Increased mutation frequency of feline immunodeficiency virus lacking functional deoxyuridine-triphosphatase.

Abstract

Feline immunodeficiency virus (FIV) encodes the enzyme deoxyuridine-triphosphatase (DU; EC 3.6.1.23) between the coding regions for reverse transcriptase and integrase in the pol gene. Here, we report the in vivo infection of cats with a DU- variant of the PPR strain of FIV and compare its growth properties and tissue distribution with those of wild-type FIV-PPR. The results reveal several important points: (i) DU- FIV is able to infect the cat, with kinetics similar to that observed with wild-type FIV; (ii) both wild-type and DU- FIV-infected specific-pathogen free cats mount a strong humoral antibody response which is able to limit the virus burden in both groups of animals; (iii) the virus burden is reduced in the DU- FIV-infected cats, particularly in tissues such as spleen and salivary gland; and (iv) the mutation frequency in DU- FIVs integrated in the DNA of primary macrophages after 9 months of infection is approximately 5-fold greater than the frequency observed in DU- FIV DNA integrated in T lymphocytes. Mutation rate with wild-type FIV remains the same in both cell types in vivo. The dominant mutations seen in macrophages with DU- FIV are G-->A base changes, consistent with an increased misincorporation of deoxyuridine into viral DNA of DU- FIVs during reverse transcription. Because this enzyme is absent from human immunodeficiency virus type 1 and other primate lentiviruses, virus replication in cell environments with low DU activity may lead to increased mutation and contribute to the rapid expansion of the viral repertoire.

Vpr-mediated Incorporation of UNG2 into HIV-1 Particles Is Required to Modulate the Virus Mutation Rate and for Replication in Macrophages

“…Interestingly, replication of feline immunodeficiency virus, caprine-arthritis-encephalitis virus, or equine infectious anemia, which lacks functional a dUTP pyrophosphatase activity, is severely affected in nondividing host cells (e.g. primary macrophages) (42)(43)(44). Altogether, these results indicate that uracil misincorporation in viral DNA strands during reverse transcription is deleterious for the ongoing steps of the virus life cycle.…”

Uracil DNA glycosylase initiates degradation of HIV-1 cDNA containing misincorporated dUTP and prevents viral integration

“…The observed mutations were predominantly G/C→A/T transition mutations, consistent with the natural mutational drift observed in HIV-1 (35). It should also be noted that an increase in transition mutations has been observed in dUTPase-deficient nonprimate lentiviruses (36,37); therefore, the slight increase in transition mutations on RTX treatment may be the result of uracil misincorporation. However, the inhibitory effects of RTX on viral integration cannot be reasonably attributed to these at most small increases in the mutation frequency, because these effects are completely dependent on the presence of hUNG2 activity.…”

FIV: from lentivirus to lentivector

“…Other differences are a Rev response element (RRE) that overlaps the 3 end of env rather than the SU-TM junction, and a pol-encoded dUTPase, which is thought to facilitate reverse transcription under conditions of low nucleotide tension [40]. Yet the relative simplicity of the FIV genome could be advantageous for understanding singular lentiviral properties, i.e., for fostering understanding of lentiviral pathogenesis in an interdisciplinary way [39,41].…”