Most neutralizing human monoclonal antibodies target novel epitopes requiring both Lassa virus glycoprotein subunits.

Lassa fever is a severe multisystem disease that often has haemorrhagic manifestations. The epitopes of the Lassa virus (LASV) surface glycoproteins recognized by naturally infected human hosts have not been identified or characterized. Here we have cloned 113 human monoclonal antibodies (mAbs) specific for LASV glycoproteins from memory B cells of Lassa fever survivors from West Africa. One-half bind the GP2 fusion subunit, one-fourth recognize the GP1 receptor-binding subunit and the remaining fourth are specific for the assembled glycoprotein complex, requiring both GP1 and GP2 subunits for recognition. Notably, of the 16 mAbs that neutralize LASV, 13 require the assembled glycoprotein complex for binding, while the remaining 3 require GP1 only. Compared with non-neutralizing mAbs, neutralizing mAbs have higher binding affinities and greater divergence from germline progenitors. Some mAbs potently neutralize all four LASV lineages. These insights from LASV human mAb characterization will guide strategies for immunotherapeutic development and vaccine design.

Lassa fever in post-conflict sierra leone.

BACKGROUND: Lassa fever (LF), an often-fatal hemorrhagic disease caused by Lassa virus (LASV), is a major public health threat in West Africa. When the violent civil conflict in Sierra Leone (1991 to 2002) ended, an international consortium assisted in restoration of the LF program at Kenema Government Hospital (KGH) in an area with the world's highest incidence of the disease. METHODOLOGY/PRINCIPAL FINDINGS: Clinical and laboratory records of patients presenting to the KGH Lassa Ward in the post-conflict period were organized electronically. Recombinant antigen-based LF immunoassays were used to assess LASV antigenemia and LASV-specific antibodies in patients who met criteria for suspected LF. KGH has been reestablished as a center for LF treatment and research, with over 500 suspected cases now presenting yearly. Higher case fatality rates (CFRs) in LF patients were observed compared to studies conducted prior to the civil conflict. Different criteria for defining LF stages and differences in sensitivity of assays likely account for these differences. The highest incidence of LF in Sierra Leone was observed during the dry season. LF cases were observed in ten of Sierra Leone's thirteen districts, with numerous cases from outside the traditional endemic zone. Deaths in patients presenting with LASV antigenemia were skewed towards individuals less than 29 years of age. Women self-reporting as pregnant were significantly overrepresented among LASV antigenemic patients. The CFR of ribavirin-treated patients presenting early in acute infection was lower than in untreated subjects. CONCLUSIONS/SIGNIFICANCE: Lassa fever remains a major public health threat in Sierra Leone. Outreach activities should expand because LF may be more widespread in Sierra Leone than previously recognized. Enhanced case finding to ensure rapid diagnosis and treatment is imperative to reduce mortality. Even with ribavirin treatment, there was a high rate of fatalities underscoring the need to develop more effective and/or supplemental treatments for LF.

Toxoplasma gondii expresses two mitogen-activated protein kinase genes that represent distinct protozoan subfamilies.

All eukaryotes express mitogen-activated protein kinases (MAPKs) that govern diverse cellular processes including proliferation, differentiation, and survival. Even though these proteins are highly conserved throughout nature, MAPKs from closely related species often possess distinct signature sequences, making them well suited as drug discovery targets. Based on the central amino acid in the TXY dual phosphorylation loop, mammalian MAPKs are classified as extracellular signal-regulated kinases (ERKs), c-Jun amino-terminal kinases (JNKs), or p38 stress-response MAPKs. The presence of MAPKs in nonmetazoan eukaryotes suggests significant evolutionary conservation of these important signalling pathways. We recently cloned a novel stress-response MAPK gene (tgMAPK1) from Toxoplasma gondii, an obligate intracellular human parasite that can cause life-threatening infections in immunocompromised patients, and we now present data on a second T. gondii MAPK gene (tgMAPK2) that we cloned. We show that tgMAPK1 and tgMAPK2 are members of two distinct and previously unknown protozoan MAPK subfamilies that we have named pzMAPKl/pzMAPK3 and pzMAPK2. Our phylogenetic analysis of a collection of protozoan and metazoan MAPK genes in relation to ERK8-like genes demonstrates that an ERK8-like family, which includes the pzMAPK2 subfamily, is represented across a large variety of eukaryotic kingdoms and is evolutionarily very distant from other MAPK families.