David D. Ho

Intermittent Shedding of Human Immunodeficiency Virus in Semen: Implications for Sexual Transmission

PURPOSE We attempt to increase our understanding of human immunodeficiency virus (HIV) shedding in semen. MATERIALS AND METHODS We followed 16 seropositive men for up to 27 months by HIV cocultivation, with a subset evaluated using the polymerase chain reaction. RESULTS The proportion with at least 1 HIV positive semen culture increased from 3 of 16 subjects (19%) at visit 1 to 10 (63%) by visit 5. Overall, HIV was cultured from 25 of 114 specimens (22%). Shedding was intermittent for each of the 10 men with at least 1 positive culture and seminal shedding patterns were highly variable. CONCLUSIONS By culture and polymerase chain reaction, HIV is shed intermittently in the semen. If cultures are performed often enough most seropositive men shed HIV in the semen.

Distinction of human immunodeficiency virus type 1 neutralization and infection enhancement by human monoclonal antibodies to glycoprotein 120.

There is increasing evidence that sera from HIV-1-infected individuals contain antibodies that enhance infection by HIV-1 in vitro. Previous work has demonstrated that complement receptors on T lymphoid cells and Fc receptors for IgG (Fc gamma R) on monocytic cells are required for enhanced infection by antibody-complexed HIV-1. Characterization of such infection-enhancing antibodies is essential because immunogenic epitopes which induce enhancing antibodies should be excluded from HIV-1 vaccines. This study was conducted to identify enhancing antibodies involved in Fc R-mediated enhancement of HIV-1 infection employing IgG human monoclonal antibodies (HMAbs) reactive against gp120 of HIV-1, which were produced by B cell lines derived from an HIV-1-infected individual. A potent neutralizing HMAb N70-1.5e did not enhance infection by HIV-1 (IIIB and MN strains), whereas HMAb N70-2.3a mediated enhancement of HIV-1 infection, but had little neutralizing activity. A competition radio immunoassay demonstrated that the two antibodies bind to distinct epitopes. These results indicated that enhancing and neutralizing antibodies can be induced by different epitopes on gp120, suggesting the potential for development of safe vaccines against HIV-1 by exclusion of immunogenic epitopes for enhancing antibodies. We made attempts to identify the epitope on gp120 that is recognized by the enhancing antibody N70-2.3a by using recombinant HIV-1 proteins and found that the antibody binds to a conformational site of nonvariable sequences in the carboxyl half (aa 272-509) of gp120.

Isolation and quantitation of HIV in peripheral blood.

Quantitation of replication‐competent human immunodeficiency virus (HIV) in peripheral blood of infected individuals is critical for investigations of HIV pathogenesis and therapy. In this unit, the basic protocol determines the HIV titer in seropositive blood by measuring the tissue culture infectious dose (TCID) by an end‐point dilution method. A second basic protocol utilizes the PHA‐stimulated T cell blasts (activated T cells) in co‐culture with PBMC as described in the first basic protocol for the short‐term growth of HIV in vitro. An describes the accumulative method of determining 50% tissue culture infectious dose (TCID50) of HIV using the Reed‐Muench equation when multiple replicates of a given sample are employed in the assay. A consequence of HIV infection is the depletion of CD4+ target cells, evidenced by syncytia formation or single‐cell death; two support protocols detail the evaluation of these cytopathic effects.

RETRACTED: Characterization of long-term survivors of human immunodeficiency virus type 1 infection

A small population of HIV-1-infected individuals remains clinically healthy and immunologically normal for more than ten years. We have studied ten subjects who have been asymptomatic with normal and stable CD4+ lymphocyte counts, despite 12 to 16 years of HIV-1 infection, to gain information on the determinants of nonprogression. Multiple methods were used to determine the viral load in their blood. Plasma cultures were uniformly negative for infectious virus. However, particle-associated HIV-1 RNA was detectable in four subjects using a sensitive branched DNA amplification assay. In peripheral blood mononuclear cells (PBMC), infectious HIV-1 was quantified in three subjects using a standard limiting-dilution culture method. Infectious virus was recovered from another subject using a CD8-depleted culture. In contrast, six subjects had no detectable infectious virus in PBMC. All had detectable viral DNA in PBMC by a quantitative polymerase chain reaction assay, but the copy numbers were low, ranging from 10 to 100 copies per 10(6) PBMC in all but two subjects. Overall, the viral burden in the plasma and PBMC of long-term survivors was orders of magnitude lower than those typically found in progressors. Possible mechanisms for low levels of HIV-1 in vivo were examined experimentally.