BackgroundDengue viruses (DENVs) are mosquito-borne viruses which can cause disease ranging from mild fever to severe dengue infection. These viruses are endemic in several tropical and subtropical regions. Multiple outbreaks of DENV serotypes 1, 2 and 3 (DENV-1, DENV-2 and DENV-3) have been reported from the western region in Saudi Arabia since 1994. Strains from at least two genotypes of DENV-1 (Asia and America/Africa genotypes) have been circulating in western Saudi Arabia until 2006. However, all previous studies reported from Saudi Arabia were based on partial sequencing data of the envelope (E) gene without any reports of full genome sequences for any DENV serotypes circulating in Saudi Arabia.FindingsHere, we report the isolation and the first complete genome sequence of a DENV-1 strain (DENV-1-Jeddah-1-2011) isolated from a patient from Jeddah, Saudi Arabia in 2011. Whole genome sequence alignment and phylogenetic analysis showed high similarity between DENV-1-Jeddah-1-2011 strain and D1/H/IMTSSA/98/606 isolate (Asian genotype) reported from Djibouti in 1998. Further analysis of the full envelope gene revealed a close relationship between DENV-1-Jeddah-1-2011 strain and isolates reported between 2004–2006 from Jeddah as well as recent isolates from Somalia, suggesting the widespread of the Asian genotype in this region.ConclusionsThese data suggest that strains belonging to the Asian genotype might have been introduced into Saudi Arabia long before 2004 most probably by African pilgrims and continued to circulate in western Saudi Arabia at least until 2011. Most importantly, these results indicate that pilgrims from dengue endemic regions can play an important role in the spread of new DENVs in Saudi Arabia and the rest of the world. Therefore, availability of complete genome sequences would serve as a reference for future epidemiological studies of DENV-1 viruses.

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Middle East respiratory syndrome coronavirus (MERS-CoV) is a novel betacoronavirus that has been circulating in the Arabian Peninsula since 2012 and causing severe respiratory infections in humans. While bats were suggested to be involved in human MERS-CoV infections, a direct link between bats and MERS-CoV is uncertain. On the other hand, serological and virological data suggest dromedary camels as the potential animal reservoirs of MERS-CoV. Recently, we isolated MERS-CoV from a camel and its infected owner and provided evidence for the direct transmission of MERS-CoV from the infected camel to the patient. Here, we extend this work and show that identical MERS-CoV RNA fragments were detected in an air sample collected from the same barn that sheltered the infected camel in our previous study. These data indicate that the virus was circulating in this farm concurrently with its detection in the camel and in the patient, which warrants further investigations for the possible airborne transmission of MERS-CoV.

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Rauscher leukemia virus glycoprotein gp9/71 is synthesized in virus-infected cells by way of a 90,000 dalton glycoprotein precursor, termed Pr2a+b. This precursor could blaeled with radioactive glucosamine and methionine but not with fucose; whereas gp69/71 could be detected by labeling with radioactive glucosamine, fucose, or a mixture of amino acids but seemed to be deficient in methionine relative to Pr2a+b. Pr2a+b and gp69/71 were specifically precipitated by an antiserum prepared against phosphocellulose purified Rauscher gp69/71. Other virus-specific precursors, in addition to Pr2a+b, could be precipitatedby antiserum prepared against detergent disrupted virus. Neither Pr2a+b nor gp69/71 was precipitated from cell extracts by antisera to Rauscher p30. Tryptic maps of Pr2a+b and gp69]71 showed that these glycoproteins share many tryptic peptides. Pulse-chase experiments with 14C-labeled amino acids indicated that gp69/71 was not radio-labeled during the pulse-labeling period but slowly appeared during the chase incubations. Pr2a+b, however, was rapidly labeled and tended to disappear during long chases. Furthermore, two nonglycosylated viral proteins, termed pl5E and pl2E, are structurally related to Pr2a+b. Viral p15E and pl2E contained-the same methionine-containing tryptic peptide fraction as Pr2a+b as determined by ion-exchange chromatography. These results provide evidence that Pr2a+b is a precursor to gp69/71 and establish a structural and possible precursor-product relationship between Pr2a+b, pl5E, and pl2E. RNA tumor virus structural proteins are made by way of relatively large precursor polypeptides. In the avian system, p27, p19, p15, and p12 sequences are found in a 76,000 dalton precursor present in avian myeloblastosis virus-infected cells (1)*. In the murine system, Rauscher leukemia virus (RLV) p30 sequences are present in several precursors ranging in size from 65,000 to 200,000 daltons (2-4). Peptide sequences of another viral protein, termed pl5E (5)

BACKGROUNDAlthough virologically confirmed dengue fever has been recognized in Jeddah, Saudi Arabia, since 1994, causing yearly outbreaks, no proper seroepidemiologic studies on dengue virus have been conducted in this region. Such studies can define the extent of infection by this virus and estimate the proportion that may result in disease. The aim of this study was to measure the seroprevalence of past dengue virus infection in healthy Saudi nationals from different areas in the city of Jeddah and to investigate demographic and environmental factors that may increase exposure to infection.METHODSSera were collected from 1984 Saudi subjects attending primary health care centers in six districts of Jeddah. These included general patients of various ages seeking routine vaccinations, antenatal care or treatment of different illnesses excluding fever or suspected dengue. A number of blood donors were also tested. Serum samples were tested by enzyme immunoassay (EIA) for IgG antibodies to dengue viruses 1, 2, 3, 4. A questionnaire was completed for each patient recording various anthropometric data and factors that may indicate possible risk of exposure to mosquito bites and dengue infection. Patients with missing data and those who reported a history of dengue fever were excluded from analysis, resulting in a sample of 1939 patients to be analyzed.RESULTSThe overall prevalence of dengue virus infection as measured by anti-dengue IgG antibodies from asymptomatic residents in Jeddah was 47.8% (927/1939) and 37% (68/184) in blood donors. Infection mostly did not result in recognizable disease, as only 19 of 1956 subjects with complete information (0.1%) reported having dengue fever in the past. Anti dengue seropositivity increased with age and was higher in males than females and in residents of communal housing and multistory buildings than in villas. One of the six districts showed significant increase in exposure rate as compared to the others. Availability of public sewage was associated with lower infection at a nearly significant level. No other clear risk factors were identifiable. Infection was not related to travel abroad.CONCLUSIONSOur results indicate a relatively high exposure of Jeddah residents to infection by dengue viruses, which must be considered endemic to this region. Infection largely remained asymptomatic or was only associated with minor illness for which patients did not seek treatment. These results call for continued vigilance for clinical cases of dengue that may arise from this wide exposure. They also call for more extensive control efforts to reduce exposure to and transmission of dengue viruses.

Reverse transcriptase (RT; RNA-dependent DNA nucleotidyltransferase) from Rauscher leukemia virus is synthesized in infected cells by way of a read-through polyrotein of 200,000 molecular weight. This polyprotein (Pr200 gag-Pol) was precipitated by antiserum to RT; in a previous study all the monospecific antisera to gag proteins recognized Pr200 gag-Pol. Pr2JO gag-pol contains both p30 and RT peptide sequences. Intermediate RT-related precursors of 145,000 (Prl45 P0l), 135,000 (Prl35 P01), and 125,000 (PrI25 P0l) molecular weights were specifically recognized by precipitation from infected cell extracts by antiserum to RT. These proteins shared methionine-containing trtic peptide sequences with a virion polypeptide of 80,000 molecular weight (p80 P01) precipitable by antiserum to RT. Purification of active RT enzyme from virions labeled with [3H]methionine showed that p80 P01 was the major component, based on analysis by gel electrophoresis and tryptic peptide mapping experiments. A polypeptide (Pr80 P01), similar in size to mature viral p80 P01, was also precipitated from infected cells by antiserum to RT. Its peptide map was nearly identical to that of virion p80 P0I. Pulsechase studies showed that Pr80P01, Pr125 P01, and Pr135 P01 were stable polypeptides, whereas Pr200 gag-P0l and Pr145 P01 were unstable precursors. Pulse-chase studies wifh the protein synthesis inhibitor, cycloheximide, showed that the processing of Pr200 gag-pol occurred for a short time in the absence of protein synthesis.Type-C retrovirus genomes contain genes for their internal structural proteins, reverse transcriptase (RT; RNA-dependent DNA nucleotidyltransferase), and envelope proteins.t These coding regions have been termed gag (group antigens), pol, and env, respectively (2). RT is present in much lower amounts in virus particles and in infected cells (3-5) than either the gag or env proteins. In this report we show that RT from Rauscher leukemia virus (RLV) is made in infected cells by synthesis and processing of a 200,000dalton read-through protein containing both gag and pol determinants. MATERIALS AND METHODSCells and Virus. RLV-infected NIH Swiss mouse embryo fibroblasts (JLS-V16) and BALB/C spleen-thymus (JLS-V5) cell lines were used in these studies. Virus was produced in infected JLS-V5 cells, whereas precursors were isolated from JLS-V16 cells.Labeling of Cells and Virus. These procedures have been described (3,6).Immune Precipitation and Peptide Mapping. Antisera to leukemia virus RT were supplied by the Office of Program Resources and Logistics of the National Cancer Institute. The sera were absorbed before use with uninfected cell proteins and disrupted virus (3). Immune precipitation was performed by indirect immune precipitation (3); tryptic digestion of precursors and viral proteins (7) was as described. Viral RT. RT was assayed as described (8). The active enzyme was purified as described (9). RESULTSImmunoprecipitation of Virion Proteins with Antiserum to RT. Absorbed antiserum to partially purified RT was...