A short report on highlights of world-wide development of RIX4414: a Latin American experience.

An oral, human-derived monovalent (G1P1A) rotavirus vaccine, strain RIX4414, has been developed by GlaxoSmithKline, Rixensart, Belgium. The safety, immunogenicity and efficacy of this vaccine were evaluated in a randomized, double-blind, placebo-controlled, phase IIb trial conducted in Brazil, Mexico and Venezuela. Healthy infants were given two doses of vaccine (104.7, 105.2 or 105.8 ffu) or placebo at age 2 and 4 months, with routine DTPw-HBV and Hib vaccines. OPV was given separately, at least 2 weeks before or after administration of the study vaccine. A total of 2155 infants were enrolled, of whom 1618 received one of the three vaccine viral concentrations and 537 were given placebo. Analysis of efficacy included diarrheal episodes occurring from 2 weeks after second dose until one year of age. Efficacy rates against any rotavirus gastroenteritis, severe rotavirus gastroenteritis and hospitalizations for rotavirus disease were as high as 70% (46-84%; 95%CI), 86% (63-96%; 95%CI), and 93% (54-100%; 95%CI), respectively. For non-G1 (mainly G9) serotypes, RIX4414 vaccine conferred protection as high as 83% (40-97%; 95%CI) against severe gastroenteritis. A decrease was noted in the incidence of severe rotavirus-related gastroenteritis after first dose. It is demonstrated that two doses of RIX4414 are highly efficacious against severe rotavirus gastroenteritis and hospitalization, including disease caused by non-G1 strains, namely G9 serotypes.

Adherencia e invasión de campilobacterias termotolerantes en células HEp-2 / Termophilic campylobacter species adherence and invasion in HEp-2 cells

Las campilobacterias termotolerantes son causa frecuente de enfermedad diarreica aguda en niños en todo el mundo. En el presente estudio se evaluaron dos de los factores de virulencia de importancia en enteropatógenos: la capacidad de adherencia e invasión en células HEp-2 de diferentes especies de campylobacter (C.jejuni subsp. jejuni, C coli y C. lari), aisladas como único enteropatógeno de niños menores de 5 años con diarrea inflamatoria y secretora; además, se incluyeron aislados de niños asintomáticos. Los resultados no revelaron diferencia estadísticamente significativa en la adherencia e invasión de los aislados de ambos grupos de niños (diarrea y asintomáticos), ni entre los asilados de diarrea inflamatoria y secretora. La variación en las manifestaciones clínicas en estos pacientes y la presencia de portadores asintomáticos podría atribuirse a diferencias en el huésped, es decir, participación activa de la respuesta inmune, o al tipo de cepa involucrada, ya que se han descrito otros factores de virulencia en estos microorganismos

Rotavirus-associated medical visits and hospitalizations in South America: a prospective study at three large sentinel hospitals.

BACKGROUND: Knowledge of the impact of rotavirus-associated disease on the health care systems of South America can aid in defining strategies for diagnosis, management and prevention. Up to date information on the impact of rotavirus disease in South America is scarce. AIM: To determine prospectively the impact of rotavirus disease as a cause of medical visits and hospitalizations at three large sentinel pediatric hospitals in Argentina, Chile and Venezuela. METHODS: A 2-year prospective surveillance for rotavirus-associated medical visits and hospitalizations was conducted during 1997 through 1998 at three large sentinel public hospitals, one each in Argentina, Chile and Venezuela. A common surveillance protocol was implemented at the three sites, and a representative number of nonbloody diarrhea stool samples from children <36 months of age were tested for rotavirus by enzyme-linked immunosorbent assay. RESULTS: For our target age group, acute diarrhea-associated medical visits/hospitalizations represented 41%/2%, 5%/6% and 9%/13% of all medical visits/all hospitalizations at the Argentinean, Chilean and Venezuelan sites, respectively (P < 0.001 for difference among the three sites). Rotavirus detection rates among a total of 5,801/1,256 medical visit/hospitalization diarrhea stool samples tested were 39%/71% in Argentina, 34%/47% in Chile and 29%/38% in Venezuela (P < 0.01 by chi square for difference among the three sites). Rotavirus was associated with a mean of 1.5, 1.8 and 3% of total medical visits and 1.6, 2.8 and 5% of hospitalizations among children <36 months of age at the Argentinean, Chilean and Venezuelan sites, respectively. Seasonality was evident for medical visits at all three sites (although less striking in Chile) with peak activity occurring between November and May. Rotavirus-associated hospitalizations had a marked peak in Venezuela, represented largely by short stays, but not in Argentina and Chile. CONCLUSIONS: Rotavirus was a significant cause of medical visits at all three sentinel sites. Rotavirus caused less hospitalizations than previously reported in Argentina and Chile. On the basis of our findings we estimate that approximately 106,000/ 21,000, 48,000/8,000 and 98,000/31,000 rotavirus-associated medical visits/hospitalizations occur yearly in Argentina, Chile and Venezuela, respectively.

Rhesus rotavirus-based quadrivalent vaccine is efficacious despite age, socioeconomic conditions and seasonality in Venezuela.

This report describes the results of additional analyses of the trial carried out with the rhesus rotavirus-based quadrivalent vaccine in Venezuela. In the present study, we re-examined the data from this previous rotavirus vaccine trial to assess the statistical interaction between vaccine efficacy and (i) the duration of efficacy into the second year of life, (ii) socioeconomic conditions, and (iii) rotavirus seasonality. We found that among Venezuelan children, the rotavirus vaccine confers protection against severe diarrhea during the first 2 years of life independently of socioeconomic conditions and seasonality.

Epidemiological features of rotavirus infection in Caracas, Venezuela: implications for rotavirus immunization programs.

The epidemiological features of rotavirus infection may be quite relevant for evaluation of the performance of a rotavirus vaccine in different settings, as well as for monitoring its impact during vaccination under routine conditions. This article describes some important issues regarding rotavirus epidemiology in Venezuela, where major field trials of rotavirus vaccine have been carried out. Rotaviruses was significantly more frequently observed in inpatient (43%) than in outpatient (21%) consultations for diarrhea in infants and young children. There was a high prevalence of rotavirus illness, regardless of socioeconomic conditions, but the risk of dehydration was greater among the lower socioeconomic groups. Rotavirus disease occurs year-round, with a slight seasonal pattern. Eighty-five percent of rotavirus-positive diarrheal episodes, as well as 86% of cases of dehydration due to rotavirus, occurred during the first year of life. However, rotavirus illnesses occur less commonly during the first months of life (0-2 months), which may be a result of protection by transplacental antibodies. The pattern of acquisition of rotavirus antibody was consistent with this age distribution of disease and with optimal age for vaccination. Thus, regional epidemiological characteristics of rotavirus infection may affect optimal performance of rotavirus vaccine.

[Etiologic, clinical and socio-democratic characteristics of acute diarrhea in Venezuela]. / Características etiológicas, clínicas y sociodemográficas de la diarrea aguda en Venezuela.

In four cities of Venezuela a study was carried out to evaluate the epidemiological, clinical, and etiological characteristics of acute diarrhea in children under 5 years of age. The study was done between June 1993 and May 1995 and involved children who were seen in a hospital, 2,552 with diarrhea and 793 controls. The Fisher exact test was used for the statistical analysis of the results. Rotaviruses were the most important agents, both in terms of their frequency (30%) and their association with dehydration (58%). Following in importance were Campylobacter spp. (13%) and Escherichia coli classical O serogroups (9%), but their association with diarrhea was only statistically significant among children less than 3 months old, a fact that is particularly important from the standpoint of treatment. The importance of age was confirmed as a determining factor in the prevalence and severity of diarrhea.

Origen bacteriano de la enfermedad diarreica aguda en Mérida, Venezuela / Bacterial origin of acute diarrhea in Merida, Venezuela

464 stool specimens from children under 5 with acute diarrheal disease and other 149 specimens from the control group were studied from July, 1993, to May, 1995. The specimens were collected at the Pediatric Emergency Department of the Autonomous Institute of the Teaching Hospital of Los Andes, MÚrida, Venezuela. The presence of the internationally recommended bacterial, parasitary and viral agents was investigated. The commonest bacteria isolated as unique pathogens were: Shigella (42.85), Shigella sonnei, the most found, (66.67), and the thermotolerant Campylobacter, Aeromonas sp. and enteropathogenous Escherichia coli, with 15; 15 and 13.5, respectively. 6.5 of parasites and 24.12 of Rotavirus were also found. It was concluded that in the period of time under study the infectious and mainly, the bacterial origin is an important cause of acute diarrheal disease in Mérida.

[Bacterial origin of acute diarrhea in Merida, Venezuela]. / Origen bacteriano de la enfermedad diarreica aguda en Mérida, Venezuela.

464 stool specimens from children under 5 with acute diarrheal disease and other 149 specimens from the control group were studied from July, 1993, to May, 1995. The specimens were collected at the Pediatric Emergency Department of the Autonomous Institute of the Teaching Hospital of Los Andes, Mérida, Venezuela. The presence of the internationally recommended bacterial, parasitary and viral agents was investigated. The commonest bacteria isolated as unique pathogens were: Shigella (42.85%), Shigella sonnei, the most found, (66.67%), and the thermotolerant Campylobacter, Aeromonas sp. and enteropathogenous Escherichia coli, with 15; 15 and 13.5%, respectively. 6.5% of parasites and 24.12% of Rotavirus were also found. It was concluded that in the period of time under study the infectious and mainly, the bacterial origin is an important cause of acute diarrheal disease in Mérida.

Norwalk virus infection in Venezuela.

The presence of antibodies against Norwalk virus (NV) was studied in sera from different Venezuelan populations, using an enzyme immuno-assay (EIA) based on recombinant NV protein. Antibodies to NV were found in 47%-53% of urban subjects from Caracas, 83% of rural subjects from the west of the country, and 73%-93% of Amerindian subjects. The prevalences found in the rural and Amerindian groups were significantly higher than that in the urban group. Although about 50% of the children studied were seropositive for NV by the age of 5 years, only four (0.4%) of 1120 faecal samples from children with diarrhoea which were tested for the presence of NV antigen by sandwich EIA were found positive. An increase of at least 4-fold in the titre of anti-NV IgA was found in three (5%) of 61 pairs of sera taken during and 1 month after an acute episode of diarrhoea not due to rotavirus. NV was therefore not a predominant aetiological cause of gastro-enteritis in young children in Venezuela between 1993 and 1995, although it can be the cause of diarrhoea in infants.

Efficacy of the rhesus rotavirus-based quadrivalent vaccine in infants and young children in Venezuela.

BACKGROUND: Rotaviruses are the principal known etiologic agents of severe diarrhea among infants and young children worldwide. Although a rhesus rotavirus-based quadrivalent vaccine is highly effective in preventing severe diarrhea in developed countries, in developing countries its efficacy has been less impressive. We thus conducted a catchment study in Venezuela to assess the efficacy of the vaccine against dehydrating diarrhea. METHODS: In this randomized, double-blind, placebo-controlled trial, 2207 infants received three oral doses of the quadrivalent rotavirus vaccine (4x10(5) plaque-forming units per dose) or placebo at about two, three, and four months of age. During approximately 19 to 20 months of passive surveillance, episodes of gastroenteritis were evaluated at the hospital. RESULTS: The vaccine was safe, although 15 percent of the vaccinated infants had febrile episodes (rectal temperature, > or =38.1 degrees C) during the six days after the first dose, as compared with 7 percent of the controls (P<0.001). However, the vaccine gave 88 percent protection against severe diarrhea caused by rotavirus and 75 percent protection against dehydration, and produced a 70 percent reduction in hospital admissions. Overall, the efficacy of the vaccine against a first episode of rotavirus diarrhea was 48 percent. Horizontal transmission of vaccine virus was demonstrated in 15 percent of the vaccine recipients and 13 percent of the placebo recipients with rotavirus-positive diarrhea. CONCLUSIONS: In this study in a developing country, the quadrivalent rhesus rotavirus-based vaccine induced a high level of protection against severe diarrheal illness caused by rotavirus.

Age-specific prevalence of Escherichia coli with localized and aggregative adherence in Venezuelan infants with acute diarrhea.

To evaluate the epidemiological significance of HEp-2 cell-adherent Escherichia coli isolates in diarrheal disease, we performed a study with 513 Venezuelan infants with diarrhea and 241 age-matched controls to determine the prevalence of enteropathogenic E. coli (enteroadherent E. coli, enterotoxigenic E. coli, enteroinvasive E. coli, and enterohemorrhagic E. coli) and their correlation with O:H serotypes. E. coli isolates exhibiting localized and aggregative adherence in the HEp-2 cell assay were significantly more frequently isolated from the patients (8.5 and 26.9%, respectively) than from the controls (1.7 and 15%, respectively). This difference was significant for the group 0 to 2 months of age but for older infants. Regardless of age, E. coli isolates with diffuse adherence were found at similar frequencies in both the patients and the controls. A striking correlation between classic O serogroups and localized adherence was also observed. These findings confirm the pathogenic role of E. coli with localized and aggregative adherence in diarrheal disease, as well as the epidemiological importance of O:H serotyping for characterizing localized-adhering E. coli.

The impact of rotavirus disease in Venezuela.

Information concerning the disease burden of rotavirus, particularly in developing countries, has important implications for the use and for monitoring the impact of rotavirus vaccines. Although rotavirus has been recognized as the most frequent cause of hospitalization in the world, national estimates and specific information about the incidence of hospitalization for rotavirus gastroenteritis are very limited. Consequently, estimates of the incidence of hospitalization among children during the first 2 years of life in Venezuela were determined by extrapolation of data from a community-based study carried out in Caracas.

Efficacy of a quadrivalent rhesus rotavirus-based human rotavirus vaccine aimed at preventing severe rotavirus diarrhea in infants and young children.

The most extensively explored strategy for rotavirus vaccination has been the Jennerian approach, which uses an antigenically related rotavirus strain from an animal host as the immunogen to induce protection against the 4 epidemiologically important group A rotavirus VP7 serotypes. Because this approach has shown limited efficacy, a modified Jennerian approach was developed with the goal of achieving broader antigenic coverage. Four VP7 serotypes were incorporated into a quadrivalent vaccine comprised of three rhesus-human rotavirus reassortants, each with 10 rhesus rotavirus genes and 1 human rotavirus gene that encodes VP7 serotype 1, 2, or 4 specificity; the rhesus rotavirus itself provides coverage for VP7 serotype 3. This approach appears quite promising for preventing severe rotavirus diarrhea, including those episodes that lead to dehydration. Additional strategies under development stress the role not only of human rotavirus VP7 but also of human rotavirus VP4, the other outer capsid protein that also induces neutralizing antibodies.

Jennerian and modified Jennerian approach to vaccination against rotavirus diarrhea using a quadrivalent rhesus rotavirus (RRV) and human-RRV reassortant vaccine.

Rotaviruses are the single most important cause of severe diarrhea of infants and young children world-wide. Deaths from rotavirus diarrhea occur infrequently in developed countries; however, in developing countries, rotaviruses are estimated to cause over 870000 deaths in the under five-year age group. There is, therefore, a vital need for a vaccine to prevent severe rotavirus diarrhea in infants and young children. The most extensively evaluated strategy for rotavirus vaccination has been the "Jennerian" approach in which an antigenically related rotavirus strain from an animal host (bovine or simian [rhesus monkey]) is used as the immunogen to induce protection against the four epidemiologically important group A human rotavirus serotypes. These orally administered vaccines were safe and immunogenic but had only limited success because serotype-specific immunity was not induced consistently in the under six-month age group. Therefore, a modified "Jennerian" approach was adopted with the goal of attaining broader antigenic coverage. In this approach four serotypes are combined to form a quadrivalent vaccine comprised of (i) rhesus rotavirus (RRV) which provides coverage for VP7 serotype 3, and (ii) three human-RRV reassortants each with ten RRV genes and a single human rotavirus gene that encodes VP7 serotype 1, 2, or 4 specificity. This modified "Jennerian" approach appears to be quite promising in preventing severe diarrhea in field trials. However, if this approach fails to yield an optimal level of protection consistently, additional modified "Jennerian" strategic, are under development that consider not only human rotavirus VP7 but also human rotavirus VP4, the other outer capsid protein. In addition, a non-"Jennerian" approach includes the development of cold-adapted human rotavirus strains or cold-adapted human rotavirus reassortants as vaccine candidates.

Homotypic immune response to primary infection with rotavirus serotype G1.

Some aspects of rotavirus humoral immunity were assessed on the basis of distinguishing serotype-specific specificities (VP4/VP7) by using rotavirus reassortants, human and animal strains in neutralization assays in serum samples obtained during the acute phase, and 1, 6 and 12 months after primary natural infection. In this study, all the infecting virus strains were characterized as G type and some also as P type. Primary natural infection induces a significantly greater homotypic neutralization response than heterotypic response. In addition, there was no significant difference in the number of homotypic or heterotypic responses following reinfection. Transplacentally acquired homotypic antibodies were associated with protection against dehydration during rotavirus gastroenteritis.

Evaluation of the antigenicity and reactogenicity of varying formulations of the rhesus rotavirus-based quadrivalent and the M37 rotavirus vaccine candidates.

Three phase I trials of the rhesus rotavirus (RRV)-based quadrivalent vaccine [composed of serotype 3 (RRV), and serotypes 1 (D x RRV), 2 (DS1 x RRV), and 4 (ST3 x RRV) human rotavirus x RRV reassortants] and the M37 (nursery strain) rotavirus vaccine candidates were conducted in an attempt to find a safe and optimally antigenic formulation. Infants 10-20 weeks old received, in trial I, 1) the quadrivalent vaccine as two separate bivalent doses (1 x 10(4) PFU each of D x RRV and RRV, followed 4 weeks later by 1 x 10(4) PFU each of DS1 x RRV and ST3 x RRV) or 2) placebo; in trial II, 1) one dose of quadrivalent vaccine (10(4) PFU of each component), or 2) two doses of quadrivalent vaccine, or 3) a 10(4) PFU dose of M37 vaccine, or 4) M37 vaccine followed by the quadrivalent vaccine, or 5) placebo; in trial III, 1) a dose of a higher-titered quadrivalent vaccine (10(5) PFU of each component), or 2) two doses of higher titered quadrivalent vaccine, or 3) a dose of higher titered M37 vaccine (10(5) PFU) or 4) two doses of M37 vaccine (10(5) PFU), or 5) M37 vaccine (10(5) PFU) followed by the higher titered quadrivalent vaccine, or 6) placebo. A mild, transient fever during the first week postvaccination was associated with the bivalent or quadrivalent vaccines but not with the M37 vaccine. Fourfold or greater serum IgA ELISA responses to rotavirus were observed in 48-92% of the infants receiving quadrivalent vaccine and in 32-50% of those receiving M37 vaccine.(ABSTRACT TRUNCATED AT 250 WORDS)

Enumeration of selected leukocytes in the small intestine of BALB/c mice infected with Cryptosporidium parvum.

Neonatal, suckling BALB/c mice inoculated with Cryptosporidium parvum produce an infection characterized by continuous shedding of oocysts that spontaneously clears by the time the animals are three weeks of age. Neonatal mice were used to characterize the leukocyte subgroups present in Peyer's patches from the ileum and jejunum of Cryptosporidium-infected and healthy mice. After infection, ileal Peyer's patches showed a predominant CD8+ response, with abundant monocytes-macrophages (MOMA-2+) and nonlymphoid dendritic cells (NLDC-145+ cells). In contrast, jejunal Peyer's patches showed more T lymphocytes than ileal patches, with a predominance of CD4+ cells and many dendritic NLDC-145+ cells and MOMA-2+ cells. The present results showed that ileal and jejunal Peyer's patches are functionally different in response to Cryptosporidium parasites. These findings suggest a preferential involvement of jejunal Peyer's patches in T cell-dependent immunity against the parasite, whereas ileal patches may be associated with B cell expansion and maturation.

Serological response to rotavirus infection in newborn infants.

We report the identification of rotavirus in stools of newborn infants at the "Hospital Materno Infantil de Caricuao" (HMIC) as well as the infants' serological responses to various rotavirus strains. The serological responses of another group of rotavirus-positive neonates studied previously at the "Maternidad Concepcion Palacios" (MCP) hospital was also evaluated. Fifty-four of 266 (20%) newborns examined at HMIC shed rotavirus. The infection rate was higher among infants admitted to the nursery (75%) than in those "rooming in" with their mothers (7%) (P < .01). Eleven of the 54 neonates (20%) had diarrhea; seven of them experienced mild, short-lived episodes, whereas five had frequent diarrhea bouts or diarrhea lasting for over 3 days; the remaining 43 infants were asymptomatic. Twenty-seven of 28 rotavirus specimens tested at HMIC had VP7 serotype 4 specificity and one belonged to VP7 serotype 1; VP4 typing performed on 24 of the viruses by RNA hybridization showed these viruses to be similar to the M37 strain, a rotavirus previously associated with asymptomatic infections in newborns at MCP. IgA seroresponses were detected in eight of 11 infants born at HMIC (73%), but most failed to developed neutralization responses to homologous or heterologous strains. Newborn infants who had shed the M37 rotavirus strain at MCP reacted similarly: 16 of 24 (67%) developed a rotavirus IgA rise, but only 29% developed a neutralization response.

Reactogenicity and immunogenicity of a high-titer rhesus rotavirus-based quadrivalent rotavirus vaccine.

We evaluated the reactogenicity and antigenicity of a quadrivalent rotavirus vaccine composed of serotype 3 rhesus rotavirus (RRV) and three single-gene-substitution reassortants of RRV and human strain D (D x RRV, serotype 1), DS1 (DS1 x RRV, serotype 2), or ST3 (ST3 x RRV, serotype 4) in a double-masked study with 302 infants in Caracas, Venezuela. Three doses of the quadrivalent vaccine composed of either 10(5) PFU (low titer) or 10(6) PFU (high titer) of each component were administered to 99 and 101 infants, respectively, at 4-week intervals starting at the second month of age; 102 infants received a placebo. Postvaccination reactions were monitored by home visits every other day during the week postvaccination. The vaccine was associated with the occurrence of mild, short-lived febrile episodes in 26 and 23% of the recipients after the first doses of high- or low-titer vaccine, respectively, in comparison with 13% of the infants receiving the placebo. Febrile reactions occurred less frequently in vaccinees after the second or third dose than after the initial dose. The vaccine was not significantly associated with diarrhea or any additional symptom or sign. Serum specimens obtained shortly before the first, 4 weeks after the first, and 4 weeks after the third dose of vaccine or placebo were tested by an immunoglobulin A enzyme-linked immunosorbent assay and by neutralization assays. Seroresponses occurred significantly more often after 3 doses than after a single dose of either vaccine. Immunoglobulin A responses were observed in 80 and 79% of the infants after 3 doses of high- or low-titer vaccine, respectively. Most of the infants tested developed a neutralization response to RRV after 3 doses of the high- (90%) or low-(88%) titer vaccine. Neutralization response rates to human rotavirus serotypes 1 to 4 after 3 doses were similar in both vaccine and 87 of 90 receiving the high-titer vaccine developed seroresponses, as detected by any of the assays employed. The study indicates that 3 doses of quadrivalent vaccine at a titer of 10(6) PFU of each component offered no advantage over the lower-titer preparation for use in efficacy trials.