Novel method for production and purification of untagged pneumococcal surface protein A from clade 1.

Streptococcus pneumoniae can cause diseases with high mortality and morbidity. The licensed vaccines are based on capsular polysaccharides and induce antibodies with low cross reactivity, leading to restricted coverage of serotypes. For surpassing this limitation, new pneumococcal vaccines are needed for induction of broader protection. One important candidate is the pneumococcal surface protein A (PspA), which can be classified in 6 clades and 3 families. We have reported an efficient process for production and purification of untagged recombinant PspA from clade 4 (PspA4Pro). We now aim to obtain a highly pure recombinant PspA from clade 1 (PspA1) to be included, together with PspA4Pro, in a vaccine formulation to broaden response against pneumococci. The vector pET28a-pspA1 was constructed and used to transform Escherichia coli BL21(DE3) strain. One clone with high production of PspA1 was selected and adapted to high-density fermentation (HDF) medium. After biomass production in 6 L HDF using a bioreactor, the purification was defined after testing 3 protocols. During the batch bioreactor cultivation, plasmid stability remained above 90% and acetate formation was not detected. The final protein purification process included treatment with a cationic detergent after lysis, anion exchange chromatography, cryoprecipitation, cation exchange chromatography, and multimodal chromatography. The final purification process showed PspA1 purity of 93% with low endotoxin content and an overall recovery above 20%. The novel established process can be easily scaled-up and proved to be efficient to obtain a highly pure untagged PspA1 for inclusion in vaccine formulations. KEY POINTS: • Purification strategy for recombinant PspA1 from Streptococcus pneumoniae • Downstream processing for untagged protein antigens, the case of PspA1 • Purification strategy for PspA variants relies on buried amino acids in their sequences.

Expression of Genes by Aflatoxigenic and Nonaflatoxigenic Strains of Aspergillus flavus Isolated from Brazil Nuts.

The aims of the present study were to monitor the production of aflatoxin B1 (AFB1) and mycelial growth, and to evaluate the expression of genes directly and indirectly involved in the biosynthesis of aflatoxins by Aspergillus flavus isolated from Brazil nuts. Six previously identified A. flavus strains were grown on coconut agar at 25°C for up to 10 days. Mycotoxins were separated by high-performance liquid chromatography and fungal growth was measured daily using the diametric mycelial growth rate. Transcriptional analysis was performed by real-time polymerase chain reaction (PCR) after 2 and 7 d of incubation using specific primers (aflR, aflD, aflP, lipase, metalloprotease, and LaeA). Three (50%) of the six A. flavus isolates produced AFB1 (ICB-1, ICB-12, and ICB-54) and three (50%) were not aflatoxigenic (ICB-141, ICB-161, and ICB-198). Aflatoxin production was observed from d 2 of incubation (1.5 ng/g for ICB-54) and increased gradually with time of incubation until d 10 (15,803.6 ng/g for ICB-54). Almost all A. flavus isolates exhibited a similar gene expression pattern after 2 d of incubation (p > 0.10). After 7 d of incubation, the LaeA (p < 0.05) and metalloprotease (p < 0.05) genes were the most expressed by nonaflatoxigenic strains, whereas aflatoxigenic isolates exhibited higher expression of the aflR (p < 0.05) and aflD genes (p < 0.05). Our results suggest that the expression of aflR and aflD is correlated with aflatoxin production in A. flavus and that overexpression of aflR could affect the transcriptional and aflatoxigenic pattern (ICB-54). Elucidation of the molecular mechanisms that regulate the secondary metabolism of toxigenic fungi may permit the rational silencing of the genes involved and consequently the programmed inhibition of aflatoxin production. Knowledge of the conditions, under which aflatoxin genes are expressed, should contribute to the development of innovative and more cost-effective strategies to reduce and prevent aflatoxin contamination in Brazil nuts.

Fungal diversity and natural occurrence of deoxynivalenol and zearalenone in freshly harvested wheat grains from Brazil.

This study investigated the fungal diversity and presence of deoxynivalenol and zearalenone in 150 samples of freshly harvested wheat grains collected in three regions of Brazil (Sao Paulo, Parana, and Rio Grande do Sul). Analysis of the mycobiota showed a predominance of Alternaria sp., Fusarium sp. and Epicoccum sp. Microdochium nivale (23%), a fungus rarely found in Brazilian crops, was detected in Sao Paulo. Four members of the Fusarium graminearum species complex were isolated: F. graminearum s.s. (37%), Fusarium meridionale (46%), Fusarium cortaderiae (13%), and Fusarium austroamericanum (3%). Toxin analysis revealed 99% contamination with deoxynivalenol (mean 706 µg/kg). The frequency of zearalenone varied greatly across regions: wheat grains from Rio Grande do Sul (84%) and Sao Paulo (12%) had median concentrations of 70.9 and 57.9 µg/kg, respectively. ZEA was not detected in the samples from Parana. A total of six samples were above the maximum tolerated level recommended by the European Commission for ZEA in wheat grains. This study provided new insights into the natural mycobiota of Brazilian wheat, demonstrating contamination of most samples with deoxynivalenol and high frequency of zearalenone in samples from Rio Grande do Sul.

Monitoring and determination of fungi and mycotoxins in stored Brazil nuts.

Brazil nut (Bertholletia excelsa) is an important commodity from the Brazilian Amazon, and approximately 37,000 tons (3.36 × 107 kg) of Brazil nuts are harvested each year. However, substantial nut contamination by Aspergillus section Flavi occurs, with subsequent production of mycotoxins. In this context, the objective of the present investigation was to evaluate the presence of fungi and mycotoxins (aflatoxins and cyclopiazonic acid) in 110 stored samples of cultivated Brazil nut (55 samples of nuts and 55 samples of shells) collected monthly for 11 months in Itacoatiara, State of Amazonas, Brazil. The samples were inoculated in duplicate onto Aspergillus flavus and Aspergillus parasiticus agar and potato dextrose agar for the detection of fungi, and the presence of mycotoxins was determined by high-performance liquid chromatography. The most prevalent fungi in nuts and shells were Aspergillus spp., Fusarium spp., and Penicillium spp. A polyphasic approach was used for identification of Aspergillus species. Aflatoxins and cyclopiazonic acid were not detected in any of the samples analyzed. The low water activity of the substrate was a determinant factor for the presence of fungi and the absence of aflatoxin in Brazil nut samples. The high frequency of isolation of aflatoxigenic Aspergillus section Flavi strains, mainly A. flavus, and their persistence during storage increase the chances of aflatoxin production on these substrates and indicates the need for good management practices to prevent mycotoxin contamination in Brazil nuts.

Polyphasic approach to the identification of Aspergillus section Flavi isolated from Brazil nuts.

The aim of this study was to use a polyphasic approach to identify Aspergillus section Flavi isolated from Brazil nuts collected in the Amazon forest: investigation of macro- and microscopic morphology, production of extrolites, heat-resistance fungi, and sequencing of DNA regions. The following Aspergillus section Flavi species were identified: Aspergillus flavus (75.5%), Aspergillus nomius (22.3%), and Aspergillus parasiticus (2.2%). All A. nomius and A. parasiticus isolates produced aflatoxins B and G, but not cyclopiazonic acid (CPA). A. flavus isolates were more diversified and a high frequency of mycotoxigenic strains was observed. The polyphasic approach permitted the reliable identification of section Flavi species. The rate of mycotoxigenic strains was high (92.7%) and mainly included A. flavus strains producing elevated levels of aflatoxins and CPA. These results highlight the possibility of co-occurrence of both toxins, increasing their potential toxic effect in this commodity.

Fungi, mycotoxins and phytoalexin in peanut varieties, during plant growth in the field.

The aim of the present study was to analyze the mycobiota, occurrence of mycotoxins (aflatoxins and cyclopiazonic acid), and production of phytoalexin (trans-resveratrol) in two peanut varieties (Runner IAC 886 and Caiapó) during plant growth in the field. Climatic factors (rainfall, relative humidity and temperature) and water activity were also evaluated. The results showed a predominance of Fusarium spp. in kernels and pods, followed by Penicillium spp. and Aspergillus flavus. Aflatoxins were detected in 20% and 10% of samples of the IAC 886 and Caiapó varieties, respectively. Analysis showed that 65% of kernel samples of the IAC 886 variety and 25% of the Caiapó variety were contaminated with cyclopiazonic acid. trans-Resveratrol was detected in 6.7% of kernel samples of the IAC 886 variety and in 20% of the Caiapó variety. However, trans-resveratrol was found in 73.3% of leaf samples in the two varieties studied.

Mycoflora and fumonisin contamination in Brazilian sorghum from sowing to harvest.

BACKGROUND: The aim of this study was to characterise the mycoflora and the presence of fumonisin in sorghum grains, correlating the results with the environment and abiotic factors. RESULTS: Fifty samples (five collections of ten samples each) of sorghum were analysed. All samples were found to be contaminated with fungi, with higher frequencies of Cladosporium spp. (61.8%) and Helminthosporium spp. (33.4%). Fusarium verticillioides was isolated from 15.1% of the samples, with 38% of them being contaminated with fumonisin B(1) (FB(1)) at levels ranging from 50 to 368.78 ng g(-1). Regarding abiotic factors, temperature, water activity and rainfall showed a positive correlation with the frequency of F. verticillioides and FB(1) production. There was a significant positive correlation between relative air humidity and FB(1) production. The results obtained from sexual crosses between standard F mating tester strains and the isolated strains confirmed that the strains isolated were F. verticillioides. CONCLUSION: It can be concluded that the decrease in F. verticillioides and fumonisin contamination occurred owing to atypical climatic factors during the period of sorghum cultivation, when there was any occurrence of rain and the level of water activity of grains did not reach 0.58.

Influência de nutrientes no crescimento fúngico e na produção de fumonisinas e aflatoxinas em grão de milho / The nutrients effect on mycoflora, and for fumonisins and aflatoxins production in corn grain

O presente experimento teve como objetivo correlacionar os resultados obtidos da microbiota fúngica e produção de micotoxinas com os níveis de nitrogênio, zinco e boro utilizados no plantio do milho. Foram realizados tratamentos com quatro concentrações de nitrogênio (0, 50, 100 e 150 kg/ha) de forma interativa com duas concentrações de zinco (0,5 e 1,0 kg/ha), duas concentrações de boro (0,25 e 0,5 kg/ha) e duas concentrações de zinco mais boro (0,5 e 1,0; 0,25 e 0,5 kg/ha respectivamente), perfazendo um total de 25 tratamentos. A média de contaminação das amostras de milho pelos gêneros Aspergillus, Penicillium e Fusarium foi de 42,7; 38,9 e 41,5% respectivamente, principalmente na faixa de 0,53 a0,63 de atividade de água. A análise de fumonisinas revelou uma contaminação em 100% das amostras,em níveis que variaram de 1,7 a 27,9 mg/kg para FB1 e de 0,3 a 11,2 mg/kg para FB2. Foi detectada aflatoxina B1 em 7 amostras de milho (16,0 a 1858,3 g/kg) e B2 em 3 amostras (14,6 a 110,3 g/kg). A análise de Variância demonstrou que o nitrogênio foi positivamente significativo (p<0,05) sobre a porcentagem de contaminação pelo gênero Fusarium, enquanto que para o gênero Aspergillus foi negativamente significativo (p<0,10).

Mycoflora and occurrence of alternariol and alternariol monomethyl ether in Brazilian sunflower from sowing to harvest.

The present study aimed to analyze the mycoflora and the occurrence of alternariol (AOH) and alternariol monomethyl ether (AME) in grain samples of sunflower during different stages of plant development in Nova Odessa, State of São Paulo, Brazil. The data obtained were correlated with the presence of fungi in soil, wind-dispersed fungi, and the predominant climatic conditions of the region where the experiment was carried out. Analysis of the mycoflora revealed the presence of Fusarium verticillioides and Alternaria alternata in 70% and 46% of the samples, respectively. The profile of wind-dispersed fungi also showed F. verticillioides as the most frequently isolated fungus (68%), although A. alternata was detected in 28% of samples. In soil, Penicillium was the most frequent species (49.9%), followed by F. verticillioides (47.7%) and A. alternata (10.9%). Regarding water activity, sunflower grains presenting a high frequency of isolation of F. verticillioides and A. alternatahad a water activity ranging from 0.92 to 0.96, and statistical analysis revealed a negative linear correlation between the isolation of fungi and water activity. HPLC analysis showed that 18% of the sunflower grains were contaminated with alternariol (24.9-170.9 ng/g) and 10% with alternariol monomethyl ether (14.1-108.6 ng/g). The contamination of sunflower grains with AOH and AME in the field was low when compared to the LD50 necessary to cause toxicity to animals. However, the contamination with other toxigenic fungi such as F. verticillioides may indicate the presence of other mycotoxins in sunflower grains and a possible synergistic effect between them. This is the first report of the natural occurrence of alternariol and alternariol monomethyl ether in sunflower grains in Brazil.