Role of Env in Resistance of Feline Immunodeficiency Virus (FIV)-Infected Cats to Superinfection by a Second FIV Strain as Determined by Using a Chimeric Virus

Abstract

A more or less pronounced resistance to superinfection by a second strain of the infecting virus has been observed in many lentivirus-infected hosts. We used a chimeric feline immunodeficiency virus (FIV), designated FIV , containing a large part of the env gene of a clade B virus (strain M2) and all the rest of the genome of a clade A virus (a p34TF10 molecular clone of the Petaluma strain modified to grow in lymphoid cells), to gain insights into such resistance. FIV was infectious and moderately pathogenic for cats and in vitro exhibited the neutralization specificity of the env donor. The experiments performed were bidirectional, in that cats preinfected with either parental virus were challenged with FIV and vice versa. The preinfected animals were partially or completely protected relative to what was observed in naïve control animals, most likely due, at least in part, to the circumstance that in all the preinfecting/challenge virus combinations examined, the first and the second virus shared significant viral components. Based on the proportions of complete protection observed, the role of a strongly matched viral envelope appeared to be modest and possibly dependent on the time interval between the first and the second infection. Furthermore, complete protection and the presence of measurable neutralizing antibodies capable of blocking the second virus in vitro were not associated.

Neutralising antibody response in domestic cats immunised with a commercial feline immunodeficiency virus (FIV) vaccine

“…Following a 72 h incubation in 6 well culture clusters (Corning), culture fluids containing HIV(FIV)-luciferase pseudotypes (hereafter referred to as HIV(FIV)-luc, with the FIV Env in parenthesis) were harvested, centrifuged at 1000 rpm (∼200 × g ) for 5 min, passed through 0.45 μm filters and stored at −80 °C until required. HIV(FIV) luciferase pseudotypes ( n = 43) were prepared, bearing 12 Envs from cat SV1, 24 field Envs isolated from 24 naturally infected American cats [26] and 7 reference FIV Envs reported previously [27–33] , in order to assess neutralising antibody (NAb) responses in plasma samples and to determine the nature of the Env-receptor interaction.…”

Feline immunodeficiency virus latency

“…Kraase et al found variably detectable proviral burden in cats infected with FIV-A for 322 weeks (~6 years), but significantly increased viral env evolution relative to 12 weeks post infection [66], suggestive of ongoing viral replication. In two studies of FIV superinfection, viral loads in both plasma and PBMC remained detectable over 9 months [67] or three years [68] in cats infected with just one subtype, but declined significantly or was undetectable in cats pre-infected with another, attenuated or chimeric subtype. Kohmoto et al observed 3 experimentally FIV-infected cats over the course of 8 years, and found that the one animal that developed FAIDS had a very high plasma viral load (2 10 titration) whereas the other two were undetectable [37].…”

Reciprocal functional pseudotyping of HIV-1 and HTLV-1 viral genomes by the heterologous counterpart envelope proteins

“…(1;2) Super infection exclusion has been described for a variety of human viral diseases including; influenza A, Rubella, hepatitis C, foamy virus, rhabdoviruses, HSV-1, vaccinia, flaviviruses and HIV-1 (Berg et al, 2003; Bock et al, 1998; Claus et al, 2007; Giannecchini et al, 2007; Lee et al, 2005; Mador et al, 2002; Nethe et al, 2005; Tscherne et al, 2007; Turner and Moyer, 2008; Whitaker-Dowling et al, 1983). In HIV-1 infection Nef, Env and Vpu down regulate cell surface expression of the CD4 receptor molecule (Nethe et al, 2005; Wildum et al, 2006).…”