Volgens een studie van Makarova, Petros en kollega's is de antistoffen-afweerresponse
in het bloed van muizen 3 weken na infektie met XMRV nagenoeg verdwenen.
Een mogelijke verklaring voor deze observatie is de lage immunogeniciteit van XMRV
(de mate waarin XMRV een afweerreaktie uitlokt, bijv. in de vorm van antistoffen),
mogelijk omdat XMRV het afweersysteem weet te onderdrukken (overlevingsmechanisme).
Volgens de auteurs bevestigt hun studie de bevindingen van Villinger at al. bij makaken.
Kanttekening: bij makaken duurt het veel langer aleer de antistoffen-afweer afneemt.
Overigens wil het afnemen van de hoeveelheid antistoffen uiteraard niet zeggen dat
de infektie uit het bloed en het lichaam verdwenen is: retrovirussen nestelen zich in het DNA.
Volgens de auteurs zouden hun bevindingen (dat afweerstoffen al vrij snel niet meer in het bloed te vinden zijn)
mede de tegenstrijdige resultaten van studies kunnen verklaren.
Antibody responses against xenotropic murine leukemia virus-related virus envelope in a murine model
PLoS ONE. 2002. 6(4): e18272. doi:10.1371/journal.pone.0018272
Makarova N, Zhao C, Zhang Y, Bhosle S, Suppiah S, Rhea JM, Kozyr N, Arnold RS, Ly H, Molinaro RJ, Parslow TG, Hunter E, Liotta D, Petros P, Blackwell JL.
http://www.plosone.org/article/info:doi/10.1371/journal.pone.0018272
Background
Xenotropic murine leukemia virus-related virus (XMRV)
was recently discovered to be the first human gammaretrovirus
that is associated with chronic fatigue syndrome and prostate cancer (PC).
Although a mechanism for XMRV carcinogenesis is yet to be established,
this virus belongs to the family of gammaretroviruses
well known for their ability to induce cancer in the infected hosts.
Since its original identification
XMRV has been detected in several independent investigations;
however, at this time significant controversy remains
regarding reports of XMRV detection/prevalence
in other cohorts and cell type/tissue distribution.
The potential risk of human infection,
coupled with the lack of knowledge about the basic biology of XMRV,
warrants further research, including investigation of adaptive immune responses.
To study immunogenicity in vivo,
we vaccinated mice
with a combination of recombinant vectors
expressing codon-optimized sequences of XMRV gag and env genes and
virus-like particles (VLP) that had the size and morphology of live infectious XMRV.
Results
Immunization elicited
Env-specific binding and neutralizing antibodies (NAb) against XMRV in mice.
The peak titers for
ELISA-binding antibodies and NAb were 1:1024 and 1:464, respectively;
however, high ELISA-binding and NAb titers
were not sustained and persisted for less than three weeks after immunizations.
Conclusions
Vaccine-induced XMRV Env antibody titers were transiently high,
but their duration was short.
The relatively rapid diminution in antibody levels
may in part explain the differing prevalences reported
for XMRV in various prostate cancer and chronic fatigue syndrome cohorts.
The low level of immunogenicity observed in the present study
may be characteristic of a natural XMRV infection in humans.
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