Identification of cellular genes affecting the infectivity of foot-and-mouth disease virus.

Foot-and-mouth disease virus (FMDV) produces one of the most infectious of all livestock diseases, causing extensive economic loss in areas of breakout. Like other viral pathogens, FMDV recruits proteins encoded by host cell genes to accomplish the entry, replication, and release of infectious viral particles. To identify such host-encoded proteins, we employed an antisense RNA strategy and a lentivirus-based library containing approximately 40,000 human expressed sequence tags (ESTs) to randomly inactivate chromosomal genes in a bovine kidney cell line (LF-BK) that is highly susceptible to FMDV infection and then isolated clones that survived multiple rounds of exposure to the virus. Here, we report the identification of ESTs whose expression in antisense orientation limited host cell killing by FMDV and restricted viral propagation. The role of one such EST, that of ectonucleoside triphosphate diphosphohydrolase 6 (NTPDase6; also known as CD39L2), a membrane-associated ectonucleoside triphosphate diphosphohydrolase that previously was not suspected of involvement in the propagation of viral pathogens and which we now show is required for normal synthesis of FMDV RNA and proteins, is described in this report.

Phenotype-based identification of host genes required for replication of African swine fever virus.

African swine fever virus (ASFV) produces a fatal acute hemorrhagic fever in domesticated pigs that potentially is a worldwide economic threat. Using an expressed sequence tag (EST) library-based antisense method of random gene inactivation and a phenotypic screen for limitation of ASFV replication in cultured human cells, we identified six host genes whose cellular functions are required by ASFV. These included three loci, BAT3 (HLA-B-associated transcript 3), C1qTNF (C1q and tumor necrosis factor-related protein 6), and TOM40 (translocase of outer mitochondrial membrane 40), for which antisense expression from a tetracycline-regulated promoter resulted in reversible inhibition of ASFV production by >99%. The effects of antisense transcription of the BAT3 EST and also of expression in the sense orientation of this EST, which encodes amino acid residues 450 to 518 of the mature BAT3 protein, were investigated more extensively. Sense expression of the BAT3 peptide, which appears to reversibly interfere with BAT3 function by a dominant negative mechanism, resulted in decreased synthesis of viral DNA and proteins early after ASFV infection, altered transcription of apoptosis-related genes as determined by cDNA microarray analysis, and increased cellular sensitivity to staurosporine-induced apoptosis. Antisense transcription of BAT3 reduced ASFV production without affecting abundance of the virus macromolecules we assayed. Our results, which demonstrate the utility of EST-based functional screens for the detection of host genes exploited by pathogenic viruses, reveal a novel collection of cellular genes previously not known to be required for ASFV infection.

SOS response induction by beta-lactams and bacterial defense against antibiotic lethality.

The SOS response aids bacterial propagation by inhibiting cell division during repair of DNA damage. We report that inactivation of the ftsI gene product, penicillin binding protein 3, by either beta-lactam antibiotics or genetic mutation induces SOS in Escherichia coli through the DpiBA two-component signal transduction system. This event, which requires the SOS-promoting recA and lexA genes as well as dpiA, transiently halts bacterial cell division, enabling survival to otherwise lethal antibiotic exposure. Our findings reveal defective cell wall synthesis as an unexpected initiator of the bacterial SOS response, indicate that beta-lactam antibiotics are extracellular stimuli of this response, and demonstrate a novel mechanism for mitigation of antimicrobial lethality.

Recurrent parotitis in selective IgA deficiency.

Recurrent parotitis is an uncommon condition in children. In most cases the etiology is unknown, although the disease is occasionally associated with viral infections, autoimmune disorders and immunodeficiency. We describe, for the first time, a child with recurrent parotitis and isolated immunoglobulin A (IgA) deficiency, without autoimmune disease. As IgA is the main immunoglobulin secreted into the mucosal surfaces, including that of the respiratory and gastrointestinal tracts, and into the saliva, the lack of IgA may be involved in the pathogenesis of recurrent parotitis. We recommend that IgA and other immunoglobulins be tested in all cases of recurrent parotitis.

Large T-cell lymphoma in a 13-year-old girl with hyperimmunoglobulinemia E syndrome.

Large T-cell lymphoma was diagnosed in a 13-year-old girl with hyperimmunoglobulinemia E syndrome (HIES). Her past medical history included severe dermatitis, recurrent pneumonia, urinary tract infections, mucocutaneous herpetic infections, fungal skin infections, and staphylococcal sepsis. The diagnosis of HIES, based on the clinical features and a serum IgE level of >20000 IU/ml, was established when the girl was 6 years old. This is the eighth case of lymphoma in a patient with HIES reported in the English-language medical literature. HIES has not usually been considered a predisposing factor for malignancy, but in view of the rarity of HIES and the young age of the patients, this association seems to be more than coincidental. A link between lymphoma and Epstein-Barr virus (EBV) infection in patients with HIES has been proposed. Serological tests for EBV in our patient were positive 6 years prior to the development of the lymphoma; however, examination for EBV DNA in the lymph node biopsy failed to detect EBV in the tumor.

Topical treatment of tinea capitis in a neonate.

Tinea capitis is the most common fungal skin infection in children. Given that this infection invades the hair shaft and the pilosebaceous unit, systemic antifungal therapy is the gold standard of treatment. Despite the neonate's increased susceptibility to infections, tinea capitis is rare in this population. We present the case of a 16-day-old infant with tinea capitis caused by Microsporum canis and effectively treated with topical bifonazole 1%.