Ultrastructural Features of Alkhumra Hemorrhagic Fever Virus Infection of Cells Under In Vivo and In Vitro Conditions

Alkhumra hemorrhagic fever virus (AHFV) is an emerging novel flavivirus that was discovered in Saudi Arabia in 1995. The virus has since caused several outbreaks in the country that resulted in case fatality rates ranging from 1% to 25%. Meager information has been published on the ultrastructural features of the virus on cells under in vitro or in vivo conditions. The present electron microscopic study examined and compared the intracellular growth of the AHFV on the LLC-MK2 cells and brain cells of new born Wistar rats, inoculated intracerebrally. The cytopathological changes in both cell systems were noted, and localization of the virus particles in different cellular components was observed. Both apoptotic and lytic cell interactions were seen in the electron micrographs of both the LLC-MK2 and the rat brain cells. The results were discussed in relation to similar situations reported for other virus members of the genus Flavivirus.

Electron Microscopy of Alkhumra Hemorrhagic Fever Virus

Alkhumra hemorrhagic fever virus (AHFV) is a newly described zoonotic flavivirus that was first isolated during 1994-1995 from the Alkhumra district south of Jeddah, Saudi Arabia. Subsequently, the virus was also isolated from Makkah city (2001-2003) and Najran (2008-2009), Saudi Arabia. The virus causes acute febrile illness with hepatitis, hemorrhagic manifestations, and encephalitis. A case fatality rate of 25% was reported among hospitalized patients. Although several biological and molecular characteristics of the virus have been published, no data are available on electron microscopic features of the virus. In this article, we describe the morphological features and metrics of the AHFV particles under electron microscopy, and localization of the virus particles in brain cells of newborn Wistar rats and in Rhesus monkey (Macaca mulatta) kidney epithelial cells (LLC-MK2). Virus particles in both the LLC-MK2 cells and the rat brain cells showed dark hexagonal core (capsid) and a translucent envelope. The mean diameter of the enveloped virus particle was 40.59 ± 1.29 nm in the rat brain cells (n = 154) and 40.97 ± 1.40 nm in the LLC-MK2 cells (n = 105; p > 0.05). The virus particles, both in vitro and in vivo, were enclosed into cytoplasmic vesicles. In conclusion, the shape, size, and diameter of the AHFV particle lie within the framework of the genus Flavivirus, family Flaviviridae.

Complete genome sequencing and genetic characterization of Alkhumra hemorrhagic fever virus isolated from Najran, Saudi Arabia

BACKGROUND

Alkhumra hemorrhagic fever virus (AHFV) is a newly described flavivirus first isolated in 1994-1995 from the Alkhumra district south of Jeddah, Saudi Arabia. Subsequently, the virus was also isolated from Makkah (2001-2003) and Najran (2008-2009), Saudi Arabia.

METHODS

The full-length genome of an AHFV strain isolated from patients in Najran (referred to as AHFV/997/NJ/09/SA) was PCR amplified and sequenced, and compared with the sequences of 18 other AHFV strains previously isolated from Jeddah and Makkah, dengue virus (DENV), Kyasanur forest disease virus (KFDV), Langat virus, Omsk hemorrhagic fever virus (OHFV), and tick-borne encephalitis virus (TBEV).

RESULTS

The RNA of the AHFV/997/NJ/09/SA strain was found to have 10,546 nucleotides encoding for a single 3,416-amino acid polyprotein, whereas the previously reported AHFV strains were composed of 10,685-10,749 nucleotides. The AHFV/997/NJ/09/SA strain showed about 99% homology with the previously reported AHFV strains. The KFDV, Langat virus, TBEV, and OHFV isolates formed a separate cluster with a variable homology. The most important variations were observed in the core protein and NS4a gene sequences of two AHFV isolates.

CONCLUSION

The variation in the number of nucleotides and phylogenetic analysis with the other AHFV isolates could have resulted from recombination of circulating virus strains.

Susceptibility of tick cell lines to infection with Alkhumra haemorrhagic fever virus

BACKGROUND

Although Alkhumra haemorrhagic fever virus (AHFV) has been isolated from ticks, epidemiological data suggest that it is transmitted from livestock to humans by direct contact with animals or by mosquito bites, but not by ticks. This study was carried out to assess the ability of the virus to replicate in tick cells in vitro.

METHODS

AHFV was inoculated into cell lines derived from the hard ticks Hyalomma anatolicum (HAE/CTVM9) and Rhipicephalus appendiculatus (RAE/CTVM1) and the soft tick Ornithodoros moubata (OME/CTVM24). Inoculated cells were directly examined every week for 4 weeks by real-time reverse transcription PCR and by IFAT using polyclonal antibodies.

RESULTS

AHFV RNA was detected in all three inoculated tick cell lines throughout the 4-week observation period at levels up to almost twice that of the inoculum, but none of them exhibited a cytopathic effect. AHFV antigen could be detected in all three cell lines by IFAT. Titration of tick cell culture suspension in LLC-MK2 cells yielded AHFV titres of 10(6.6) 50% tissue culture infective dose (TCID50)/ml for OME/CTVM24 and 10(5.5) TCID50/ml for RAE/CTVM1 cells after 4 weeks of culturing; no viable virus was detected in HAE/CTVM9 cells.

CONCLUSION

This is the first description of propagation of AHFV in tick cells.

Outbreak of viral hemorrhagic fever caused by dengue virus type 3 in Al-Mukalla, Yemen

Background

Investigations were conducted by the authors to explore an outbreak of viral hemorrhagic fever (VHF) reported in 2010 from Al-Mukalla city, the capital of Hadramout in Yemen.

Methods

From 15–17 June 2010, the outbreak investigation period, specimens were obtained within 7 days after onset of illness of 18 acutely ill patients hospitalized with VHF and 15 household asymptomatic contacts of 6 acute cases. Additionally, 189 stored sera taken from acutely ill patients with suspected VHF hospitalized in the preceding 12 months were obtained from the Ministry of Health of Yemen. Thus, a total of 222 human specimens were collected; 207 specimens from acute cases and 15 specimens from contacts. All samples were tested with RT-PCR for dengue (DENV), Alkhumra (ALKV), Rift Valley Fever (RVFV), Yellow Fever (YFV), and Chikungunya (CHIKV) viruses. Samples were also tested for DENV IgM, IgG, and NS1-antigen. Medical records of patients were reviewed and demographic, clinical, and laboratory data was collected.

Results

Of 207 patients tested, 181 (87.4%) patients were confirmed to have acute dengue with positive dengue NS1-antigen (97 patients, 46.9%) and/or IgM (163 patients, 78.7%). Of the 181 patients with confirmed dengue, 100 (55.2%) patients were IgG-positive. DENV RNA was detected in 2 (1%) patients with acute symptoms; both samples were molecularly typed as DENV type 3. No other VHF viruses were detected. For the 15 contacts tested, RT-PCR tests for the five viruses were negative, one contact was dengue IgM positive, and another one was dengue IgG positive. Of the 181 confirmed dengue patients, 120 (66.3%) patients were males and the median age was 24 years. The most common manifestations included fever (100%), headache (94.5%), backache (93.4%), malaise (88.4%), arthralgia (85.1%), myalgia (82.3%), bone pain (77.9%), and leukopenia (76.2%). Two (1.1%) patients died.

Conclusions

DENV-3 was confirmed to be the cause of an outbreak of VHF in Al-Mukalla. It is important to use both IgM and NS1-antigen tests to confirm acute dengue particularly under the adverse field conditions, where proper storage and transportation of specimens are missing, which substantially reduce the sensitivity of the RT-PCR for detecting DENV RNA.

Trypsin-dependent hemagglutination of erythrocytes of a variety of mammalian and avian species by Alkhumra hemorrhagic fever virus

Alkhumra hemorrhagic fever virus (AHFV) is an emerging flavivirus that was discovered in 1994-1995 in Saudi Arabia. Clinical manifestations of AHFV infection include hemorrhagic fever, hepatitis, and encephalitis, with a reported mortality rate as high as 25 %. Biological characteristics of this virus have not been well defined. Agglutination of erythrocytes (hemagglutination) is a laboratory tool for studying the attachment of viruses to cellular receptors. The envelope protein contains sites for attachment to host receptors to initiate the process of infection and is thus an essential component of the virion. In the present study, we examined the ability of AHFV to agglutinate erythrocytes of 13 mammalian and avian species (human group O+, camel, cow, sheep, goat, rabbit, guinea pig, mouse, rat, chicken, duck, goose and turkey) with and without trypsin-treatment. Without trypsin treatment, AHFV failed to agglutinate erythrocytes of all examined species. Following trypsin treatment, AHFV agglutinated erythrocytes of five species, namely, goose, human group O+, rat, guinea pig, and mouse, in descending order of sensitivity. This trypsin-dependent hemagglutination test has potential for use in serological and functional studies of AHFV.

Successful propagation of Alkhumra (misnamed as Alkhurma) virus in C6/36 mosquito cells

Epidemiological data suggest that Alkhumra (misnamed as Alkhurma) virus (ALKV) is transmitted from livestock animals to humans by direct contact with animals or by the mosquito bites, but not by ticks. To assess the ability of the virus to replicate in mosquito cells, serum and plasma of seven acutely febrile patients with clinically suspected ALKV infection reported in Najran, Saudi Arabia in 2009 were inoculated onto Aedes albopictus mosquito cells (C6/36) and directly examined with ALKV-RNA-specific real time RT-PCR as well as indirect immunfluorescence assay (IFA) using ALKV-specific polyclonal antibodies. The isolated virus was titrated in the mammalian rhesus monkey kidney cells (LLC-MK2). Five of the seven specimens were RT-PCR- and culture-positive demonstrating cytopathic effects in the form of cell rounding and aggregation appearing on day 3 post inoculation with syncytia eventually appearing on day 8 post inoculation. Identification of ALKV-RNA in the cell culture was confirmed with RT-PCR and IFA. The virus titre was 3.2×10(6) tissue culture infective dose 50 (TCID(50)) per mL. Three more viral passages were successfully made in the C6/36 cells. This is the first description of propagation of ALKV in mosquito cells.

Alkhumra (Alkhurma) virus outbreak in Najran, Saudi Arabia: epidemiological, clinical, and laboratory characteristics

OBJECTIVE

After its first appearance in Alkhumra district of Jeddah in 1994-1995, and then in Makkah in 2001-2003, the new hemorrhagic fever virus, known as Alkhumra (misnamed as Alkhurma) virus (ALKV), has subsequently been reported from Najran, in the south border of Saudi Arabia.

METHODS

This is a descriptive cohort study summarizing the epidemiological, clinical, and laboratory characteristics of ALKV infected patients diagnosed in Najran from 1 August 2003 through 31 December 2009.

RESULTS

A total of 148 suspected cases were reported, of which 78 (52.7%) cases were laboratory confirmed; 2 cases in 2003, 1 case in 2004, 4 cases in 2005, 1 case in 2007, 12 cases in 2008, and 58 cases in 2009. The cases were reported year round but 64.1% (50/78) of them occurred in the summer time. Twenty-five (32.1%) cases occurred as clusters in 5 families. The virus seemed to be transmitted from livestock animals to humans by direct contact with these animals and likely by mosquito bites. Ticks did not seem to be involved in the transmission of infection from animals to humans. Clinical and laboratory features included fever (100%), headache (85.9%), malaise (85.9%), arthralgia (83.3%), anorexia (82.1%), myalgia (82.1%), backache (71.8%), nausea and vomiting (71.8%), chills (60.3%), retro-orbital pain (55.1%), diarrhea (51.3%), abdominal pain (48.7%), hemorrhagic manifestations (25.6%), central nervous system manifestations (23.1%), leucopenia (87.7%), elevated liver enzymes (85.7%), prolonged partial thromboplastin time (52.6%), thrombocytopenia (46.2%), elevated creatine kinase level (45.7%), and elevated lactate dehydrogenase (25.0%).

CONCLUSION

ALKV infection has now been recognized outside its original boundaries in Saudi Arabia which may herald its identification in other countries.