biostatistics, IRCCS "Saverio de Bellis," Via F. Valente, 4, 70013 Castellana Grotte (BA), Italy. Phone: 39 080 4960248. Fax: 39 080 4961394. E-mail: irccsbiblio{at}mail.media.it.
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Journal of Clinical Microbiology, July 1999, p. 2371-2372, Vol. 37, No. 7
0095-1137/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
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