title: HIV-1 suppression during acute scrub-typhus infection.
abstract: BACKGROUND
  In HIV-1-infected individuals, viral load has been reported to rise transiently if an acute infection with another organism occurs. Our study was prompted by the unexpected finding that HIV-1 copy number fell during an acute infection with Orientia tsutsugamushi, the causative agent of scrub typhus.
  
  
  METHODS
  Serial HIV-1 viral load determinations were made in ten Thai adults with scrub typhus, who were not receiving antiretroviral therapy, and in five HIV-1-infected patients who had other infections (four malaria, one leptospirosis), during and after acute infections. Sera from HIV-1-infected patients with scrub typhus and from mice immunised with O. tsutsugamushi were examined for HIV-1-suppressive activity.
  
  
  RESULTS
  Median viral load 3 days after admission was significantly lower in the scrub-typhus group than in patients with other infections (193% vs 376% of day 28 values, p=0.03). In four O. tsutsugamushi-infected patients HIV-1 RNA copy number fell by three-fold or more compared with day 28 values, and HIV-1 copy numbers were below the assay threshold in two patients with scrub typhus. Five of seven HIV-1 isolates from non-typhus patients with CD4 lymphocytes less than 200 cells/microL were syncytia-inducing variants, whereas all ten isolates from O. tsutsugamushi-infected individuals matched by CD4-cell count were non-syncytia inducing (p=0.03). Sera from an HIV-1-negative patient with scrub typhus had potent HIV-1-suppressive activity in vitro. Sera from typhus-infected mice inhibited HIV-1 syncytia formation and bound by immunofluorescence to HIV-1-infected lymphocytes.
  
  
  CONCLUSIONS
  HIV-1-suppressive factors are produced during some scrub-typhus infection and should be investigated further in the search for novel strategies for the treatment and prevention of AIDS.
authors.affiliation: Retrovirology Department, USAMC, Armed Forces Research Institute of Medical Sciences, Bangkok, Thailand.
authors.forename: G
authors.initials: G
authors.lastname: Watt
authors.forename: P
authors.initials: P
authors.lastname: Kantipong
authors.forename: M
authors.initials: M
authors.lastname: de Souza
authors.forename: P
authors.initials: P
authors.lastname: Chanbancherd
authors.forename: K
authors.initials: K
authors.lastname: Jongsakul
authors.forename: R
authors.initials: R
authors.lastname: Ruangweerayud
authors.forename: L D
authors.initials: LD
authors.lastname: Loomis-Price
authors.forename: V
authors.initials: V
authors.lastname: Polonis
authors.forename: K S
authors.initials: KS
authors.lastname: Myint
authors.forename: D L
authors.initials: DL
authors.lastname: Birx
authors.forename: A E
authors.initials: AE
authors.lastname: Brown
authors.forename: S
authors.initials: S
authors.lastname: Krishna
mesh_terms: D000208:Acute Disease; D000328:Adult; D005260:Female; D005455:Fluorescent Antibody Technique; D015497:HIV-1 / Q000276:immunology; D006801:Humans; D007108:Immune Tolerance; D008297:Male; D012367:RNA, Viral / Q000032:analysis; D012612:Scrub Typhus / Q000821:virology*; D019562:Viral Load
chemical_list: D012367:RNA, Viral