Scientific explanation on how union Minister's goat got AIDS !

[Guest guest]

Dear FORUM,

This referes the posting " AIDS gets Union Minister's goat, he's positive: it's

no deadly disease Saturday January 31 2004 "

Well, in its own bizarre way, this DOES point to a possibly important issue.

ELISA tests are very sensitive but not as specific as we would like. Which is

why in the west, a Western Blot test is used to follow-up the HIV+ ELISA to

assure that an infection is present.

Goats may have other viruses, such as Caprine Encephalitis (CAEV) which is a

retrovirus. This may cross-react with an HIV ELISA, producing a false positive.

It does NOT indicate that that animal is infected with HIV-1, but rather

highlights a limitation of the test. By contrast, humans will NOT likely have

CAEV. But it could cause false positives on human tests (see the reference

below).

In general, I do not think this is an issue. What IS an issue is assurance of

accuracy in HIV diagnosis and access to accurate, inexpensive diagnostics.

Western Blot costs must be brought down somehow. Or perhaps use of

heat-dissociated p24? This and PCR however are not use to diagnose HIV directly,

only viral load.

M.

E-mail: <fiar@...>

***

Tesoro-Cruz E, - R, Kretschmer-Schmid R, Aguilar-Setien A.

Cross-reactivity between caprine arthritis-encephalitis virus and type 1

human immunodeficiency virus. Arch Med Res. 2003 Sep-Oct;34(5):362-6.

Unidad de Investigacion Medica en Inmunologia, Centro Medico Nacional Siglo

XXI, Instituto Mexicano del Seguro Social, Mexico City, DF, Mexico.

BACKGROUND: Caprine arthritis encephalitis (CAE) is caused by the

lentivirus caprine arthritis-encephalitis virus (CAEV), a member of the

Retroviridae family that also includes the human immunodeficiency virus

(HIV). Serum of CAEV-infected goats cross-reacts with HIV-1 antigens in

enzyme-linked immunosorbent assay (ELISA) tests. We attempted to identify

the proteins responsible for this cross-reactivity. METHODS: Fifty selected

human sera (30 positive, 10 negative, and 10 indeterminate to HIV-1 by

Western blot) and 50 selected goat sera (33 positive and 17 negative to

CAEV by ELISA) were evaluated. Human and goat sera were tested by Western

blot against HIV-1 and CAEV antigens. RESULTS: Cross-reactivity between

surface glycoproteins gp120 (HIV-1) and gp135 (CAEV) was specific. Positive

reaction of human sera to CAEV gp135 was more intense than that of goat

sera to HIV-1 gp120. Surface glycoprotein sequences of the two viruses were

compared by Lasergene software (Dynex Technologies, Inc., Chantilly, VA,

USA). Three homologous regions were identified: the first in the internal

domain of gp120; the second in the beta3 loop, and still another-with the

greatest homology-in a short sequence of the proximal region of the

external domain of gp120 between loops beta4 and beta8. CONCLUSIONS:

Surface glycoproteins of HIV-1 and CAEV share structural regions essential

for viral adsorption and for induction of neutralizing antibodies. Thus,

human contact with CAEV eventually could be a possible source of HIV-1

false positive reactions and must be considered in the interpretation of

HIV serologic results.

PMID: 14602501 [PubMed - in process]