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The human immunodeficiency virus type 1 (HIV-1) nef gene was originally described as a negative regulator of transcription from the viral long terminal repeat promoter. This observation has been disputed, and the function of Nef remains unclear. In vivo experiments have indicated that an intact nef gene is required for disease progression in macaques infected with simian immunodeficiency virus, suggesting a role for Nef in the pathogenesis of AIDS. We and others have previously shown that expression of Nef in cells bearing surface CD4 results in a sustained decrease in surface CD4 expression. This was demonstrated for Nef from two laboratory strains of HIV-1, Bru and SF2. Because both of these isolates were passaged in vitro prior to molecular cloning and in vitro passage can result in mutations which might alter nef gene function, we have analyzed two primary isolates of Nef for their ability to suppress cell surface CD4 expression. The nef genes of HIV-1 isolates from two patients with fewer than 200 CD4+ T cells per mm3 of blood were introduced into human and mouse T-cell lines by retrovirus-mediated gene transfer. Expression of Nef from both isolates correlated with a decrease in surface expression of both human and mouse CD4. To determine whether the ability to suppress surface CD4 expression is a general function of Nef, we also tested an artificially generated consensus nef gene derived from analysis of 54 patient isolates of HIV-1. Expression of the consensus Nef protein also correlated with decreased cell surface CD4 expression in both mouse and human T-cell lines. These results suggest that the ability to suppress cell surface CD4 expression is an intrinsic feature of HIV-1 Nef.

Oral fluids are rarely a vehicle for HIV-1 infection in vivo, unlike other mucosal secretions. This unique property raises questions regarding (1) the molecular mechanisms responsible for the lack of salivary transmission, (2) the extent to which oral immunological responses mirror responses at other mucosal sites, (3) the use of promising salivary markers of HIV-1 disease progression, (4) the relationship between oral and blood viral loads, (5) cofactors that influence oro-genital transmission, and (6) the feasibility of oral-based antibody testing for HIV-1 diagnosis in the home. This paper discusses these questions and provides background summaries, findings from new studies, consensus opinions, practical relevance to developing countries, and suggestions for future research agenda on each of the key topics.

Infection of monocytes with human immunodeficiency virus type 1(Ba-L) (HIV-1(Ba-L)) is significantly inhibited by treatment with the serine protease inhibitor, secretory leukocyte protease inhibitor (SLPI). SLPI does not appear to act on virus directly, but rather the inhibitory activity is most likely due to interaction with the host cell. The current study was initiated to investigate how SLPI interacts with monocytes to inhibit infection. SLPI was found to bind to monocytes with high affinity to a single class of receptor sites (approximately 7,000 receptors per monocyte, K(D) = 3.6 nmol/L). The putative SLPI receptor was identified as a surface protein with a molecular weight of 55 +/- 5 kD. A well-characterized function of SLPI is inhibition of neutrophil elastase and cathepsin G. However, two SLPI mutants (or muteins) that contain single amino acid substitutions and exhibit greatly reduced protease inhibitory activity still bound to monocytes and retained anti-HIV-1 activity. SLPI consists of two domains, of which the C-terminal domain contains the protease inhibiting region. However, when tested independently, neither domain had potent anti-HIV-1 activity. SLPI binding neither prevented virus binding to monocytes nor attenuated the infectivity of any virus progeny that escaped inhibition by SLPI. A polymerase chain reaction (PCR)-based assay for newly generated viral DNA demonstrated that SLPI blocks at or before viral DNA synthesis. Therefore, it most likely inhibits a step of viral infection that occurs after virus binding but before reverse transcription. Taken together, the unique antiviral activity of SLPI, which may be independent of its previously characterized antiprotease activity, appears to reside in disruption of the viral infection process soon after virus binding.

Unlike many other malignancies, cancers of the mouth and surrounding tissues continue to cause considerable mortality and morbidity in this country. Therefore, early detection, diagnosis, and treatment of patients with oral cancer must be a high priority for all health care providers. This review is aimed at heightening the awareness of clinicians to the early signs and symptoms of oral cancer. Recognition of early lesions is crucial for improved long-term patient survival. Factors such as advanced age, tobacco and/or alcohol use, chronic sum exposure, and a previous diagnosis of cancer can alert clinicians to patients who may be at risk for developing oral cancer. Because most oral malignancies are asymptomatic and may mimic benign conditions, any suspicious lesion should be carefully examined and, if appropriate, referred immediately for histological examination. Measures such as annual oral cancer screening examinations and patient education that stress early signs and symptoms of oral cancer can also help to reduce the risk in high-risk individuals.

Saliva contains factors that inhibit infection with the human immunodeficiency virus type 1 (HIV-1) in vitro. One of these factors was recently identified as secretory leukocyte protease inhibitor (SLPI), a salivary protein which blocked HIV-1 infectivity of monocytes and primary T cells at physiologic concentrations (J Clin Invest 1995; 96: 456). Here, we confirm and extend the original report by demonstrating that SLPI protects primary monocytes and peripheral blood mononuclear cells against infection with HIV-1 Ba-L, IIIB and NL4-3. Thus, SLPI may provide a natural barrier against oral transmission of HIV-1.

Various cobalamins act as important enzyme cofactors and modulate cellular function. We investigated cobalamins for their abilities to modify productive human immunodeficiency virus-1 (HIV-1) infection of hematopoietic cells in vitro. We show that hydroxocobalamin (OH-Cbl), methylcobalamin (Me-Cbl), and adenosylcobalamin Ado-Cbl (Ado-Cbl) inhibit HIV-1 infection of normal human blood monocytes and lymphocytes. The inhibitory effects were noted when analyzing the monocytotropic strains HIV-1-BaL and HIV-1-ADA as well as the lymphocytotropic strain HIV-1-LAI. Cobalamins did not modify binding of gp120 to CD4 or block early steps in viral life cycle, inhibit reverse transcriptase, inhibit induction of HIV-1 expression from cells with established or latent infection, or modify monocyte interferon-alpha production. Because of the ability to achieve high blood and tissue levels of cobalamins in vivo and the general lack of toxicity, cobalamins should be considered as potentially useful agents for the treatment of HIV-1 infection.