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From an immunological point of view, the healthy liver has been usually associated with the phenomenon of tolerance. A microenvironment of regulatory cytokines produced by liver Kuppfer cells and liver sinusoidal endothelial cells has contributed, together with resident dendritic cells, to generate a tolerogenic environment in this tissue. In this review we discussed the intrahepatic responses to different sorts of liver injury, such as hepatotrophic viruses, alcohol or putative self-antigens. In each case we analyzed the impact of different cytokines in the clinical outcome of the different pathological situations.

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BACKGROUND: Children are a reservoir of hepatitis A virus and must be considered as primary targets of any immunization strategy. The safety and immunogenicity were evaluated for a new formulation of an inactivated hepatitis A vaccine, Avaxim 80 units, containing one-half the antigen dose of the adult formulation. METHODS: The safety of two doses of this vaccine given 6 months apart was evaluated in an open study in 537 Argentinean children 12 months to 15 years old. Immunogenicity was evaluated at Weeks 0, 2, 24 and 27 in a subgroup of 120 subjects. RESULTS: Two weeks after the first vaccine dose, >99% of initially seronegative children had seroconverted (titers > or =20 mIU/ml), with a geometric mean titer of 98.5 mIU/ml. Before booster at 24 weeks all subjects had seroconverted. A strong anamnestic response was observed after the second dose at which time the geometric mean titer had increased >35-fold, and antibody titers were consistent with long term protection. Immediate adverse reactions were observed in 3 of 537 (0.6%) subjects after the first dose. Local reactions were mild and transient and did not increase with subsequent doses. Among the systemic events reported during the 7-day follow-up period, 37 cases of fever after the first dose and 22 cases after the second dose were reported. Only 3 cases of fever were clearly related to vaccination (< or =38.2 degrees C) after the first injection, all of which subsided in less than 1 day. CONCLUSIONS: This study demonstrated the safety and immunogenicity of a pediatric formulation of hepatitis A vaccine in children ages 12 months to 15 years in healthy children ages 12 to 47 months.

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The prevalence of antibodies to hepatitis A and B virus was assessed in 3,653 subjects across four regions of Brazil. The anti-HAV and anti-HBc seroprevalence were 64.7% and 7.9%, respectively. The highest anti-HAV (92.8%) and anti-HBc (21.4%) rates were seen in the Northern region. In other regions, anti-HAV seroprevalence over 90% was only reached in the more elderly, indicating an intermediate endemicity and a significantly higher anti-HAV prevalence was seen in the low socioeconomic group between 1-30 years. With respect to anti-HBc seroprevalence an increase was seen in adolescents and there was a significantly higher anti-HBc prevalence in the lower socioeconomic group between 1-20 years. A 3.1% anti-HBc prevalence was seen in one-year-old infants, suggesting a vertical transmission. The major findings of this study indicate that the pre-adolescent and adolescent population in some Brazilian cities are at greatest risk from both hepatitis A and B infection, but for different reasons.

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In the past, Latin America was considered to be an area of high endemicity for hepatitis A virus (HAV) infection, with most people infected in early childhood. A seroepidemiological study was recently undertaken in six countries to determine whether this pattern has changed. The highest seroprevalence of antibodies to HAV (anti-HAV) was found in Mexico and the Dominican Republic. Analysis of the different age groups showed that at age 6-10 years, 30% of children in Chile and 54-55% in Brazil, Venezuela and Argentina had been infected, compared with almost 70% in Mexico and 80% in the Dominican Republic. At age 11-15 years, nearly 90% in Mexico and 91% in the Dominican Republic had been infected, compared with 54% in Argentina, 62% in Venezuela, 60% in Brazil and 70% in Chile. By age 31-40 years, over 80% of the populations in all six countries had been exposed to HAV. In all of the countries except Brazil and Venezuela, the seroprevalence of anti-HAV was significantly higher in females than in males. In Mexico, Argentina and Brazil, anti-HAV seroprevalence was significantly higher in the low socioeconomic groups than in the middle/high socioeconomic groups. The results show that there has been a shift from high to medium endemicity of HAV infection throughout Latin America, which may result in more clinical cases in adolescents and adults and a greater potential for outbreaks. The vaccination strategy for hepatitis A should thus be reviewed.

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OBJECTIVE: This study evaluated the seroprevalence of hepatitis A virus (HAV) antibodies in 360 middle-class subjects from Buenos Aires City and its outskirts. METHODS: The study population included 360 individuals between 10 and 89 years of age, from the socioeconomic middle class in Buenos Aires City and some suburban areas of Buenos Aires province. Antibodies to hepatitis A virus were determined by enzyme immunoassay test kits. RESULTS: The overall prevalence of HAV antibodies was 42.2%. The highest percentage of seronegativity was found in the subgroup of younger people without a history of symptomatic hepatitis and living in houses with more than one bathroom (86.9%). In the subgroup aged 21 to 60 years, the highest rates of seronegativity were found in individuals with higher level of education living in houses with tap water (66.6%). In both groups, seronegativity may be correlated with a higher socioeconomic status. CONCLUSIONS: In the middle-class community studied, more than 50% of people under 30 years of age were unprotected against HAV. Thus, the use of a vaccine against hepatitis A has to be considered for the prevention of symptomatic hepatitis, especially in adults at risk of infection, such as those who travel to areas with poor sanitation, taking into consideration that the severity of the disease increases with age.

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In a multicenter study, hepatitis A virus (HAV) seroprevalence was surveyed in six countries in Latin America in which in 12,000 subjects were stratified for age. The highest rates of seroprevalence were recorded in the Dominican Republic (89.0%) and Mexico (81.0%), with lower rates in Brazil (64.7%), Chile (58.1%), Venezuela (55.7%), and Argentina (55.0%). The seroprevalence of HAV in children between 1 and 5 years of age was less than 50%, except in the Dominican Republic. In the 5-10-year-old age group, seroprevalence rates have also decreased compared with previous reports. This suggests that the epidemiology is shifting from high to intermediate endemicity, with the population susceptible to HAV infection shifting from children to adolescents and adults. Furthermore, data from Brazil, Argentina, and Mexico show that HAV seroprevalence is significantly lower in people living in medium and high socioeconomic conditions. This study suggests the need for appropriate vaccination programs to be implemented targeting children, adolescents, and adults, particularly in higher socioeconomic groups.

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We conducted a cross-sectional study to determine the seroprevalence of antibodies against hepatitis A and hepatitis E viruses (HAV and HEV) in the population of two rural areas, Camiri and Villa Montes, of the Chaco region, south-eastern Bolivia. HAV antibodies were detected in 461 (94.1%) of 490 serum samples tested, not differing significantly between sexes and study areas. The HAV seropositivity rate (64.7%) was high even in the youngest age group (1-5 years). The prevalence of HEV was 7.3%, with no significant differences between sexes. The prevalence of HEV antibodies in the population of the Camiri area (10.4%) was significantly higher than in the Villa Montes area (4.4%), possibly due to the better quality of drinking water in the Villa Montes area. In the population /= 31 year-old group. This is consistent with findings in other countries. This is the first report of the prevalence of HEV infection in Bolivia.

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BACKGROUND: The epidemiology of hepatitis A virus (HAV) infection is closely associated to the level of hygiene and sanitation of the population. Newly industrialising areas experience a transition from high to intermediate endemicity, which is characterized by a shift in the exposure age to HAV, from early childhood to school ages or adolescence. AIM: To measure the prevalence of HAV antibodies in subjects living in urban Santiago. SUBJECTS AND METHODS: A HAV antibody survey in five medium and low socioeconomic level urban districts of northern Santiago, was conducted in 1996. Healthy subjects aged 1 to 39 years old were recruited from randomly selected households. RESULTS: Five hundred three subjects were studied. Anti HAV antibodies were found in 13.2, 29.5, 59.6, 78.1, 95.6 and 98.2% of individuals aged 1 to 4, 5 to 9, 10 to 14, 15 to 19, 20 to 29 and 30 to 39 years old, respectively. CONCLUSIONS: The profile of positive antibodies is compatible with an intermediate pattern of transmission of HAV. The current data supports the idea that infection is shifting towards older ages. A progressive increase in the number of susceptible school age children and teenagers is propitious for the occurrence of common source hepatitis A outbreaks.

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Background: The epidemiology of hepatitis A virus (HAV) infection is closely associated to the level of hygiene and sanitation of the population. Newly industrialising areas experience a transition from high to intermediate endemicity, which is characterized by a shift in the exposure age to HAV, from early childhood to school ages or adolescence. Aim: To measure the prevalence of HAV antibodies in subjects living in urban Santiago. Subjects and methods: A HAV antibody survey in five medium and low socioeconomic level urban districts of northern Santiago, was conducted in 1996. Healthy subjects aged 1 to 39 years old were recruited from randomly selected households. Results: Five hundred three subjects were studied. Anti HAV antibodies were found in 13.2, 29.5, 59.6, 78.1, 95.6 and 98.2 percent of individuals aged 1 to 4, 5 to 9, 10 to 14, 15 to 19, 20 to 29 and 30 to 39 years old, respectively. Conclusions: The profile of positive antibodies is compatible with an intermediate pattern of transmission of HAV. The current data supports the idea that infection is shifting towards older ages. A progressive increase in the number of susceptible school age children and teenagers is propitious for the occurrence of common source hepatitis A outbreaks

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BACKGROUND: As sanitary and economic conditions improve, the prevalence of antibodies to hepatitis A is now significantly lower. AIM: To evaluate the prevalence of hepatitis A virus antibodies in healthy Chilean adults. MATERIAL AND METHODS: Antibodies to hepatitis A virus were measured, using a commercial ELISA assay, in 215 voluntary blood donors (163 male, aged 19 to 30 years old) and 295 medical students and health personnel (156 male, aged 19 to 39 years old), residing in Valdivia, Chile. RESULTS: Antibodies against hepatitis A virus were found in 68.2% of the total sample (351/510). Ninety percent of flood donors and 54% of health personnel and students were positive (p < 0.01). Age specific prevalence in blood donors 19 to 22, 23 to 29 and 27 to 30 years old was 81.0%, 95.2% and 95.6% respectively. Among the same age groups in medical students, the prevalence was 47.9%, 53.2% and 61.9% respectively (p < 0.01). CONCLUSIONS: This study indicates a reduction in the prevalence of hepatitis A virus antibodies among adults in Valdivia (Chile). Differences detected between individuals are probably related to different socioeconomic levels. Medical students have an increased risk for hepatitis A infections than the general population.

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La hepatitis A es una antigua enfermedad infecciosa importante a nivel mundial. Se trasmite vía fecal-oral por lo que su incidencia está relacionada con los niveles higiénicos y de saneamiento en cada comunidad. Esta revisión contempla la historia del desarrollo de las vacunas inactivas y de las atenuadas. En una perspectiva futura se muestra el desarrollo de vacunas inactivas en liposomas y combinaciones de vacunas. Se analizan la inmunogenicidad, protección a largo plazo y eficacia de las vacunas inactivas autorizadas por el FDA de EE.UU- HAVRIX© y VAQTA©, haciendo hincapié en el mecanismo mediante el cual las vacunas inactivas son capaces de interrumpir la transmisión del virus, responsables de la salud del niño y conocedores del medio ambiente en que éste se desarrolla, decidirán en conjunto la indicación individual de la vacuna. En términos de salud pública, las estrategias de vacunación dependerán de las realidades epidemiológicas de cada país y comunidad, teniendo presente que existen lugares en el mundo con alta, intermedia y baja endemia. En Chile replantearse las medidas de control de la hepatitis A. El análisis de las tendencias de morbilidad, comprueba que prácticamente no ha habido impacto favorable de las medidas de higiene y saneamiento ambiental. Por otro lado, los estudios de seroprevalencia muestran una tendencia en el desplazamiento de los susceptibles a edades mayores en quienes la hepatitis A implica mayor gravedad

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Hepatitis A virus (HAV), is an RNA virus in the picornavirus family. It is transmitted faecal-orally by contaminated food drink. It has a worldwide distribution, and like other enteric infectious diseases it is typically an infection of childhood, related to conditions of crowding and poor hygiene. HAV causes only acute hepatitis and has never been associated with chronic liver disease such as seen with hepatitis B virus or hepatitis C virus. Infection with HAV may be prevented by improving levels of sanitation and hygiene and immunization with HAV vaccine. Between January 1995 and August 1998, 339 individuals were recruited into the study of the epidemiology of HAV. Sera from the participants were tested for anti-HAV IgG using the Enzyme Linked Immunosorbent Assay (ELISA) technique (Abbot Laboratories, Abbort Park, IL 60064). Social and demographic data were collected using questionnaires. The age of the participants ranged from 3-90 years. There was 128 males and 211 females. The average age of males and females was 25 years. The seroprevalence of HAV in the population using ELISA was 59.9 percent. Age and source of water supply were found to be the major contributors to exposure to HAV. The seroprevalence of HAV in Jamaica is higher than the seen generally in developed countries, although the age related acquisition was similar. Improved water supply, educating the public on the epidemiology of HAV and immunization in the preschool age children could reduce the prevalence of HAV in Jamaica.(Au)

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Background: As sanitary conditions of a population improve, hepatitis A virus infection occurs at higher ages,thus decreasing the prevalence of antibodies against the virus. In the eighties, the prevalence of antibodies among children was 97 percent and depended on the socioeconomic level. Aim: To assess the prevalence of antibodies against hepatitis A virus in school age children living in Valdivia. Subjects and methods: Two thousand three hundred thirty three school age children were studied. Total antibodies against hepatitis A virus were detected using an ELISA kit from Abbott. Children were stratified in age groups and school were classified as private, subsidized, municipal or foster homes. Results: Antibodies were positive in 65 percent of children (59 percent in children aged 6 to 8 years old, 66 percent in children aged 9 to 11 years and 69 percent in children aged 12 to 15 years. In private schools, the prevalence was 26 percent, in subsidized schools the figure was 54 percent, in municipal schools 73 percent and in foster homes 91 percent. Conclusions: The general prevalence of antibodies against hepatitis A virus is higher in low socioeconomic level children. There is a global decrease in the prevalence of these antibodies in the last years

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Two seroprevalence studies of viral hepatitis A and hepatitis E were conducted in El Paso, Tex, and Cd Juárez, Mexico. Subjects were randomly selected, low-income pregnant women. Blood from 557 women in El Paso and 307 women in Cd Juárez, obtained from routine prenatal testing, was analyzed for antibodies to hepatitis A and hepatitis E. Women from both cities showed high seroprevalence rates of hepatitis A (75.8% in El Paso and 96.1% in Cd Juárez). Rates increased significantly by age, with 100% of women in Cd Juárez older than 28 years testing positive. Nationality and ethnicity were significantly associated with hepatitis A seroprevalence: Mexican nationals, 96.1%; US Hispanics, 78.8%; and US Caucasians, 36.4% (P < .001). With respect to hepatitis E, 0.4% of women in El Paso and 1.6% of women in Cd Juárez tested positive for anti-HEV. The rate of hepatitis A seroprevalence was higher for women with lower educational levels and for women residing in crowded households, but these findings were not statistically significant.

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BACKGROUND: As sanitary conditions of a population improve, hepatitis A virus infection occurs at higher ages, thus decreasing the prevalence of antibodies against the virus. In the eighties, the prevalence of antibodies among children was 97% and depended on the socioeconomic level. AIM: To assess the prevalence of antibodies against hepatitis A virus in school age children living in Valdivia. SUBJECTS AND METHODS: Two thousand three hundred thirty three school age children were studied. Total antibodies against hepatitis A virus were detected using an ELISA kit from Abbott. Children were stratified in age groups and school were classified as private, subsidized, municipal or foster homes. RESULTS: Antibodies were positive in 65% of children (59% in children aged 6 to 8 years old, 66% in children aged 9 to 11 years and 69% in children aged 12 to 15 years. In private schools, the prevalence was 26%, in subsidized schools the figure was 54%, in municipal schools 73% and in foster homes 91%. CONCLUSIONS: The general prevalence of antibodies against hepatitis A virus is higher in low socioeconomic level children. There is a global decrease in the prevalence of these antibodies in the last years.

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OBJECTIVES: A cross-sectional study investigated the association of hepatitis A seropositivity with environmental and personal risk factors among children in a United States-Mexico border community. METHODS: Hepatitis A serological markers and a questionnaire identifying risk factors were evaluated for 523 primary school children. RESULTS: Of the children studied, 16.9% tested positive for total antihepatitis A virus. Risk factors included being in the first grade, low maternal educational attainment, living in Mexico for more than 6 months, household crowding, and inadequate excreta disposal systems. CONCLUSIONS: To decrease enteric disease, improvements in excreta disposal infrastructures and educational programs are needed. Hepatitis A vaccine should be administered before school age.

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The hepatitis A and E virus (HAV and HEV) share the fecal-oral mechanism. Hepatitis A is an endemo-epidemic disease in Uruguay but no data on the epidemiologic pattern of the HEV is available. The aims of this study were to update the epidemiologic behavior of the HAV in Montevideo and demonstrate the circulation of the HEV in Uruguay. Two hundred fourteen patients who consulted in the Policlínica de Nutrición y Digestivo were studied, 185 (86%) of whom were anti HAV (HAVAB, Abbot) positive. 81.8% (117/143) of those residents in Montevideo and 95.7% (68/71) of those who were from the inland were anti-HAV positive. From the Montevideo population 55.8% cases under the age of 40 years were anti-HAV positive and occurred in 97.6% of those older (p < 0.001). Considering the health care conditions of the positive patients in Montevideo, 95.6% (43/45) had septic chambers and 75.5% (74/98) disposed of toilet facilities (p < 0.001). It is concluded that although the global prevalence has been maintained since 1982, there is a change in the epidemiologic pattern with greater risk of infection in patients under the age of 40 years proceeding from areas without toilet facilities. The prevalence of total antibodies for HEV (EIA, Abbot) was 2.8% in this population. An association was observed with HAV in 2.2% (4/185). Moreover, a sample of 252 blood donors from the National Blood Service was analyzed with 5 being found to be anti HEV positive, with only 3 (1.2%) being confirmed in the Center for Disease Control in the United States. Although no definitive conclusions may be drawn from the present study, from an epidemiologic point of view, it has been shown that there is evidence of the circulation of HEV in Uruguay, in both the out patient and in blood donor populations.

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Se analizaron los datos con relación a la prevalencia de anticuerpos IgG e IgM contra el virus de la hepatitis A (VHA), mediante la técnica de ELISA en 450 ninos sin antecedentes de hepatitis, con edades comprendidas entre los 3 meses y 17 años de edad, que acudieron a consulta al Instituto Nacional de Pediatría de la ciudad de México en el período comprendido de septiembre de 1992 a junio de 1993. La prevalencia de anticuerpos IgG en la población estudiada, fue del 83.6 por ciento. De los niños menores de un año el 50 por ciento mostraron anticuerpo, el 80 por ciento a los 3 años 80 por ciento, y el 96 por ciento a los 10 años de edad. Sólo 9 niños de los 450 tuvieron además anticuerpos IgM contra el virus de la hepatitis A. Se concluye que la prevalencia de HVA en la población que estudiamos es semejante a lo referido hace 13 años en México.

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Se analizaron los datos con relación a la prevalencia de anticuerpos IgG e IgM contra el virus de la hepatitis A (VHA), mediante la técnica de ELISA en 450 ninos sin antecedentes de hepatitis, con edades comprendidas entre los 3 meses y 17 años de edad, que acudieron a consulta al Instituto Nacional de Pediatría de la ciudad de México en el período comprendido de septiembre de 1992 a junio de 1993. La prevalencia de anticuerpos IgG en la población estudiada, fue del 83.6 por ciento. De los niños menores de un año el 50 por ciento mostraron anticuerpo, el 80 por ciento a los 3 años 80 por ciento, y el 96 por ciento a los 10 años de edad. Sólo 9 niños de los 450 tuvieron además anticuerpos IgM contra el virus de la hepatitis A. Se concluye que la prevalencia de HVA en la población que estudiamos es semejante a lo referido hace 13 años en México. (AU)

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