Parotid salivary basic proline-rich proteins inhibit HIV-I infectivity.
OBJECTIVE
The objective of this study was to investigate the molecular nature, spectrum of activity and mechanism(s) of action of those human parotid basic proline-rich proteins that exhibit anti-HIV-I activity.


METHODS
Fractions containing the basic proline-rich proteins were obtained from human parotid saliva of presumed HIV-I non-infected human subjects and characterized with respect to their purity, apparent molecular size and their ability to inhibit the infectivity of T-tropic and M-tropic strains of HIV-I.


METHODS
Stimulated parotid saliva samples were collected from human subjects who denied having any risk factors for HIV-I infection and whose parotid salivas inhibited HIV-I infectivity. Such samples were subjected to affinity, molecular sieve and ion exchange chromatography to isolate individual salivary components. Those fractions demonstrating anti-HIV-I activity were analyzed by SDS-PAGE in order to assess their purity and determine their apparent molecular weights. HIV-I inhibitory activity was determined using HIV-I strains LAI and BaL in a Hela cell-derived multinuclear activation of a galactosidase indicator (MAGI) assay. Amino acid analyses were performed on some fractions.


RESULTS
Recombinant gp120-CH-Sepharose chromatography of one subject's parotid saliva revealed specific binding of human parotid basic proline-rich proteins, most prominently one with an apparent molecular weight of 37 kDa. Molecular sieve and cation exchange chromatography yielded a fraction greatly enriched in this protein which amino acid analysis confirmed was proline-rich. A similar fraction from two other subjects also contained basic proline-rich proteins of similar molecular size. These fractions inhibited both T-tropic and M-tropic strains of HIV-I when assayed in the MAGI system. Since SLPI activity is not observable in the MAGI assay, this inhibition was not due to SLPI. The presence of thrombospondin-I (TSP-I) in the active fractions was precluded on the basis of SDS-PAGE examination.


CONCLUSIONS
Specific basic proline-rich proteins in human parotid saliva possess significant anti-HIV-I activity independent of that attributable to SLPI or TSP-I. Since the inhibition is detectable with the MAGI assay, its mechanism of action involves virus-host cell interaction prior to the introduction of the tat gene product into the host cell and may be through the binding of the basic proline-rich proteins to the HIV-I gp120 coat of the virus.
Robinovitch
M R
MR
Department of Periodontics and Oral Biology, School of Dentistry, University of Washington, Seattle, WA 98195, USA.
Ashley
R L
RL
Iversen
J M
JM
Vigoren
E M
EM
Oppenheim
F G
FG
Lamkin
M
M
D000596:Amino Acids / Q000032:analysis; D002135:Calcium-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D002846:Chromatography, Affinity; D002847:Chromatography, Agarose; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D005696:Galactosidases; D015699:HIV Envelope Protein gp120; D015497:HIV-1 / Q000145:classification / Q000472:pathogenicity*; D006367:HeLa Cells; D006801:Humans; D008970:Molecular Weight; D010306:Parotid Gland / Q000378:metabolism; D010455:Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D010750:Phosphoproteins / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D011392:Proline / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D055232:Proline-Rich Protein Domains; D011485:Protein Binding; D012471:Salivary Proteins and Peptides / Q000737:chemistry / Q000302:isolation & purification / Q000502:physiology*; D014774:Virulence
D000596:Amino Acids; D002135:Calcium-Binding Proteins; D015699:HIV Envelope Protein gp120; D010455:Peptides; D010750:Phosphoproteins; D012471:Salivary Proteins and Peptides; D011392:Proline; D005696:Galactosidases