Genetic basis of viral persistence: single amino acid change in the viral glycoprotein affects ability of lymphocytic choriomeningitis virus to persist in adult mice.

Abstract

SummaryThis study has identified a single amino acid change in the viral glycoprotein that profoundly affects the ability of lymphocytic choriomeningitis virus (LCMV) to persist in its natural host . Adult immunocompetent mice infected with a variant--of the Armstrong strain, spleen isolate clone 13 (svA/svA), harbor virus for several months and exhibit suppressed T cell responses . In contrast, adult mice infected with a reassortant virus (svA/wtA) that contains the L segment of the spleen variant and the S segment of the parental wt Armstrong, make potent LCMV specific CTL responses and clear the infection within 2-4 wk . These two viruses, spleen variant clone 13 and the reassortant svA/wtA, are identical in their noncoding regions and show no amino acid changes in any of their viral genes except for one substitution in the glycoprotein . The reassortant virus svA/wtA has a phenylalanine at amino acid residue 260 of the glycoprotein, whereas the spleen variant clone 13 has a leucine at this position . This study constitutes one of the first reports defining the genetic basis of viral persistence at the whole animal level, and identifying a single mutation that markedly increases the ability of a virus to persist in its natural host . S uccessful resolution of a viral infection depends upon a critical balance between the extent of viral spread and replication, and the magnitude of the host's immune response. We have been studying infection of mice with lymphocytic choriomeningitis virus (LCMV)t as a model system to understand the host and viral determinants that lead to viral clearance or persistence (1-4) . Infection of immunocompetent adult mice with the Armstrong strain of LCMV induces a potent antiviral T cellresponse and virus is eliminated within 2 wk . This clearance is mediated by CD8 * virus-specific cytotoxic T lymphocytes (4-7) . In contrast, infection of adult mice with a naturally selected isolate of Armstrong, spleen variant clone 13, results in a disseminated infection, with virus persisting for several months (1, 2). This chronic infection is associated with suppressed T cell responses and susceptibility to opportunistic infection (1, 2, 8) .The LCMV genome consists of two segments of singlestranded RNA, a large (L) segment of 7 .2 kb and a small (S) segment of 3 .4 kb (9-12) . The L RNA segment codes for a large protein, L (molecular mass 250 kD), that is be-1 Abbreviations used in this paper. L, large; LCMV, lymphocytic choriomeningitis virus; S, small; sv, spleen variants; wt, wild type.lieved to be the viral polymerase, and also contains a second open reading frame, designated Z, that encodes for a protein of "10-12 kD. The S segment codes for the three major structural proteins : the internal nucleocapsid protein (NP ; 63 kD) and the two surface glycoproteins GP-1 (43 kD) and GP-2 (36 kD) that are derived from a common precursor polypeptide, GP-C. After coinfwtion of cells with two different LCMV strains, recombinants are generated by reassortment of genome segments. This permits genetic a...

Dynamic Regulation of T Cell Immunity by CD43

“…Previous reports have suggested that functional inactivation or down-modulation of immune responses during chronic infection are critical for host survival (33)(34)(35). When previously uninfected adult mice are infected with LCMV clone 13 i.v., the virus replicates and disseminates rapidly (36). It can persist in the serum for up to 100 days, and remains indefinitely in some tissues.…”

Distinct CD8 T Cell Functions Mediate Susceptibility to Histoplasmosis During Chronic Viral Infection

“…Infected animals are not able to clear the infection, and virus titer is high in all tissues (19). Although T cell-mediated immunopathology is observed in these mice, mortality is rarely seen (25).…”

“…We have previously reported that infection of adult mice with LCMV clone 13 results in chronic infection associated with susceptibility to opportunistic histoplasmosis (4,19). Mice infected with this viral isolate are unable to mount an effective immune response against Histoplasma and succumb to a sublethal dose of the fungus.…”

Effector CD8 T cells dedifferentiate into long-lived memory cells

“…Effector and memory antigen-specific CD8 T cells were identified and purified by Fluorescence Activated Cell Sorting (FACS) using H-2D b tetramers bound to LCMV peptide GP33-41 conjugated to a fluorophore, along with CD8, CD44, CD127, Klrg1 and CD62L-fluorophore conjugated antibodies as previously described. 11,14,25,26 . To generate LCMV-specific CD8 T cell chimeras, transgenic P14 CD8 T cells with an engineered TCR that recognize the epitope GP33-41 of LCMV were harvested from naïve P14 TCR transgenic mice and adoptively transferred intravenously to C57BL/6 mice (cell# / mouse is specified in the figure legend) 11,27–29 .…”