HIV-1 ina strains nyingi; baadhi ya strains ni T-cell tropic (T-tropic) na zinatumia CXCR4 kama co-receptor, wakati strains nyingine ni macrophage-tropic (M-tropic) na zinatumia CCR5 kama co-receptor.
Kuna strains chache za HIV-1 ambazo zaweza ku-bind hata CCR3 ama chemokine receptors zingine kwenye cells ambazo zinazi-express hizo chemokines lakini bado roles zao (including CCR3) kwenye HIV-1 infection iko unclear.
Science haiendi kwa logic tu la sivyo mambo yangekuwa marahisi. Ndio maana tafiti zaendelea kila siku hata kwa magonjwa ambayo yamejulikana miaka zaidi ya 100 iliyopita. Usipoelewa logic yawezekana ume-miss point ama kwa present knowledge/technology tuliyonayo bado kuna kitu tunaki-miss, tunatakiwa tukigundue. Hivyo usipende kuwa rigid, go back to your lab ama journals na waweza kujifunza kitu kipya.