B cells are able to alter the effector function(s) associated with their secreted B cell receptors (more commonly known as antibodies) using class-switch recombination (CSR). CSR affects the isotope of the B cell receptor.
There are five different isotypes - IgM, IgD, IgG, IgA and IgE - and IgG can be further subdivided into four subclasses - IgG1, IgG2, IgG3 and IgG4.
Based on what you know about the different effector functions elicited by the isotypes and IgG subclasses, which isotype(s) and/or subclass(es) do you predict are most relevant for providing protection and blocking spread of human immunodeficiency virus (HIV)?
Note: For the purposes of this question, both IgA1 and IgA2 are grouped together simply as IgA.