155LB
Discovery of New Human T-lymphotropic Viruses Reveals Frequent and Ongoing Zoonotic Retrovirus Introductions
Nathan Wolfe*1, W Heneine2, J Carr3, A Garcia2, V Shanmugam2, U Tamoufe4, J Torimiro4, A Prosser2, M LeBreton4, E Mpoudi-Ngole4, F McCutchan3, D Birx3, T Folks2, D Burke1, and W Switzer2
1Johns Hopkins Univ, Bloomberg Sch of Publ Hlth, Baltimore, MD, USA; 2CDC, Atlanta, GA, USA; 3US Military HIV Research Program, Rockville, MD, USA; and 4Johns Hopkins Walter Reed Cameroon Program, Yaounde, Cameroon
Background: The entry of
primate retroviruses into humans has lead to 2 pandemics (HIV and human T-lymphotropic virus [HTLV]). It is believed that the
emergence of these viruses has been limited by the rarity of successful
cross-species transmission. However, little is known about the frequency of
retroviral zoonoses and the mechanisms of retroviral emergence.
Methods:
To
examine the frequency of retrovirus cross-species transmission we examined blood
specimens from 930 individuals who reported exposure to freshly hunted primate
bush-meat in Cameroon.
Plasma samples were screened serologically using an HTLV-1/2 EIA followed by
confirmation with an HTLV Western blot assay. Peripheral blood lymphocyte DNA available from Western blot-reactive persons
were then examined using PCR in
several viral gene regions followed by phylogenetic
analysis with other known HTLV and simian T-lymphotropic viruses (STLV).
Results:
Plasma samples from 90 persons (9.7%) were
Western blot-reactive and proviral sequences were PCR-amplified from the peripheral blood lymphocyte DNA of 13 Western blot-reactive persons. Phylogenetic analysis revealed that 2 primate hunters were
found to be infected with 2 novel viruses we designated HTLV-3 and HTLV-4.
HTLV-3 falls within the diversity of STLV-3, a simian virus not seen before in
humans. HTLV-4 is distinct from all known HTLV and STLV by the formation of a
new phylogenetic lineage with high bootstrap support.
Phylogenetic analysis showed that the 11 remaining
persons were infected with a broad diversity of HTLV-1/STLV-1, including STLV-1
from mandrills (n = 3) and other STLV-1 variants (n = 2) not previously seen in
humans.
Conclusions:
We
report that bush-meat hunters in central Africa
who are exposed to infected primates are regularly infected with novel HTLV. We
discovered at least 6 viruses that had crossed from infected primates,
including 2 novel human retrovirus species, HTLV-3 and HTLV-4. The findings
demonstrate that cross-species transmission following primate exposure is not the
rate-limiting step in retrovirus emergence and suggest that emergence may be
predicted by surveillance of human populations exposed to animal reservoirs.
Keywords: simian; zoonosis; emergence
