The person-to-person transmission of the hepatitis A virus primarily occurs in enclosed spaces, particularly in the presence of inadequate hygiene conditions and a high proportion of susceptible individuals. Thus, intimate family contact stands out as a risk factor for HAV infection dissemination. The present study aimed to evaluate the occurrence of household HAV transmission. Blood samples were collected from patients with hepatitis A (index cases) and their family members (contacts) that were referred to an ambulatory care clinic specializing in viral hepatitis. A total of 97 samples were collected from 30 families with a confirmed hepatitis A case (index case). Serological and molecular techniques for the diagnosis of hepatitis A were conducted on all samples. HAV infection (anti-HAV IgM + and/or HAV RNA +) was detected in 34.3% (23/67) of the contacts; 34.3% (23/67) of the contacts were immune to HAV, and 31.4% (21/67) were susceptible. In the household contacts, HAV immunity was significantly associated with older age; susceptibility to infection and HAV infection were associated with younger age. Household outbreaks were detected in 16/30 families studied. Co-circulation of subgenotypes IA and IB was found in the household outbreaks, and person-to-person transmission was evidenced in six of the household outbreaks, with 100% homology between the index case and contact strains. The results demonstrated the relevance of HAV household transmission, reaffirming the need for hepatitis A vaccine administration in susceptible contacts and effective infection control procedures to prevent the extension of household outbreaks.
The replication of hepatitis A virus (HAV) is via a complementary negative-strand RNA. Each negative strand may serve as a template for the synthesis of many positive strands. The aim of this study was to detect the intermediate replicative (negative strand) of HAV in order to monitor its replication in vitro and in vivo. Real-time polymerase chain reaction (PCR) was standardized to detect the intermediate replicative of HAV in cell culture and liver from non-human primates infected experimentally. HAV primers from the 5' non-translated region and VP3 were used in the cDNA synthesis of negative-strand RNA. The negative strand was detected in the infected cell lines and liver by highly strand-specific rTth recombinant Thermus thermophilus DNA polymerase reverse transcription followed by quantitative PCR. The results indicate that the negative-strand HAV RNA can be detected in vivo and in vitro. This model is an approach for assessing the dynamic patterns of replication and should represent a valuable tool for the monitoring of HAV replications in cell cultures and for the evaluation of experimental infections in animal models.
A strategy adopted by different countries to reduce the number of new cases of hepatitis A is the vaccination. However, the mosaic of the epidemiological profile in developing countries has hampered the establishment of a unified nationwide vaccination program. To determinate national vaccination policies, the results of epidemiological studies need to be carefully considered. For this monitoring, the use of oral fluid is very important due to the painless and non invasive collection characteristics. There are few studies investigating which oral fluid collection device is optimal to detect low antibody levels and its use in selecting individuals for vaccination. So, the present study aimed to evaluate different oral fluid collection devices to detect humoral immune response against hepatitis A virus and its application in epidemiological studies. Therefore, 90 matched serum and oral fluid samples were collected from volunteers with different immune status, under ideal conditions of collection (optimization panel); and 224 matched samples in difficult-to-access areas (epidemiological study). Serum was collected by venipuncture and the oral fluid was obtained using three commercial devices: Salivette(®), OraSure(®) and ChemBio(®). Serum and oral fluid were submitted to a commercial immunoblot to detect total anti-HAV antibodies. The optimization panel demonstrated that ChemBio(®) device had the best performance (100% agreement), followed by OraSure(®) (95.4%) and Salivette(®) (90.8%). The optimal collection device (ChemBio(®)), tested in a difficult-to-access area and evaluated under precarious conditions of collection, showed similar prevalence of total anti-HAV between serum and oral fluid, 80.8% and 79%, respectively. A follow-up was performed to evaluate the stability of oral fluid and it was observed that 210 days after the collection it was possible to detect anti-HAV antibodies. Oral fluid can be used to detect low levels of specific-antibody, being important to select age groups to be vaccinated. Therewith, the choice of proper collection device is essential to evaluate HAV antibodies in the epidemiological scenario.
The yellow fever (YF) vaccine consists of an attenuated virus, and despite its relative safety, some adverse events following YF vaccination have been described. At the end of 2016, Brazil experienced the most massive sylvatic yellow fever outbreak over the last 70 years and an intense campaign of YF vaccination occurred in Minas Gerais state in Southeast Brazil from 2016 to 2018. The present study aimed to develop a genotyping tool and investigate 21 cases of suspected adverse events following YF vaccination. Initial in silico analyses were performed using partial NS5 nucleotide sequences to verify the discriminatory potential between wild-type and vaccine viruses. Samples from patients were screened for the presence of the YFV RNA, using 5′UTR as the target, and then used for amplification of partial NS5 gene amplification, sequencing, and phylogenetic analysis. Genotyping indicated that 17 suspected cases were infected by the wild-type yellow fever virus, but four cases remained inconclusive. The genotyping tool was efficient in distinguishing the vaccine from wild-type virus, and it has the potential to be used for the differentiation of all yellow fever virus genotypes.
Despite the increasing numbers of studies investigating hepatitis A diagnostic through saliva, the frequency and the pattern of hepatitis A virus (HAV) markers in this fluid still remains unknown. To address this issue, we carried on a longitudinal study to examine the kinetics of HAV markers in saliva, in comparison with serum samples. The present study followed-up ten patients with acute hepatitis A infection during 180 days post diagnosis (dpd). Total anti-HAV was detected in paired serum and saliva samples until the end of the follow-up, showing a peak titer at 90th. However, total anti-HAV level was higher in serum than in saliva samples. This HAV marker showed a probability of 100% to be detected in both serum and saliva during 180 dpd. The IgM anti-HAV could be detected in saliva up to 150 dpd, showing the highest frequency at 30th, when it was detected in all individuals. During the first month of HAV infection, this acute HAV marker showed a detection probability of 100% in paired samples. The detection of IgM anti-HAV in saliva was not dependent on its level in serum, HAV-RNA detection and/or viral load, since no association was found between IgM anti-HAV positivity in saliva and any of these parameter (p>0.05). Most of the patients (80%) were found to contain HAV-RNA in saliva, mainly at early acute phase (30th day). However, it was possible to demonstrate the HAV RNA presence in paired samples for more than 90 days, even after seroconversion. No significant relationship was observed between salivary HAV-RNA positivity and serum viral load, demonstrating that serum viral load is not predictive of HAV-RNA detection in saliva. Similar viral load was seen in paired samples (on average 104 copies/mL). These data demonstrate that the best diagnostic coverage can be achieved by salivary anti-HAV antibodies and HAV-RNA tests during 30–90 dpd. The long detection and high probability of specific-HAV antibodies positivity in saliva samples make the assessment of salivary antibodies a useful tool for diagnosis and epidemiological studies. The high frequency of HAV-RNA in saliva and the probability of detection of about 50%, during the first 30 dpd, demonstrate that saliva is also useful for molecular investigation of hepatitis A cases, mainly during the early course of infection. Therefore, the collection of saliva may provide a simple, cheap and non-invasive means of diagnosis, epidemiological surveys and monitoring of hepatitis A infection purposes.
Aim: We evaluated the accuracy of a commercial rapid immunochromatographic test (rapid test [RT]) for hepatitis A (HA) diagnosis and epidemiological studies. Materials & methods: The accuracy of a RT was evaluated in laboratory and in field conditions. Predictive modeling estimated the test performance in a hypothetical population. Results: The RT showed sensitivities of 66–86%, and specificities of 21–100%, depending on the antibody isotype (IgM or IgG) analyzed and prevalence of infection. Conclusion: The RT is a good alternative for diagnostic in HA outbreaks. The predictive model indicates that it should not be used alone for HA diagnosis in low prevalence populations. These data can be used in the future to strengthen decision-making during the implementation of rapid diagnostic methods in health services.
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