HIV can be shed in the tonsils says study

The oropharynx (the middle part of the throat that includes the soft palate, the base of the tongue, and the tonsils) could be a source of infectious HIV in individuals with a high HIV viral load and intact tonsils, according to a small study conducted in the US and Peru and published in the July 1^st edition of the Journal of Infectious Diseases.

Infectious HIV is rarely detected in saliva, however the oropharynx has not been studied carefully as a potential source of HIV shedding. Investigators wished to establish the frequency and quantity of HIV shedding in the middle part of the throat and the factors associated with the oropharyngeal shedding of HIV.

Between 1999 and 2001, 64 HIV-positive gay men were recruited in Seattle, in the USA and in Lima, Peru. The men were either naïve to antiretroviral therapy or on a stable anti-HIV treatment regimen.

There were significant baseline differences between the men from Seattle and Lima. The men from Seattle were older (average 39 years versus 27 years), more likely to be receiving anti-HIV therapy (69.7% versus 12.9%), more likely to have had their tonsils removed (42.3% versus 12.9%), and had lower HIV viral loads in both plasma (1600 copies/mL versus 55,000 copies /mL) and the pharynx (1,300 copies/mL versus 70,000 copies/mL).

In univariate analysis, men receiving anti-HIV therapy had lower pharyngeal viral loads than men not (undetectable versus 45,000 copies/mL, p=0.001), as did men who had had their tonsils removed (1,300 copies/mL versus 35,000 copies/mL, p=0.056), and men with a higher CD4 cell count (p=0.035). In a mixed effects model, only use of anti-HIV therapy (use versus none), CD4 cell count and removal of the tonsils were found to be significantly associated with a lower pharyngeal viral load. In this model, a man who had had his tonsils removed would have a viral load almost 0.9 log¹⁰/mL lower than a man with a similar CD4 cell count, who was also taking anti-HIV drugs.

HIV was successfully cultured from the surface of the tonsils of four of 14 men (29%), who had intact tonsils and who had a pharyngeal viral load of above 50,000 copies/mL on one or more study visit. All the four men were from Lima.

The investigators note that current use of anti-HIV therapy and the absence of tonsils were the strongest predictors of lower pharyngeal HIV viral load. They add that anti-HIV therapy affected HIV viral load in the pharynx independent of its effect on plasma, “perhaps because of the differential penetration of antiretrovirals into lymphoid tissue or the kinetics of viral replication in the oropharnyx.”

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