Identification of the Virus of Lymphocytic Choriomeningitis

Multifunctional nature of the arenavirus RING finger protein Z

Arenaviruses are a family of enveloped negative-stranded RNA viruses that can cause severe human disease ranging from encephalitis symptoms to fulminant hemorrhagic fever. The bi‑segmented RNA genome encodes four polypeptides: the nucleoprotein NP, the surface glycoprotein GP, the polymerase L, and the RING finger protein Z. Although it is the smallest arenavirus protein with a length of 90 to 99 amino acids and a molecular weight of approx. 11 kDa, the Z protein has multiple functions in the viral life cycle including (i) regulation of viral RNA synthesis, (ii) orchestration of viral assembly and budding, (iii) interaction with host cell proteins, and (iv) interferon antagonism. In this review, we summarize our current understanding of the structural and functional role of the Z protein in the arenavirus replication cycle.

LYMPHOCYTIC CHORIOMENINGITIS IN THE SYRIAN HAMSTER

The virus of lymphocytic choriomeningitis produces an intense systemic infection in Syrian hamsters with few if any clinical and pathological signs of disease. Specific soluble antigen is demonstrable in the spleen of infected animals until about the 14th day when antisoluble substance antibodies make their appearance. Circulating virus disappears after the 4th week and neutralizing antibodies are present in serum in detectable amounts shortly thereafter; both types of antibody persist for at least several months. The viruses of St. Louis encephalitis and lymphocytic choriomeningitis can be concurrently passed in series in the brains of hamsters. The resultant disease is indistinguishable from that caused by the virus of St. Louis encephalitis alone.

COMPLEMENT FIXATION WITH THE NEUROTROPIC VIRUSES

Antigens capable of fixing complement specifically with the appropriate antibodies have been prepared from brain tissue of hamsters and mice infected with the viruses of St. Louis, Japanese, Western, and Eastern encephalitis, and with the West Nile virus. The antigens were freed of the material which reacts with normal serum by means of centrifugation at relatively high speed. In addition, the infectivity of the preparation was destroyed by irradiation with ultraviolet light. Cross reactions were demonstrated by means of the complement-fixation technique with materials from animals infected with the viruses of Eastern and Western equine encephalitis. No relationship was detectable by this procedure between St. Louis, Japanese, and West Nile viruses. These findings emphasize the need for further investigation and correlation of the immunological reactions of the groups of neurotropic viruses, since the equine agents are apparently unrelated when studied by neutralization and cross-immunity tests while these methods provide evidence of the presence of common antigenic structures in the St. Louis, Japanese, and West Nile agents.