TRANSFUSÃO DE PLASMA CONVALESCENTE EM COVID19: ASSOCIAÇÃO ENTRE ANTICORPOS NEUTRALIZANTES E REDUÇÃO DE CARGA VIRAL

Introdução

A transfusão de plasma convalescente tem sido utilizada como terapêutica alternativa no tratamento de COVID19 nos últimos meses. Avaliamos o impacto dos anticorpos neutralizantes produzidos pelos pacientes e dos anticorpos presentes nas unidades transfundidas na redução da carga  viral em pacientes em tratamento hospitalar de COVID19.

Materiais e métodos

Foram avaliados consecutivamente 29 pacientes admitidos para tratamento hospitalar de COVID19 em um único centro. Doses de 300 a 600 ml de plasma convalescente foram administradas ao longo de 2 dias. Foram coletados swabs nasais a cada 48 h a partir do D0 (dia de transfusão de plasma convalescente) até a alta hospitalar, a fim de determinar a carga viral por digital droplet PCR (ddPCR) dos alvos N1 e N2 do gene N (nucleocapsídeo) para análise de redução de carga viral, sendo considerado o número de cópias virais por 1000 células presente na amostra. Mensuramos os títulos de anticorpos neutralizantes (cytopathic effect-based virus neutralization test  -SARS-CoV-2 GenBank MT126808.1) dos pacientes (NAbsP) antes da transfusão (D0)  e títulos de anticorpos neutralizantes das unidades de plasma transfundidas (NAbsT). Para análise de associação entre NAbsP e redução de carga viral, os pacientes foram divididos em dois grupos de acordo com o status de NAbsP no D0: título de NabsP inferior a 80 e título de NabsP igual ou superior a 80. Para esta análise, foi utilizado o teste de Mann-Whitney . Para verificar a associação entre NAbsT e redução de carga viral, os pacientes foram divididos em três grupos: aqueles que receberam transfusão de plasma convalescente com título de NAbsT até 160, título de NAbsT entre 160-640 e NAbsT superior a 640. Para esta análise, foi utilizado o  teste de Kruskall-Wallis.

Resultados

Pacientes com baixos títulos de neutralizantes à admissão (NAbsP inferior a 80) apresentaram redução de carga viral significativamente maior (p=0,009) que pacientes com NAbsP igual ou superior a 80. Com relação ao impacto da transfusão de plasma, observou-se que quanto maior o título de anticorpos neutralizantes transfundidos maior foi a redução da carga viral; porém, tal achado não apresentou significância estatística (p = 0,528).

Discussão

O combate e eliminação da viremia através dos anticorpos neutralizantes presentes no plasma convalescente compreende uma das justificativas da sua aplicação como terapia alternativa para COVID19. Contudo, estudos prévios demonstraram resultados contraditórios em relação ao seu impacto no clearance viral. Na presente casuística, pacientes com baixos títulos de anticorpos neutralizantes apresentaram maior redução de carga viral após a transfusão de plasma convalescente do que pacientes com altos títulos. Pacientes que já apresentavam títulos elevados de neutralizantes parecem não se beneficiar da transfusão de plasma no que se refere à redução de carga viral. A estratificação dos pacientes de acordo com os níveis basais de anticorpos neutralizantes parece ser um ponto importante a ser discutido no tratamento de COVID19 com plasma convalescente e fornece uma explicação plausível para os resultados controversos previamente observados.

Zoonotic potential of a novel bat morbillivirus

Bats are significant reservoir hosts for many viruses with zoonotic potential1. SARS-CoV-2, Ebola virus, and Nipah virus are examples of such viruses that have caused deadly epidemics and pandemics when spilled over from bats into human and animal populations2,3. Careful surveillance of viruses in bats is critical for identifying potential zoonotic pathogens. However, metagenomic surveys in bats often do not result in full-length viral sequences that can be used to regenerate such viruses for targeted characterization4. Here, we identify and characterize a novel morbillivirus from a vespertilionid bat species (Myotis riparius) in Brazil, which we term myotis bat morbillivirus (MBaMV). There are 7 species of morbilliviruses including measles virus (MeV), canine distemper virus (CDV) and rinderpest virus (RPV)5. All morbilliviruses cause severe disease in their natural hosts6–10, and pathogenicity is largely determined by species specific expression of canonical morbillivirus receptors, CD150/SLAMF111 and NECTIN412. MBaMV used Myotis spp CD150 much better than human and dog CD150 in fusion assays. We confirmed this using live MBaMV that was rescued by reverse genetics. Surprisingly, MBaMV replicated efficiently in primary human myeloid but not lymphoid cells. Furthermore, MBaMV replicated in human epithelial cells and used human NECTIN4 almost as well as MeV. Our results demonstrate the unusual ability of MBaMV to infect and replicate in some human cells that are critical for MeV pathogenesis and transmission. This raises the specter of zoonotic transmission of a bat morbillivirus.

NS1-based ELISA test efficiently detects dengue infections without cross-reactivity with Zika virus

OBJECTIVES

The aim of this study was to achieve greater specificity of dengue virus (DENV) serological tests based on a recombinant antigen derived from non-structural protein 1 (ΔNS1) with regard to cross-reactive Zika virus (ZIKV) anti-NS1 antibody responses. This is of relevance in endemic regions for the serological discrimination of both DENV and ZIKV, such as Brazil and other tropical countries.

METHODS

The ΔNS1 proteins were obtained as recombinant antigens and were evaluated as solid-phase-bound antigens in the ELISA test to detect anti-NS1 IgG antibodies. The performance of the ∆NS1-based DENV IgG ELISA was assessed with both mouse and human serum samples previously exposed to DENV or ZIKV.

RESULTS

The ∆NS1-based DENV IgG ELISA detected anti-DENV NS1 IgG without cross-reactivity with ZIKV-positive serum samples. The sensitivity and specificity of the assay determined using samples previously characterized by real-time PCR (qRT-PCR) or plaque reduction neutralization assay (PRNT) were 82% and 93%, respectively.

CONCLUSION

The ∆NS1-based DENV IgG ELISA conferred enhanced diagnostic specificity for anti-DENV serological tests and may be particularly useful for serological analyses in endemic regions for both DENV and ZIKV transmission.

Prevalence of Measles Antibodies in São José do Rio Preto, São Paulo, Brazil: A serological survey model

Measles is an acute and highly contagious but vaccine-preventable infectious disease. Despite years of being considered eliminated, decreased vaccination rates have produced virus reemergence in several countries, including Brazil. Measles can be controlled through immunization programs, through which aim to achieve 95% coverage with two doses of the vaccine. Measles can also be controlled if suspected cases can be properly identified in order to contain outbreaks. This cross-sectional study determined the prevalence of measles antibodies and their correlation with rubella antibodies (resulting from the combination vaccine used in Brazil's public immunization program) in individuals aged higher 10 years old in São José do Rio Preto, São Paulo State, Brazil, participants of a prospective cohort of arbovirosis surveillance before virus reemergence in the country. Our findings presented that 32.9% of individuals aged 10-40 years old had not antibodies against measles; 39.3% of total individuals with documented evidence of measles vaccination did not have anti-measles IgG, though only 20.2% of individuals with documented evidence of rubella vaccination lacked anti-rubella IgG. Besides, the most of measles cases reported in the city, following the virus spreading in the country, occurred especially in groups defined by us as susceptible. Because the combination MMR vaccine is part of Brazil's national vaccine schedule, the possible reasons for this relatively high rate of seronegativity need to be investigated further, once that it reflects outbreak risk.

Re-emergence of rabies virus maintained by canid populations in Paraguay

Paraguay has registered no human cases of rabies since 2004, and the last case in dogs, reported in 2009, was due to a variant maintained in the common vampire bat "Desmodus rotundus". In 2014, a dog was diagnosed as positive for rabies with aggression towards a boy and all required measures of control were successfully adopted. Epidemiological investigation revealed that the dog was not vaccinated and had been attacked by a crab-eating fox, "zorro" (Cerdocyon thous). The sample was diagnosed by the Official Veterinary Service of the Country and sent to the Center on Rabies Research from the University of São Paulo, Brazil, for antigenic and genetic characterization. A second sample from a dog positive for rabies in the same region in 2015 and 11 samples from a rabies outbreak from Asuncion in 1996 were also characterized. The antigenic profile of the samples, AgV2, was compatible with one of the variants maintained by dogs in Latin America. In genetic characterization, the samples segregated in the canine (domestic and wild species)-related group in an independent subgroup that also included samples from Argentina. These results and the epidemiology of the case indicate that even with the control of rabies in domestic animals, the virus can still circulate in wildlife and may be transmitted to domestic animals and humans, demonstrating the importance of continuous and improved surveillance and control of rabies, including in wild species, to prevent outbreaks in controlled areas.

Epidemiological and molecular characterization of rubella virus isolated in São Paulo, Brazil during 1997-2004

Rubella virus (RV) infection during the early stages of pregnancy can lead to serious birth defects, known as the congenital rubella syndrome (CRS). In 2003, the Pan American Health Organization (PAHO) adopted a resolution calling for the elimination of rubella and the congenital rubella syndrome (CRS) in the Americas by the year 2010. Brazil will have implemented the recommended PAHO strategy for elimination and interruption of endemic rubella virus transmission. The characterization of genotypes during the final stages of rubella elimination is important for determining whether new rubella isolates represent endemic transmission or importations. Samples (blood, urine, cerebrospinal fluid, and throat swabs) collected from patients with symptoms suggestive of rubella infection in 1997-2004 were isolated in cell culture and genotyped. Twenty-eight sequences were analyzed and two genotypes were identified: 1a and 1G. The information reported in this paper will contribute to understanding the molecular epidemiology of RV in São Paulo, Brazil.

Phylogenetic analysis of rubella virus strains during an outbreak in São Paulo, 2007-2008

Rubella virus (RV) is an important human pathogen that causes rubella, an acute contagious disease. It also causes severe birth defects collectively known as congenital rubella syndrome when infection occurs during the first trimester of pregnancy. Here, we present the phylogenetic analysis of RV that circulated in São Paulo during the 2007-2008 outbreak. Samples collected from patients diagnosed with rubella were isolated in cell culture and sequenced. RV RNA was obtained from samples or RV-infected cell cultures and amplified by reverse transcriptase-polymerase chain reaction. Sequences were assigned to genotypes by phylogenetic analysis using RV reference sequences. Seventeen sequences were analyzed, and three genotypes were identified: 1a, 1G, and 2B. Genotypes 1a and 1G, which were isolated in 2007, were responsible for sporadic rubella cases in São Paulo. Thereafter, in late 2007, the epidemiological conditions changed, resulting in a large RV outbreak with the clear dominance of genotype 2B. The results of this study provide new approaches for monitoring the progress of elimination of rubella from São Paulo, Brazil.

Detection of hantaviruses in Brazilian rodents by SYBR-Green-based real-time RT-PCR

Current knowledge of the pathogenic hantavirus indicates that wild rodents are its primary natural reservoir. Specific primers to detect the presence of viral genomes were developed using an SYBR-Green-based real-time RT-PCR protocol. One hundred sixty-four rodents native to the Atlantic Forest biome were captured in São Paulo State, Brazil, and their tissues were tested. The presence of hantavirus RNA was detected in sixteen rodents: three specimens of Akodon montensis, three of Akodon cursor, two of Necromys lasiurus, one of Juliomys sp., one of Thaptomys nigrita, five of Oligoryzomys nigripes, and one of Oryzomys sp. This SYBR Green real-time RT-PCR method for detection of hantavirus may be useful for surveying hantaviruses in Brazil.

Hospital-acquired human bocavirus in infants

Human bocavirus (HBoV) is a respiratory pathogen that affects young children. We screened 511 nasopharyngeal aspirates for hospital-acquired HBoV from infants hospitalised with respiratory infection from January to December 2008. Among 55 children with HBoV infection, 10 cases were hospital-acquired. Compared with the community-acquired cases, coinfection with other respiratory viruses in these patients was uncommon. HBoV should be considered for inclusion in screening protocols for nosocomial childhood respiratory infections, especially in intensive care units.

Performance of indirect immunofluorescence assay, immunochromatography assay and reverse transcription-polymerase chain reaction for detecting human respiratory syncytial virus in nasopharyngeal aspirate samples

Comparison of the use of indirect immunofluorescence assay (IFA), immunochromatography assay (ICA-BD) and reverse transcription-polymerase chain reaction (RT-PCR) for detecting human respiratory syncytial virus (HRSV) in 306 nasopharyngeal aspirates samples (NPA) was performed in order to assess their analytical performance. By comparing the results obtained using ICA-BD with those using IFA, we found relative indices of 85.0% for sensitivity and 91.2% for specificity, and the positive (PPV) and negative (NPV) predictive values were 85.0% and 91.2%, respectively. The relative indices for sensitivity and specificity as well as the PPV and NPV for RT-PCR were 98.0%, 89.0%, 84.0% and 99.0%, respectively, when compared to the results of IFA. In addition, comparison of the results of ICA-BD and those of RT-PCR yielded relative indices of 79.5% for sensitivity and 95.4% for specificity, as well as PPV and NPV of 92.9% and 86.0%, respectively. Although RT-PCR has shown the best performance, the substantial agreement between the ICA-BD and IFA results suggests that ICA-BD, also in addition to being a rapid and facile assay, could be suitable as an alternative diagnostic screening for HRSV infection in children.

Seroprevalence of human parvovirus B19 in a suburban population in São Paulo, Brazil

OBJECTIVE

To analyze the prevalence of IgG antibodies to human parvovirus B19.

METHODS

Cross-sectional study in a suburban community in São Paulo, Southeastern Brazil, between November 1990 and January 1991. Randomly selected (N=435) representative samples of sera were collected from healthy children older than 15 days old and adults up to 40 years old. IgG antibodies were detected using ELISA.

RESULTS

High prevalence of IgG antibodies to B19 parvovirus was found in 87% of newborns. The prevalence of maternally derived IgG antibodies exponentially plunged up to the 19th month of age. Low prevalence of antibodies was found in the first 4 years of life, increasing up to 72% in those aged 31-40 years. It was estimated that the average age of first infection in this population is 21 +/- 7 years old and the optimal age for vaccination with a hypothetical vaccine would be 1 year of age.

CONCLUSIONS

Parvovirus B19 IgG antibody prevalence was high in newborns and those aged 31-40 years. The analysis by age groups showed a pattern similar to that found in previous studies, i.e., low prevalence of infection in children that increases with age.

Genetic diversity of environmental Aspergillus flavus strains in the state of São Paulo, Brazil by random amplified polymorphic DNA

Aspergillus flavus is a very important toxigenic fungus that produces aflatoxins, a group of extremely toxic substances to man and animals. Toxigenic fungi can grow in feed crops, such as maize, peanuts, and soybeans, being thus of high concern for public health. There are toxigenic and non-toxigenic A. flavus variants, but the necessary conditions for expressing the toxigenic potential are not fully understood. Therefore, we have studied total-DNA polymorphism from toxigenic and non toxigenic A. flavus strains isolated from maize crops and soil at two geographic locations, 300 km apart, in the Southeast region of Brazil. Total DNA from each A. flavus isolate was extracted and subjected to polymerase chain reaction amplification with five randomic primers through the RAPD (random amplified polymorphic DNA) technique. Phenetic and cladistic analyses of the data, based on bootstrap analyses, led us to conclude that RAPD was not suitable to discriminate toxigenic from non toxigenic strains. But the present results support the use of RAPD for strain characterization, especially for preliminary evaluation over extensive collections.

Experimental rabies infection in haematophagous bats Desmodus rotundus

In order to determine the susceptibility and serum neutralizing antibody response of Desmodus rotundus to rabies virus, bats were inoculated with a virus isolated from a naturally infected haematophagous bat. Bats were divided into four groups of 10 animals each. Dilutions of rabies virus containing 100, 1000, 10,000 and 100,000 MICLD50 (lethal dose 50% for mice inoculated by the intracerebral route) were administrated in the pectoral muscle. The presence of rabies virus was detected in brain and salivary glands by fluorescent antibody, mouse inoculation and RT-PCR. The observed mortality for each virus dose was 0, 20, 20 and 60% respectively. Serum neutralizing antibodies were tested for by the rapid fluorescent focus inhibition test, and antibody titres greater than 0.5 IU/ml were found in 53% of bats 30 days after virus inoculation. Resistance to infection was seen in bats that developed low or no detectable antibody response as well as in bats with high titres. Among the 10 bats that died of rabies, eight showed signs of paralytic rabies and two bats showed no clinical signs.

Detection of influenza, parainfluenza, adenovirus and respiratory syncytial virus during asthma attacks in children older than 2 years old

BACKGROUND

Viral upper respiratory tract infections (URTI) have been correlated with the onset of asthma attacks in children and viral identification was reported in 14-49 % of nasal samples. The aim of the present study was to detect influenza, parainfluenza, adenovirus and respiratory syncytial virus (RSV) in older children during acute asthma attacks.

METHODS

A total of 104 children (2-14 years) were included in four groups: group I: asthmatics with acute attack and URTI; group II: asthmatics without URTI (group I children, 30 days later); group III: non-asthmatics with URTI; group IV: non-asthmatic, asymptomatic children. A diagnosis of URTI was considered when (3 symptoms (cough and/or sneeze, nasal obstruction, hypertrophy of turbinates, pain and/or retropharynx hyperemia, headache and fever) in asthmatics and at least 2 symptoms in non-asthmatics were present, starting within 7 days. Samples of nasal mucosa cells (n = 123) were collected, and culture and indirect immunofluorescence were carried out to identify respiratory syncytial virus, adenovirus, influenza A and B, parainfluenza 1,2 and 3 and rhinovirus.

RESULTS

Viral identification rates were higher in the asthmatic groups: 13.9 % in group I, 11.1 % in group II; 2.8 % in group III and 0 in group IV. The following viruses were identified: RSV 2/36, rhinovirus 1/36, adenovirus 1/36 and parainfluenzae 1/36 in group I; adenovirus 2/18 in group II; RSV 1/36 in group III.

CONCLUSIONS

The rate of viral identification was higher in asthmatic children, whether symptomatic or not, suggesting a possible susceptibility to viral infections. Virus could also be a triggering factor in attacks, although it is not the most preponderant in older children.

Molecular analysis of a Measles virus isolate from Brazil: a case originating in Japan

This study reports on molecular analysis of a Measles virus (MV) isolate from a patient who was infected in Japan but showed symptoms after arriving to Brazil. This patient had typical clinical measles infection symptoms: fever, rash, cough and coryza. After isolating the virus in B95a cells, a fragment of the nucleoprotein (N) gene was amplified by reverse transcription-polymerase chain reaction (RT-PCR) and subjected to direct nucleotide sequencing. The sequence data showed that the MV isolate of concern is of the D5 genotype.

Immune response to respiratory syncytial virus in young Brazilian children

We have evaluated the cellular and humoral immune response to primary respiratory syncytial virus (RSV) infection in young infants. Serum specimens from 65 patients <=12 months of age (39 males and 26 females, 28 cases <3 months and 37 cases > or = 3 months; median 3 3.9 months) were tested for anti-RSV IgG and IgG subclass antibodies by EIA. Flow cytometry was used to characterize cell surface markers expressed on peripheral blood mononuclear cells (PBMC) from 29 RSV-infected children. There was a low rate of seroconversion in children <3 months of age, whose acute-phase PBMC were mostly T lymphocytes (63.0 +/- 9.0%). In contrast, a higher rate of seroconversion was observed in children >3 months of age, with predominance of B lymphocytes (71.0 +/- 17.7%). Stimulation of PBMC with RSV (2 x 10(5) TCID50) for 48 h did not induce a detectable increase in intracellular cytokines and only a few showed a detectable increase in RSV-specific secreted cytokines. These data suggest that age is an important factor affecting the infants' ability to develop an immune response to RSV.

Detection of human parvovirus B19 in a patient with hepatitis

Parvovirus B19 has been associated by some investigators with cases of severe hepatitis. The aim of the present study was to determine the presence of active parvovirus B19 infection among 129 Brazilian patients with non-A-E hepatitis. The patients were assayed for antibodies against parvovirus B19, IgM class, by ELISA. In IgM-positive cases, parvovirus B19 DNA was assayed by PCR in serum and liver tissue and parvovirus VP1 antigen in liver tissue was assayed by immunohistochemistry. Antibodies against parvovirus B19, IgM class, were detected in 3 (2.3%) of 129 patients with non-A-E hepatitis. Previous surgery and blood transfusions were reported by these 3 patients. One patient was a 56-year-old female with severe hepatitis, with antimitochondrial antibody seropositivity and submassive necrosis at liver biopsy, who responded to corticosteroid therapy. Strong evidence for active parvovirus B19 infection was found in this patient, with parvovirus B19 DNA being detected by PCR in liver tissue. Furthermore, parvovirus VP1 antigen was also detected in liver tissue by immunohistochemistry. The other two IgM-positive patients were chronic hepatitis cases, but active infection was not proven, since neither viral DNA nor antigen were detected in their liver tissues. This and other reports suggest a possible relation between parvovirus B19 infection and some cases of hepatitis.

Clinical patterns and seasonal trends in respiratory syncytial virus hospitalizations in São Paulo, Brazil

The respiratory viruses are recognized as the most frequent lower respiratory tract pathogens for infants and young children in developed countries but less is known for developing populations. The authors conducted a prospective study to evaluate the occurrence, clinical patterns, and seasonal trends of viral infections among hospitalized children with lower respiratory tract disease (Group A). The presence of respiratory viruses in children's nasopharyngeal was assessed at admission in a pediatric ward. Cell cultures and immunofluorescence assays were used for viral identification. Complementary tests included blood and pleural cultures conducted for bacterial investigation. Clinical data and radiological exams were recorded at admission and throughout the hospitalization period. To better evaluate the results, a non- respiratory group of patients (Group B) was also constituted for comparison. Starting in February 1995, during a period of 18 months, 414 children were included- 239 in Group A and 175 in Group B. In Group A, 111 children (46.4%) had 114 viruses detected while only 5 children (2.9%) presented viruses in Group B. Respiratory Syncytial Virus was detected in 100 children from Group A (41.8%), Adenovirus in 11 (4.6%), Influenza A virus in 2 (0.8%), and Parainfluenza virus in one child (0.4%). In Group A, aerobic bacteria were found in 14 cases (5.8%). Respiratory Syncytial Virus was associated to other viruses and/or bacteria in six cases. There were two seasonal trends for Respiratory Syncytial Virus cases, which peaked in May and June. All children affected by the virus were younger than 3 years of age, mostly less than one year old. Episodic diffuse bronchial commitment and/or focal alveolar condensation were the clinical patterns more often associated to Respiratory Syncytial Virus cases. All children from Group A survived. In conclusion, it was observed that Respiratory Syncytial Virus was the most frequent pathogen found in hospitalized children admitted for severe respiratory diseases. Affected children were predominantly infants and boys presenting bronchiolitis and focal pneumonias. Similarly to what occurs in other subtropical regions, the virus outbreaks peak in the fall and their occurrence extends to the winter, which parallels an increase in hospital admissions due to respiratory diseases.

[Aplastic crisis in sickle cell anemia induced by parvovírus B19]

PURPOSE: Transient aplastic crisis is reported in an eight-month old child with sickle cell anemia and acute B19 parvovirus infection. This fact is uncommon in this age. PATIENT AND METHODS: The authors review the literature and describe a clinical case of an eight-month old child with sickle cell anemia presented with profound anemia and reticulocytopenia. His peripheral blood was analyzed for parvovirus B19 using the polymerase chain reaction (PCR), and for anti B19 immunoglobulin Ig M, and Ig G by enzyme-linked immunosorbent assay (ELISA). RESULTS: An eight-month old child with sickle cell anemia was admitted to the hospital with fever and profound anemia (HB = 3.8g/ dl) and reticulocytopenia (2%). A diagnosis of aplastic crisis was established. The results indicate that Ig M and PCR were positive and Ig G negative. The patient needed erytrocyte transfusion, and was discharged on hospital day 4. CONCLUSIONS: The clinical and laboratory features indicate that human parvovirus B19 was the etiologic agent of an aplastic crisis in an eight-month old child. According to the international literature this event is uncommon for this age; in addition, this is the first time it appears in the Brazilian literature.

Molecular characterization of canine parvovirus in Brazil by polymerase chain reaction assay

Canine parvovirus (CPV) was first isolated in 1978 in the USA. Analysis of CPV isolates by monoclonal antibodies and restriction enzymes have shown that after the first emergence of CPV (CPV-2) it evolved to give rise to new antigenic types, which were designated CPV type 2a and type 2b. These new types have replaced the original CPV type 2, although the proportions of each of the new antigenic types vary in different countries. In Brazil, CPV-like infections were first observed in 1979, however, there has been no information concerning the antigenic types of CPV prevailing in South America. In this study, we designed a PCR assay to type canine parvovirus strains in fecal samples collected from symptomatic dogs during 1980 through 1986 and 1990 through 1995. Our data showed that the CPV epizootic in Brazil followed the same pattern observed in the USA of emergence of CPV-2 followed by replacement by the variants CPV-2a and 2b. The predominant strain found during 1980 was CPV-2a, which was substantially replaced by CPV-2b from 1990 to 1995.

Molecular characterization of porcine rotaviruses from the southern region of Brazil: characterization of an atypical genotype G[9] strain

The G (VP7) and P (VP4) serotype distribution of Brazilian porcine rotaviruses was determined using reverse transcription-PCR genotyping methods. Common porcine G types G3, G4, and G5 were detected in combination with P types [6] and [7]. The detection of nonporcine G types and unusual G-P combinations and the characterization of an atypical virus indicated that interspecies transmission may contribute to the genetic diversity of porcine rotaviruses.

Genetic characterization of adenovirus strains isolated from patients with acute conjunctivitis in the city of São Paulo, Brazil

Genome analysis was carried out on adenovirus strains isolated from patients with acute follicular conjunctivitis in the city of São Paulo, Brazil. Eighteen conjunctival scrapings, collected between December 1993 and March 1994, were analyzed by two methods: a combination of polymerase chain reaction with restriction fragment length polymorphism and viral DNA restriction analysis, carried out using 10 restriction endonucleases: BamHI, BglI, BglII, HindIII, KpnI, SacI, SalI, SmaI, XbaI, and XhoI. Among 11 adenovirus detected by cell culture isolation, nine were Ad8, and two were Ad7. By restriction analysis the Ad8 isolates were typed as two new variants-Ad8/D11 (seven of nine samples) and Ad8/D12 (two of nine samples). Ad7 isolates were identified as a subtype of the widespread genome type Ad7b and the virulent type Ad7h, a predominant genome type circulating in Argentina, Chile, and Uruguay but absent in Brazil until 1991.

[Viral infections in hospitalized children affected by acute lower respiratory tract disease]

OBJECTIVE: To evaluate the frequency of the main respiratory viruses in hospitalized children affected by acute lower respiratory tract disease at a university hospital. METHODS: This is a prospective trial that included two cohorts of hospitalized children in the period from April to July 1996. The groups were selected according to the presence of lower respiratory tract disease on admission: Group A- with acute disease (history of less than 7 days) and B- without present or recent respiratory disease. The parameters for defining lower respiratory tract disease included physical and/or radiological pulmonary changes. Clinical and radiological criteria were established for the classification of lower respiratory tract diseases in group A. Nasopharyngeal swab was collected from all children on admission for viral detection by cellular cultures and direct immunofluorescence. RESULTS: 201 cases were selected, 126 in group A and 75 in group B. Viruses were identified in 71 children from groupA(56.4%) and only in 3 from group B (4.0%). The predominant agent in group A was respiratory syncytial virus, identified in 66 cases; adenovirus (4) and influenza (1) were detected in other patients. In group B two patients with respiratory syncytial virus and one with adenovirus were identified. The patients from group A affected by respiratory syncytial virus were younger (median age 3 months versus 13 months) and more wheezy on physical examination (78.7%) than the other patients of the group (33.3%). This virus was associated to most of the bronchiolitis cases (84%) and to half of the pneumonia cases (46.4%). CONCLUSION: The authors found a significant presence of viruses in the majority of children hospitalized with acute lower respiratory tract disease. The respiratory syncytial virus was the predominant agent identified. These results are similar to others previously reported both in developed and some developing countries. The authors emphasize that the present study evaluated only partially the possibility of simultaneous infection by other pathogens and that the present protocol was conducted during the season with the highest incidence of respiratory syncytial virus.

Molecular characterization of Brazilian avian pneumovirus isolates: comparison between immunochemiluminescent Southern blot and nested PCR

Avian pneumovirus (APV) causes acute respiratory tract infection both in turkeys (turkey rhinotracheitis) and chickens (swollen head syndrome (SHS)) with sudden onset and rapid spread through the flocks. In this study, an immunochemiluminescent Southern blot RT-PCR assay was employed to detect a F gene transcript of the APV in two European turkey isolates and two Brazilian chicken isolates. Limiting dilution PCR was carried out to compare the sensitivity of immunochemiluminescent Southern blot assay and nested PCR assay (nPCR). The sensitivity and specificity of immunochemiluminescent Southern blot RT-PCR assay were comparable to that of nPCR, and at least 100 fold more sensitive than a single PCR amplification. Sequence analysis of the 175 bp product of the F gene revealed 100% identity with APV sequences described earlier.

Detection of porcine parvovirus DNA by the polymerase chain reaction assay using primers to the highly conserved nonstructural protein gene, NS-1

Porcine parvovirus (PPV) infection is associated with reproductive losses in swine and its causative agent, the PPV, has been isolated worldwide. Serological surveys and virus isolation studies throughout Brazil confirm the occurrence of PPV infection in this country. The most common methods to detect PPV infection are fluorescent antibody staining of fetal tissues, hemagglutination assay of tissue extracts and virus isolation from fetal tissues. Non-specificity and low sensitivity are the major drawbacks of these techniques. The development of a polymerase chain reaction (PCR) and nested-PCR assays for PPV DNA detection from infected cell lines and clinical samples is described. The primers were designed to a highly conserved region of the PPV genome which codes for the non-structural protein, NS-1. Results showed that PCR could detect PPV in titres at least 10(6) higher than the hemagglutination assay. The PCR and nested-PCR assays were used to detect successfully PPV DNA in clinical samples.

Survey of Parvovirus B19 Infection in a Cohort of Pregnant Women in Belém, Brazil

In our study, 300 pregnant women were screened for the presence of human parvovirus B19 IgG and IgM antibodies by an enzyme-linked immunosorbent assay (ELISA). Overall, 253 (84.3%) were found to be IgG-positive and IgM-negative (IgG+gM ), 42 (14%) had neither IgG nor IgM antibodies (IgG /IgM ) and 5 (1.7%) were both IgM- and IgG-positive (IgG+/IgM+). Maternal serology was performed routinely for cytomegalovirus, rubella, toxoplasmosis and syphilis. All IgG /IgM and IgG+/IgM+ women were followed up till the time of delivery, venous blood sample being taken monthly from each one; one IgG /IgM mother seroconverted to IgG+/IgM and B19 DNA was detected by nested polymerase chain reaction technique (PCR) in her serum. All babies born to IgG+/IgM+ mothers (and from that who seroconverted) were IgG+IgM , no B19 DNA could be detected in their sera and no adverse effects were documented either by ultrasonographic examination or the detection of maternal serum alpha-fetoprotein. While 5 of these mothers delivered normal children at term, one gave birth to a premature (low-weight) baby who developed severe anemia and had convulsions; this mother was found to have toxoplasma-specific IgM. As based on serial testing of sera, it is notable that B19 IgM may last up to six months. Our data indicates a low incidence rate of B19 infection in pregnancy in our region, at least during interepidemic periods. In addition, it suggests that recent B19 infection represents a low risk for the development of adverse fetal outcomes.

Genetic diversity of human parvovirus B19: sequence analysis of the VP1/VP2 gene from multiple isolates

To evaluate the genetic variability of human parvovirus B19, the complete coding region of the VP1/VP2 structural proteins of 29 B19 isolates obtained from 25 infected patients were sequenced and compared with each other and with two previously published B19 isolates. The VP1/VP2 gene was amplified by PCR using B19-specific oligonucleotide primers and the amplification products were sequenced directly. Overall, the average nucleotide and predicted amino acid identity among B19 isolates was high. Sequential virus isolates from the same cases and isolates obtained from two cases linked by transmission in the same household were essentially identical. Sequence variation was minimal among isolates obtained from a single community-wide B19 outbreak, ranging between 0 and 10 (0.4%) base substitutions, although there appeared to be more than one genetic lineage circulating in the outbreak. A comparison with 18 additional isolates from distinct epidemiological settings found greater variability. These isolates differed from each other by between 11 (0.5%) and 112 (4.8%) base substitutions. B19 isolates from Xi'an, China, were significantly different from other isolates at both the nucleotide and amino acid levels, and were more closely related to a single isolate from Japan, obtained 10 years earlier, than to isolates from other countries. Isolates examined in this study included distinct genotypes from patients with similar clinical presentations and similar genotypes from patients with diverse clinical presentations. These data suggest that geographically defined genetic lineages of B19 may exist and that no particular B19 genotype was associated with a particular clinical outcome.

A combined staphylococcal coagglutination assay for rapid identification of rotavirus and adenovirus (COARA)

An improved staphylococcal coagglutination test was developed for rapid detection, in a single assay, of rotavirus and adenovirus in stool samples (COARA). Suspensions of Staphylococcus aureus coated respectively with anti-rotavirus and anti-adenovirus sera were used to identify these viruses in 327 stool samples of children. The samples were also tested by an enzyme immunoassay. The data analysis has demonstrated a high degree of correlation between the two assays.

Polymerase chain reaction and a liquid-phase, nonisotopic hybridization for species-specific and sensitive detection of malaria infection

In the present study, we describe a polymerase chain reaction (PCR)-based enzyme-linked immunosorbent assay for the detection of malaria infection. The target region of the 18S ribosomal DNA is amplified by a PCR using an 18S rRNA, genus-specific, biotinylated (5') and an unlabeled primer (3') pair. The detection probes are digoxigenin-labeled DNA oligonucleotides derived from species-specific rRNA sequences. The amplified fragments are allowed to hybridize with the species-specific, digoxigenin-labeled oligonucleotide probes. The oligo/DNA complex is allowed to bind onto streptavidin-coated microtiter plates, followed by incubation with a peroxidase-streptavidin conjugate and a colorimetric-peroxidase substrate. The resulting test demonstrated specificity for the four human Plasmodium species, and was able to detect a level of parasitemia of at least 0.0001% in a laboratory-induced P. falciparum infection in monkeys. This liquid hybridization assay is sensitive, specific, simple, and reliable, with wide applicability in epidemiologic studies, accurate detection of mixed infections, detection of low-level parasitemia, and evaluation of chemotherapy and vaccine efficacy.

Chemiluminescent microwell hybridization assay for direct detection of human parvovirus B19 DNA

A method for the direct detection of human parvovirus DNA in serum samples that uses a digoxigenin-labeled RNA probe to hybridize with target B19 DNA, followed by capture of the hybrid onto a microtiter plate wells previously coated with a second oligonucleotide probe was developed. The captured hybrid is then detected with anti-digoxigenin-alkaline phosphatase conjugate and chemiluminescent substrate and the reaction read on a scintillation counter. The relative sensitivities of the microwell and standard dot blot hybridization assays were compared. The chemiluminescent microwell hybridization assay was more sensitive than dot-blot hybridization and could be performed in a few hours. This format, therefore, permits rapid and sensitive detection of parvovirus DNA suitable for the clinical setting.

Detection of human parvovirus B19 DNA PCR products by RNA probe hybridization enzyme immunoassay

We have developed an RNA probe hybridization enzyme immunoassay for detection of human parvovirus B19 PCR-amplified DNA. The assay is easy to perform and increases assay sensitivity without the added inconvenience and risk of false-positive results associated with nested PCR.

Immunochemiluminescent Southern blot assay for polymerase chain reaction detection of human parvovirus B19 DNA

Human parvovirus B19 is not only an acute self-limited infection causing erythema infectiosum, transient aplastic crisis, foetal hydrops and arthritis but can also be a chronic infection causing chronic anaemia and associated with chronic neuropathy and vasculitis. Serologic studies have proven to be the most sensitive way to detect acute infection in the immunologically normal patient while polymerase chain reaction (PCR) assays for B19 DNA are the most sensitive way to detect chronic infection. The ability to detect B19 in clinical specimens can be further increased with a second amplification step using nested primers. However, nested PCR is both time consuming and enhances the risk of false-positive results due to contaminating DNA. In this study, we developed a sensitive immunochemiluminescent Southern blot assay for detecting PCR amplified B19 DNA with a digoxigenin labelled primer. The sensitivity and specificity of this assay were comparable to nested PCR and at least 100-fold more sensitive than a single PCR amplification.

Chronic parvovirus B19 infection and systemic necrotising vasculitis: opportunistic infection or aetiological agent?

We describe three patients who had infection with human parvovirus B19 in association with new-onset systemic necrotising vasculitis syndromes, two with features of polyarteritis nodosa and one with features of Wegener's granulomatosis. Chronic B19 infection, lasting 5 months to more than 3 years, was shown by enzyme immunoassay for IgG and IgM antibodies to B19 and polymerase chain reaction for B19 DNA in serum and tissue samples. The patients had atypical serological responses to the B19 infection, although none had a recognisable immunodeficiency disorder. Treatment with corticosteroids and cyclophosphamide did not control vasculitis. Intravenous immunoglobulin (IVIG) therapy led to rapid improvement of the systemic vascultis manifestations, clearing of the chronic parvovirus infection, and long-term remission. These observations suggest an aetiological relation between parvovirus B19 infection and systemic necrotising vasculitis in these patients and indicate a potentially curative role for IVIG in such disorders.

Multiple primer pairs for polymerase chain reaction (PCR) amplification of human parvovirus B19 DNA

Human parvovirus B19 is the etiologic agent of erythema infectiosum and transient aplastic crisis in patients with hemolytic anemias and has been associated with fetal death, arthritis, and chronic anemia. Acute B19 infection is best diagnosed by detection of IgM antibodies, whereas the diagnosis of chronic infection often requires the sensitivity of PCR to demonstrate presence of virus over time. To improve our ability to detect B19 DNA by polymerase chain reaction (PCR), we evaluated 19 primers combined into 16 different primer pairs for their ability to detect temporally and geographically diverse B19 isolates. All 16 pairs reacted with all isolates tested but with different sensitivity. Sequence analysis showed few nucleotide changes compared with published sequences. These changes did not explain observed differences in sensitivity between primer pairs. The most sensitive primer pairs detected 350 to 3500 DNA copies after 35 cycles. A second amplification cycle with nested primers improved the sensitivity 100-fold. These 16 primer pairs provide the diagnostic virologist with multiple options for B19 PCR assays.

Viral, bacterial and parasitic pathogens associated with severe diarrhoea in the city of São Paulo, Brazil

Viral, bacterial and parasitic pathogens associated with diarrhoea were studied in infants and young children admitted to the paediatric clinic of the University Hospital of São Paulo during the period of 13 months. A recognised pathogenic organism was detected in 78% of the diarrhoeic patients, 6% of whom had a mixed infection with two agents. Enteropathogenic E. coli (EPEC) was the most common enteropathogen detected (22%), followed by rotavirus (19%) and adenovirus (10%). Altogether 6% had diarrhoea associated with Salmonella or Shigella and 3% showed diarrhoeal illness associated with astrovirus. Infants less than 6 months of age were most commonly infected with enterobacteria (35%), mainly enteropathogenic E. coli (30%), whereas children 6 months to 2 years presented more often with viruses (38%), mainly rotaviruses (25%). Enteropathogens were found during all seasons of the year and rotaviruses showed a seasonal variation.

An exonuclease-amplification coupled capture technique improves detection of PCR product

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Comparison of staphylococcal co-agglutination with other assays for rapid diagnosis of rotavirus infection in humans, calves and piglets

Co-agglutination was used for rapid diagnosis of rotavirus infection. Staphylococcus aureus Cowan I sensitized with rabbit antiserum to rotavirus demonstrated the presence of this virus in stools of children, calves and piglets with clinical signs of diarrhea. A total of 415 fecal samples were examined by the co-agglutination test and the results were compared with those of ELISA, electrophoresis in polyacrylamide gel and latex agglutination. The co-agglutination test, when compared to these three methods, presented a correlation which varied between 87.2 and 94.2%.

[Occurrence of human astrovirus in São Paulo City, Brazil]

Human astrovirus was detected during a 13-month longitudinal study of the incidence of diarrhoea viruses among hospitalized children (less than 2 years of age) in a pediatric clinic of the city of S. Paulo (University Hospital). Serial fecal samples (intervals of 4 days) were collected from 146 children with and without acute diarrhoea at admission and during their stay in the hospital. Two (3%) of the 67 children with diarrhoea were positive at admission to the clinic by the highly sensitive ASTROVIRUS BIOTIN-AVIDIN ELISA, using CDC monoclonal antibodies (MAb SE7). All 79 children without diarrhoea (controls) were negative for astrovirus at admission. However, astrovirus was detected in 7 (4.8%) of the 146 hospitalized children during their stay in the clinic. Three of the positives shed astroviruses in 2 successive stool samples. All children positive for astrovirus were negative for rotavirus, adenovirus and bacterial and parasitic enteric agents. This is the first study of the detection of human astrovirus in Brazil. Astrovirus appears to be a significant cause of infantile gastroenteritis among young children in this country.