IMMUNOLOGICAL CROSS-REACTION BETWEEN HIV TYPE-1 P17 AND MYCOPLASMA-HYORHINIS VARIABLE LIPOPROTEIN

Monoclonal antibodies directed against the HIV-1 matrix protein p17 th at react with a component present on the surface of HIV-l-infected cel ls have previously been described, In this study we show that one of t hese monoclonal antibodies binds to persistently HIV-l-infected cell l ines that are coinfected with Mycoplasma hyorhinis, but not to cell li nes that are uninfected with mycoplasma. Mycoplasma-infected cells sec rete HIV-1 at a higher rate, have a slight increase in cell surface ex pression of gp120 and gp41, and are less sensitive to immunotoxins tha n uninfected cells, The anti-p17 antibody binds to a protein of M. hyo rhinis grown in cell-free culture, The variable expression and size of the protein among strains is typical of the variable lipoprotein (Vlp ) system of M. hyorhinis, Confirmation of the reactivity of the antibo dy with a Vlp was provided by demonstrating its specific binding to re combinant VlpF expressed in E. coli, and to a synthetic peptide repres enting the carboxy-terminal region of VlpF, but not to other recombina nt Vlp products or peptides, This is a true cross-reaction because the antibody also binds to recombinant p17 expressed in E. coli and the b inding is inhibited by the VlpF peptide, These analyses highlight the potential of mycoplasma contamination of tissue culture cell lines to cause anomalous results, With regard to HIV-1, mycoplasma infection of cells results in increased rates of virus secretion, and introduces a potential confounding immunologic cross-reaction as well. The existen ce of a cell surface form of p17 is unlikely.