title: Chronic HIV-2 infection protects against total CD4+ cell depletion and rapid disease progression induced by SHIV89.6p challenge.
abstract: OBJECTIVE
  To better understand HIV-1 sexual transmission risk, we have studied the susceptibility of HIV-2-exposed, uninfected (EU) female pig-tailed macaques to intravaginal (IVAG) re-challenge with the homologous HIV-2 strain, followed by heterologous SHIV89.6p.
  
  
  METHODS
  Nine female macaques, previously protected by a post-exposure prophylaxis (PEP) regimen, along with one mock-treated EU animal, were re-exposed to HIV-2 by the IVAG route approximately 1.5 years later. A single follow-up challenge was performed approximately 1 year later with SHIV89.6p to assess susceptibility of chronic HIV-2-infected animals to further re-infection and pathogenic effects with a heterologous virus, somewhat mimicking HIV-1.
  
  
  RESULTS
  Eight of ten macaques (80%) became infected systemically with HIV-2, and plasma or cervicovaginal vRNA levels did not appreciably differ from prior historic non-PEP control macaques. Interestingly, all eight HIV-2-infected females were susceptible to SHIV89.6p infection by either intravenous (n = 4) or IVAG exposure (n = 4) after one inoculation. Plasma vRNA levels in these groups were controlled by week 8 and there were no decrease in CD4+ T cells > 50%. The remaining two HIV-2 EU macaques, inoculated intrarectally with SHIV89.6p, were unable to control virus replication and succumbed to disease by week 25 or week 61.
  
  
  CONCLUSIONS
  Our findings demonstrate that successful PEP regimens to prevent an initial infection do not have any lasting protective effects. The observed lack of cross-protection against SHIV89.6p transmission among chronic HIV-2-infected macaques provides modeling support for limited epidemiologic data indicating that human HIV-2 infection does not protect against HIV-1 infection, but may serve to alter overt clinical outcome.
authors.affiliation: HIV/AIDS and Retrovirology Branch, Division of AIDS, STD, and TB Laboratory Research, National Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, 30333, USA. rxo1@cdc.gov
authors.forename: Ron A
authors.initials: RA
authors.lastname: Otten
authors.forename: Debra R
authors.initials: DR
authors.lastname: Adams
authors.forename: Caryn N
authors.initials: CN
authors.lastname: Kim
authors.forename: Jennifer K
authors.initials: JK
authors.lastname: Pullium
authors.forename: Tamela
authors.initials: T
authors.lastname: Sawyer
authors.forename: Eddie
authors.initials: E
authors.lastname: Jackson
authors.forename: Thomas M
authors.initials: TM
authors.lastname: Folks
authors.forename: Sal
authors.initials: S
authors.lastname: Butera
mesh_terms: D000818:Animals; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology / Q000821:virology; D002908:Chronic Disease; D018450:Disease Progression; D004198:Disease Susceptibility; D005260:Female; D015658:HIV Infections / Q000276:immunology* / Q000517:prevention & control / Q000635:transmission; D015498:HIV-2 / Q000276:immunology*; D008231:Lymphopenia / Q000276:immunology / Q000821:virology; D008254:Macaca nemestrina; D012367:RNA, Viral / Q000097:blood; D016097:Simian Acquired Immunodeficiency Syndrome / Q000276:immunology*; D015302:Simian Immunodeficiency Virus / Q000276:immunology*
chemical_list: D012367:RNA, Viral