Lysozyme and RNases as anti-HIV components in beta-core preparations of human chorionic gonadotropin

Abstract

Human chorionic gonadotropin (hCG) preparations contain activity against HIV type 1 (HIV-1). However, there has been controversy about whether some biological activities of hCG beta-subunit (hCGbeta) preparations are caused by the beta-subunit itself or other proteins present in the preparations. We report here the purification, characterization, and identification of three enzymes with anti-HIV activity present in the beta-core fraction of hCGbeta prepared from the urine of pregnant women. The N-terminal amino acid sequence of one protein is identical to human urinary lysozyme C, and those of the other two are identical to human RNase A and urinary RNase U. We thus refer to these proteins as AVL (antiviral lysozyme) and AVR (antiviral RNases). In addition to HIV-1 inhibition, AVL is capable of lysing Micrococcus lysodeikticus. AVR digests a variety of RNA substrates, including RNA from HIV-1-infected cells. We also find that lysozyme from chicken egg white, human milk, and human neutrophils and RNase A from bovine pancreas possess activity against HIV-1. These findings may offer additional strategies for the treatment of HIV-1 infection.

Figure 1

(A) HPLC separation of hCG β-core fragment, human urinary AVL, and AVR from a crude β-core preparations. The elution profile of a representative reverse-phase liquid chromatogram of 2.5 mg run is shown. Details are described in Methods. (B) Characterization of AVL and AVR. SDS/PAGE was carried out on crude β-core (Sephadex G100 gel chromatography fractionated), fractions P1-P7 of C18 reverse-phase HPLC, pure β-core, AVL, AVR, lysozyme, and RNase. Each lane contains about 5–10 μg of sample. The presence (+) or absence (−) of anti-HIV, lysozyme, and RNase activities are shown under the SDS/PAGE pattern. Proteins smaller than 11 kDa were not separated in this SDS/PAGE system.

Figure 2

AVR and AVL are active in HIV-1 inhibition. Dose–response anti-HIV activities of AVL, AVR, pure β-core, chicken egg white lysozyme, and bovine pancreatic RNase were assayed by viral production (p24 ELISA) in (A) ACH2 lymphocytes and (B) U1 monocytes. Each data point is the mean of triplicate. Identical dose–response anti-HIV activity was obtained for human milk lysozyme and human neutrophil lysozyme (data not shown).

Figure 3

RNase activity of AVR. (A) RNase activity of AVR was assayed by degradation of total RNA isolated from HIV-infected ACH2 lymphocytes. AVR demonstrated potent RNase activity comparable to that of bovine pancreatic RNase A, whereas pure β-core and AVL showed no RNase activity. (B) Dose-dependent RNase activity of AVR.