ELECTRON MICROSCOPY (EM) AND POLYMERASE CHAIN REACTION (PCR) GIVE DISCORDANT RESULTS IN ATTEMPTS TO MEASURE "VIRAL LOAD
Etienne de Harven*, MD and Gordon T. Stewart**, MD
In early studies on avian as well as on murine leukemias the presence in the peripheral blood of RNA tumor viruses (since then called retroviruses) was described as "viremia" and was readily demonstrated by transmission electron microscopy, the viral particles being isolated and purified from the biood plasma of the leukemic experimental animals. The methods used for isolation and purification were simpie and reproducible. They included sucrose gradient sedimentation at the 1.16gr/mi density (O'Connor et al, Science 144 : 1144-1147, 1964), or two steps of ultrafiltration (de Harven, Pathologie-Biologie, 13, pp 125-134, 1965), followed by ultracentrifugation to sediment the virai particles as a pellet, suitable for study under the electron microscope by routine ultrathin section methods.
About thirty years later, in the study of patients suffering from the AiDS syndrome and of asymptomatic so-called ''HIV+" individuals, a similar viremia was suspected. The so-called "HlV" virus particles had been reported as being of similar diameter, shape and ultrastructure as those of avian and murine leukemias and, consequently, had been expected to respond similarly to isolation and purification methods, using blood plasma samples.
Most surprinsingly, direct isolation and purification of the so-called "HIV" virus from the blood plasma of AIDS patients or from "HIV+,' asymptomatic individuals has never been reported. Reviewing the world-wide iiterature, it appears clearly that nobody ever succeeded in demonstrating the "HIV~ virus by electron microscopy from plasma samples from AIDS or HIV+ individuals. All the electron microscopic evidence for socalled HIV originated from highly complex mixed cell cultures systems, never directly from patients.
The Polymerase Chain Reaction (PCR) methodology is currently being used to quantify `'viral load" in AIDS and in HIV+ individuals. One could have thought that identifying individuals with high "viral load" by PCR would have been easily correlated with demonstration of virus particles by electron microscopy. This has not been the case. HIV particles have never been seen by electron microsopy in the plasma of patients, even those with so-called "high viral load" by PCR. This total absence of correlation between EM and PCR results has to be placed in the context of remarks repeatedly made by Kary Mullis himseif and indicating that the PCR technology is not a scientifically acceptable approach to the measurement of "viral load".
Unquestionably, measuring "viral load" by PCR technology has to be fully reappraised before any further credit is given to PCR data in the management of AIDS and of HIV+ individuals.
* Etienne de Harven M.D., Emeritus Professor of Pathology, University of Toronto, Canada
** Gordon T. Stewart M.D., Emeritus Professor of Public Heaith, University of Glasgow, UK