Transcytosis of HIV-1 through vaginal epithelial cells is dependent on trafficking to the endocytic recycling pathway.
BACKGROUND
While it is accepted that viruses can enter epithelial cells by endocytosis, the lack of an established biological mechanism for the trafficking of infectious virions through vaginal epithelial cells and their release from the plasma membrane has contributed to ongoing controversy about whether endocytosis is a mere artifact of some cell culture systems and whether squamous vaginal epithelial cells are even relevant as it pertains to HIV-1 transmission.


RESULTS
In this study, we investigated the intracellular trafficking pathway that HIV-1 exploits to transcytose vaginal epithelial cells. The reduction of endosome tubulation by recycling endosome inhibitors blocked transcytosis of HIV-1 in a cell culture and transwell system. In addition, we demonstrate that although heat-inactivated virus was endocytosed as efficiently as native virus, heat-inactivated virus was trafficked exclusively to the lysosomal pathway for degradation following endocytosis. Lysosomal protease-specific inhibitors blocked the degradation of inactivated virions. Immunofluorescence analysis not only demonstrated that HIV-1 was inside the cells but the different colocalization pattern of native vs. heat inactivated virus with transferrin provided conclusive evidence that HIV-1 uses the recycling pathway to get across vaginal epithelial cells.


CONCLUSIONS
Altogether, our findings demonstrate the precise intracellular trafficking pathway utilized by HIV-1 in epithelial cells, confirms that HIV-1 transcytosis through vaginal epithelial cells is a biological phenomenon and brings to light the differential intracellular trafficking of native vs heat-inactivated HIV-1 which with further exploration could prove to provide valuable insights that could be used in the prevention of transcytosis/transmission of HIV-1 across the mucosal epithelia.
Center for AIDS Health Disparities Research, Meharry Medical College, Nashville, Tennessee, United States of America; Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee, United States of America.
Ballington L
BL
Kinlock
Center for AIDS Health Disparities Research, Meharry Medical College, Nashville, Tennessee, United States of America.
Yudi
Y
Wang
Center for AIDS Health Disparities Research, Meharry Medical College, Nashville, Tennessee, United States of America; Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee, United States of America.
Tiffany M
TM
Turner
Center for AIDS Health Disparities Research, Meharry Medical College, Nashville, Tennessee, United States of America; Institute of Gastroenterology and Institute of Human Virology, Sun Yat-sen University, Guangzhou, Guangdong, Peoples of Republic of China.
Chenliang
C
Wang
Center for AIDS Health Disparities Research, Meharry Medical College, Nashville, Tennessee, United States of America; Department of Microbiology and Immunology, Meharry Medical College, Nashville, Tennessee, United States of America.
Bindong
B
Liu
D018929:Cell Culture Techniques / Q000379:methods; D002460:Cell Line; D002462:Cell Membrane / Q000821:virology; D011992:Endosomes / Q000378:metabolism; D004847:Epithelial Cells / Q000821:virology*; D005260:Female; D015658:HIV Infections / Q000503:physiopathology / Q000821:virology; D015497:HIV-1 / Q000502:physiology*; D006358:Hot Temperature; D006801:Humans; D008247:Lysosomes / Q000821:virology; D008856:Microscopy, Fluorescence; D021381:Protein Transport; D057900:Transcytosis; D014621:Vagina / Q000166:cytology* / Q000821:virology; D014771:Virion