Identification of MaTu-MX agent as a new strain of lymphocytic choriomeningitis virus (LCMV) and serological indication of horizontal spread of LCMV in human population

In this study we elucidated the molecular character of MaTu-MX, previously described as an unusual transmissible agent. Amino acid sequencing of pepti des generated from a 58-kDa MX-related protein purified from MaTu human car cinoma cells allowed us to identify it as a nucleoprotein (NP) of lymphocyt ic choriomeningitis virus (LCMV). Northern blot analysis detected LCMV-spec ific RNAs in MaTu cells. Comparative immunoprecipitations showed cross-reac tivity between NP of LCMV strain WE end MX NP. Using RT-PCR, we have cloned MX NP cDNA. According to sequence comparison, MX LCMV is as closely relate d to both LCMV strains WE and Armstrong as these strains are to one another . Based on this finding we propose that MX is a new strain of LCMV. We also showed that the stability of MX NP in MaTu cells is very high and that the virus is transmissible by cell-to-cell contact or by cell-free extract to human HeLa and monkey Vero cells, but not to human AGS, canine MDCK, mouse NIH 3T3, and hamster CHO cells. Finally, employing MX LCMV NP in immunoprec ipitation and solid-phase radioimmunoassay, we found 37.5% prevalence of an ti-LCMV antibodies in human sera, suggesting possible horizontal spread of the virus in the human population. (C) 1999 Academic Press.