María B. Isa

Diarrhea and Enteric Emerging Viruses in HIV-Infected Patients

To evaluate the prevalence of enteric viruses and their possible association with diarrhea, 244 stool samples were collected from HIV-infected and uninfected patients with or without diarrhea (subgroups I-a, Ib, II-a, and II-b, respectively). Subjects were screened by polyacrylamide gel electrophoresis, latex agglutination, and enzyme immunoassays for rotaviruses, adenoviruses, picobirnaviruses, and astroviruses. Enteric viruses were found significantly more often in specimens from HIV patients (20%) than in specimens from uninfected HIV patients (0%) (p < 0.05). Picobirnavirus was detected in 14.63% of 82 HIV-infected patients with diarrhea, but it was detected neither in those without diarrhea (0%) (p < 0.05) nor in the groups of uninfected HIV subjects (0%) (p < 0.05). Nor could astrovirus (subgroups I-a [4.00%] versus subgroup I-b [5.26%],p > 0.05) or enteric adenovirus (subgroup I-a [1.22%] versus subgroup I-b [0%], p > 0.05) be linked to the diarrhea disorder in HIV-infected patients. Rotaviruses were not detected in any of the clinical subgroups studied. Enteric viruses were detected in 15 of 93 (16.13%) of the HIV-infected patients with CD4+ T cell count <200/microl and 3 of 19 (15.79%) of those HIV-infected individuals with a CD4+ T cell count 200-499/microl, showing no significant difference (p > 0.05). According to our data, unusual enteric viruses such as picobirnavirus, astrovirus, and enteric adenovirus occur in HIV-infected population in Córdoba, Argentina. However, only picobirnaviruses could be significantly associated with diarrhea in these patients.

The epidemiology of acute viral gastroenteritis in hospitalized children in Cordoba city, Argentina: an insight of disease burden

Information concerning the disease burden of viral gastroenteritis has important implications for the use and monitoring the impact of public health policies. The present study, carried out in Córdoba city, Argentina, documents the epidemiology of severe viral diarrhea as well as the burden of viral gastrointestinal disease in the hospital children admission. A total of 133 stools were collected from hospitalized children (Town Childhood Hospital) suffering from acute diarrhea and studied for the presence of Group A rotavirus, astrovirus and adenovirus 40/41 by enzyme-immuno assay, between November 1997 and October 1998. Enteric viruses accounted for 42.1% of the total diarrheal cases analyzed. Group A rotaviruses, astroviruses, adenoviruses 40/41 and mixed infections were found in 35.3, 4.5, 1.5, and 0.8% studied specimens respectively. We estimated that 1 in 27 children in the 0-35 month-old cohort/range would be annually hospitalized for a viral gastroenteritis illness. The major impact on viral diarrhea lies on rotaviral infection, accounting for 84.0% of the viral diarrheal cases analyzed and for approximately one third of severe diarrheas requiring hospital admission in Córdoba City, Argentina.

Molecular Diversity of Partial-Length Genomic Segment 2 of Human Picobirnavirus

Objectives: This study was carried out in order to evaluate the efficacy of the recently developed picobirnavirus (PBV) sets of primers and to establish the phylogenetic relationships of Argentine strains with PBV strains isolated in China and the USA. Methods: Thirteen fecal specimens tested as positive for PBV by polyacrylamide gel electrophoresis were analyzed by reverse transcription-polymerase chain reaction assays using primers target to the genomic segments 2 of PBV strains isolated in China and the USA. The amplicons were sequenced and analyzed. Results: Primers derived from the China strain produced amplicons in only 4 of the 13 specimens (30.76%). No sample was revealed as positive with the primers derived from the US strain. DNA sequencing of polymerase chain reaction products differed in nucleic acid and amino acid sequences by 13.9–42.28% and 18.1–51.1%, respectively. Despite this strain diversity, three domains of conserved nucleotide sequences as well as the amino acid motif D-S-D typical of RNA-dependent RNA polymerase gene of double-strand RNA viruses were identified. Comparatively, these conserved regions were also identified in homologous PBV strains from the USA and China. Phylogenetic analysis showed no time or geographic clustering. Conclusions: These findings provide evidence that PBV may represent an emerging heterogeneous group of viruses.

Correlation between rotavirus A genotypes detected in hospitalized children and sewage samples in 2006, Córdoba, Argentina

Routine rotavirus A (RV‐A) surveillance is based on clinical cases, so only symptomatic infections are reported. The objective of this study was to determine whether the RV‐A genotypes and cold seasonal pattern described in patients with diarrhea is reflected by sewage surveillance, which could be representative of the RV‐A genotypes circulating in the population. The genotype distribution of RV‐A in effluent samples from a local sewage treatment plant was compared to those from local clinical cases. A total of 52 sewage samples and 70 stool specimens from children with acute non‐bacterial diarrhea were collected from January to December 2006. The effluent specimens were concentrated and RNA extracts from concentrated sewage and clinical samples were genotyped for the rotavirus VP7 gene. The proportional distribution of the RV‐A G‐genotypes in sewage and clinical samples during the cold season was similar: G1 accounted for 26.6% of the typed sewage isolates and 28.8% of the clinical infections; G3 type accounted for 21.9% and 25.8%; G2 type 15.6% and 10.6%; G4 type 17.2% and 21.2%; G8 type 1.6% and 0%; and the G9 type 17.2% and 13.6%, respectively. A similar picture of RV‐A genotype detection was obtained in sewage samples collected during the cold and warm seasons. The results indicate that there is a correlation between genotypes of RV‐A isolates from human diarrheic patients and of those from sewage samples. In addition, sewage monitoring highlighted the uniform all‐year RV‐A circulation, which was in contrast to the peak incidence of RV‐A infection in the community. J. Med. Virol. 82: 1277–1281, 2010.

Picobirnavirus causes persistent infection in pigs.

A study aimed to further understand the biology of porcine picobirnaviruses (PBV) was conducted between November 2003 and January 2008, on a farm located in the outskirts of Córdoba City, Argentina. PBV prevalence was examined by polyacrylamide gel electrophoresis and silver staining (PAGE S/S) on a total of 265 samples collected from pigs divided into four groups, according to age and physiological status. PBV detection rate was highest in the group of sows sampled within the lactogenic period (38.02%; p<0.05), followed by pregnant sows (15.09%), piglets aged 2-5 months of age (18.42%) and adult (> or =50 weeks) male pigs (0%). In addition, 103 samples collected in 3 follow-up studies were analyzed by PAGE S/S and reverse transcription followed by PCR (RT-PCR). Two of these studies followed female pigs from weaning up to slaughter and a third one from weaning up to 4 pregnancy periods. The results provide evidence that PBV establishes a persistent infection in the host with periods of silence intermingled with periods of low and high viral excretion. High PBV excretion levels were detected by PAGE S/S and were conditioned by age (primary infection) and host physiological status. Low PBV excretion levels were detected by RT-PCR throughout the entire study period. Sequence analysis of selected amplicons indicated that the virus excreted through the follow-up study was the same. These results suggest that porcine PBV is maintained in nature by transmission from infected asymptomatic individuals to susceptible ones.

Childhood astrovirus-associated diarrhea in the ambulatory setting in a Public Hospital in Cordoba city, Argentina.

Human astroviruses have been increasingly identified as important agents of diarrheal disease in children. However, the disease burden of astrovirus infection is still incompletely assessed. This paper reports results on the epidemiological and clinical characteristics of astrovirus-associated diarrhea, as well as the impact of astrovirus infection on the ambulatory setting at a Public Hospital in Córdoba city, Argentina. From February 2001 through January 2002, 97 randomly selected outpatient visits for diarrhea among children < 36 months old were enrolled. A single specimen of stool from each child was collected and tested for astrovirus antigen by enzyme immunoassay. Astroviruses were detected in 12.37% of the diarrheal episodes. All the positive cases occurred in children 4 to 18 months, but the highest rate was in children aged 4 to 6 months (23.80%). The clinical symptoms of astrovirus associated-diarrhea were fever 41.66%, vomiting 25.00% and dehydration 8.33%; overall 16.66% required hospitalization. Astrovirus was identified through the year and no seasonally pattern was detected (cool semester 15.21% versus warm semester 9.80% p > 0.05). According to our estimation about one out of seventy-four children in this cohort would be assisted annually for an astroviral-diarrheal episode in the Public Hospital and one out of eight diarrheal cases could be attributed to astrovirus infection. Astrovirus is a common symptomatic infection in pediatric outpatient visits in the public hospital in the study area, contributing 12.37% of the overall morbidity from diarrhea.

Comparison of Immunoglobulin G Subclass Profiles Induced by Measles Virus in Vaccinated and Naturally Infected Individuals

ABSTRACT A total of 258 human sera positive for measles antibodies were divided into four different groups: group 1 contained 54 sera from children after natural measles infection (immunoglobulin M [IgM] positive, early infection phase), group 2 contained 28 sera from children after measles vaccination (IgM positive, early infection phase), group 3 contained 100 sera from healthy adults (natural long-lasting immunity), and group 4 contained 76 sera from healthy children (postvaccinal long-lasting immunity). In the early phase of infection, the percent distributions of measles virus-specific IgG isotypes were similar between natural and postvaccinal immune responses. IgG1 and IgG4 were the dominant isotypes, with mean levels of detection of 100% (natural infection) and 100% (postvaccinal) for IgG1 and 96% (natural infection) and 92% (postvaccinal) for IgG4. In comparison, the IgG4 geometric mean titer (GMT) in the early phase of natural infection was significantly higher than the IgG4 GMT detected in the postvaccinal immune response (80 versus 13; 95% confidence interval). In the memory phase, IgG2 and IgG3 responses decreased significantly in both natural infection and postvaccinal groups, while IgG1 levels were maintained. In contrast, the IgG4 postvaccinal immune response decreased strongly in the memory phase, whereas IgG4 natural long-lasting immunity remained unchanged (9 versus 86%; P < 0.05). The results obtained suggest that IgG4 isotype could be used in the early phase of infection as a quantitative marker and in long-lasting immunity as a qualitative marker to differentiate between natural and postvaccinal immune responses.

Measles Virus-Specific Immunoglobulin G Isotype Immune Response in Early and Late Infections

ABSTRACT A total of 154 human serum samples (32 acute-phase and 22 convalescent-phase serum samples obtained within a week and between days 8 and 26 after the onset of rash, respectively, and 100 samples drawn from healthy immune adults) were processed by an immunofluorescence assay for the detection of immunoglobulin M (IgM), total immunoglobulin G (IgG), IgG1, IgG2, IgG3, and IgG4 measles virus-specific antibodies. In the acute phase, IgG1 was seen first, followed by IgG2, IgG3, and IgG4 responses, the mean seropositivity of which gradually increased during convalescence, reaching 100% (standard deviation [SD], 84 to 100%), 57% (SD, 34 to 80%), 86% (SD, 66 to 100%), and 86% (SD, 66 to 100%), respectively. IgG2 rose and fell in connection with IgG3 subclass antibodies, showing a rate of detection of IgG2 and/or IgG3 subclass antibodies of 95.5% (range, 100 to 86.5%) in the convalescent phase of infection. The mean percentage of measles IgG2 and IgG3 seropositivity dropped significantly during the memory phase, to 2% (range, 2 to 6%) and 3% (range, 3 to 7%), respectively (P < 0.05); meanwhile IgG1 and IgG4 subclass responses remained relatively unmodified in samples obtained years after infection (mean 100% [SD, 96 to 100%] and 86% [SD, 79 to 93%], respectively). Results obtained defined two highly different immune isotypic response patterns. One pattern is restrictive to IgG2 and/or IgG3 in the convalescent phase and is kinetically similar to the IgM antibody response, so its detection could be referred to as a recent viral activity. On the other hand, IgG1 and IgG4 were detected in both the convalescent and memory phases of the immune response, but their isolated occurrence without IgG2 and IgG3 could be related to the long-lasting immunity.

Rotavirus seasonality in urban sewage from Argentina: effect of meteorological variables on the viral load and the genetic diversity.

In Argentina, the rotavirus disease exhibits seasonal variations, being most prevalent in the fall and winter months. To deepen the understanding of rotavirus seasonality in our community, the influence of meteorological factors on the rotavirus load and the genetic diversity in urban raw sewage from Córdoba city, Argentina were evaluated. Wastewater samples were collected monthly during a three-year study period and viral particles were concentrated by polyethylene glycol precipitation. RT-nested PCR was applied for rotavirus detection, and VP7/VP4 characterization and real-time PCR for rotavirus quantification. Both molecular techniques showed relatively similar sensitivity rates and revealed rotavirus presence in urban wastewater in cold and warm seasons, indicating its circulation in the local community all year round. However, a slight trend for rotavirus circulation was noted by real-time PCR in the fall and winter seasons, showing a significantly higher peak of rotavirus concentration at mean temperatures lower than 18°C and also higher, although not statistically different during drier weather. VP7 and VP4 gene characterization showed that G1 and P[8] genotypes were dominant, and temporal variations in genotype distribution were not observed. Rotavirus spread is complex and our results point out that weather factors alone cannot explain the seasonal quantitative pattern of the rotavirus disease. Therefore, alternative transmission routes, changes in human behavior and susceptibility, and the stability and survivability of the virus might all together contribute to the seasonality of rotavirus. The results obtained here provide evidence regarding the dynamics of rotavirus circulation and maintenance in Argentina.

Genetic and evolutionary characterization of norovirus from sewage and surface waters in Córdoba City, Argentina

Noroviruses (NoVs) are among the most common viral agents that cause gastroenteritis in humans of all ages worldwide. They are excreted in the feces and introduced into environmental waters as raw or treated sewage. In this work, sewage and water samples collected from the Suquía River in the city of Córdoba, Argentina, were evaluated for the presence of NoV. Phylogenetic analysis demonstrated that the main genotype detected was GII.4, belonging to the widely-distributed 2006b variant, followed by strains related to the putative recombinant GII.g virus. Detected NoVs were more phylogenetically related with recent viruses from other countries than with previous local sequences, suggesting a rapid and wide spread of viral strains that prevents a geographically structured phylogeny. A Bayesian coalescent analysis demonstrated that variants isolated in this work have a most recent common ancestor placed in 2007-2008 with estimated substitution rates of 3.7-5.8×10(-3)s/s/y. Environmental samples showed a mixture of both viral types, pointing up to the co-circulation and the risk of mixed infections and recombination. This is the first report on the detection and characterization of NoV in sewage and river water in Argentina.