Abstracts lodged for International AIDS Conference in Bangkok in July, 2004 - News note - Feb 12, 2004

More than 10, 000 Abstracts are expected to be lodged for this vital annual conference and only 500 are expected to be chosen for presentation.

The LemonAIDS team leader, Professor Roger Short and his PhD student, Scott McCoombe, will travel to Bangkok for the conference in the hope of presenting their Abstracts which have already been lodged.

1. Lemon and Lime juice as potent natural microbicides

R V Short (1), S G McCoombe (1), C L V Maslin (2), S M Crowe(2)

1 - The University of Melbourne, Melbourne, Australia;
2 - Macfarlane Burnet Institute for Medical Research and Public Health, Melbourne, Australia
Contact e-mail: s.mccoombe@pgrad.unimelb.edu.au

Background
There is no doubt that an acceptable, affordable, safe and effective vaginal microbicide is urgently needed to protect women from HIV transmission. Lemons and limes are indigenous to South East Asia, and have been used intravaginally as an effective contraceptive for several centuries. The contraceptive effect is due to the low pH immobilising sperm. It is widely known that HIV is susceptible to acidity, so we have studied the antiviral properties of lime and lemon juice on cultures of live HIV.

Methods:
We developed a cell culture system to measure toxicity of lemon or lime juice on human peripheral blood monoclear cells (PBMC), as well as inhibition of infectivity of HIV after exposure to different dilutions of lemon or lime juice for variable periods of time. Following exposure to lemon juice, the virus is cultured with PBMC for 2 weeks. HIV replication in PBMC is monitored by reverse transcriptase activity. We are currently measuring the ability of lemon juice to inactivate HIV in the ejaculates of HIV-positive men.

Prof. Roger Short (AM)
Prof. Roger Short (AM)
Reproductive biologist
Photo: Lucy Di Paolo
Courtesy: Monash Journal

Results:
The pH of lemon juice ranged from 2.3-2.5. A 2% lemon juice solution in culture (pH 5.7) exposed to the virus for 1 hour had no inhibitory effect on HIV replication and was non-toxic to the PBMCs.

A 5% solution (pH 4.0) for 1 hour halved HIV replication and was also non-toxic. A 10% solution for one hour (pH 3.4) reduced HIV replication by two-thirds and was also non-toxic. A 20% solution (pH 2.9) after only 2 minutes exposure also reduced viral load by 90% but 25% of cells showed toxicity. Ongoing research on the effect of lemon juice on virus in the ejaculate of HIV-positive men will be presented at the meeting.

Conclusions:
The microbicidal properties of lemon juice are probably due to the low pH produced by citric acid. Toxicity to PBMCs found at higher concentrations of lemon juice needs further assessment in more appropriate cell culture models. Provided that clinical trials confirm that intravaginal lemon juice is acceptable, safe and effective, it could prove to be Nature's own microbicide.

2. Circumcision

How HIV-1 enters the human penis

Scott G McCoombe, Paul U Cameron, Roger V Short.

Background:
The most recent evidence suggests that circumcised men are 8 times less likely to become infected by HIV-1 than uncircumcised men.

Immunocompetent cells expressing specific HIV-1 receptors are present in all the mucosal surfaces of the penis. Once HIV-1 binds to a receptor, the target cell then transports it to the regional lymph node where infection of CD4 T cells is established. To determine where HIV-1 enters the penis we have studied the distribution of HIV-1 target cells in the glans penis, frenulum, foreskin and urethral meatus from 5 fresh, uncircumcised penises obtained at autopsy. We also measured the thickness of the overlying layer of keratin which potentially prevents HIV-1 gaining access to these penile receptors.

Methods:
Langerhans cells, dendritic cells, macrophages and T-cells were studied using immunohistochemical staining techniques on fresh-frozen penile sections examined by confocal microscopy. Keratin thickness was measured using histochemical staining and light microscopy.

Results:
HIV-1 target cells expressing CD4 and CCR5 were found in the inner and outer foreskin, frenulum and glans penis, but at a very low level in the urethral meatus and penile urethra. Dendritic cells, macrophages and T cells expressing these receptors were observed in high densities in the dermis in all regions of the penis except the urethra. HIV-1 susceptible Langerhans cells in the inner foreskin and frenulum were closer to the epithelial surface, but less frequent than in the outer foreskin and glans. The outstanding feature was that there was little if any protective covering of keratin overlying the inner foreskin and frenulum, in contrast to the glans penis and outer foreskin which were heavily keratinized, thus protecting them from viral entry.

Scott McCoombe
Scott McCoombe

Conclusions:
HIV-1 is most likely to enter the penis of uncircumcised men via superficial Langerhans cells on the inner aspect of the foreskin and frenulum since these sites are not keratinised. The major protective effect of male circumcision can best be explained by the removal of most of the readily accessible HIV-1 receptor sites in the foreskin and frenulum.

 

 

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