CXCR4 and HIV-1 infection: As examples pertinent to HIV research, nanobodies 238D2 and 238D4 bind to cellular CXCR4 (C-X-C chemokine receptor type 4 or CD184) and neutralize X4 strains of HIV-1 by blocking this coreceptor [8], intracellular nanobodies (intrabodies) to Rev inhibit multimerization to interfere with virus production [9], and an anti-p24 nanobody has been employed as a detector of p24 Gag antigen in designing miniaturized diagnostic tests of HIV-1 infection [10,11].