Many viral infections result in a wide spectrum of illnesses, from unapparent to severe. In the case of Lassa virus infection, the most severe manifestation is a fatal hemorrhagic fever. However, many people, even those that develop severe signs and symptoms of Lassa Fever, survive infection, and some, perhaps many, persons can be infected with the virus and never develop severe or even clinically significant disease. This has been suggested to occur in other severe viral hemorrhagic fevers as well, such as Ebola.
The Consortium have recently established unique clinical resources in West Africa. A detailed description of the patient cohorts available, including acutely infected, convalescent, and previously exposed persons, will be investigated. This will allow us to assess the reactivity of serum from a clinically diverse cohort of Lassa virus-exposed persons to a defined set of specific B cell epitopes (antibodies). A set of appropriately cloned, mutated and expressed Lassa proteins and other cross-reactive proteins (i.e. Junin virus proteins) and synthetic peptides, will allow an evaluation of the reactivities to particular epitopes, or a panel of epitopes representative of divergent antigenic sites on the proteins of the Lassa virus (LASV) and other arenaviruses. Analyses then will define statistically significant correlations, if present, between reactivity to given B cell epitopes and Lassa Fever related disease outcomes among the population of people exposed to LASV.
We have developed sensitive recombinant antigen-based IgG- and IgM-capture assays that can be used to elucidate elements of adaptive humoral immunity to LASV in humans. Blood samples will be examined using these newly developed ELISA as well as other methods to assess B cell immune responses. We will determine IgG and IgM titers individually to each of the major LASV structural proteins, namely GP1, GP2, and NP using serum samples collected longitudinally throughout the stay of consenting Lassa Fever patients. IgM- and IgG-capture ELISA, microplates will be coated with purified recombinant LASV antigens. The ELISA will also be used to assess antibody titers to the individual Lassa virus proteins by quantifying responses to serum dilutions and will include ELISA configured with recombinant LASV proteins engineered to contain specific mutations in an identified epitope. Because samples will be collected longitudinally we will be able to assess qualitative, quantitative and temporal variations in the responses to these LASV proteins in patients with severe or mild disease as well as in patients that die from or survive Lassa Fever.