Background:  Chemokines are natural ligands for chemokine receptors, which can block viral entry by interfering with viral binding with the receptor. Enhanced production of chemokines may protect some individuals from getting infected despite repeated exposure (EU) to HIV. Because no information was available regarding paired levels of chemokines in the blood and cervicovaginal secretions of EU women, we determined these levels in our EU cohort.

Methods:  We studied 10 EU women and 9 apparently healthy women at the Immunodeficiency Clinic, Post Graduate Institute of Medical Education and Research (PGIMER), Chandigarh, India. All were negative for HIV infection by ELISA and PCR. Peripheral blood mononuclear cells were stimulated by 200 µL of p24 antigen (4 µg/mL) in each well and, after 48-hour culture in RPMI, the culture supernatant was separated for chemokine measurement. Cervicovaginal samples were obtained by a single cotton-tipped swab that was inserted into the cervix, gently rotated through 360°, and placed in 4 mL of sterile phosphate buffered saline. Macrophage inhibitory protein (MIP) 1-a, MIP 1-β, and stromal-derived factor (SDF)-1 were measured using a commercially available ELISA. Descriptive statistics were used and p value < 0.05 was regarded significant.  

Results:  The mean age of the EU and healthy women was 32.8±5.7 and 30.6±8.7 years, respectively. The mean duration of last sexual exposure was 50.5±29.5 days among EU. Mean MIP-1a levels in the peripheral blood were 2630±613 pg/mL and 405±76 among EU and healthy women, respectively (p < 0.01). Mean MIP-1β levels in the peripheral blood were 1230±462 pg/mL and 313+145 pg/mL, among EU and healthy women, respectively (p < 0.01). SDF- levels were 220±77pg/mL and 194±54 pg/mL in EU and healthy women (p not significant). Median MIP-1a levels among EU and healthy women were 12.5 pg/mL and 0 pg/mL, respectively (p < 0.01). Median MIP-1β levels among EU and healthy women were 7.5 pg/mL and 0 pg/mL, respectively (p < 0.01 for each group). Median SDF-1 levels in the 2 groups were 0 pg/mL. There was no correlation between blood and genital chemokine levels in either group.

Conclusions:  Elevated levels of MIP-1a and MIP-1β in the peripheral blood and cervicovaginal secretions of EU may have a role in protecting these individuals from getting infected. This could have implications in vaccine development against HIV infection. The discordance between the peripheral blood and genital secretions might be accounted for by the 2 being separate immunological compartments.